# PostGIS 3.5.1 Manual

### The PostGIS Development Group

Abstract

PostGIS is an extension to the PostgreSQL object-relational database system which allows GIS (Geographic Information Systems) objects to be stored in the database. PostGIS includes support for GiST-based R-Tree spatial indexes, and functions for analysis and processing of GIS objects.

This is the manual for version 3.5.1

This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Feel free to use this material any way you like, but we ask that you attribute credit to the PostGIS Project and wherever possible, a link back to https://postgis.net.

# Chapter 1. Introduction

PostGIS is a spatial extension for the PostgreSQL relational database that was created by Refractions Research Inc, as a spatial database technology research project. Refractions is a GIS and database consulting company in Victoria, British Columbia, Canada, specializing in data integration and custom software development.

PostGIS is now a project of the OSGeo Foundation and is developed and funded by many FOSS4G developers and organizations all over the world that gain great benefit from its functionality and versatility.

The PostGIS project development group plans on supporting and enhancing PostGIS to better support a range of important GIS functionality in the areas of OGC and SQL/MM spatial standards, advanced topological constructs (coverages, surfaces, networks), data source for desktop user interface tools for viewing and editing GIS data, and web-based access tools.

## 1.1. Project Steering Committee

The PostGIS Project Steering Committee (PSC) coordinates the general direction, release cycles, documentation, and outreach efforts for the PostGIS project. In addition the PSC provides general user support, accepts and approves patches from the general PostGIS community and votes on miscellaneous issues involving PostGIS such as developer commit access, new PSC members or significant API changes.

Raúl Marín Rodríguez

  MVT support, Bug fixing, Performance and stability improvements, GitHub curation, alignment of PostGIS with PostgreSQL releases

Regina Obe

  CI and website maintenance, Windows production and experimental builds, documentation, alignment of PostGIS with PostgreSQL releases, X3D support, TIGER geocoder support, management functions.

Darafei Praliaskouski

  Index improvements, bug fixing and geometry/geography function improvements, SFCGAL, raster, GitHub curation, and ci maintenance.

Paul Ramsey (Chair)

  Co-founder of PostGIS project. General bug fixing, geography support, geography and geometry index support (2D, 3D, nD index and anything spatial index), underlying geometry internal structures, GEOS functionality integration and alignment with GEOS releases, alignment of PostGIS with PostgreSQL releases, loader/dumper, and Shapefile GUI loader.

Sandro Santilli

  Bug fixes and maintenance, ci maintenance, git mirror management, management functions, integration of new GEOS functionality and alignment with GEOS releases, topology support, and raster framework and low level API functions.

## 1.2. Core Contributors Present

Nicklas Avén

  Distance function enhancements (including 3D distance and relationship functions) and additions, Tiny WKB (TWKB) output format and general user support

Loïc Bartoletti

  SFCGAL enhancements and maintenance and ci support

Dan Baston

  Geometry clustering function additions, other geometry algorithm enhancements, GEOS enhancements and general user support

Martin Davis

  GEOS enhancements and documentation

Björn Harrtell

  MapBox Vector Tile, GeoBuf, and Flatgeobuf functions. Gitea testing and GitLab experimentation.

Aliaksandr Kalenik

  Geometry Processing, PostgreSQL gist, general bug fixing

## 1.3. Core Contributors Past

Bborie Park

  Prior PSC Member. Raster development, integration with GDAL, raster loader, user support, general bug fixing, testing on various OS (Slackware, Mac, Windows, and more)

Mark Cave-Ayland

  Prior PSC Member. Coordinated bug fixing and maintenance effort, spatial index selectivity and binding, loader/dumper, and Shapefile GUI Loader, integration of new and new function enhancements.

Jorge Arévalo

  Raster development, GDAL driver support, loader

Olivier Courtin

  (Emeritus) Input/output XML (KML,GML)/GeoJSON functions, 3D support and bug fixes.

Chris Hodgson

  Prior PSC Member. General development, site and buildbot maintenance, OSGeo incubation management

Mateusz Loskot

  CMake support for PostGIS, built original raster loader in python and low level raster API functions

Kevin Neufeld

  Prior PSC Member. Documentation and documentation support tools, buildbot maintenance, advanced user support on PostGIS newsgroup, and PostGIS maintenance function enhancements.

Dave Blasby

  The original developer/Co-founder of PostGIS. Dave wrote the server side objects, index bindings, and many of the server side analytical functions.

Jeff Lounsbury

  Original development of the Shapefile loader/dumper.

Mark Leslie

  Ongoing maintenance and development of core functions. Enhanced curve support. Shapefile GUI loader.

Pierre Racine

  Architect of PostGIS raster implementation. Raster overall architecture, prototyping, programming support

David Zwarg

  Raster development (mostly map algebra analytic functions)

## 1.4. Other Contributors

Individual Contributors

  Alex Bodnaru | Gino Lucrezi | Maxime Guillaud
  Alex Mayrhofer | Greg Troxel | Maxime van Noppen
  Andrea Peri | Guillaume Lelarge | Maxime Schoemans
  Andreas Forø Tollefsen | Giuseppe Broccolo | Michael Fuhr
  Andreas Neumann | Han Wang | Mike Toews
  Andrew Gierth | Hans Lemuet | Nathan Wagner
  Anne Ghisla | Haribabu Kommi | Nathaniel Clay
  Antoine Bajolet | Havard Tveite | Nikita Shulga
  Arthur Lesuisse | IIDA Tetsushi | Norman Vine
  Artur Zakirov | Ingvild Nystuen | Patricia Tozer
  Barbara Phillipot | Jackie Leng | Rafal Magda
  Ben Jubb | James Addison | Ralph Mason
  Bernhard Reiter | James Marca | Rémi Cura
  Björn Esser | Jan Katins | Richard Greenwood
  Brian Hamlin | Jan Tojnar | Robert Coup
  Bruce Rindahl | Jason Smith | Roger Crew
  Bruno Wolff III | Jeff Adams | Ron Mayer
  Bryce L. Nordgren | Jelte Fennema | Sam Peters
  Carl Anderson | Jim Jones | Sebastiaan Couwenberg
  Charlie Savage | Joe Conway | Sergei Shoulbakov
  Chris Mayo | Jonne Savolainen | Sergey Fedoseev
  Christian Schroeder | Jose Carlos Martinez Llari | Shinichi Sugiyama
  Christoph Berg | Jörg Habenicht | Shoaib Burq
  Christoph Moench-Tegeder | Julien Rouhaud | Silvio Grosso
  Dane Springmeyer | Kashif Rasul | Stefan Corneliu Petrea
  Dapeng Wang | Klaus Foerster | Steffen Macke
  Daryl Herzmann | Kris Jurka | Stepan Kuzmin
  Dave Fuhry | Laurenz Albe | Stephen Frost
  David Garnier | Lars Roessiger | Steven Ottens
  David Skea | Leo Hsu | Talha Rizwan
  David Techer | Loic Dachary | Teramoto Ikuhiro
  Dian M Fay | Luca S. Percich | Tom Glancy
  Dmitry Vasilyev | Lucas C. Villa Real | Tom van Tilburg
  Eduin Carrillo | Maria Arias de Reyna | Victor Collod
  Esteban Zimanyi | Marc Ducobu | Vincent Bre
  Eugene Antimirov | Mark Sondheim | Vincent Mora
  Even Rouault | Markus Schaber | Vincent Picavet
  Florian Weimer | Markus Wanner | Volf Tomáš
  Frank Warmerdam | Matt Amos | Zuo Chenwei
  George Silva | Matt Bretl |
  Gerald Fenoy | Matthias Bay |

Corporate Sponsors

  These are corporate entities that have contributed developer time, hosting, or direct monetary funding to the PostGIS project. In alphabetical order:

  - Aiven
  - Arrival 3D
  - Associazione Italiana per l'Informazione Geografica Libera (GFOSS.it)
  - AusVet
  - Avencia
  - Azavea
  - Boundless
  - Cadcorp
  - Camptocamp
  - Carto
  - Crunchy Data
  - City of Boston (DND)
  - City of Helsinki
  - Clever Elephant Solutions
  - Cooperativa Alveo
  - Deimos Space
  - Faunalia
  - Geographic Data BC
  - HighGo
  - Hunter Systems Group
  - >The National Institute for Agricultural and Food Research and Technology (INIA-CSIC)
  - ISciences, LLC
  - Kontur
  - Lidwala Consulting Engineers
  - LISAsoft
  - Logical Tracking & Tracing International AG
  - Maponics
  - Michigan Tech Research Institute
  - Natural Resources Canada
  - Norwegian Forest and Landscape Institute
  - Norwegian Institute of Bioeconomy Research (NIBIO)
  - OSGeo
  - Oslandia
  - Palantir Technologies
  - Paragon Corporation
  - R3 GIS
  - Refractions Research
  - Regione Toscana - SITA
  - Safe Software
  - Sirius Corporation plc
  - Stadt Uster
  - UC Davis Center for Vectorborne Diseases
  - Université Laval
  - U.S. Department of State (HIU)
  - Zonar Systems

Crowd Funding Campaigns

  Crowd funding campaigns are campaigns we run to get badly wanted features funded that can service a large number of people. Each campaign is specifically focused on a particular feature or set of features. Each sponsor chips in a small fraction of the needed funding and with enough people/organizations contributing, we have the funds to pay for the work that will help many. If you have an idea for a feature you think many others would be willing to co-fund, please post to the PostGIS newsgroup your thoughts and together we can make it happen.

  PostGIS 2.0.0 was the first release we tried this strategy. We used PledgeBank and we got two successful campaigns out of it.

  postgistopology - 10 plus sponsors each contributed $250 USD to build toTopoGeometry function and beef up topology support in 2.0.0. It happened.

  postgis64windows - 20 someodd sponsors each contributed $100 USD to pay for the work needed to work out PostGIS 64-bit issues on windows. It happened.

Important Support Libraries

  The GEOS geometry operations library

  The GDAL Geospatial Data Abstraction Library used to power much of the raster functionality introduced in PostGIS 2. In kind, improvements needed in GDAL to support PostGIS are contributed back to the GDAL project.

  The PROJ cartographic projection library

  Last but not least, PostgreSQL, the giant that PostGIS stands on. Much of the speed and flexibility of PostGIS would not be possible without the extensibility, great query planner, GIST index, and plethora of SQL features provided by PostgreSQL.

# Chapter 2. PostGIS Installation

This chapter details the steps required to install PostGIS.

## 2.1. Short Version

To compile assuming you have all the dependencies in your search path:

    tar -xvzf postgis-3.5.1.tar.gz
    cd postgis-3.5.1
    ./configure
    make
    make install

Once PostGIS is installed, it needs to be enabled (Section 3.3, “Creating spatial databases”) or upgraded (Section 3.4, “Upgrading spatial databases”) in each individual database you want to use it in.

## 2.2. Compiling and Install from Source

Many OS systems now include pre-built packages for PostgreSQL/PostGIS. In many cases compilation is only necessary if you want the most bleeding edge versions or you are a package maintainer. This section includes general compilation instructions, if you are compiling for Windows etc or another OS, you may find additional more detailed help at PostGIS User contributed compile guides and PostGIS Dev Wiki. Pre-Built Packages for various OS are listed in PostGIS Pre-built Packages If you are a windows user, you can get stable builds via Stackbuilder or PostGIS Windows download site We also have very bleeding-edge windows experimental builds that are built usually once or twice a week or whenever anything exciting happens. You can use these to experiment with the in progress releases of PostGIS

The PostGIS module is an extension to the PostgreSQL backend server. As such, PostGIS 3.5.1 requires full PostgreSQL server headers access in order to compile. It can be built against PostgreSQL versions 12 - 17. Earlier versions of PostgreSQL are not supported.

Refer to the PostgreSQL installation guides if you haven't already installed PostgreSQL. https://www.postgresql.org .

For GEOS functionality, when you install PostgreSQL you may need to explicitly link PostgreSQL against the standard C++ library:
    LDFLAGS=-lstdc++ ./configure [YOUR OPTIONS HERE]
This is a workaround for bogus C++ exceptions interaction with older development tools. If you experience weird problems (backend unexpectedly closed or similar things) try this trick. This will require recompiling your PostgreSQL from scratch, of course.

The following steps outline the configuration and compilation of the PostGIS source. They are written for Linux users and will not work on Windows or Mac.

### 2.2.1. Getting the Source

Retrieve the PostGIS source archive from the downloads website https://download.osgeo.org/postgis/source/postgis-3.5.1.tar.gz

    wget https://download.osgeo.org/postgis/source/postgis-3.5.1.tar.gz
    tar -xvzf postgis-3.5.1.tar.gz
    cd postgis-3.5.1

This will create a directory called `postgis-3.5.1` in the current working directory.

Alternatively, checkout the source from the git repository https://git.osgeo.org/gitea/postgis/postgis/ .

    git clone https://git.osgeo.org/gitea/postgis/postgis.git postgis
    cd postgis
    sh autogen.sh

Change into the newly created `postgis` directory to continue the installation.

    ./configure

### 2.2.2. Install Requirements

PostGIS has the following requirements for building and usage:

Required

- PostgreSQL 12 - 17. A complete installation of PostgreSQL (including server headers) is required. PostgreSQL is available from https://www.postgresql.org .

  For a full PostgreSQL / PostGIS support matrix and PostGIS/GEOS support matrix refer to https://trac.osgeo.org/postgis/wiki/UsersWikiPostgreSQLPostGIS

- GNU C compiler (`gcc`). Some other ANSI C compilers can be used to compile PostGIS, but we find far fewer problems when compiling with `gcc`.

- GNU Make (`gmake` or `make`). For many systems, GNU `make` is the default version of make. Check the version by invoking `make -v`. Other versions of `make` may not process the PostGIS `Makefile` properly.

- Proj reprojection library. Proj 6.1 or above is required. The Proj library is used to provide coordinate reprojection support within PostGIS. Proj is available for download from https://proj.org/ .

- GEOS geometry library, version 3.8.0 or greater, but GEOS 3.12+ is required to take full advantage of all the new functions and features. GEOS is available for download from https://libgeos.org .

- LibXML2, version 2.5.x or higher. LibXML2 is currently used in some imports functions (ST_GeomFromGML and ST_GeomFromKML). LibXML2 is available for download from https://gitlab.gnome.org/GNOME/libxml2/-/releases.

- JSON-C, version 0.9 or higher. JSON-C is currently used to import GeoJSON via the function ST_GeomFromGeoJson. JSON-C is available for download from https://github.com/json-c/json-c/releases/.

- GDAL, version 3+ is preferred. This is required for raster support. https://gdal.org/download.html.

- If compiling with PostgreSQL+JIT, LLVM version >=6 is required https://trac.osgeo.org/postgis/ticket/4125.

Optional

- GDAL (pseudo optional) only if you don't want raster you can leave it out. Also make sure to enable the drivers you want to use as described in Section 3.2, “Configuring raster support”.

- GTK (requires GTK+2.0, 2.8+) to compile the shp2pgsql-gui shape file loader. http://www.gtk.org/ .

- SFCGAL, 1.4.1 or higher is required and 1.5.0+ is needed to be able to use all functionality. SFCGAL can be used to provide additional 2D and 3D advanced analysis functions to PostGIS cf Chapter 8, SFCGAL Functions Reference. And also allow to use SFCGAL rather than GEOS for some 2D functions provided by both backends (like ST_Intersection or ST_Area, for instance). A PostgreSQL configuration variable `postgis.backend` allow end user to control which backend he want to use if SFCGAL is installed (GEOS by default). Nota: SFCGAL 1.2 require at least CGAL 4.3 and Boost 1.54 (cf: https://sfcgal.org) https://gitlab.com/sfcgal/SFCGAL/.

- In order to build the Section 12.1, “Address Standardizer” you will also need PCRE http://www.pcre.org (which generally is already installed on nix systems). Section 12.1, “Address Standardizer” will automatically be built if it detects a PCRE library, or you pass in a valid `--with-pcre-dir=/path/to/pcre` during configure.

- To enable ST_AsMVT protobuf-c library 1.1.0 or higher (for usage) and the protoc-c compiler (for building) are required. Also, pkg-config is required to verify the correct minimum version of protobuf-c. See protobuf-c. By default, Postgis will use Wagyu to validate MVT polygons faster which requires a c++11 compiler. It will use CXXFLAGS and the same compiler as the PostgreSQL installation. To disable this and use GEOS instead use the `--without-wagyu` during the configure step.

- CUnit (`CUnit`). This is needed for regression testing. http://cunit.sourceforge.net/

- DocBook (`xsltproc`) is required for building the documentation. Docbook is available from http://www.docbook.org/ .

- DBLatex (`dblatex`) is required for building the documentation in PDF format. DBLatex is available from http://dblatex.sourceforge.net/ .

- ImageMagick (`convert`) is required to generate the images used in the documentation. ImageMagick is available from http://www.imagemagick.org/ .

### 2.2.3. Build configuration

As with most linux installations, the first step is to generate the Makefile that will be used to build the source code. This is done by running the shell script

./configure

With no additional parameters, this command will attempt to automatically locate the required components and libraries needed to build the PostGIS source code on your system. Although this is the most common usage of ./configure, the script accepts several parameters for those who have the required libraries and programs in non-standard locations.

The following list shows only the most commonly used parameters. For a complete list, use the --help or --help=short parameters.

`--with-library-minor-version`

  Starting with PostGIS 3.0, the library files generated by default will no longer have the minor version as part of the file name. This means all PostGIS 3 libs will end in `postgis-3`. This was done to make pg_upgrade easier, with downside that you can only install one version PostGIS 3 series in your server. To get the old behavior of file including the minor version: e.g. `postgis-3.0` add this switch to your configure statement.

`--prefix=PREFIX`

  This is the location the PostGIS loader executables and shared libs will be installed. By default, this location is the same as the detected PostgreSQL installation.

  This parameter is currently broken, as the package will only install into the PostgreSQL installation directory. Visit http://trac.osgeo.org/postgis/ticket/635 to track this bug.

`--with-pgconfig=FILE`

  PostgreSQL provides a utility called pg_config to enable extensions like PostGIS to locate the PostgreSQL installation directory. Use this parameter (--with-pgconfig=/path/to/pg_config) to manually specify a particular PostgreSQL installation that PostGIS will build against.

`--with-gdalconfig=FILE`

  GDAL, a required library, provides functionality needed for raster support gdal-config to enable software installations to locate the GDAL installation directory. Use this parameter (--with-gdalconfig=/path/to/gdal-config) to manually specify a particular GDAL installation that PostGIS will build against.

`--with-geosconfig=FILE`

  GEOS, a required geometry library, provides a utility called geos-config to enable software installations to locate the GEOS installation directory. Use this parameter (--with-geosconfig=/path/to/geos-config) to manually specify a particular GEOS installation that PostGIS will build against.

`--with-xml2config=FILE`

  LibXML is the library required for doing GeomFromKML/GML processes. It normally is found if you have libxml installed, but if not or you want a specific version used, you'll need to point PostGIS at a specific `xml2-config` confi file to enable software installations to locate the LibXML installation directory. Use this parameter (>--with-xml2config=/path/to/xml2-config) to manually specify a particular LibXML installation that PostGIS will build against.

`--with-projdir=DIR`

  Proj is a reprojection library required by PostGIS. Use this parameter (--with-projdir=/path/to/projdir) to manually specify a particular Proj installation directory that PostGIS will build against.

`--with-libiconv=DIR`

  Directory where iconv is installed.

`--with-jsondir=DIR`

  JSON-C is an MIT-licensed JSON library required by PostGIS ST_GeomFromJSON support. Use this parameter (--with-jsondir=/path/to/jsondir) to manually specify a particular JSON-C installation directory that PostGIS will build against.

`--with-pcredir=DIR`

  PCRE is an BSD-licensed Perl Compatible Regular Expression library required by address_standardizer extension. Use this parameter (--with-pcredir=/path/to/pcredir) to manually specify a particular PCRE installation directory that PostGIS will build against.

`--with-gui`

  Compile the data import GUI (requires GTK+2.0). This will create shp2pgsql-gui graphical interface to shp2pgsql.

`--without-raster`

  Compile without raster support.

`--without-topology`

  Disable topology support. There is no corresponding library as all logic needed for topology is in postgis-3.5.1 library.

`--with-gettext=no`

  By default PostGIS will try to detect gettext support and compile with it, however if you run into incompatibility issues that cause breakage of loader, you can disable it entirely with this command. Refer to ticket http://trac.osgeo.org/postgis/ticket/748 for an example issue solved by configuring with this. NOTE: that you aren't missing much by turning this off. This is used for international help/label support for the GUI loader which is not yet documented and still experimental.

`--with-sfcgal=PATH`

  By default PostGIS will not install with sfcgal support without this switch. `PATH` is an optional argument that allows to specify an alternate PATH to sfcgal-config.

`--without-phony-revision`

  Disable updating postgis_revision.h to match current HEAD of the git repository.

If you obtained PostGIS from the code repository , the first step is really to run the script ./autogen.sh This script will generate the configure script that in turn is used to customize the installation of PostGIS. If you instead obtained PostGIS as a tarball, running ./autogen.sh is not necessary as configure has already been generated.

### 2.2.4. Building

Once the Makefile has been generated, building PostGIS is as simple as running

make

The last line of the output should be "`PostGIS was built successfully. Ready to install.`"

As of PostGIS v1.4.0, all the functions have comments generated from the documentation. If you wish to install these comments into your spatial databases later, run the command which requires docbook. The postgis_comments.sql and other package comments files raster_comments.sql, topology_comments.sql are also packaged in the tar.gz distribution in the doc folder so no need to make comments if installing from the tar ball. Comments are also included as part of the CREATE EXTENSION install.

make comments

Introduced in PostGIS 2.0. This generates html cheat sheets suitable for quick reference or for student handouts. This requires xsltproc to build and will generate 4 files in doc folder `topology_cheatsheet.html`, `tiger_geocoder_cheatsheet.html`, `raster_cheatsheet.html`, `postgis_cheatsheet.html`

You can download some pre-built ones available in html and pdf from PostGIS / PostgreSQL Study Guides

make cheatsheets

### 2.2.5. Building PostGIS Extensions and Deploying them

The PostGIS extensions are built and installed automatically if you are using PostgreSQL 9.1+.

If you are building from source repository, you need to build the function descriptions first. These get built if you have docbook installed. You can also manually build with the statement:

make comments

Building the comments is not necessary if you are building from a release tar ball since these are packaged pre-built with the tar ball already.

The extensions should automatically build as part of the make install process. You can if needed build from the extensions folders or copy files if you need them on a different server.

    cd extensions
    cd postgis
    make clean
    make
    export PGUSER=postgres #overwrite psql variables
    make check #to test before install
    make install
    # to test extensions
    make check RUNTESTFLAGS=--extension

`make check` uses psql to run tests and as such can use psql environment variables. Common ones useful to override are `PGUSER`,`PGPORT`, and `PGHOST`. Refer to psql environment variables

The extension files will always be the same for the same version of PostGIS and PostgreSQL regardless of OS, so it is fine to copy over the extension files from one OS to another as long as you have the PostGIS binaries already installed on your servers.

If you want to install the extensions manually on a separate server different from your development, You need to copy the following files from the extensions folder into the `PostgreSQL / share / extension` folder of your PostgreSQL install as well as the needed binaries for regular PostGIS if you don't have them already on the server.

- These are the control files that denote information such as the version of the extension to install if not specified. `postgis.control, postgis_topology.control`.

- All the files in the /sql folder of each extension. Note that these need to be copied to the root of the PostgreSQL share/extension folder `extensions/postgis/sql/*.sql`, `extensions/postgis_topology/sql/*.sql`

Once you do that, you should see `postgis`, `postgis_topology` as available extensions in PgAdmin -> extensions.

If you are using psql, you can verify that the extensions are installed by running this query:

    SELECT name, default_version,installed_version
    FROM pg_available_extensions WHERE name LIKE 'postgis%' or name LIKE 'address%';

                 name             | default_version | installed_version
    ------------------------------+-----------------+-------------------
     address_standardizer         | 3.5.1         | 3.5.1
     address_standardizer_data_us | 3.5.1         | 3.5.1
     postgis                      | 3.5.1         | 3.5.1
     postgis_raster               | 3.5.1         | 3.5.1
     postgis_sfcgal               | 3.5.1         |
     postgis_tiger_geocoder       | 3.5.1         | 3.5.1
     postgis_topology             | 3.5.1         |
    (6 rows)

If you have the extension installed in the database you are querying, you'll see mention in the `installed_version` column. If you get no records back, it means you don't have postgis extensions installed on the server at all. PgAdmin III 1.14+ will also provide this information in the `extensions` section of the database browser tree and will even allow upgrade or uninstall by right-clicking.

If you have the extensions available, you can install postgis extension in your database of choice by either using pgAdmin extension interface or running these sql commands:

    CREATE EXTENSION postgis;
    CREATE EXTENSION postgis_raster;
    CREATE EXTENSION postgis_sfcgal;
    CREATE EXTENSION fuzzystrmatch; --needed for postgis_tiger_geocoder
    --optional used by postgis_tiger_geocoder, or can be used standalone
    CREATE EXTENSION address_standardizer;
    CREATE EXTENSION address_standardizer_data_us;
    CREATE EXTENSION postgis_tiger_geocoder;
    CREATE EXTENSION postgis_topology;

In psql you can use to see what versions you have installed and also what schema they are installed.

    \connect mygisdb
    \x
    \dx postgis*

    List of installed extensions
    -[ RECORD 1 ]-------------------------------------------------
    Name        | postgis
    Version     | 3.5.1
    Schema      | public
    Description | PostGIS geometry, geography, and raster spat..
    -[ RECORD 2 ]-------------------------------------------------
    Name        | postgis_raster
    Version     | 3.0.0dev
    Schema      | public
    Description | PostGIS raster types and functions
    -[ RECORD 3 ]-------------------------------------------------
    Name        | postgis_tiger_geocoder
    Version     | 3.5.1
    Schema      | tiger
    Description | PostGIS tiger geocoder and reverse geocoder
    -[ RECORD 4 ]-------------------------------------------------
    Name        | postgis_topology
    Version     | 3.5.1
    Schema      | topology
    Description | PostGIS topology spatial types and functions

Extension tables `spatial_ref_sys`, `layer`, `topology` can not be explicitly backed up. They can only be backed up when the respective `postgis` or `postgis_topology` extension is backed up, which only seems to happen when you backup the whole database. As of PostGIS 2.0.1, only srid records not packaged with PostGIS are backed up when the database is backed up so don't go around changing srids we package and expect your changes to be there. Put in a ticket if you find an issue. The structures of extension tables are never backed up since they are created with `CREATE EXTENSION` and assumed to be the same for a given version of an extension. These behaviors are built into the current PostgreSQL extension model, so nothing we can do about it.

If you installed 3.5.1, without using our wonderful extension system, you can change it to be extension based by running the below commands to package the functions in their respective extension. Installing using `unpackaged` was removed in PostgreSQL 13, so you are advised to switch to an extension build before upgrading to PostgreSQL 13.

    CREATE EXTENSION postgis FROM unpackaged;
    CREATE EXTENSION postgis_raster FROM unpackaged;
    CREATE EXTENSION postgis_topology FROM unpackaged;
    CREATE EXTENSION postgis_tiger_geocoder FROM unpackaged;

### 2.2.6. Testing

If you wish to test the PostGIS build, run

make check

The above command will run through various checks and regression tests using the generated library against an actual PostgreSQL database.

If you configured PostGIS using non-standard PostgreSQL, GEOS, or Proj locations, you may need to add their library locations to the `LD_LIBRARY_PATH` environment variable.

Currently, the make check relies on the `PATH` and `PGPORT` environment variables when performing the checks - it does not use the PostgreSQL version that may have been specified using the configuration parameter --with-pgconfig. So make sure to modify your PATH to match the detected PostgreSQL installation during configuration or be prepared to deal with the impending headaches.

If successful, make check will produce the output of almost 500 tests. The results will look similar to the following (numerous lines omitted below):

         CUnit - A unit testing framework for C - Version 2.1-3
         http://cunit.sourceforge.net/

    	.
    	.
    	.

    Run Summary:    Type  Total    Ran Passed Failed Inactive
                  suites     44     44    n/a      0        0
                   tests    300    300    300      0        0
                 asserts   4215   4215   4215      0      n/a
    Elapsed time =    0.229 seconds

    	.
    	.
    	.

    Running tests

    	.
    	.
    	.

    Run tests: 134
    Failed: 0

    -- if you build with SFCGAL

    	.
    	.
    	.

    Running tests

    	.
    	.
    	.

    Run tests: 13
    Failed: 0

    -- if you built with raster support

    	.
    	.
    	.

    Run Summary:    Type  Total    Ran Passed Failed Inactive
                  suites     12     12    n/a      0        0
                   tests     65     65     65      0        0
                 asserts  45896  45896  45896      0      n/a

    	.
    	.
    	.

    Running tests

    	.
    	.
    	.

    Run tests: 101
    Failed: 0

    -- topology regress

    .
    .
    .

    Running tests

    	.
    	.
    	.

    Run tests: 51
    Failed: 0

    -- if you built --with-gui, you should see this too

         CUnit - A unit testing framework for C - Version 2.1-2
         http://cunit.sourceforge.net/

    	.
    	.
    	.

    Run Summary:    Type  Total    Ran Passed Failed Inactive
                  suites      2      2    n/a      0        0
                   tests      4      4      4      0        0
                 asserts      4      4      4      0      n/a

The `postgis_tiger_geocoder` and `address_standardizer` extensions, currently only support the standard PostgreSQL installcheck. To test these use the below. Note: the make install is not necessary if you already did make install at root of PostGIS code folder.

For address_standardizer:

    cd extensions/address_standardizer
    make install
    make installcheck

Output should look like:

    ============== dropping database "contrib_regression" ==============
    DROP DATABASE
    ============== creating database "contrib_regression" ==============
    CREATE DATABASE
    ALTER DATABASE
    ============== running regression test queries        ==============
    test test-init-extensions     ... ok
    test test-parseaddress        ... ok
    test test-standardize_address_1 ... ok
    test test-standardize_address_2 ... ok

    =====================
     All 4 tests passed.
    =====================

For tiger geocoder, make sure you have postgis and fuzzystrmatch extensions available in your PostgreSQL instance. The address_standardizer tests will also kick in if you built postgis with address_standardizer support:

    cd extensions/postgis_tiger_geocoder
    make install
    make installcheck

output should look like:

    ============== dropping database "contrib_regression" ==============
    DROP DATABASE
    ============== creating database "contrib_regression" ==============
    CREATE DATABASE
    ALTER DATABASE
    ============== installing fuzzystrmatch               ==============
    CREATE EXTENSION
    ============== installing postgis                     ==============
    CREATE EXTENSION
    ============== installing postgis_tiger_geocoder      ==============
    CREATE EXTENSION
    ============== installing address_standardizer        ==============
    CREATE EXTENSION
    ============== running regression test queries        ==============
    test test-normalize_address   ... ok
    test test-pagc_normalize_address ... ok

    =====================
    All 2 tests passed.
    =====================

### 2.2.7. Installation

To install PostGIS, type

make install

This will copy the PostGIS installation files into their appropriate subdirectory specified by the --prefix configuration parameter. In particular:

- The loader and dumper binaries are installed in `[prefix]/bin`.

- The SQL files, such as `postgis.sql`, are installed in `[prefix]/share/contrib`.

- The PostGIS libraries are installed in `[prefix]/lib`.

If you previously ran the make comments command to generate the `postgis_comments.sql`, `raster_comments.sql` file, install the sql file by running

make comments-install

`postgis_comments.sql`, `raster_comments.sql`, `topology_comments.sql` was separated from the typical build and installation targets since with it comes the extra dependency of xsltproc.

## 2.3. Installing and Using the address standardizer

The `address_standardizer` extension used to be a separate package that required separate download. From PostGIS 2.2 on, it is now bundled in. For more information about the address_standardize, what it does, and how to configure it for your needs, refer to Section 12.1, “Address Standardizer”.

This standardizer can be used in conjunction with the PostGIS packaged tiger geocoder extension as a replacement for the Normalize_Address discussed. To use as replacement refer to Section 2.4.2, “Using Address Standardizer Extension with Tiger geocoder”. You can also use it as a building block for your own geocoder or use it to standardize your addresses for easier compare of addresses.

The address standardizer relies on PCRE which is usually already installed on many Nix systems, but you can download the latest at: http://www.pcre.org. If during Section 2.2.3, “Build configuration”, PCRE is found, then the address standardizer extension will automatically be built. If you have a custom pcre install you want to use instead, pass to configure `--with-pcredir=/path/to/pcre` where `/path/to/pcre` is the root folder for your pcre include and lib directories.

For Windows users, the PostGIS 2.1+ bundle is packaged with the address_standardizer already so no need to compile and can move straight to `CREATE EXTENSION` step.

Once you have installed, you can connect to your database and run the SQL:

    CREATE EXTENSION address_standardizer;

The following test requires no rules, gaz, or lex tables

    SELECT num, street, city, state, zip
     FROM parse_address('1 Devonshire Place PH301, Boston, MA 02109');

Output should be

     num |         street         |  city  | state |  zip
    -----+------------------------+--------+-------+-------
     1   | Devonshire Place PH301 | Boston | MA    | 02109

## 2.4. Installing, Upgrading Tiger Geocoder, and loading data

Extras like Tiger geocoder may not be packaged in your PostGIS distribution. If you are missing the tiger geocoder extension or want a newer version than what your install comes with, then use the `share/extension/postgis_tiger_geocoder.*` files from the packages in Windows Unreleased Versions section for your version of PostgreSQL. Although these packages are for windows, the postgis_tiger_geocoder extension files will work on any OS since the extension is an SQL/plpgsql only extension.

### 2.4.1. Tiger Geocoder Enabling your PostGIS database

1. These directions assume your PostgreSQL installation already has the postgis_tiger_geocoder extension installed.

2. Connect to your database via psql or pgAdmin or some other tool and run the following SQL commands. Note that if you are installing in a database that already has postgis, you don't need to do the first step. If you have `fuzzystrmatch` extension already installed, you don't need to do the second step either.

       CREATE EXTENSION postgis;
       CREATE EXTENSION fuzzystrmatch;
       CREATE EXTENSION postgis_tiger_geocoder;
       --this one is optional if you want to use the rules based standardizer (pagc_normalize_address)
       CREATE EXTENSION address_standardizer;

   If you already have postgis_tiger_geocoder extension installed, and just want to update to the latest run:

       ALTER EXTENSION postgis UPDATE;
       ALTER EXTENSION postgis_tiger_geocoder UPDATE;

   If you made custom entries or changes to `tiger.loader_platform` and `tiger.loader_variables` you may need to update these.

3. To confirm your install is working correctly, run this sql in your database:

       SELECT na.address, na.streetname,na.streettypeabbrev, na.zip
       	FROM normalize_address('1 Devonshire Place, Boston, MA 02109') AS na;

   Which should output

        address | streetname | streettypeabbrev |  zip
       ---------+------------+------------------+-------
       	   1 | Devonshire | Pl               | 02109

4. Create a new record in `tiger.loader_platform` table with the paths of your executables and server.

   So for example to create a profile called debbie that follows `sh` convention. You would do:

       INSERT INTO tiger.loader_platform(os, declare_sect, pgbin, wget, unzip_command, psql, path_sep,
       		   loader, environ_set_command, county_process_command)
       SELECT 'debbie', declare_sect, pgbin, wget, unzip_command, psql, path_sep,
       	   loader, environ_set_command, county_process_command
         FROM tiger.loader_platform
         WHERE os = 'sh';

   And then edit the paths in the declare_sect column to those that fit Debbie's pg, unzip,shp2pgsql, psql, etc path locations.

   If you don't edit this `loader_platform` table, it will just contain common case locations of items and you'll have to edit the generated script after the script is generated.

5. As of PostGIS 2.4.1 the Zip code-5 digit tabulation area `zcta5` load step was revised to load current zcta5 data and is part of the Loader_Generate_Nation_Script when enabled. It is turned off by default because it takes quite a bit of time to load (20 to 60 minutes), takes up quite a bit of disk space, and is not used that often.

   To enable it, do the following:

       UPDATE tiger.loader_lookuptables SET load = true WHERE table_name = 'zcta520';

   If present the Geocode function can use it if a boundary filter is added to limit to just zips in that boundary. The Reverse_Geocode function uses it if the returned address is missing a zip, which often happens with highway reverse geocoding.

6. Create a folder called `gisdata` on root of server or your local pc if you have a fast network connection to the server. This folder is where the tiger files will be downloaded to and processed. If you are not happy with having the folder on the root of the server, or simply want to change to a different folder for staging, then edit the field `staging_fold` in the `tiger.loader_variables` table.

7. Create a folder called temp in the `gisdata` folder or wherever you designated the `staging_fold` to be. This will be the folder where the loader extracts the downloaded tiger data.

8. Then run the Loader_Generate_Nation_Script SQL function make sure to use the name of your custom profile and copy the script to a .sh or .bat file. So for example to build the nation load:

       psql -c "SELECT Loader_Generate_Nation_Script('debbie')" -d geocoder -tA > /gisdata/nation_script_load.sh

9. Run the generated nation load commandline scripts.

       cd /gisdata
       sh nation_script_load.sh

10. After you are done running the nation script, you should have three tables in your `tiger_data` schema and they should be filled with data. Confirm you do by doing the following queries from psql or pgAdmin

        SELECT count(*) FROM tiger_data.county_all;

         count
        -------
          3235
        (1 row)

        SELECT count(*) FROM tiger_data.state_all;

         count
        -------
            56
        (1 row)

    This will only have data if you marked zcta5 to be loaded

        SELECT count(*) FROM tiger_data.zcta5_all;

         count
        -------
          33933
        (1 row)

11. By default the tables corresponding to `bg`, `tract`, `tabblock20` are not loaded. These tables are not used by the geocoder but are used by folks for population statistics. If you wish to load them as part of your state loads, run the following statement to enable them.

        UPDATE tiger.loader_lookuptables SET load = true WHERE load = false AND lookup_name IN('tract', 'bg', 'tabblock20');

    Alternatively you can load just these tables after loading state data using the Loader_Generate_Census_Script

12. For each state you want to load data for, generate a state script Loader_Generate_Script.

    DO NOT Generate the state script until you have already loaded the nation data, because the state script utilizes county list loaded by nation script.

13.     psql -c "SELECT Loader_Generate_Script(ARRAY['MA'], 'debbie')" -d geocoder -tA > /gisdata/ma_load.sh

14. Run the generated commandline scripts.

        cd /gisdata
        sh ma_load.sh

15. After you are done loading all data or at a stopping point, it's a good idea to analyze all the tiger tables to update the stats (include inherited stats)

        SELECT install_missing_indexes();
        vacuum (analyze, verbose) tiger.addr;
        vacuum (analyze, verbose) tiger.edges;
        vacuum (analyze, verbose) tiger.faces;
        vacuum (analyze, verbose) tiger.featnames;
        vacuum (analyze, verbose) tiger.place;
        vacuum (analyze, verbose) tiger.cousub;
        vacuum (analyze, verbose) tiger.county;
        vacuum (analyze, verbose) tiger.state;
        vacuum (analyze, verbose) tiger.zcta5;
        vacuum (analyze, verbose) tiger.zip_lookup_base;
        vacuum (analyze, verbose) tiger.zip_state;
        vacuum (analyze, verbose) tiger.zip_state_loc;

### 2.4.2. Using Address Standardizer Extension with Tiger geocoder

One of the many complaints of folks is the address normalizer function Normalize_Address function that normalizes an address for prepping before geocoding. The normalizer is far from perfect and trying to patch its imperfectness takes a vast amount of resources. As such we have integrated with another project that has a much better address standardizer engine. To use this new address_standardizer, you compile the extension as described in Section 2.3, “Installing and Using the address standardizer” and install as an extension in your database.

Once you install this extension in the same database as you have installed `postgis_tiger_geocoder`, then the Pagc_Normalize_Address can be used instead of Normalize_Address. This extension is tiger agnostic, so can be used with other data sources such as international addresses. The tiger geocoder extension does come packaged with its own custom versions of rules table ( `tiger.pagc_rules`) , gaz table (`tiger.pagc_gaz`), and lex table (`tiger.pagc_lex`). These you can add and update to improve your standardizing experience for your own needs.

### 2.4.3. Required tools for tiger data loading

The load process downloads data from the census website for the respective nation files, states requested, extracts the files, and then loads each state into its own separate set of state tables. Each state table inherits from the tables defined in `tiger` schema so that its sufficient to just query those tables to access all the data and drop a set of state tables at any time using the Drop_State_Tables_Generate_Script if you need to reload a state or just don't need a state anymore.

In order to be able to load data you'll need the following tools:

- A tool to unzip the zip files from census website.

  For Unix like systems: `unzip` executable which is usually already installed on most Unix like platforms.

  For Windows, 7-zip which is a free compress/uncompress tool you can download from http://www.7-zip.org/

- `shp2pgsql` commandline which is installed by default when you install PostGIS.

- `wget` which is a web grabber tool usually installed on most Unix/Linux systems.

  If you are on windows, you can get pre-compiled binaries from http://gnuwin32.sourceforge.net/packages/wget.htm

If you are upgrading from tiger_2010, you'll need to first generate and run Drop_Nation_Tables_Generate_Script. Before you load any state data, you need to load the nation wide data which you do with Loader_Generate_Nation_Script. Which will generate a loader script for you. Loader_Generate_Nation_Script is a one-time step that should be done for upgrading (from a prior year tiger census data) and for new installs.

To load state data refer to Loader_Generate_Script to generate a data load script for your platform for the states you desire. Note that you can install these piecemeal. You don't have to load all the states you want all at once. You can load them as you need them.

After the states you desire have been loaded, make sure to run the:

    SELECT install_missing_indexes();

as described in Install_Missing_Indexes.

To test that things are working as they should, try to run a geocode on an address in your state using Geocode

### 2.4.4. Upgrading your Tiger Geocoder Install and Data

First upgrade your postgis_tiger_geocoder extension as follows:

    ALTER EXTENSION postgis_tiger_geocoder UPDATE;

Next drop all nation tables and load up the new ones. Generate a drop script with this SQL statement as detailed in Drop_Nation_Tables_Generate_Script

    SELECT drop_nation_tables_generate_script();

Run the generated drop SQL statements.

Generate a nation load script with this SELECT statement as detailed in Loader_Generate_Nation_Script

For windows

    SELECT loader_generate_nation_script('windows');

For unix/linux

    SELECT loader_generate_nation_script('sh');

Refer to Section 2.4.1, “Tiger Geocoder Enabling your PostGIS database” for instructions on how to run the generate script. This only needs to be done once.

You can have a mix of different year state tables and can upgrade each state separately. Before you upgrade a state you first need to drop the prior year state tables for that state using Drop_State_Tables_Generate_Script.

## 2.5. Common Problems during installation

There are several things to check when your installation or upgrade doesn't go as you expected.

1. Check that you have installed PostgreSQL 12 or newer, and that you are compiling against the same version of the PostgreSQL source as the version of PostgreSQL that is running. Mix-ups can occur when your (Linux) distribution has already installed PostgreSQL, or you have otherwise installed PostgreSQL before and forgotten about it. PostGIS will only work with PostgreSQL 12 or newer, and strange, unexpected error messages will result if you use an older version. To check the version of PostgreSQL which is running, connect to the database using psql and run this query:

       SELECT version();

   If you are running an RPM based distribution, you can check for the existence of pre-installed packages using the rpm command as follows: rpm -qa | grep postgresql

2. If your upgrade fails, make sure you are restoring into a database that already has PostGIS installed.

       SELECT postgis_full_version();

Also check that configure has correctly detected the location and version of PostgreSQL, the Proj library and the GEOS library.

1. The output from configure is used to generate the `postgis_config.h` file. Check that the `POSTGIS_PGSQL_VERSION`, `POSTGIS_PROJ_VERSION` and `POSTGIS_GEOS_VERSION` variables have been set correctly.

# Chapter 3. PostGIS Administration

## 3.1. Performance Tuning

Tuning for PostGIS performance is much like tuning for any PostgreSQL workload. The only additional consideration is that geometries and rasters are usually large, so memory-related optimizations generally have more of an impact on PostGIS than other types of PostgreSQL queries.

For general details about optimizing PostgreSQL, refer to Tuning your PostgreSQL Server.

For PostgreSQL 9.4+ configuration can be set at the server level without touching `postgresql.conf` or `postgresql.auto.conf` by using the `ALTER SYSTEM` command.

    ALTER SYSTEM SET work_mem = '256MB';
    -- this forces non-startup configs to take effect for new connections
    SELECT pg_reload_conf();
    -- show current setting value
    -- use SHOW ALL to see all settings
    SHOW work_mem;

In addition to the Postgres settings, PostGIS has some custom settings which are listed in Section 7.22, “Grand Unified Custom Variables (GUCs)”.

### 3.1.1. Startup

These settings are configured in `postgresql.conf`:

constraint_exclusion

- Default: partition

- This is generally used for table partitioning. The default for this is set to "partition" which is ideal for PostgreSQL 8.4 and above since it will force the planner to only analyze tables for constraint consideration if they are in an inherited hierarchy and not pay the planner penalty otherwise.

shared_buffers

- Default: ~128MB in PostgreSQL 9.6

- Set to about 25% to 40% of available RAM. On windows you may not be able to set as high.

max_worker_processes This setting is only available for PostgreSQL 9.4+. For PostgreSQL 9.6+ this setting has additional importance in that it controls the max number of processes you can have for parallel queries.

- Default: 8

- Sets the maximum number of background processes that the system can support. This parameter can only be set at server start.

### 3.1.2. Runtime

work_mem - sets the size of memory used for sort operations and complex queries

- Default: 1-4MB

- Adjust up for large dbs, complex queries, lots of RAM

- Adjust down for many concurrent users or low RAM.

- If you have lots of RAM and few developers:

      SET work_mem TO '256MB';

maintenance_work_mem - the memory size used for VACUUM, CREATE INDEX, etc.

- Default: 16-64MB

- Generally too low - ties up I/O, locks objects while swapping memory

- Recommend 32MB to 1GB on production servers w/lots of RAM, but depends on the # of concurrent users. If you have lots of RAM and few developers:

      SET maintenance_work_mem TO '1GB';

max_parallel_workers_per_gather

This setting is only available for PostgreSQL 9.6+ and will only affect PostGIS 2.3+, since only PostGIS 2.3+ supports parallel queries. If set to higher than 0, then some queries such as those involving relation functions like `ST_Intersects` can use multiple processes and can run more than twice as fast when doing so. If you have a lot of processors to spare, you should change the value of this to as many processors as you have. Also make sure to bump up `max_worker_processes` to at least as high as this number.

- Default: 0

- Sets the maximum number of workers that can be started by a single `Gather` node. Parallel workers are taken from the pool of processes established by `max_worker_processes`. Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. Setting this value to 0, which is the default, disables parallel query execution.

## 3.2. Configuring raster support

If you enabled raster support you may want to read below how to properly configure it.

As of PostGIS 2.1.3, out-of-db rasters and all raster drivers are disabled by default. In order to re-enable these, you need to set the following environment variables `POSTGIS_GDAL_ENABLED_DRIVERS` and `POSTGIS_ENABLE_OUTDB_RASTERS` in the server environment. For PostGIS 2.2, you can use the more cross-platform approach of setting the corresponding Section 7.22, “Grand Unified Custom Variables (GUCs)”.

If you want to enable offline raster:

    POSTGIS_ENABLE_OUTDB_RASTERS=1

Any other setting or no setting at all will disable out of db rasters.

In order to enable all GDAL drivers available in your GDAL install, set this environment variable as follows

    POSTGIS_GDAL_ENABLED_DRIVERS=ENABLE_ALL

If you want to only enable specific drivers, set your environment variable as follows:

    POSTGIS_GDAL_ENABLED_DRIVERS="GTiff PNG JPEG GIF XYZ"

If you are on windows, do not quote the driver list

Setting environment variables varies depending on OS. For PostgreSQL installed on Ubuntu or Debian via apt-postgresql, the preferred way is to edit `/etc/postgresql/`10`/`main`/environment` where 10 refers to version of PostgreSQL and main refers to the cluster.

On windows, if you are running as a service, you can set via System variables which for Windows 7 you can get to by right-clicking on Computer->Properties Advanced System Settings or in explorer navigating to `Control Panel\All Control Panel Items\System`. Then clicking Advanced System Settings ->Advanced->Environment Variables and adding new system variables.

After you set the environment variables, you'll need to restart your PostgreSQL service for the changes to take effect.

## 3.3. Creating spatial databases

### 3.3.1. Spatially enable database using EXTENSION

If you are using PostgreSQL 9.1+ and have compiled and installed the extensions/postgis modules, you can turn a database into a spatial one using the EXTENSION mechanism.

Core postgis extension includes geometry, geography, spatial_ref_sys and all the functions and comments. Raster and topology are packaged as a separate extension.

Run the following SQL snippet in the database you want to enable spatially:

          CREATE EXTENSION IF NOT EXISTS plpgsql;
          CREATE EXTENSION postgis;
          CREATE EXTENSION postgis_raster; -- OPTIONAL
          CREATE EXTENSION postgis_topology; -- OPTIONAL

### 3.3.2. Spatially enable database without using EXTENSION (discouraged)

This is generally only needed if you cannot or don't want to get PostGIS installed in the PostgreSQL extension directory (for example during testing, development or in a restricted environment).

Adding PostGIS objects and function definitions into your database is done by loading the various sql files located in `[prefix]/share/contrib` as specified during the build phase.

The core PostGIS objects (geometry and geography types, and their support functions) are in the `postgis.sql` script. Raster objects are in the `rtpostgis.sql` script. Topology objects are in the `topology.sql` script.

For a complete set of EPSG coordinate system definition identifiers, you can also load the `spatial_ref_sys.sql` definitions file and populate the `spatial_ref_sys` table. This will permit you to perform ST_Transform() operations on geometries.

If you wish to add comments to the PostGIS functions, you can find them in the `postgis_comments.sql` script. Comments can be viewed by simply typing \dd [function_name] from a psql terminal window.

Run the following Shell commands in your terminal:

        DB=[yourdatabase]
        SCRIPTSDIR=`pg_config --sharedir`/contrib/postgis-3.4/

        # Core objects
        psql -d ${DB} -f ${SCRIPTSDIR}/postgis.sql
        psql -d ${DB} -f ${SCRIPTSDIR}/spatial_ref_sys.sql
        psql -d ${DB} -f ${SCRIPTSDIR}/postgis_comments.sql # OPTIONAL

        # Raster support (OPTIONAL)
        psql -d ${DB} -f ${SCRIPTSDIR}/rtpostgis.sql
        psql -d ${DB} -f ${SCRIPTSDIR}/raster_comments.sql # OPTIONAL

        # Topology support (OPTIONAL)
        psql -d ${DB} -f ${SCRIPTSDIR}/topology.sql
        psql -d ${DB} -f ${SCRIPTSDIR}/topology_comments.sql # OPTIONAL

## 3.4. Upgrading spatial databases

Upgrading existing spatial databases can be tricky as it requires replacement or introduction of new PostGIS object definitions.

Unfortunately not all definitions can be easily replaced in a live database, so sometimes your best bet is a dump/reload process.

PostGIS provides a SOFT UPGRADE procedure for minor or bugfix releases, and a HARD UPGRADE procedure for major releases.

Before attempting to upgrade PostGIS, it is always worth to backup your data. If you use the -Fc flag to pg_dump you will always be able to restore the dump with a HARD UPGRADE.

### 3.4.1. Soft upgrade

If you installed your database using extensions, you'll need to upgrade using the extension model as well. If you installed using the old sql script way, you are advised to switch your install to extensions because the script way is no longer supported.

#### 3.4.1.1. Soft Upgrade 9.1+ using extensions

If you originally installed PostGIS with extensions, then you need to upgrade using extensions as well. Doing a minor upgrade with extensions, is fairly painless.

If you are running PostGIS 3 or above, then you should use the PostGIS_Extensions_Upgrade function to upgrade to the latest version you have installed.

    SELECT postgis_extensions_upgrade();

If you are running PostGIS 2.5 or lower, then do the following:

    ALTER EXTENSION postgis UPDATE;
    SELECT postgis_extensions_upgrade();
    -- This second call is needed to rebundle postgis_raster extension
    SELECT postgis_extensions_upgrade();

If you have multiple versions of PostGIS installed, and you don't want to upgrade to the latest, you can explicitly specify the version as follows:

    ALTER EXTENSION postgis UPDATE TO "3.5.1";
    ALTER EXTENSION postgis_topology UPDATE TO "3.5.1";

If you get an error notice something like:

    No migration path defined for … to 3.5.1

Then you'll need to backup your database, create a fresh one as described in Section 3.3.1, “Spatially enable database using EXTENSION” and then restore your backup on top of this new database.

If you get a notice message like:

    Version "3.5.1" of extension "postgis" is already installed

Then everything is already up to date and you can safely ignore it. UNLESS you're attempting to upgrade from an development version to the next (which doesn't get a new version number); in that case you can append "next" to the version string, and next time you'll need to drop the "next" suffix again:

    ALTER EXTENSION postgis UPDATE TO "3.5.1next";
    ALTER EXTENSION postgis_topology UPDATE TO "3.5.1next";

If you installed PostGIS originally without a version specified, you can often skip the reinstallation of postgis extension before restoring since the backup just has `CREATE EXTENSION postgis` and thus picks up the newest latest version during restore.

If you are upgrading PostGIS extension from a version prior to 3.0.0, you will have a new extension postgis_raster which you can safely drop, if you don't need raster support. You can drop as follows:
    DROP EXTENSION postgis_raster;

#### 3.4.1.2. Soft Upgrade Pre 9.1+ or without extensions

This section applies only to those who installed PostGIS not using extensions. If you have extensions and try to upgrade with this approach you'll get messages like:

    can't drop … because postgis extension depends on it

NOTE: if you are moving from PostGIS 1.* to PostGIS 2.* or from PostGIS 2.* prior to r7409, you cannot use this procedure but would rather need to do a HARD UPGRADE.

After compiling and installing (make install) you should find a set of `*_upgrade.sql` files in the installation folders. You can list them all with:

    ls `pg_config --sharedir`/contrib/postgis-3.5.1/*_upgrade.sql

Load them all in turn, starting from `postgis_upgrade.sql`.

    psql -f postgis_upgrade.sql -d your_spatial_database

The same procedure applies to raster, topology and sfcgal extensions, with upgrade files named `rtpostgis_upgrade.sql`, `topology_upgrade.sql` and `sfcgal_upgrade.sql` respectively. If you need them:

    psql -f rtpostgis_upgrade.sql -d your_spatial_database

    psql -f topology_upgrade.sql -d your_spatial_database

    psql -f sfcgal_upgrade.sql -d your_spatial_database

You are advised to switch to an extension based install by running

    psql -c "SELECT postgis_extensions_upgrade();"

If you can't find the `postgis_upgrade.sql` specific for upgrading your version you are using a version too early for a soft upgrade and need to do a HARD UPGRADE.

The PostGIS_Full_Version function should inform you about the need to run this kind of upgrade using a "procs need upgrade" message.

### 3.4.2. Hard upgrade

By HARD UPGRADE we mean full dump/reload of postgis-enabled databases. You need a HARD UPGRADE when PostGIS objects' internal storage changes or when SOFT UPGRADE is not possible. The Release Notes appendix reports for each version whether you need a dump/reload (HARD UPGRADE) to upgrade.

The dump/reload process is assisted by the postgis_restore script which takes care of skipping from the dump all definitions which belong to PostGIS (including old ones), allowing you to restore your schemas and data into a database with PostGIS installed without getting duplicate symbol errors or bringing forward deprecated objects.

Supplementary instructions for windows users are available at Windows Hard upgrade.

The Procedure is as follows:

1. Create a "custom-format" dump of the database you want to upgrade (let's call it `olddb`) include binary blobs (-b) and verbose (-v) output. The user can be the owner of the db, need not be postgres super account.

       pg_dump -h localhost -p 5432 -U postgres -Fc -b -v -f "/somepath/olddb.backup" olddb

2. Do a fresh install of PostGIS in a new database -- we'll refer to this database as `newdb`. Please refer to Section 3.3.2, “Spatially enable database without using EXTENSION (discouraged)” and Section 3.3.1, “Spatially enable database using EXTENSION” for instructions on how to do this.

   The spatial_ref_sys entries found in your dump will be restored, but they will not override existing ones in spatial_ref_sys. This is to ensure that fixes in the official set will be properly propagated to restored databases. If for any reason you really want your own overrides of standard entries just don't load the spatial_ref_sys.sql file when creating the new db.

   If your database is really old or you know you've been using long deprecated functions in your views and functions, you might need to load `legacy.sql` for all your functions and views etc. to properly come back. Only do this if _really_ needed. Consider upgrading your views and functions before dumping instead, if possible. The deprecated functions can be later removed by loading `uninstall_legacy.sql`.

3. Restore your backup into your fresh `newdb` database using postgis_restore. Unexpected errors, if any, will be printed to the standard error stream by psql. Keep a log of those.

       postgis_restore "/somepath/olddb.backup" | psql -h localhost -p 5432 -U postgres newdb 2> errors.txt

Errors may arise in the following cases:

1. Some of your views or functions make use of deprecated PostGIS objects. In order to fix this you may try loading `legacy.sql` script prior to restore or you'll have to restore to a version of PostGIS which still contains those objects and try a migration again after porting your code. If the `legacy.sql` way works for you, don't forget to fix your code to stop using deprecated functions and drop them loading `uninstall_legacy.sql`.

2. Some custom records of spatial_ref_sys in dump file have an invalid SRID value. Valid SRID values are bigger than 0 and smaller than 999000. Values in the 999000.999999 range are reserved for internal use while values > 999999 can't be used at all. All your custom records with invalid SRIDs will be retained, with those > 999999 moved into the reserved range, but the spatial_ref_sys table would lose a check constraint guarding for that invariant to hold and possibly also its primary key ( when multiple invalid SRIDS get converted to the same reserved SRID value ).

   In order to fix this you should copy your custom SRS to a SRID with a valid value (maybe in the 910000..910999 range), convert all your tables to the new srid (see UpdateGeometrySRID), delete the invalid entry from spatial_ref_sys and re-construct the check(s) with:

       ALTER TABLE spatial_ref_sys ADD CONSTRAINT spatial_ref_sys_srid_check check (srid > 0 AND srid < 999000 );

       ALTER TABLE spatial_ref_sys ADD PRIMARY KEY(srid));

   If you are upgrading an old database containing french IGN cartography, you will have probably SRIDs out of range and you will see, when importing your database, issues like this :

        WARNING: SRID 310642222 converted to 999175 (in reserved zone)

   In this case, you can try following steps : first throw out completely the IGN from the sql which is resulting from postgis_restore. So, after having run :

       postgis_restore "/somepath/olddb.backup" > olddb.sql

   run this command :

       grep -v IGNF olddb.sql > olddb-without-IGN.sql

   Create then your newdb, activate the required Postgis extensions, and insert properly the french system IGN with : this script After these operations, import your data :

       psql -h localhost -p 5432 -U postgres -d newdb -f olddb-without-IGN.sql  2> errors.txt

# Chapter 4. Data Management

## 4.1. Spatial Data Model

### 4.1.1. OGC Geometry

The Open Geospatial Consortium (OGC) developed the Simple Features Access standard (SFA) to provide a model for geospatial data. It defines the fundamental spatial type of Geometry, along with operations which manipulate and transform geometry values to perform spatial analysis tasks. PostGIS implements the OGC Geometry model as the PostgreSQL data types geometry and geography.

Geometry is an abstract type. Geometry values belong to one of its concrete subtypes which represent various kinds and dimensions of geometric shapes. These include the atomic types Point, LineString, LinearRing and Polygon, and the collection types MultiPoint, MultiLineString, MultiPolygon and GeometryCollection. The Simple Features Access - Part 1: Common architecture v1.2.1 adds subtypes for the structures PolyhedralSurface, Triangle and TIN.

Geometry models shapes in the 2-dimensional Cartesian plane. The PolyhedralSurface, Triangle, and TIN types can also represent shapes in 3-dimensional space. The size and location of shapes are specified by their coordinates. Each coordinate has a X and Y ordinate value determining its location in the plane. Shapes are constructed from points or line segments, with points specified by a single coordinate, and line segments by two coordinates.

Coordinates may contain optional Z and M ordinate values. The Z ordinate is often used to represent elevation. The M ordinate contains a measure value, which may represent time or distance. If Z or M values are present in a geometry value, they must be defined for each point in the geometry. If a geometry has Z or M ordinates the coordinate dimension is 3D; if it has both Z and M the coordinate dimension is 4D.

Geometry values are associated with a spatial reference system indicating the coordinate system in which it is embedded. The spatial reference system is identified by the geometry SRID number. The units of the X and Y axes are determined by the spatial reference system. In planar reference systems the X and Y coordinates typically represent easting and northing, while in geodetic systems they represent longitude and latitude. SRID 0 represents an infinite Cartesian plane with no units assigned to its axes. See Section 4.5, “Spatial Reference Systems”.

The geometry dimension is a property of geometry types. Point types have dimension 0, linear types have dimension 1, and polygonal types have dimension 2. Collections have the dimension of the maximum element dimension.

A geometry value may be empty. Empty values contain no vertices (for atomic geometry types) or no elements (for collections).

An important property of geometry values is their spatial extent or bounding box, which the OGC model calls envelope. This is the 2 or 3-dimensional box which encloses the coordinates of a geometry. It is an efficient way to represent a geometry's extent in coordinate space and to check whether two geometries interact.

The geometry model allows evaluating topological spatial relationships as described in Section 5.1.1, “Dimensionally Extended 9-Intersection Model”. To support this the concepts of interior, boundary and exterior are defined for each geometry type. Geometries are topologically closed, so they always contain their boundary. The boundary is a geometry of dimension one less than that of the geometry itself.

The OGC geometry model defines validity rules for each geometry type. These rules ensure that geometry values represents realistic situations (e.g. it is possible to specify a polygon with a hole lying outside the shell, but this makes no sense geometrically and is thus invalid). PostGIS also allows storing and manipulating invalid geometry values. This allows detecting and fixing them if needed. See Section 4.4, “Geometry Validation”

#### 4.1.1.1. Point

A Point is a 0-dimensional geometry that represents a single location in coordinate space.

    POINT (1 2)
    POINT Z (1 2 3)
    POINT ZM (1 2 3 4)

#### 4.1.1.2. LineString

A LineString is a 1-dimensional line formed by a contiguous sequence of line segments. Each line segment is defined by two points, with the end point of one segment forming the start point of the next segment. An OGC-valid LineString has either zero or two or more points, but PostGIS also allows single-point LineStrings. LineStrings may cross themselves (self-intersect). A LineString is closed if the start and end points are the same. A LineString is simple if it does not self-intersect.

    LINESTRING (1 2, 3 4, 5 6)

#### 4.1.1.3. LinearRing

A LinearRing is a LineString which is both closed and simple. The first and last points must be equal, and the line must not self-intersect.

    LINEARRING (0 0 0, 4 0 0, 4 4 0, 0 4 0, 0 0 0)

#### 4.1.1.4. Polygon

A Polygon is a 2-dimensional planar region, delimited by an exterior boundary (the shell) and zero or more interior boundaries (holes). Each boundary is a LinearRing.

    POLYGON ((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

#### 4.1.1.5. MultiPoint

A MultiPoint is a collection of Points.

    MULTIPOINT ( (0 0), (1 2) )

#### 4.1.1.6. MultiLineString

A MultiLineString is a collection of LineStrings. A MultiLineString is closed if each of its elements is closed.

    MULTILINESTRING ( (0 0,1 1,1 2), (2 3,3 2,5 4) )

#### 4.1.1.7. MultiPolygon

A MultiPolygon is a collection of non-overlapping, non-adjacent Polygons. Polygons in the collection may touch only at a finite number of points.

    MULTIPOLYGON (((1 5, 5 5, 5 1, 1 1, 1 5)), ((6 5, 9 1, 6 1, 6 5)))

#### 4.1.1.8. GeometryCollection

A GeometryCollection is a heterogeneous (mixed) collection of geometries.

    GEOMETRYCOLLECTION ( POINT(2 3), LINESTRING(2 3, 3 4))

#### 4.1.1.9. PolyhedralSurface

A PolyhedralSurface is a contiguous collection of patches or facets which share some edges. Each patch is a planar Polygon. If the Polygon coordinates have Z ordinates then the surface is 3-dimensional.

    POLYHEDRALSURFACE Z (
      ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
      ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
      ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
      ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
      ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
      ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

#### 4.1.1.10. Triangle

A Triangle is a polygon defined by three distinct non-collinear vertices. Because a Triangle is a polygon it is specified by four coordinates, with the first and fourth being equal.

    TRIANGLE ((0 0, 0 9, 9 0, 0 0))

#### 4.1.1.11. TIN

A TIN is a collection of non-overlapping Triangles representing a Triangulated Irregular Network.

    TIN Z ( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

### 4.1.2. SQL/MM Part 3 - Curves

The ISO/IEC 13249-3 SQL Multimedia - Spatial standard (SQL/MM) extends the OGC SFA to define Geometry subtypes containing curves with circular arcs. The SQL/MM types support 3DM, 3DZ and 4D coordinates.

All floating point comparisons within the SQL-MM implementation are performed to a specified tolerance, currently 1E-8.

#### 4.1.2.1. CircularString

CircularString is the basic curve type, similar to a LineString in the linear world. A single arc segment is specified by three points: the start and end points (first and third) and some other point on the arc. To specify a closed circle the start and end points are the same and the middle point is the opposite point on the circle diameter (which is the center of the arc). In a sequence of arcs the end point of the previous arc is the start point of the next arc, just like the segments of a LineString. This means that a CircularString must have an odd number of points greater than 1.

    CIRCULARSTRING(0 0, 1 1, 1 0)

    CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0)

#### 4.1.2.2. CompoundCurve

A CompoundCurve is a single continuous curve that may contain both circular arc segments and linear segments. That means that in addition to having well-formed components, the end point of every component (except the last) must be coincident with the start point of the following component.

    COMPOUNDCURVE( CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))

#### 4.1.2.3. CurvePolygon

A CurvePolygon is like a polygon, with an outer ring and zero or more inner rings. The difference is that a ring can be a CircularString or CompoundCurve as well as a LineString.

As of PostGIS 1.4 PostGIS supports compound curves in a curve polygon.

    CURVEPOLYGON(
      CIRCULARSTRING(0 0, 4 0, 4 4, 0 4, 0 0),
      (1 1, 3 3, 3 1, 1 1) )

Example: A CurvePolygon with the shell defined by a CompoundCurve containing a CircularString and a LineString, and a hole defined by a CircularString

    CURVEPOLYGON(
      COMPOUNDCURVE( CIRCULARSTRING(0 0,2 0, 2 1, 2 3, 4 3),
                     (4 3, 4 5, 1 4, 0 0)),
      CIRCULARSTRING(1.7 1, 1.4 0.4, 1.6 0.4, 1.6 0.5, 1.7 1) )

#### 4.1.2.4. MultiCurve

A MultiCurve is a collection of curves which can include LineStrings, CircularStrings or CompoundCurves.

    MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4))

#### 4.1.2.5. MultiSurface

A MultiSurface is a collection of surfaces, which can be (linear) Polygons or CurvePolygons.

    MULTISURFACE(
      CURVEPOLYGON(
        CIRCULARSTRING( 0 0, 4 0, 4 4, 0 4, 0 0),
        (1 1, 3 3, 3 1, 1 1)),
      ((10 10, 14 12, 11 10, 10 10), (11 11, 11.5 11, 11 11.5, 11 11)))

### 4.1.3. WKT and WKB

The OGC SFA specification defines two formats for representing geometry values for external use: Well-Known Text (WKT) and Well-Known Binary (WKB). Both WKT and WKB include information about the type of the object and the coordinates which define it.

Well-Known Text (WKT) provides a standard textual representation of spatial data. Examples of WKT representations of spatial objects are:

- POINT(0 0)

- POINT Z (0 0 0)

- POINT ZM (0 0 0 0)

- POINT EMPTY

- LINESTRING(0 0,1 1,1 2)

- LINESTRING EMPTY

- POLYGON((0 0,4 0,4 4,0 4,0 0),(1 1, 2 1, 2 2, 1 2,1 1))

- MULTIPOINT((0 0),(1 2))

- MULTIPOINT Z ((0 0 0),(1 2 3))

- MULTIPOINT EMPTY

- MULTILINESTRING((0 0,1 1,1 2),(2 3,3 2,5 4))

- MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0),(1 1,2 1,2 2,1 2,1 1)), ((-1 -1,-1 -2,-2 -2,-2 -1,-1 -1)))

- GEOMETRYCOLLECTION(POINT(2 3),LINESTRING(2 3,3 4))

- GEOMETRYCOLLECTION EMPTY

Input and output of WKT is provided by the functions ST_AsText and ST_GeomFromText:

    text WKT = ST_AsText(geometry);
    geometry = ST_GeomFromText(text WKT, SRID);

For example, a statement to create and insert a spatial object from WKT and a SRID is:

    INSERT INTO geotable ( geom, name )
      VALUES ( ST_GeomFromText('POINT(-126.4 45.32)', 312), 'A Place');

Well-Known Binary (WKB) provides a portable, full-precision representation of spatial data as binary data (arrays of bytes). Examples of the WKB representations of spatial objects are:

- WKT: POINT(1 1)

  WKB: 0101000000000000000000F03F000000000000F03

- WKT: LINESTRING (2 2, 9 9)

  WKB: 0102000000020000000000000000000040000000000000004000000000000022400000000000002240

Input and output of WKB is provided by the functions ST_AsBinary and ST_GeomFromWKB:

    bytea WKB = ST_AsBinary(geometry);
    geometry = ST_GeomFromWKB(bytea WKB, SRID);

For example, a statement to create and insert a spatial object from WKB is:

    INSERT INTO geotable ( geom, name )
      VALUES ( ST_GeomFromWKB('\x0101000000000000000000f03f000000000000f03f', 312), 'A Place');

## 4.2. Geometry Data Type

PostGIS implements the OGC Simple Features model by defining a PostgreSQL data type called `geometry`. It represents all of the geometry subtypes by using an internal type code (see GeometryType and ST_GeometryType). This allows modelling spatial features as rows of tables defined with a column of type `geometry`.

The `geometry` data type is opaque, which means that all access is done via invoking functions on geometry values. Functions allow creating geometry objects, accessing or updating all internal fields, and compute new geometry values. PostGIS supports all the functions specified in the OGC Simple feature access - Part 2: SQL option (SFS) specification, as well many others. See Chapter 7, PostGIS Reference for the full list of functions.

PostGIS follows the SFA standard by prefixing spatial functions with "ST_". This was intended to stand for "Spatial and Temporal", but the temporal part of the standard was never developed. Instead it can be interpreted as "Spatial Type".

The SFA standard specifies that spatial objects include a Spatial Reference System identifier (SRID). The SRID is required when creating spatial objects for insertion into the database (it may be defaulted to 0). See ST_SRID and Section 4.5, “Spatial Reference Systems”

To make querying geometry efficient PostGIS defines various kinds of spatial indexes, and spatial operators to use them. See Section 4.9, “Spatial Indexes” and Section 5.2, “Using Spatial Indexes” for details.

### 4.2.1. PostGIS EWKB and EWKT

OGC SFA specifications initially supported only 2D geometries, and the geometry SRID is not included in the input/output representations. The OGC SFA specification 1.2.1 (which aligns with the ISO 19125 standard) adds support for 3D (ZYZ) and measured (XYM and XYZM) coordinates, but still does not include the SRID value.

Because of these limitations PostGIS defined extended EWKB and EWKT formats. They provide 3D (XYZ and XYM) and 4D (XYZM) coordinate support and include SRID information. Including all geometry information allows PostGIS to use EWKB as the format of record (e.g. in DUMP files).

EWKB and EWKT are used for the "canonical forms" of PostGIS data objects. For input, the canonical form for binary data is EWKB, and for text data either EWKB or EWKT is accepted. This allows geometry values to be created by casting a text value in either HEXEWKB or EWKT to a geometry value using `::geometry`. For output, the canonical form for binary is EWKB, and for text it is HEXEWKB (hex-encoded EWKB).

For example this statement creates a geometry by casting from an EWKT text value, and outputs it using the canonical form of HEXEWKB:

    SELECT 'SRID=4;POINT(0 0)'::geometry;
      geometry
      ----------------------------------------------------
      01010000200400000000000000000000000000000000000000

PostGIS EWKT output has a few differences to OGC WKT:

- For 3DZ geometries the Z qualifier is omitted:

  OGC: POINT Z (1 2 3)

  EWKT: POINT (1 2 3)

- For 3DM geometries the M qualifier is included:

  OGC: POINT M (1 2 3)

  EWKT: POINTM (1 2 3)

- For 4D geometries the ZM qualifier is omitted:

  OGC: POINT ZM (1 2 3 4)

  EWKT: POINT (1 2 3 4)

EWKT avoids over-specifying dimensionality and the inconsistencies that can occur with the OGC/ISO format, such as:

- POINT ZM (1 1)

- POINT ZM (1 1 1)

- POINT (1 1 1 1)

PostGIS extended formats are currently a superset of the OGC ones, so that every valid OGC WKB/WKT is also valid EWKB/EWKT. However, this might vary in the future, if the OGC extends a format in a way that conflicts with the PosGIS definition. Thus you SHOULD NOT rely on this compatibility!

Examples of the EWKT text representation of spatial objects are:

- POINT(0 0 0) -- XYZ

- SRID=32632;POINT(0 0) -- XY with SRID

- POINTM(0 0 0) -- XYM

- POINT(0 0 0 0) -- XYZM

- SRID=4326;MULTIPOINTM(0 0 0,1 2 1) -- XYM with SRID

- MULTILINESTRING((0 0 0,1 1 0,1 2 1),(2 3 1,3 2 1,5 4 1))

- POLYGON((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0))

- MULTIPOLYGON(((0 0 0,4 0 0,4 4 0,0 4 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((-1 -1 0,-1 -2 0,-2 -2 0,-2 -1 0,-1 -1 0)))

- GEOMETRYCOLLECTIONM( POINTM(2 3 9), LINESTRINGM(2 3 4, 3 4 5) )

- MULTICURVE( (0 0, 5 5), CIRCULARSTRING(4 0, 4 4, 8 4) )

- POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)), ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)), ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )

- TRIANGLE ((0 0, 0 10, 10 0, 0 0))

- TIN( ((0 0 0, 0 0 1, 0 1 0, 0 0 0)), ((0 0 0, 0 1 0, 1 1 0, 0 0 0)) )

Input and output using these formats is available using the following functions:

    bytea EWKB = ST_AsEWKB(geometry);
    text EWKT = ST_AsEWKT(geometry);
    geometry = ST_GeomFromEWKB(bytea EWKB);
    geometry = ST_GeomFromEWKT(text EWKT);

For example, a statement to create and insert a PostGIS spatial object using EWKT is:

    INSERT INTO geotable ( geom, name )
      VALUES ( ST_GeomFromEWKT('SRID=312;POINTM(-126.4 45.32 15)'), 'A Place' )

## 4.3. Geography Data Type

The PostGIS `geography` data type provides native support for spatial features represented on "geographic" coordinates (sometimes called "geodetic" coordinates, or "lat/lon", or "lon/lat"). Geographic coordinates are spherical coordinates expressed in angular units (degrees).

The basis for the PostGIS geometry data type is a plane. The shortest path between two points on the plane is a straight line. That means functions on geometries (areas, distances, lengths, intersections, etc) are calculated using straight line vectors and cartesian mathematics. This makes them simpler to implement and faster to execute, but also makes them inaccurate for data on the spheroidal surface of the earth.

The PostGIS geography data type is based on a spherical model. The shortest path between two points on the sphere is a great circle arc. Functions on geographies (areas, distances, lengths, intersections, etc) are calculated using arcs on the sphere. By taking the spheroidal shape of the world into account, the functions provide more accurate results.

Because the underlying mathematics is more complicated, there are fewer functions defined for the geography type than for the geometry type. Over time, as new algorithms are added the capabilities of the geography type will expand. As a workaround one can convert back and forth between geometry and geography types.

Like the geometry data type, geography data is associated with a spatial reference system via a spatial reference system identifier (SRID). Any geodetic (long/lat based) spatial reference system defined in the `spatial_ref_sys` table can be used. (Prior to PostGIS 2.2, the geography type supported only WGS 84 geodetic (SRID:4326)). You can add your own custom geodetic spatial reference system as described in Section 4.5.2, “User-Defined Spatial Reference Systems”.

For all spatial reference systems the units returned by measurement functions (e.g. ST_Distance, ST_Length, ST_Perimeter, ST_Area) and for the distance argument of ST_DWithin are in meters.

### 4.3.1. Creating Geography Tables

You can create a table to store geography data using the CREATE TABLE SQL statement with a column of type `geography`. The following example creates a table with a geography column storing 2D LineStrings in the WGS84 geodetic coordinate system (SRID 4326):

    CREATE TABLE global_points (
        id SERIAL PRIMARY KEY,
        name VARCHAR(64),
        location geography(POINT,4326)
      );

The geography type supports two optional type modifiers:

- the spatial type modifier restricts the kind of shapes and dimensions allowed in the column. Values allowed for the spatial type are: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION. The geography type does not support curves, TINS, or POLYHEDRALSURFACEs. The modifier supports coordinate dimensionality restrictions by adding suffixes: Z, M and ZM. For example, a modifier of 'LINESTRINGM' only allows linestrings with three dimensions, and treats the third dimension as a measure. Similarly, 'POINTZM' requires four dimensional (XYZM) data.

- the SRID modifier restricts the spatial reference system SRID to a particular number. If omitted, the SRID defaults to 4326 (WGS84 geodetic), and all calculations are performed using WGS84.

Examples of creating tables with geography columns:

- Create a table with 2D POINT geography with the default SRID 4326 (WGS84 long/lat):

      CREATE TABLE ptgeogwgs(gid serial PRIMARY KEY, geog geography(POINT) );

- Create a table with 2D POINT geography in NAD83 longlat:

      CREATE TABLE ptgeognad83(gid serial PRIMARY KEY, geog geography(POINT,4269) );

- Create a table with 3D (XYZ) POINTs and an explicit SRID of 4326:

      CREATE TABLE ptzgeogwgs84(gid serial PRIMARY KEY, geog geography(POINTZ,4326) );

- Create a table with 2D LINESTRING geography with the default SRID 4326:

      CREATE TABLE lgeog(gid serial PRIMARY KEY, geog geography(LINESTRING) );

- Create a table with 2D POLYGON geography with the SRID 4267 (NAD 1927 long lat):

      CREATE TABLE lgeognad27(gid serial PRIMARY KEY, geog geography(POLYGON,4267) );

Geography fields are registered in the `geography_columns` system view. You can query the `geography_columns` view and see that the table is listed:

    SELECT * FROM geography_columns;

Creating a spatial index works the same as for geometry columns. PostGIS will note that the column type is GEOGRAPHY and create an appropriate sphere-based index instead of the usual planar index used for GEOMETRY.

    -- Index the test table with a spherical index
    CREATE INDEX global_points_gix ON global_points USING GIST ( location );

### 4.3.2. Using Geography Tables

You can insert data into geography tables in the same way as geometry. Geometry data will autocast to the geography type if it has SRID 4326. The EWKT and EWKB formats can also be used to specify geography values.

    -- Add some data into the test table
    INSERT INTO global_points (name, location) VALUES ('Town', 'SRID=4326;POINT(-110 30)');
    INSERT INTO global_points (name, location) VALUES ('Forest', 'SRID=4326;POINT(-109 29)');
    INSERT INTO global_points (name, location) VALUES ('London', 'SRID=4326;POINT(0 49)');

Any geodetic (long/lat) spatial reference system listed in `spatial_ref_sys` table may be specified as a geography SRID. Non-geodetic coordinate systems raise an error if used.

    -- NAD 83 lon/lat
    SELECT 'SRID=4269;POINT(-123 34)'::geography;
                        geography
    ----------------------------------------------------
     0101000020AD1000000000000000C05EC00000000000004140

    -- NAD27 lon/lat
    SELECT 'SRID=4267;POINT(-123 34)'::geography;
                        geography
    ----------------------------------------------------
     0101000020AB1000000000000000C05EC00000000000004140

    -- NAD83 UTM zone meters - gives an error since it is a meter-based planar projection
    SELECT 'SRID=26910;POINT(-123 34)'::geography;

    ERROR:  Only lon/lat coordinate systems are supported in geography.

Query and measurement functions use units of meters. So distance parameters should be expressed in meters, and return values should be expected in meters (or square meters for areas).

    -- A distance query using a 1000km tolerance
    SELECT name FROM global_points WHERE ST_DWithin(location, 'SRID=4326;POINT(-110 29)'::geography, 1000000);

You can see the power of geography in action by calculating how close a plane flying a great circle route from Seattle to London (LINESTRING(-122.33 47.606, 0.0 51.5)) comes to Reykjavik (POINT(-21.96 64.15)) (map the route).

The geography type calculates the true shortest distance of 122.235 km over the sphere between Reykjavik and the great circle flight path between Seattle and London.

    -- Distance calculation using GEOGRAPHY
    SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geography, 'POINT(-21.96 64.15)'::geography);
       st_distance
    -----------------
     122235.23815667

The geometry type calculates a meaningless cartesian distance between Reykjavik and the straight line path from Seattle to London plotted on a flat map of the world. The nominal units of the result is "degrees", but the result doesn't correspond to any true angular difference between the points, so even calling them "degrees" is inaccurate.

    -- Distance calculation using GEOMETRY
    SELECT ST_Distance('LINESTRING(-122.33 47.606, 0.0 51.5)'::geometry, 'POINT(-21.96 64.15)'::geometry);
          st_distance
    --------------------
     13.342271221453624

### 4.3.3. When to use the Geography data type

The geography data type allows you to store data in longitude/latitude coordinates, but at a cost: there are fewer functions defined on GEOGRAPHY than there are on GEOMETRY; those functions that are defined take more CPU time to execute.

The data type you choose should be determined by the expected working area of the application you are building. Will your data span the globe or a large continental area, or is it local to a state, county or municipality?

- If your data is contained in a small area, you might find that choosing an appropriate projection and using GEOMETRY is the best solution, in terms of performance and functionality available.

- If your data is global or covers a continental region, you may find that GEOGRAPHY allows you to build a system without having to worry about projection details. You store your data in longitude/latitude, and use the functions that have been defined on GEOGRAPHY.

- If you don't understand projections, and you don't want to learn about them, and you're prepared to accept the limitations in functionality available in GEOGRAPHY, then it might be easier for you to use GEOGRAPHY than GEOMETRY. Simply load your data up as longitude/latitude and go from there.

Refer to Section 13.11, “PostGIS Function Support Matrix” for compare between what is supported for Geography vs. Geometry. For a brief listing and description of Geography functions, refer to Section 13.4, “PostGIS Geography Support Functions”

### 4.3.4. Geography Advanced FAQ

- 4.3.4.1. Do you calculate on the sphere or the spheroid?
- 4.3.4.2. What about the date-line and the poles?
- 4.3.4.3. What is the longest arc you can process?
- 4.3.4.4. Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?

4.3.4.1. | Do you calculate on the sphere or the spheroid?
| By default, all distance and area calculations are done on the spheroid. You should find that the results of calculations in local areas match up will with local planar results in good local projections. Over larger areas, the spheroidal calculations will be more accurate than any calculation done on a projected plane. All the geography functions have the option of using a sphere calculation, by setting a final boolean parameter to 'FALSE'. This will somewhat speed up calculations, particularly for cases where the geometries are very simple.
4.3.4.2. | What about the date-line and the poles?
| All the calculations have no conception of date-line or poles, the coordinates are spherical (longitude/latitude) so a shape that crosses the dateline is, from a calculation point of view, no different from any other shape.
4.3.4.3. | What is the longest arc you can process?
| We use great circle arcs as the "interpolation line" between two points. That means any two points are actually joined up two ways, depending on which direction you travel along the great circle. All our code assumes that the points are joined by the *shorter* of the two paths along the great circle. As a consequence, shapes that have arcs of more than 180 degrees will not be correctly modelled.
4.3.4.4. | Why is it so slow to calculate the area of Europe / Russia / insert big geographic region here ?
| Because the polygon is so darned huge! Big areas are bad for two reasons: their bounds are huge, so the index tends to pull the feature no matter what query you run; the number of vertices is huge, and tests (distance, containment) have to traverse the vertex list at least once and sometimes N times (with N being the number of vertices in the other candidate feature). As with GEOMETRY, we recommend that when you have very large polygons, but are doing queries in small areas, you "denormalize" your geometric data into smaller chunks so that the index can effectively subquery parts of the object and so queries don't have to pull out the whole object every time. Please consult ST_Subdivide function documentation. Just because you *can* store all of Europe in one polygon doesn't mean you *should*.

## 4.4. Geometry Validation

PostGIS is compliant with the Open Geospatial Consortium’s (OGC) Simple Features specification. That standard defines the concepts of geometry being simple and valid. These definitions allow the Simple Features geometry model to represent spatial objects in a consistent and unambiguous way that supports efficient computation. (Note: the OGC SF and SQL/MM have the same definitions for simple and valid.)

### 4.4.1. Simple Geometry

A simple geometry is one that has no anomalous geometric points, such as self intersection or self tangency.

A `POINT` is inherently simple as a 0-dimensional geometry object.

`MULTIPOINT`s are simple if no two coordinates (`POINT`s) are equal (have identical coordinate values).

A `LINESTRING` is simple if it does not pass through the same point twice, except for the endpoints. If the endpoints of a simple LineString are identical it is called closed and referred to as a Linear Ring.

(a) and (c) are simple `LINESTRING`s. (b) and (d) are not simple. (c) is a closed Linear Ring.

(a) | (b)
(c) | (d)

A `MULTILINESTRING` is simple only if all of its elements are simple and the only intersection between any two elements occurs at points that are on the boundaries of both elements.

(e) and (f) are simple `MULTILINESTRING`s. (g) is not simple.

(e) | (f) | (g)

`POLYGON`s are formed from linear rings, so valid polygonal geometry is always simple.

To test if a geometry is simple use the ST_IsSimple function:

    SELECT
       ST_IsSimple('LINESTRING(0 0, 100 100)') AS straight,
       ST_IsSimple('LINESTRING(0 0, 100 100, 100 0, 0 100)') AS crossing;

     straight | crossing
    ----------+----------
     t        | f

Generally, PostGIS functions do not require geometric arguments to be simple. Simplicity is primarily used as a basis for defining geometric validity. It is also a requirement for some kinds of spatial data models (for example, linear networks often disallow lines that cross). Multipoint and linear geometry can be made simple using ST_UnaryUnion.

### 4.4.2. Valid Geometry

Geometry validity primarily applies to 2-dimensional geometries (`POLYGON`s and `MULTIPOLYGON`s) . Validity is defined by rules that allow polygonal geometry to model planar areas unambiguously.

A `POLYGON` is valid if:

1. the polygon boundary rings (the exterior shell ring and interior hole rings) are simple (do not cross or self-touch). Because of this a polygon cannot have cut lines, spikes or loops. This implies that polygon holes must be represented as interior rings, rather than by the exterior ring self-touching (a so-called "inverted hole").

2. boundary rings do not cross

3. boundary rings may touch at points but only as a tangent (i.e. not in a line)

4. interior rings are contained in the exterior ring

5. the polygon interior is simply connected (i.e. the rings must not touch in a way that splits the polygon into more than one part)

(h) and (i) are valid `POLYGON`s. (j-m) are invalid. (j) can be represented as a valid `MULTIPOLYGON`.

(h) | (i) | (j)
(k) | (l) | (m)

A `MULTIPOLYGON` is valid if:

1. its element `POLYGON`s are valid

2. elements do not overlap (i.e. their interiors must not intersect)

3. elements touch only at points (i.e. not along a line)

(n) is a valid `MULTIPOLYGON`. (o) and (p) are invalid.

(n) | (o) | (p)

These rules mean that valid polygonal geometry is also simple.

For linear geometry the only validity rule is that `LINESTRING`s must have at least two points and have non-zero length (or equivalently, have at least two distinct points.) Note that non-simple (self-intersecting) lines are valid.

    SELECT
       ST_IsValid('LINESTRING(0 0, 1 1)') AS len_nonzero,
       ST_IsValid('LINESTRING(0 0, 0 0, 0 0)') AS len_zero,
       ST_IsValid('LINESTRING(10 10, 150 150, 180 50, 20 130)') AS self_int;

     len_nonzero | len_zero | self_int
    -------------+----------+----------
     t           | f        | t

`POINT` and `MULTIPOINT` geometries have no validity rules.

### 4.4.3. Managing Validity

PostGIS allows creating and storing both valid and invalid Geometry. This allows invalid geometry to be detected and flagged or fixed. There are also situations where the OGC validity rules are stricter than desired (examples of this are zero-length linestrings and polygons with inverted holes.)

Many of the functions provided by PostGIS rely on the assumption that geometry arguments are valid. For example, it does not make sense to calculate the area of a polygon that has a hole defined outside of the polygon, or to construct a polygon from a non-simple boundary line. Assuming valid geometric inputs allows functions to operate more efficiently, since they do not need to check for topological correctness. (Notable exceptions are that zero-length lines and polygons with inversions are generally handled correctly.) Also, most PostGIS functions produce valid geometry output if the inputs are valid. This allows PostGIS functions to be chained together safely.

If you encounter unexpected error messages when calling PostGIS functions (such as "GEOS Intersection() threw an error!"), you should first confirm that the function arguments are valid. If they are not, then consider using one of the techniques below to ensure the data you are processing is valid.

If a function reports an error with valid inputs, then you may have found an error in either PostGIS or one of the libraries it uses, and you should report this to the PostGIS project. The same is true if a PostGIS function returns an invalid geometry for valid input.

To test if a geometry is valid use the ST_IsValid function:

    SELECT ST_IsValid('POLYGON ((20 180, 180 180, 180 20, 20 20, 20 180))');
    -----------------
     t

Information about the nature and location of an geometry invalidity are provided by the ST_IsValidDetail function:

    SELECT valid, reason, ST_AsText(location) AS location
        FROM ST_IsValidDetail('POLYGON ((20 20, 120 190, 50 190, 170 50, 20 20))') AS t;

     valid |      reason       |                  location
    -------+-------------------+---------------------------------------------
     f     | Self-intersection | POINT(91.51162790697674 141.56976744186045)

In some situations it is desirable to correct invalid geometry automatically. Use the ST_MakeValid function to do this. (`ST_MakeValid` is a case of a spatial function that does allow invalid input!)

By default, PostGIS does not check for validity when loading geometry, because validity testing can take a lot of CPU time for complex geometries. If you do not trust your data sources, you can enforce a validity check on your tables by adding a check constraint:

    ALTER TABLE mytable
      ADD CONSTRAINT geometry_valid_check
    	CHECK (ST_IsValid(geom));

## 4.5. Spatial Reference Systems

A Spatial Reference System (SRS) (also called a Coordinate Reference System (CRS)) defines how geometry is referenced to locations on the Earth's surface. There are three types of SRS:

- A geodetic SRS uses angular coordinates (longitude and latitude) which map directly to the surface of the earth.

- A projected SRS uses a mathematical projection transformation to "flatten" the surface of the spheroidal earth onto a plane. It assigns location coordinates in a way that allows direct measurement of quantities such as distance, area, and angle. The coordinate system is Cartesian, which means it has a defined origin point and two perpendicular axes (usually oriented North and East). Each projected SRS uses a stated length unit (usually metres or feet). A projected SRS may be limited in its area of applicability to avoid distortion and fit within the defined coordinate bounds.

- A local SRS is a Cartesian coordinate system which is not referenced to the earth's surface. In PostGIS this is specified by a SRID value of 0.

There are many different spatial reference systems in use. Common SRSes are standardized in the European Petroleum Survey Group EPSG database. For convenience PostGIS (and many other spatial systems) refers to SRS definitions using an integer identifier called a SRID.

A geometry is associated with a Spatial Reference System by its SRID value, which is accessed by ST_SRID. The SRID for a geometry can be assigned using ST_SetSRID. Some geometry constructor functions allow supplying a SRID (such as ST_Point and ST_MakeEnvelope). The EWKT format supports SRIDs with the `SRID=n;` prefix.

Spatial functions processing pairs of geometries (such as overlay and relationship functions) require that the input geometries are in the same spatial reference system (have the same SRID). Geometry data can be transformed into a different spatial reference system using ST_Transform and ST_TransformPipeline. Geometry returned from functions has the same SRS as the input geometries.

### 4.5.1. SPATIAL_REF_SYS Table

The `SPATIAL_REF_SYS` table used by PostGIS is an OGC-compliant database table that defines the available spatial reference systems. It holds the numeric SRIDs and textual descriptions of the coordinate systems.

The `spatial_ref_sys` table definition is:

    CREATE TABLE spatial_ref_sys (
      srid       INTEGER NOT NULL PRIMARY KEY,
      auth_name  VARCHAR(256),
      auth_srid  INTEGER,
      srtext     VARCHAR(2048),
      proj4text  VARCHAR(2048)
    )

The columns are:

`srid`

  An integer code that uniquely identifies the Spatial Reference System (SRS) within the database.

`auth_name`

  The name of the standard or standards body that is being cited for this reference system. For example, "EPSG" is a valid `auth_name`.

`auth_srid`

  The ID of the Spatial Reference System as defined by the Authority cited in the `auth_name`. In the case of EPSG, this is the EPSG code.

`srtext`

  The Well-Known Text representation of the Spatial Reference System. An example of a WKT SRS representation is:

      PROJCS["NAD83 / UTM Zone 10N",
        GEOGCS["NAD83",
      	DATUM["North_American_Datum_1983",
      	  SPHEROID["GRS 1980",6378137,298.257222101]
      	],
      	PRIMEM["Greenwich",0],
      	UNIT["degree",0.0174532925199433]
        ],
        PROJECTION["Transverse_Mercator"],
        PARAMETER["latitude_of_origin",0],
        PARAMETER["central_meridian",-123],
        PARAMETER["scale_factor",0.9996],
        PARAMETER["false_easting",500000],
        PARAMETER["false_northing",0],
        UNIT["metre",1]
      ]

  For a discussion of SRS WKT, see the OGC standard Well-known text representation of coordinate reference systems.

`proj4text`

  PostGIS uses the PROJ library to provide coordinate transformation capabilities. The `proj4text` column contains the PROJ coordinate definition string for a particular SRID. For example:

      +proj=utm +zone=10 +ellps=clrk66 +datum=NAD27 +units=m

  For more information see the PROJ web site. The `spatial_ref_sys.sql` file contains both `srtext` and `proj4text` definitions for all EPSG projections.

When retrieving spatial reference system definitions for use in transformations, PostGIS uses fhe following strategy:

- If `auth_name` and `auth_srid` are present (non-NULL) use the PROJ SRS based on those entries (if one exists).

- If `srtext` is present create a SRS using it, if possible.

- If `proj4text` is present create a SRS using it, if possible.

### 4.5.2. User-Defined Spatial Reference Systems

The PostGIS `spatial_ref_sys` table contains over 3000 of the most common spatial reference system definitions that are handled by the PROJ projection library. But there are many coordinate systems that it does not contain. You can add SRS definitions to the table if you have the required information about the spatial reference system. Or, you can define your own custom spatial reference system if you are familiar with PROJ constructs. Keep in mind that most spatial reference systems are regional and have no meaning when used outside of the bounds they were intended for.

A resource for finding spatial reference systems not defined in the core set is http://spatialreference.org/

Some commonly used spatial reference systems are: 4326 - WGS 84 Long Lat, 4269 - NAD 83 Long Lat, 3395 - WGS 84 World Mercator, 2163 - US National Atlas Equal Area, and the 60 WGS84 UTM zones. UTM zones are one of the most ideal for measurement, but only cover 6-degree regions. (To determine which UTM zone to use for your area of interest, see the utmzone PostGIS plpgsql helper function.)

US states use State Plane spatial reference systems (meter or feet based) - usually one or 2 exists per state. Most of the meter-based ones are in the core set, but many of the feet-based ones or ESRI-created ones will need to be copied from spatialreference.org.

You can even define non-Earth-based coordinate systems, such as Mars 2000 This Mars coordinate system is non-planar (it's in degrees spheroidal), but you can use it with the `geography` type to obtain length and proximity measurements in meters instead of degrees.

Here is an example of loading a custom coordinate system using an unassigned SRID and the PROJ definition for a US-centric Lambert Conformal projection:

    INSERT INTO spatial_ref_sys (srid, proj4text)
    VALUES ( 990000,
      '+proj=lcc  +lon_0=-95 +lat_0=25 +lat_1=25 +lat_2=25 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs'
    );

## 4.6. Spatial Tables

### 4.6.1. Creating a Spatial Table

You can create a table to store geometry data using the CREATE TABLE SQL statement with a column of type `geometry`. The following example creates a table with a geometry column storing 2D (XY) LineStrings in the BC-Albers coordinate system (SRID 3005):

    CREATE TABLE roads (
        id SERIAL PRIMARY KEY,
        name VARCHAR(64),
        geom geometry(LINESTRING,3005)
      );

The `geometry` type supports two optional type modifiers:

- the spatial type modifier restricts the kind of shapes and dimensions allowed in the column. The value can be any of the supported geometry subtypes (e.g. POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION, etc). The modifier supports coordinate dimensionality restrictions by adding suffixes: Z, M and ZM. For example, a modifier of 'LINESTRINGM' allows only linestrings with three dimensions, and treats the third dimension as a measure. Similarly, 'POINTZM' requires four dimensional (XYZM) data.

- the SRID modifier restricts the spatial reference system SRID to a particular number. If omitted, the SRID defaults to 0.

Examples of creating tables with geometry columns:

- Create a table holding any kind of geometry with the default SRID:

      CREATE TABLE geoms(gid serial PRIMARY KEY, geom geometry );

- Create a table with 2D POINT geometry with the default SRID:

      CREATE TABLE pts(gid serial PRIMARY KEY, geom geometry(POINT) );

- Create a table with 3D (XYZ) POINTs and an explicit SRID of 3005:

      CREATE TABLE pts(gid serial PRIMARY KEY, geom geometry(POINTZ,3005) );

- Create a table with 4D (XYZM) LINESTRING geometry with the default SRID:

      CREATE TABLE lines(gid serial PRIMARY KEY, geom geometry(LINESTRINGZM) );

- Create a table with 2D POLYGON geometry with the SRID 4267 (NAD 1927 long lat):

      CREATE TABLE polys(gid serial PRIMARY KEY, geom geometry(POLYGON,4267) );

It is possible to have more than one geometry column in a table. This can be specified when the table is created, or a column can be added using the ALTER TABLE SQL statement. This example adds a column that can hold 3D LineStrings:

    ALTER TABLE roads ADD COLUMN geom2 geometry(LINESTRINGZ,4326);

### 4.6.2. GEOMETRY_COLUMNS View

The OGC Simple Features Specification for SQL defines the `GEOMETRY_COLUMNS` metadata table to describe geometry table structure. In PostGIS `geometry_columns` is a view reading from database system catalog tables. This ensures that the spatial metadata information is always consistent with the currently defined tables and views. The view structure is:

    \d geometry_columns

                 View "public.geometry_columns"
          Column       |          Type          | Modifiers
    -------------------+------------------------+-----------
     f_table_catalog   | character varying(256) |
     f_table_schema    | character varying(256) |
     f_table_name      | character varying(256) |
     f_geometry_column | character varying(256) |
     coord_dimension   | integer                |
     srid              | integer                |
     type              | character varying(30)  |

The columns are:

`f_table_catalog, f_table_schema, f_table_name`

  The fully qualified name of the feature table containing the geometry column. There is no PostgreSQL analogue of "catalog" so that column is left blank. For "schema" the PostgreSQL schema name is used (`public` is the default).

`f_geometry_column`

  The name of the geometry column in the feature table.

`coord_dimension`

  The coordinate dimension (2, 3 or 4) of the column.

`srid`

  The ID of the spatial reference system used for the coordinate geometry in this table. It is a foreign key reference to the `spatial_ref_sys` table (see Section 4.5.1, “SPATIAL_REF_SYS Table”).

`type`

  The type of the spatial object. To restrict the spatial column to a single type, use one of: POINT, LINESTRING, POLYGON, MULTIPOINT, MULTILINESTRING, MULTIPOLYGON, GEOMETRYCOLLECTION or corresponding XYM versions POINTM, LINESTRINGM, POLYGONM, MULTIPOINTM, MULTILINESTRINGM, MULTIPOLYGONM, GEOMETRYCOLLECTIONM. For heterogeneous (mixed-type) collections, you can use "GEOMETRY" as the type.

### 4.6.3. Manually Registering Geometry Columns

Two of the cases where you may need this are the case of SQL Views and bulk inserts. For bulk insert case, you can correct the registration in the geometry_columns table by constraining the column or doing an alter table. For views, you could expose using a CAST operation. Note, if your column is typmod based, the creation process would register it correctly, so no need to do anything. Also views that have no spatial function applied to the geometry will register the same as the underlying table geometry column.

    -- Lets say you have a view created like this
    CREATE VIEW public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom, 3395) As geom, f_name
    	FROM public.mytable;

    -- For it to register correctly
    -- You need to cast the geometry
    --
    DROP VIEW public.vwmytablemercator;
    CREATE VIEW  public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom, 3395)::geometry(Geometry, 3395) As geom, f_name
    	FROM public.mytable;

    -- If you know the geometry type for sure is a 2D POLYGON then you could do
    DROP VIEW public.vwmytablemercator;
    CREATE VIEW  public.vwmytablemercator AS
    	SELECT gid, ST_Transform(geom,3395)::geometry(Polygon, 3395) As geom, f_name
    	FROM public.mytable;

    --Lets say you created a derivative table by doing a bulk insert
    SELECT poi.gid, poi.geom, citybounds.city_name
    INTO myschema.my_special_pois
    FROM poi INNER JOIN citybounds ON ST_Intersects(citybounds.geom, poi.geom);

    -- Create 2D index on new table
    CREATE INDEX idx_myschema_myspecialpois_geom_gist
      ON myschema.my_special_pois USING gist(geom);

    -- If your points are 3D points or 3M points,
    -- then you might want to create an nd index instead of a 2D index
    CREATE INDEX my_special_pois_geom_gist_nd
    	ON my_special_pois USING gist(geom gist_geometry_ops_nd);

    -- To manually register this new table's geometry column in geometry_columns.
    -- Note it will also change the underlying structure of the table to
    -- to make the column typmod based.
    SELECT populate_geometry_columns('myschema.my_special_pois'::regclass);

    -- If you are using PostGIS 2.0 and for whatever reason, you
    -- you need the constraint based definition behavior
    -- (such as case of inherited tables where all children do not have the same type and srid)
    -- set optional use_typmod argument to false
    SELECT populate_geometry_columns('myschema.my_special_pois'::regclass, false);

Although the old-constraint based method is still supported, a constraint-based geometry column used directly in a view, will not register correctly in geometry_columns, as will a typmod one. In this example we define a column using typmod and another using constraints.

    CREATE TABLE pois_ny(gid SERIAL PRIMARY KEY, poi_name text, cat text, geom geometry(POINT,4326));
    SELECT AddGeometryColumn('pois_ny', 'geom_2160', 2160, 'POINT', 2, false);

If we run in psql

    \d pois_ny;

We observe they are defined differently -- one is typmod, one is constraint

                                      Table "public.pois_ny"
      Column   |         Type          |                       Modifiers

    -----------+-----------------------+------------------------------------------------------
     gid       | integer               | not null default nextval('pois_ny_gid_seq'::regclass)
     poi_name  | text                  |
     cat       | character varying(20) |
     geom      | geometry(Point,4326)  |
     geom_2160 | geometry              |
    Indexes:
        "pois_ny_pkey" PRIMARY KEY, btree (gid)
    Check constraints:
        "enforce_dims_geom_2160" CHECK (st_ndims(geom_2160) = 2)
        "enforce_geotype_geom_2160" CHECK (geometrytype(geom_2160) = 'POINT'::text
            OR geom_2160 IS NULL)
        "enforce_srid_geom_2160" CHECK (st_srid(geom_2160) = 2160)

In geometry_columns, they both register correctly

    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'pois_ny';

    f_table_name | f_geometry_column | srid | type
    -------------+-------------------+------+-------
    pois_ny      | geom              | 4326 | POINT
    pois_ny      | geom_2160         | 2160 | POINT

However -- if we were to create a view like this

    CREATE VIEW vw_pois_ny_parks AS
    SELECT *
      FROM pois_ny
      WHERE cat='park';

    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'vw_pois_ny_parks';

The typmod based geom view column registers correctly, but the constraint based one does not.

       f_table_name   | f_geometry_column | srid |   type
    ------------------+-------------------+------+----------
     vw_pois_ny_parks | geom              | 4326 | POINT
     vw_pois_ny_parks | geom_2160         |    0 | GEOMETRY

This may change in future versions of PostGIS, but for now to force the constraint-based view column to register correctly, you need to do this:

    DROP VIEW vw_pois_ny_parks;
    CREATE VIEW vw_pois_ny_parks AS
    SELECT gid, poi_name, cat,
      geom,
      geom_2160::geometry(POINT,2160) As geom_2160
      FROM pois_ny
      WHERE cat = 'park';
    SELECT f_table_name, f_geometry_column, srid, type
    	FROM geometry_columns
    	WHERE f_table_name = 'vw_pois_ny_parks';

       f_table_name   | f_geometry_column | srid | type
    ------------------+-------------------+------+-------
     vw_pois_ny_parks | geom              | 4326 | POINT
     vw_pois_ny_parks | geom_2160         | 2160 | POINT

## 4.7. Loading Spatial Data

Once you have created a spatial table, you are ready to upload spatial data to the database. There are two built-in ways to get spatial data into a PostGIS/PostgreSQL database: using formatted SQL statements or using the Shapefile loader.

### 4.7.1. Using SQL to Load Data

If spatial data can be converted to a text representation (as either WKT or WKB), then using SQL might be the easiest way to get data into PostGIS. Data can be bulk-loaded into PostGIS/PostgreSQL by loading a text file of SQL `INSERT` statements using the `psql` SQL utility.

A SQL load file (`roads.sql` for example) might look like this:

    BEGIN;
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (1,'LINESTRING(191232 243118,191108 243242)','Jeff Rd');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (2,'LINESTRING(189141 244158,189265 244817)','Geordie Rd');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (3,'LINESTRING(192783 228138,192612 229814)','Paul St');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (4,'LINESTRING(189412 252431,189631 259122)','Graeme Ave');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (5,'LINESTRING(190131 224148,190871 228134)','Phil Tce');
    INSERT INTO roads (road_id, roads_geom, road_name)
      VALUES (6,'LINESTRING(198231 263418,198213 268322)','Dave Cres');
    COMMIT;

The SQL file can be loaded into PostgreSQL using `psql`:

    psql -d [database] -f roads.sql

### 4.7.2. Using the Shapefile Loader

The `shp2pgsql` data loader converts Shapefiles into SQL suitable for insertion into a PostGIS/PostgreSQL database either in geometry or geography format. The loader has several operating modes selected by command line flags.

There is also a `shp2pgsql-gui` graphical interface with most of the options as the command-line loader. This may be easier to use for one-off non-scripted loading or if you are new to PostGIS. It can also be configured as a plugin to PgAdminIII.

(c|a|d|p) These are mutually exclusive options:

  `-c`

    Creates a new table and populates it from the Shapefile. This is the default mode.

  `-a`

    Appends data from the Shapefile into the database table. Note that to use this option to load multiple files, the files must have the same attributes and same data types.

  `-d`

    Drops the database table before creating a new table with the data in the Shapefile.

  `-p`

    Only produces the table creation SQL code, without adding any actual data. This can be used if you need to completely separate the table creation and data loading steps.

`-?`

  Display help screen.

`-D`

  Use the PostgreSQL "dump" format for the output data. This can be combined with -a, -c and -d. It is much faster to load than the default "insert" SQL format. Use this for very large data sets.

`-s [<FROM_SRID>:]<SRID>`

  Creates and populates the geometry tables with the specified SRID. Optionally specifies that the input shapefile uses the given FROM_SRID, in which case the geometries will be reprojected to the target SRID.

`-k`

  Keep identifiers' case (column, schema and attributes). Note that attributes in Shapefile are all UPPERCASE.

`-i`

  Coerce all integers to standard 32-bit integers, do not create 64-bit bigints, even if the DBF header signature appears to warrant it.

`-I`

  Create a GiST index on the geometry column.

`-m`

  -m `a_file_name` Specify a file containing a set of mappings of (long) column names to 10 character DBF column names. The content of the file is one or more lines of two names separated by white space and no trailing or leading space. For example:

      COLUMNNAME DBFFIELD1
      AVERYLONGCOLUMNNAME DBFFIELD2

`-S`

  Generate simple geometries instead of MULTI geometries. Will only succeed if all the geometries are actually single (I.E. a MULTIPOLYGON with a single shell, or or a MULTIPOINT with a single vertex).

`-t <dimensionality>`

  Force the output geometry to have the specified dimensionality. Use the following strings to indicate the dimensionality: 2D, 3DZ, 3DM, 4D.

  If the input has fewer dimensions that specified, the output will have those dimensions filled in with zeroes. If the input has more dimensions that specified, the unwanted dimensions will be stripped.

`-w`

  Output WKT format, instead of WKB. Note that this can introduce coordinate drifts due to loss of precision.

`-e`

  Execute each statement on its own, without using a transaction. This allows loading of the majority of good data when there are some bad geometries that generate errors. Note that this cannot be used with the -D flag as the "dump" format always uses a transaction.

`-W <encoding>`

  Specify encoding of the input data (dbf file). When used, all attributes of the dbf are converted from the specified encoding to UTF8. The resulting SQL output will contain a `SET CLIENT_ENCODING to UTF8` command, so that the backend will be able to reconvert from UTF8 to whatever encoding the database is configured to use internally.

`-N <policy>`

  NULL geometries handling policy (insert*,skip,abort)

`-n`

  -n Only import DBF file. If your data has no corresponding shapefile, it will automatically switch to this mode and load just the dbf. So setting this flag is only needed if you have a full shapefile set, and you only want the attribute data and no geometry.

`-G`

  Use geography type instead of geometry (requires lon/lat data) in WGS84 long lat (SRID=4326)

`-T <tablespace>`

  Specify the tablespace for the new table. Indexes will still use the default tablespace unless the -X parameter is also used. The PostgreSQL documentation has a good description on when to use custom tablespaces.

`-X <tablespace>`

  Specify the tablespace for the new table's indexes. This applies to the primary key index, and the GIST spatial index if -I is also used.

`-Z`

  When used, this flag will prevent the generation of `ANALYZE` statements. Without the -Z flag (default behavior), the `ANALYZE` statements will be generated.

An example session using the loader to create an input file and loading it might look like this:

    # shp2pgsql -c -D -s 4269 -i -I shaperoads.shp myschema.roadstable > roads.sql
    # psql -d roadsdb -f roads.sql

A conversion and load can be done in one step using UNIX pipes:

    # shp2pgsql shaperoads.shp myschema.roadstable | psql -d roadsdb

## 4.8. Extracting Spatial Data

Spatial data can be extracted from the database using either SQL or the Shapefile dumper. The section on SQL presents some of the functions available to do comparisons and queries on spatial tables.

### 4.8.1. Using SQL to Extract Data

The most straightforward way of extracting spatial data out of the database is to use a SQL `SELECT` query to define the data set to be extracted and dump the resulting columns into a parsable text file:

    db=# SELECT road_id, ST_AsText(road_geom) AS geom, road_name FROM roads;

    road_id | geom                                    | road_name
    --------+-----------------------------------------+-----------
    	  1 | LINESTRING(191232 243118,191108 243242) | Jeff Rd
    	  2 | LINESTRING(189141 244158,189265 244817) | Geordie Rd
    	  3 | LINESTRING(192783 228138,192612 229814) | Paul St
    	  4 | LINESTRING(189412 252431,189631 259122) | Graeme Ave
    	  5 | LINESTRING(190131 224148,190871 228134) | Phil Tce
    	  6 | LINESTRING(198231 263418,198213 268322) | Dave Cres
    	  7 | LINESTRING(218421 284121,224123 241231) | Chris Way
    (6 rows)

There will be times when some kind of restriction is necessary to cut down the number of records returned. In the case of attribute-based restrictions, use the same SQL syntax as used with a non-spatial table. In the case of spatial restrictions, the following functions are useful:

`ST_Intersects`

  This function tells whether two geometries share any space.

`=`

  This tests whether two geometries are geometrically identical. For example, if 'POLYGON((0 0,1 1,1 0,0 0))' is the same as 'POLYGON((0 0,1 1,1 0,0 0))' (it is).

Next, you can use these operators in queries. Note that when specifying geometries and boxes on the SQL command line, you must explicitly turn the string representations into geometries function. The 312 is a fictitious spatial reference system that matches our data. So, for example:

    SELECT road_id, road_name
      FROM roads
      WHERE roads_geom='SRID=312;LINESTRING(191232 243118,191108 243242)'::geometry;

The above query would return the single record from the "ROADS_GEOM" table in which the geometry was equal to that value.

To check whether some of the roads passes in the area defined by a polygon:

    SELECT road_id, road_name
    FROM roads
    WHERE ST_Intersects(roads_geom, 'SRID=312;POLYGON((...))');

The most common spatial query will probably be a "frame-based" query, used by client software, like data browsers and web mappers, to grab a "map frame" worth of data for display.

When using the "&&" operator, you can specify either a BOX3D as the comparison feature or a GEOMETRY. When you specify a GEOMETRY, however, its bounding box will be used for the comparison.

Using a "BOX3D" object for the frame, such a query looks like this:

    SELECT ST_AsText(roads_geom) AS geom
    FROM roads
    WHERE
      roads_geom && ST_MakeEnvelope(191232, 243117,191232, 243119,312);

Note the use of the SRID 312, to specify the projection of the envelope.

### 4.8.2. Using the Shapefile Dumper

The `pgsql2shp` table dumper connects to the database and converts a table (possibly defined by a query) into a shape file. The basic syntax is:

    pgsql2shp [<options>] <database> [<schema>.]<table>

    pgsql2shp [<options>] <database> <query>

The commandline options are:

`-f <filename>`

  Write the output to a particular filename.

`-h <host>`

  The database host to connect to.

`-p <port>`

  The port to connect to on the database host.

`-P <password>`

  The password to use when connecting to the database.

`-u <user>`

  The username to use when connecting to the database.

`-g <geometry column>`

  In the case of tables with multiple geometry columns, the geometry column to use when writing the shape file.

`-b`

  Use a binary cursor. This will make the operation faster, but will not work if any NON-geometry attribute in the table lacks a cast to text.

`-r`

  Raw mode. Do not drop the `gid` field, or escape column names.

`-m filename`

  Remap identifiers to ten character names. The content of the file is lines of two symbols separated by a single white space and no trailing or leading space: VERYLONGSYMBOL SHORTONE ANOTHERVERYLONGSYMBOL SHORTER etc.

## 4.9. Spatial Indexes

Spatial indexes make using a spatial database for large data sets possible. Without indexing, a search for features requires a sequential scan of every record in the database. Indexing speeds up searching by organizing the data into a structure which can be quickly traversed to find matching records.

The B-tree index method commonly used for attribute data is not very useful for spatial data, since it only supports storing and querying data in a single dimension. Data such as geometry (which has 2 or more dimensions) requires an index method that supports range query across all the data dimensions. One of the key advantages of PostgreSQL for spatial data handling is that it offers several kinds of index methods which work well for multi-dimensional data: GiST, BRIN and SP-GiST indexes.

- GiST (Generalized Search Tree) indexes break up data into "things to one side", "things which overlap", "things which are inside" and can be used on a wide range of data-types, including GIS data. PostGIS uses an R-Tree index implemented on top of GiST to index spatial data. GiST is the most commonly-used and versatile spatial index method, and offers very good query performance.

- BRIN (Block Range Index) indexes operate by summarizing the spatial extent of ranges of table records. Search is done via a scan of the ranges. BRIN is only appropriate for use for some kinds of data (spatially sorted, with infrequent or no update). But it provides much faster index create time, and much smaller index size.

- SP-GiST (Space-Partitioned Generalized Search Tree) is a generic index method that supports partitioned search trees such as quad-trees, k-d trees, and radix trees (tries).

Spatial indexes store only the bounding box of geometries. Spatial queries use the index as a primary filter to quickly determine a set of geometries potentially matching the query condition. Most spatial queries require a secondary filter that uses a spatial predicate function to test a more specific spatial condition. For more information on queying with spatial predicates see Section 5.2, “Using Spatial Indexes”.

See also the PostGIS Workshop section on spatial indexes, and the PostgreSQL manual.

### 4.9.1. GiST Indexes

GiST stands for "Generalized Search Tree" and is a generic form of indexing for multi-dimensional data. PostGIS uses an R-Tree index implemented on top of GiST to index spatial data. GiST is the most commonly-used and versatile spatial index method, and offers very good query performance. Other implementations of GiST are used to speed up searches on all kinds of irregular data structures (integer arrays, spectral data, etc) which are not amenable to normal B-Tree indexing. For more information see the PostgreSQL manual.

Once a spatial data table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data (unless all your searches are based on attributes, in which case you'll want to build a normal index on the attribute fields).

The syntax for building a GiST index on a "geometry" column is as follows:

    CREATE INDEX [indexname] ON [tablename] USING GIST ( [geometryfield] );

The above syntax will always build a 2D-index. To get the an n-dimensional index for the geometry type, you can create one using this syntax:

    CREATE INDEX [indexname] ON [tablename] USING GIST ([geometryfield] gist_geometry_ops_nd);

Building a spatial index is a computationally intensive exercise. It also blocks write access to your table for the time it creates, so on a production system you may want to do in in a slower CONCURRENTLY-aware way:

    CREATE INDEX CONCURRENTLY [indexname] ON [tablename] USING GIST ( [geometryfield] );

After building an index, it is sometimes helpful to force PostgreSQL to collect table statistics, which are used to optimize query plans:

    VACUUM ANALYZE [table_name] [(column_name)];

### 4.9.2. BRIN Indexes

BRIN stands for "Block Range Index". It is a general-purpose index method introduced in PostgreSQL 9.5. BRIN is a lossy index method, meaning that a secondary check is required to confirm that a record matches a given search condition (which is the case for all provided spatial indexes). It provides much faster index creation and much smaller index size, with reasonable read performance. Its primary purpose is to support indexing very large tables on columns which have a correlation with their physical location within the table. In addition to spatial indexing, BRIN can speed up searches on various kinds of attribute data structures (integer, arrays etc). For more information see the PostgreSQL manual.

Once a spatial table exceeds a few thousand rows, you will want to build an index to speed up spatial searches of the data. GiST indexes are very performant as long as their size doesn't exceed the amount of RAM available for the database, and as long as you can afford the index storage size, and the cost of index update on write. Otherwise, for very large tables BRIN index can be considered as an alternative.

A BRIN index stores the bounding box enclosing all the geometries contained in the rows in a contiguous set of table blocks, called a block range. When executing a query using the index the block ranges are scanned to find the ones that intersect the query extent. This is efficient only if the data is physically ordered so that the bounding boxes for block ranges have minimal overlap (and ideally are mutually exclusive). The resulting index is very small in size, but is typically less performant for read than a GiST index over the same data.

Building a BRIN index is much less CPU-intensive than building a GiST index. It's common to find that a BRIN index is ten times faster to build than a GiST index over the same data. And because a BRIN index stores only one bounding box for each range of table blocks, it's common to use up to a thousand times less disk space than a GiST index.

You can choose the number of blocks to summarize in a range. If you decrease this number, the index will be bigger but will probably provide better performance.

For BRIN to be effective, the table data should be stored in a physical order which minimizes the amount of block extent overlap. It may be that the data is already sorted appropriately (for instance, if it is loaded from another dataset that is already sorted in spatial order). Otherwise, this can be accomplished by sorting the data by a one-dimensional spatial key. One way to do this is to create a new table sorted by the geometry values (which in recent PostGIS versions uses an efficient Hilbert curve ordering):

    CREATE TABLE table_sorted AS
       SELECT * FROM table  ORDER BY geom;

Alternatively, data can be sorted in-place by using a GeoHash as a (temporary) index, and clustering on that index:

    CREATE INDEX idx_temp_geohash ON table
        USING btree (ST_GeoHash( ST_Transform( geom, 4326 ), 20));
    CLUSTER table USING idx_temp_geohash;

The syntax for building a BRIN index on a `geometry` column is:

    CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geome_col] );

The above syntax builds a 2D index. To build a 3D-dimensional index, use this syntax:

    CREATE INDEX [indexname] ON [tablename]
        USING BRIN ([geome_col] brin_geometry_inclusion_ops_3d);

You can also get a 4D-dimensional index using the 4D operator class:

    CREATE INDEX [indexname] ON [tablename]
        USING BRIN ([geome_col] brin_geometry_inclusion_ops_4d);

The above commands use the default number of blocks in a range, which is 128. To specify the number of blocks to summarise in a range, use this syntax

    CREATE INDEX [indexname] ON [tablename]
        USING BRIN ( [geome_col] ) WITH (pages_per_range = [number]);

Keep in mind that a BRIN index only stores one index entry for a large number of rows. If your table stores geometries with a mixed number of dimensions, it's likely that the resulting index will have poor performance. You can avoid this performance penalty by choosing the operator class with the least number of dimensions of the stored geometries

The `geography` datatype is supported for BRIN indexing. The syntax for building a BRIN index on a geography column is:

    CREATE INDEX [indexname] ON [tablename] USING BRIN ( [geog_col] );

The above syntax builds a 2D-index for geospatial objects on the spheroid.

Currently, only "inclusion support" is provided, meaning that just the `&&`, `~` and `@` operators can be used for the 2D cases (for both `geometry` and `geography`), and just the `&&&` operator for 3D geometries. There is currently no support for kNN searches.

An important difference between BRIN and other index types is that the database does not maintain the index dynamically. Changes to spatial data in the table are simply appended to the end of the index. This will cause index search performance to degrade over time. The index can be updated by performing a `VACUUM`, or by using a special function `brin_summarize_new_values(regclass)`. For this reason BRIN may be most appropriate for use with data that is read-only, or only rarely changing. For more information refer to the manual.

To summarize using BRIN for spatial data:

- Index build time is very fast, and index size is very small.

- Index query time is slower than GiST, but can still be very acceptable.

- Requires table data to be sorted in a spatial ordering.

- Requires manual index maintenance.

- Most appropriate for very large tables, with low or no overlap (e.g. points), which are static or change infrequently.

- More effective for queries which return relatively large numbers of data records.

### 4.9.3. SP-GiST Indexes

SP-GiST stands for "Space-Partitioned Generalized Search Tree" and is a generic form of indexing for multi-dimensional data types that supports partitioned search trees, such as quad-trees, k-d trees, and radix trees (tries). The common feature of these data structures is that they repeatedly divide the search space into partitions that need not be of equal size. In addition to spatial indexing, SP-GiST is used to speed up searches on many kinds of data, such as phone routing, ip routing, substring search, etc. For more information see the PostgreSQL manual.

As it is the case for GiST indexes, SP-GiST indexes are lossy, in the sense that they store the bounding box enclosing spatial objects. SP-GiST indexes can be considered as an alternative to GiST indexes.

Once a GIS data table exceeds a few thousand rows, an SP-GiST index may be used to speed up spatial searches of the data. The syntax for building an SP-GiST index on a "geometry" column is as follows:

    CREATE INDEX [indexname] ON [tablename] USING SPGIST ( [geometryfield] );

The above syntax will build a 2-dimensional index. A 3-dimensional index for the geometry type can be created using the 3D operator class:

    CREATE INDEX [indexname] ON [tablename] USING SPGIST ([geometryfield] spgist_geometry_ops_3d);

Building a spatial index is a computationally intensive operation. It also blocks write access to your table for the time it creates, so on a production system you may want to do in in a slower CONCURRENTLY-aware way:

    CREATE INDEX CONCURRENTLY [indexname] ON [tablename] USING SPGIST ( [geometryfield] );

After building an index, it is sometimes helpful to force PostgreSQL to collect table statistics, which are used to optimize query plans:

    VACUUM ANALYZE [table_name] [(column_name)];

An SP-GiST index can accelerate queries involving the following operators:

- <<, &<, &>, >>, <<|, &<|, |&>, |>>, &&, @>, <@, and ~=, for 2-dimensional indexes,

- &/&, ~==, @>>, and <<@, for 3-dimensional indexes.

There is no support for kNN searches at the moment.

### 4.9.4. Tuning Index Usage

Ordinarily, indexes invisibly speed up data access: once an index is built, the PostgreSQL query planner automatically decides when to use it to improve query performance. But there are some situations where the planner does not choose to use existing indexes, so queries end up using slow sequential scans instead of a spatial index.

If you find your spatial indexes are not being used, there are a few things you can do:

- Examine the query plan and check your query actually computes the thing you need. An erroneous JOIN, either forgotten or to the wrong table, can unexpectedly retrieve table records multiple times. To get the query plan, execute with `EXPLAIN` in front of the query.

- Make sure statistics are gathered about the number and distributions of values in a table, to provide the query planner with better information to make decisions around index usage. VACUUM ANALYZE will compute both.

  You should regularly vacuum your databases anyways. Many PostgreSQL DBAs run VACUUM as an off-peak cron job on a regular basis.

- If vacuuming does not help, you can temporarily force the planner to use the index information by using the command SET ENABLE_SEQSCAN TO OFF;. This way you can check whether the planner is at all able to generate an index-accelerated query plan for your query. You should only use this command for debugging; generally speaking, the planner knows better than you do about when to use indexes. Once you have run your query, do not forget to run SET ENABLE_SEQSCAN TO ON; so that the planner will operate normally for other queries.

- If SET ENABLE_SEQSCAN TO OFF; helps your query to run faster, your Postgres is likely not tuned for your hardware. If you find the planner wrong about the cost of sequential versus index scans try reducing the value of `RANDOM_PAGE_COST` in `postgresql.conf`, or use SET RANDOM_PAGE_COST TO 1.1;. The default value for `RANDOM_PAGE_COST` is 4.0. Try setting it to 1.1 (for SSD) or 2.0 (for fast magnetic disks). Decreasing the value makes the planner more likely to use index scans.

- If SET ENABLE_SEQSCAN TO OFF; does not help your query, the query may be using a SQL construct that the Postgres planner is not yet able to optimize. It may be possible to rewrite the query in a way that the planner is able to handle. For example, a subquery with an inline SELECT may not produce an efficient plan, but could possibly be rewritten using a LATERAL JOIN.

For more information see the Postgres manual section on Query Planning.

# Chapter 5. Spatial Queries

The raison d'etre of spatial databases is to perform queries inside the database which would ordinarily require desktop GIS functionality. Using PostGIS effectively requires knowing what spatial functions are available, how to use them in queries, and ensuring that appropriate indexes are in place to provide good performance.

## 5.1. Determining Spatial Relationships

Spatial relationships indicate how two geometries interact with one another. They are a fundamental capability for querying geometry.

### 5.1.1. Dimensionally Extended 9-Intersection Model

According to the OpenGIS Simple Features Implementation Specification for SQL, "the basic approach to comparing two geometries is to make pair-wise tests of the intersections between the Interiors, Boundaries and Exteriors of the two geometries and to classify the relationship between the two geometries based on the entries in the resulting 'intersection' matrix."

In the theory of point-set topology, the points in a geometry embedded in 2-dimensional space are categorized into three sets:

Boundary

  The boundary of a geometry is the set of geometries of the next lower dimension. For `POINT`s, which have a dimension of 0, the boundary is the empty set. The boundary of a `LINESTRING` is the two endpoints. For `POLYGON`s, the boundary is the linework of the exterior and interior rings.

Interior

  The interior of a geometry are those points of a geometry that are not in the boundary. For `POINT`s, the interior is the point itself. The interior of a `LINESTRING` is the set of points between the endpoints. For `POLYGON`s, the interior is the areal surface inside the polygon.

Exterior

  The exterior of a geometry is the rest of the space in which the geometry is embedded; in other words, all points not in the interior or on the boundary of the geometry. It is a 2-dimensional non-closed surface.

The Dimensionally Extended 9-Intersection Model (DE-9IM) describes the spatial relationship between two geometries by specifying the dimensions of the 9 intersections between the above sets for each geometry. The intersection dimensions can be formally represented in a 3x3 intersection matrix.

For a geometry g the Interior, Boundary, and Exterior are denoted using the notation I(g), B(g), and E(g). Also, dim(s) denotes the dimension of a set s with the domain of `{0,1,2,F}`:

- `0` => point

- `1` => line

- `2` => area

- `F` => empty set

Using this notation, the intersection matrix for two geometries a and b is:

| Interior | Boundary | Exterior
--- | --- | --- | ---
Interior | dim( I(a) ∩ I(b) ) | dim( I(a) ∩ B(b) ) | dim( I(a) ∩ E(b) )
Boundary | dim( B(a) ∩ I(b) ) | dim( B(a) ∩ B(b) ) | dim( B(a) ∩ E(b) )
Exterior | dim( E(a) ∩ I(b) ) | dim( E(a) ∩ B(b) ) | dim( E(a) ∩ E(b) )

Visually, for two overlapping polygonal geometries, this looks like:

| Interior | Boundary | Exterior
--- | --- | --- | ---
Interior | dim( I(a) ∩ I(b) ) = 2 | dim( I(a) ∩ B(b) = 1 | dim( I(a) ∩ E(b) ) = 2
Boundary | dim( B(a) ∩ I(b) ) = 1 | dim( B(a) ∩ B(b) ) = 0 | dim( B(a) ∩ E(b) ) = 1
Exterior | dim( E(a) ∩ I(b) ) = 2 | dim( E(a) ∩ B(b) ) = 1 | dim( E(a) ∩ E(b) = 2

Reading from left to right and top to bottom, the intersection matrix is represented as the text string '212101212'.

For more information, refer to:

- OpenGIS Simple Features Implementation Specification for SQL (version 1.1, section 2.1.13.2)

- Wikipedia: Dimensionally Extended Nine-Intersection Model (DE-9IM)

- GeoTools: Point Set Theory and the DE-9IM Matrix

### 5.1.2. Named Spatial Relationships

To make it easy to determine common spatial relationships, the OGC SFS defines a set of named spatial relationship predicates. PostGIS provides these as the functions ST_Contains, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within. It also defines the non-standard relationship predicates ST_Covers, ST_CoveredBy, and ST_ContainsProperly.

Spatial predicates are usually used as conditions in SQL `WHERE` or `JOIN` clauses. The named spatial predicates automatically use a spatial index if one is available, so there is no need to use the bounding box operator `&&` as well. For example:

    SELECT city.name, state.name, city.geom
    FROM city JOIN state ON ST_Intersects(city.geom, state.geom);

For more details and illustrations, see the PostGIS Workshop.

### 5.1.3. General Spatial Relationships

In some cases the named spatial relationships are insufficient to provide a desired spatial filter condition.

For example, consider a linear dataset representing a road network. It may be required to identify all road segments that cross each other, not at a point, but in a line (perhaps to validate some business rule). In this case ST_Crosses does not provide the necessary spatial filter, since for linear features it returns `true` only where they cross at a point. A two-step solution would be to first compute the actual intersection (ST_Intersection) of pairs of road lines that spatially intersect (ST_Intersects), and then check if the intersection's ST_GeometryType is '`LINESTRING`' (properly dealing with cases that return `GEOMETRYCOLLECTION`s of `[MULTI]POINT`s, `[MULTI]LINESTRING`s, etc.). Clearly, a simpler and faster solution is desirable.

A second example is locating wharves that intersect a lake's boundary on a line and where one end of the wharf is up on shore. In other words, where a wharf is within but not completely contained by a lake, intersects the boundary of a lake on a line, and where exactly one of the wharf's endpoints is within or on the boundary of the lake. It is possible to use a combination of spatial predicates to find the required features: ST_Contains(lake, wharf) = TRUE ST_ContainsProperly(lake, wharf) = FALSE ST_GeometryType(ST_Intersection(wharf, lake)) = 'LINESTRING' ST_NumGeometries(ST_Multi(ST_Intersection(ST_Boundary(wharf), ST_Boundary(lake)))) = 1 ... but needless to say, this is quite complicated.

These requirements can be met by computing the full DE-9IM intersection matrix. PostGIS provides the ST_Relate function to do this:

    SELECT ST_Relate( 'LINESTRING (1 1, 5 5)',
                      'POLYGON ((3 3, 3 7, 7 7, 7 3, 3 3))' );
    st_relate
    -----------
    1010F0212

To test a particular spatial relationship, an intersection matrix pattern is used. This is the matrix representation augmented with the additional symbols `{T,*}`:

- `T` => intersection dimension is non-empty; i.e. is in `{0,1,2}`

- `*` => don't care

Using intersection matrix patterns, specific spatial relationships can be evaluated in a more succinct way. The ST_Relate and the ST_RelateMatch functions can be used to test intersection matrix patterns. For the first example above, the intersection matrix pattern specifying two lines intersecting in a line is '1*1***1**':

    -- Find road segments that intersect in a line
    SELECT a.id
    FROM roads a, roads b
    WHERE a.id != b.id
          AND a.geom && b.geom
          AND ST_Relate(a.geom, b.geom, '1*1***1**');

For the second example, the intersection matrix pattern specifying a line partly inside and partly outside a polygon is '102101FF2':

    -- Find wharves partly on a lake's shoreline
    SELECT a.lake_id, b.wharf_id
    FROM lakes a, wharfs b
    WHERE a.geom && b.geom
          AND ST_Relate(a.geom, b.geom, '102101FF2');

## 5.2. Using Spatial Indexes

When constructing queries using spatial conditions, for best performance it is important to ensure that a spatial index is used, if one exists (see Section 4.9, “Spatial Indexes”). To do this, a spatial operator or index-aware function must be used in a `WHERE` or `ON` clause of the query.

Spatial operators include the bounding box operators (of which the most commonly used is &&; see Section 7.10.1, “Bounding Box Operators” for the full list) and the distance operators used in nearest-neighbor queries (the most common being <->; see Section 7.10.2, “Distance Operators” for the full list.)

Index-aware functions automatically add a bounding box operator to the spatial condition. Index-aware functions include the named spatial relationship predicates ST_Contains, ST_ContainsProperly, ST_CoveredBy, ST_Covers, ST_Crosses, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within, ST_Within, and ST_3DIntersects, and the distance predicates ST_DWithin, ST_DFullyWithin, ST_3DDFullyWithin, and ST_3DDWithin .)

Functions such as ST_Distance do not use indexes to optimize their operation. For example, the following query would be quite slow on a large table:

    SELECT geom
    FROM geom_table
    WHERE ST_Distance( geom, 'SRID=312;POINT(100000 200000)' ) < 100

This query selects all the geometries in `geom_table` which are within 100 units of the point (100000, 200000). It will be slow because it is calculating the distance between each point in the table and the specified point, ie. one `ST_Distance()` calculation is computed for every row in the table.

The number of rows processed can be reduced substantially by using the index-aware function ST_DWithin:

    SELECT geom
    FROM geom_table
    WHERE ST_DWithin( geom, 'SRID=312;POINT(100000 200000)', 100 )

This query selects the same geometries, but it does it in a more efficient way. This is enabled by `ST_DWithin()` using the `&&` operator internally on an expanded bounding box of the query geometry. If there is a spatial index on `geom`, the query planner will recognize that it can use the index to reduce the number of rows scanned before calculating the distance. The spatial index allows retrieving only records with geometries whose bounding boxes overlap the expanded extent and hence which might be within the required distance. The actual distance is then computed to confirm whether to include the record in the result set.

For more information and examples see the PostGIS Workshop.

## 5.3. Examples of Spatial SQL

The examples in this section make use of a table of linear roads, and a table of polygonal municipality boundaries. The definition of the `bc_roads` table is:

    Column    | Type              | Description
    ----------+-------------------+-------------------
    gid       | integer           | Unique ID
    name      | character varying | Road Name
    geom      | geometry          | Location Geometry (Linestring)

The definition of the `bc_municipality` table is:

    Column   | Type              | Description
    ---------+-------------------+-------------------
    gid      | integer           | Unique ID
    code     | integer           | Unique ID
    name     | character varying | City / Town Name
    geom     | geometry          | Location Geometry (Polygon)

- 5.3.1. What is the total length of all roads, expressed in kilometers?
- 5.3.2. How large is the city of Prince George, in hectares?
- 5.3.3. What is the largest municipality in the province, by area?
- 5.3.4. What is the length of roads fully contained within each municipality?
- 5.3.5. Create a new table with all the roads within the city of Prince George.
- 5.3.6. What is the length in kilometers of "Douglas St" in Victoria?
- 5.3.7. What is the largest municipality polygon that has a hole?

5.3.1. | What is the total length of all roads, expressed in kilometers?
| You can answer this question with a very simple piece of SQL:
    SELECT sum(ST_Length(geom))/1000 AS km_roads FROM bc_roads;

    km_roads
    ------------------
    70842.1243039643
5.3.2. | How large is the city of Prince George, in hectares?
| This query combines an attribute condition (on the municipality name) with a spatial calculation (of the polygon area):
    SELECT
      ST_Area(geom)/10000 AS hectares
    FROM bc_municipality
    WHERE name = 'PRINCE GEORGE';

    hectares
    ------------------
    32657.9103824927
5.3.3. | What is the largest municipality in the province, by area?
| This query uses a spatial measurement as an ordering value. There are several ways of approaching this problem, but the most efficient is below:
    SELECT
      name,
      ST_Area(geom)/10000 AS hectares
    FROM bc_municipality
    ORDER BY hectares DESC
    LIMIT 1;

    name           | hectares
    ---------------+-----------------
    TUMBLER RIDGE  | 155020.02556131
Note that in order to answer this query we have to calculate the area of every polygon. If we were doing this a lot it would make sense to add an area column to the table that could be indexed for performance. By ordering the results in a descending direction, and them using the PostgreSQL "LIMIT" command we can easily select just the largest value without using an aggregate function like MAX().
5.3.4. | What is the length of roads fully contained within each municipality?
| This is an example of a "spatial join", which brings together data from two tables (with a join) using a spatial interaction ("contained") as the join condition (rather than the usual relational approach of joining on a common key):
    SELECT
      m.name,
      sum(ST_Length(r.geom))/1000 as roads_km
    FROM bc_roads AS r
    JOIN bc_municipality AS m
      ON ST_Contains(m.geom, r.geom)
    GROUP BY m.name
    ORDER BY roads_km;

    name                        | roads_km
    ----------------------------+------------------
    SURREY                      | 1539.47553551242
    VANCOUVER                   | 1450.33093486576
    LANGLEY DISTRICT            | 833.793392535662
    BURNABY                     | 773.769091404338
    PRINCE GEORGE               | 694.37554369147
    ...
This query takes a while, because every road in the table is summarized into the final result (about 250K roads for the example table). For smaller datasets (several thousand records on several hundred) the response can be very fast.
5.3.5. | Create a new table with all the roads within the city of Prince George.
| This is an example of an "overlay", which takes in two tables and outputs a new table that consists of spatially clipped or cut resultants. Unlike the "spatial join" demonstrated above, this query creates new geometries. An overlay is like a turbo-charged spatial join, and is useful for more exact analysis work:
    CREATE TABLE pg_roads as
    SELECT
      ST_Intersection(r.geom, m.geom) AS intersection_geom,
      ST_Length(r.geom) AS rd_orig_length,
      r.*
    FROM bc_roads AS r
    JOIN bc_municipality AS m
      ON ST_Intersects(r.geom, m.geom)
    WHERE
      m.name = 'PRINCE GEORGE';
5.3.6. | What is the length in kilometers of "Douglas St" in Victoria?
    SELECT
      sum(ST_Length(r.geom))/1000 AS kilometers
    FROM bc_roads r
    JOIN bc_municipality m
      ON ST_Intersects(m.geom, r.geom
    WHERE
      r.name = 'Douglas St'
      AND m.name = 'VICTORIA';

    kilometers
    ------------------
    4.89151904172838
5.3.7. | What is the largest municipality polygon that has a hole?
    SELECT gid, name, ST_Area(geom) AS area
    FROM bc_municipality
    WHERE ST_NRings(geom) > 1
    ORDER BY area DESC LIMIT 1;

    gid  | name         | area
    -----+--------------+------------------
    12   | SPALLUMCHEEN | 257374619.430216

# Chapter 6. Performance Tips

## 6.1. Small tables of large geometries

### 6.1.1. Problem description

Current PostgreSQL versions (including 9.6) suffer from a query optimizer weakness regarding TOAST tables. TOAST tables are a kind of "extension room" used to store large (in the sense of data size) values that do not fit into normal data pages (like long texts, images or complex geometries with lots of vertices), see the PostgreSQL Documentation for TOAST for more information).

The problem appears if you happen to have a table with rather large geometries, but not too many rows of them (like a table containing the boundaries of all European countries in high resolution). Then the table itself is small, but it uses lots of TOAST space. In our example case, the table itself had about 80 rows and used only 3 data pages, but the TOAST table used 8225 pages.

Now issue a query where you use the geometry operator && to search for a bounding box that matches only very few of those rows. Now the query optimizer sees that the table has only 3 pages and 80 rows. It estimates that a sequential scan on such a small table is much faster than using an index. And so it decides to ignore the GIST index. Usually, this estimation is correct. But in our case, the && operator has to fetch every geometry from disk to compare the bounding boxes, thus reading all TOAST pages, too.

To see whether your suffer from this issue, use the "EXPLAIN ANALYZE" postgresql command. For more information and the technical details, you can read the thread on the PostgreSQL performance mailing list: http://archives.postgresql.org/pgsql-performance/2005-02/msg00030.php

and newer thread on PostGIS https://lists.osgeo.org/pipermail/postgis-devel/2017-June/026209.html

### 6.1.2. Workarounds

The PostgreSQL people are trying to solve this issue by making the query estimation TOAST-aware. For now, here are two workarounds:

The first workaround is to force the query planner to use the index. Send "SET enable_seqscan TO off;" to the server before issuing the query. This basically forces the query planner to avoid sequential scans whenever possible. So it uses the GIST index as usual. But this flag has to be set on every connection, and it causes the query planner to make misestimations in other cases, so you should "SET enable_seqscan TO on;" after the query.

The second workaround is to make the sequential scan as fast as the query planner thinks. This can be achieved by creating an additional column that "caches" the bbox, and matching against this. In our example, the commands are like:

    SELECT AddGeometryColumn('myschema','mytable','bbox','4326','GEOMETRY','2');
    UPDATE mytable SET bbox = ST_Envelope(ST_Force2D(geom));

Now change your query to use the && operator against bbox instead of geom_column, like:

    SELECT geom_column
    FROM mytable
    WHERE bbox && ST_SetSRID('BOX3D(0 0,1 1)'::box3d,4326);

Of course, if you change or add rows to mytable, you have to keep the bbox "in sync". The most transparent way to do this would be triggers, but you also can modify your application to keep the bbox column current or run the UPDATE query above after every modification.

## 6.2. CLUSTERing on geometry indices

For tables that are mostly read-only, and where a single index is used for the majority of queries, PostgreSQL offers the CLUSTER command. This command physically reorders all the data rows in the same order as the index criteria, yielding two performance advantages: First, for index range scans, the number of seeks on the data table is drastically reduced. Second, if your working set concentrates to some small intervals on the indices, you have a more efficient caching because the data rows are spread along fewer data pages. (Feel invited to read the CLUSTER command documentation from the PostgreSQL manual at this point.)

However, currently PostgreSQL does not allow clustering on PostGIS GIST indices because GIST indices simply ignores NULL values, you get an error message like:

    lwgeom=# CLUSTER my_geom_index ON my_table;
    ERROR: cannot cluster when index access method does not handle null values
    HINT: You may be able to work around this by marking column "geom" NOT NULL.

As the HINT message tells you, one can work around this deficiency by adding a "not null" constraint to the table:

    lwgeom=# ALTER TABLE my_table ALTER COLUMN geom SET not null;
    ALTER TABLE

Of course, this will not work if you in fact need NULL values in your geometry column. Additionally, you must use the above method to add the constraint, using a CHECK constraint like "ALTER TABLE blubb ADD CHECK (geometry is not null);" will not work.

## 6.3. Avoiding dimension conversion

Sometimes, you happen to have 3D or 4D data in your table, but always access it using OpenGIS compliant ST_AsText() or ST_AsBinary() functions that only output 2D geometries. They do this by internally calling the ST_Force2D() function, which introduces a significant overhead for large geometries. To avoid this overhead, it may be feasible to pre-drop those additional dimensions once and forever:

    UPDATE mytable SET geom = ST_Force2D(geom);
    VACUUM FULL ANALYZE mytable;

Note that if you added your geometry column using AddGeometryColumn() there'll be a constraint on geometry dimension. To bypass it you will need to drop the constraint. Remember to update the entry in the geometry_columns table and recreate the constraint afterwards.

In case of large tables, it may be wise to divide this UPDATE into smaller portions by constraining the UPDATE to a part of the table via a WHERE clause and your primary key or another feasible criteria, and running a simple "VACUUM;" between your UPDATEs. This drastically reduces the need for temporary disk space. Additionally, if you have mixed dimension geometries, restricting the UPDATE by "WHERE dimension(geom)>2" skips re-writing of geometries that already are in 2D.

# Chapter 7. PostGIS Reference

The functions given below are the ones which a user of PostGIS is likely to need. There are other functions which are required support functions to the PostGIS objects which are not of use to a general user.

PostGIS has begun a transition from the existing naming convention to an SQL-MM-centric convention. As a result, most of the functions that you know and love have been renamed using the standard spatial type (ST) prefix. Previous functions are still available, though are not listed in this document where updated functions are equivalent. The non ST_ functions not listed in this documentation are deprecated and will be removed in a future release so STOP USING THEM.

## 7.1. PostGIS Geometry/Geography/Box Data Types

Abstract

This section lists the custom PostgreSQL data types installed by PostGIS to represent spatial data.

Each data type describes its type casting behavior. A type cast converts values of one data type into another type. PostgreSQL allows defining casting behavior for custom types, along with the functions used to convert type values. Casts can have automatic behavior, which allows automatic conversion of a function argument to a type supported by the function.

Some casts have explicit behavior, which means the cast must be specified using the syntax `CAST(myval As sometype)` or `myval::sometype`. Explicit casting avoids the issue of ambiguous casts, which can occur when using an overloaded function which does not support a given type. For example, a function may accept a box2d or a box3d, but not a geometry. Since geometry has an automatic cast to both box types, this produces an "ambiguous function" error. To prevent the error use an explicit cast to the desired box type.

All data types can be cast to `text`, so this does not need to be specified explicitly.

## Name

box2d — The type representing a 2-dimensional bounding box.

## Description

`box2d` is a spatial data type used to represent the two-dimensional bounding box enclosing a geometry or collection of geometries. For example, the ST_Extent aggregate function returns a `box2d` object.

The representation contains the values `xmin, ymin, xmax, ymax`. These are the minimum and maximum values of the X and Y extents.

`box2d` objects have a text representation which looks like `BOX(1 2,5 6)`.

## Casting Behavior

This table lists the automatic and explicit casts allowed for this data type:

Cast To | Behavior
box3d | automatic
geometry | automatic

## See Also

Section 13.7, “PostGIS Box Functions”

## Name

box3d — The type representing a 3-dimensional bounding box.

## Description

`box3d` is a PostGIS spatial data type used to represent the three-dimensional bounding box enclosing a geometry or collection of geometries. For example, the ST_3DExtent aggregate function returns a `box3d` object.

The representation contains the values `xmin, ymin, zmin, xmax, ymax, zmax`. These are the minimum and maximum values of the X, Y and Z extents.

`box3d` objects have a text representation which looks like `BOX3D(1 2 3,5 6 5)`.

## Casting Behavior

This table lists the automatic and explicit casts allowed for this data type:

Cast To | Behavior
box | automatic
box2d | automatic
geometry | automatic

## See Also

Section 13.7, “PostGIS Box Functions”

## Name

geometry — The type representing spatial features with planar coordinate systems.

## Description

`geometry` is a fundamental PostGIS spatial data type used to represent a feature in planar (Euclidean) coordinate systems.

All spatial operations on geometry use the units of the Spatial Reference System the geometry is in.

## Casting Behavior

This table lists the automatic and explicit casts allowed for this data type:

Cast To | Behavior
box | automatic
box2d | automatic
box3d | automatic
bytea | automatic
geography | automatic
text | automatic

## See Also

Section 4.1, “Spatial Data Model”, Section 13.3, “PostGIS SQL-MM Compliant Functions”

## Name

geometry_dump — A composite type used to describe the parts of complex geometry.

## Description

`geometry_dump` is a composite data type containing the fields:

- `geom` - a geometry representing a component of the dumped geometry. The geometry type depends on the originating function.

- `path[]` - an integer array that defines the navigation path within the dumped geometry to the `geom` component. The path array is 1-based (i.e. `path[1]` is the first element.)

It is used by the `ST_Dump*` family of functions as an output type to explode a complex geometry into its constituent parts.

## See Also

Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”

## Name

geography — The type representing spatial features with geodetic (ellipsoidal) coordinate systems.

## Description

`geography` is a spatial data type used to represent a feature in geodetic coordinate systems. Geodetic coordinate systems model the earth using an ellipsoid.

Spatial operations on the geography type provide more accurate results by taking the ellipsoidal model into account.

## Casting Behavior

This table lists the automatic and explicit casts allowed for this data type:

Cast To | Behavior
geometry | explicit

## See Also

Section 4.3, “Geography Data Type”, Section 13.4, “PostGIS Geography Support Functions”

## 7.2. Table Management Functions

Abstract

These functions assist in defining tables containing geometry columns.

## Name

AddGeometryColumn — Adds a geometry column to an existing table.

## Synopsis

`text AddGeometryColumn(` varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

`text AddGeometryColumn(` varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

`text AddGeometryColumn(` varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid, varchar type, integer dimension, boolean use_typmod=true`)`;

## Description

Adds a geometry column to an existing table of attributes. The `schema_name` is the name of the table schema. The `srid` must be an integer value reference to an entry in the SPATIAL_REF_SYS table. The `type` must be a string corresponding to the geometry type, eg, 'POLYGON' or 'MULTILINESTRING' . An error is thrown if the schemaname doesn't exist (or not visible in the current search_path) or the specified SRID, geometry type, or dimension is invalid.

Changed: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads from system catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior of PostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: `ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326);` Changed: 2.0.0 If you require the old behavior of constraints use the default `use_typmod`, but set it to false.

Changed: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geometry typmod tables geometries and used without wrapper functions will register themselves correctly because they inherit the typmod behavior of their parent table column. Views that use geometry functions that output other geometries will need to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns. Refer to Section 4.6.3, “Manually Registering Geometry Columns”.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based.

## Examples

    -- Create schema to hold data
    CREATE SCHEMA my_schema;
    -- Create a new simple PostgreSQL table
    CREATE TABLE my_schema.my_spatial_table (id serial);

    -- Describing the table shows a simple table with a single "id" column.
    postgis=# \d my_schema.my_spatial_table
    							 Table "my_schema.my_spatial_table"
     Column |  Type   |                                Modifiers
    --------+---------+-------------------------------------------------------------------------
     id     | integer | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)

    -- Add a spatial column to the table
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom',4326,'POINT',2);

    -- Add a point using the old constraint based behavior
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geom_c',4326,'POINT',2, false);

    --Add a curvepolygon using old constraint behavior
    SELECT AddGeometryColumn ('my_schema','my_spatial_table','geomcp_c',4326,'CURVEPOLYGON',2, false);

    -- Describe the table again reveals the addition of a new geometry columns.
    \d my_schema.my_spatial_table
                                addgeometrycolumn
    -------------------------------------------------------------------------
     my_schema.my_spatial_table.geomcp_c SRID:4326 TYPE:CURVEPOLYGON DIMS:2
    (1 row)

                                        Table "my_schema.my_spatial_table"
      Column  |         Type         |                                Modifiers
    ----------+----------------------+-------------------------------------------------------------------------
     id       | integer              | not null default nextval('my_schema.my_spatial_table_id_seq'::regclass)
     geom     | geometry(Point,4326) |
     geom_c   | geometry             |
     geomcp_c | geometry             |
    Check constraints:
        "enforce_dims_geom_c" CHECK (st_ndims(geom_c) = 2)
        "enforce_dims_geomcp_c" CHECK (st_ndims(geomcp_c) = 2)
        "enforce_geotype_geom_c" CHECK (geometrytype(geom_c) = 'POINT'::text OR geom_c IS NULL)
        "enforce_geotype_geomcp_c" CHECK (geometrytype(geomcp_c) = 'CURVEPOLYGON'::text OR geomcp_c IS NULL)
        "enforce_srid_geom_c" CHECK (st_srid(geom_c) = 4326)
        "enforce_srid_geomcp_c" CHECK (st_srid(geomcp_c) = 4326)

    -- geometry_columns view also registers the new columns --
    SELECT f_geometry_column As col_name, type, srid, coord_dimension As ndims
        FROM geometry_columns
        WHERE f_table_name = 'my_spatial_table' AND f_table_schema = 'my_schema';

     col_name |     type     | srid | ndims
    ----------+--------------+------+-------
     geom     | Point        | 4326 |     2
     geom_c   | Point        | 4326 |     2
     geomcp_c | CurvePolygon | 4326 |     2

## See Also

DropGeometryColumn, DropGeometryTable, Section 4.6.2, “GEOMETRY_COLUMNS View”, Section 4.6.3, “Manually Registering Geometry Columns”

## Name

DropGeometryColumn — Removes a geometry column from a spatial table.

## Synopsis

`text DropGeometryColumn(` varchar table_name, varchar column_name`)`;

`text DropGeometryColumn(` varchar schema_name, varchar table_name, varchar column_name`)`;

`text DropGeometryColumn(` varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name`)`;

## Description

Removes a geometry column from a spatial table. Note that schema_name will need to match the f_table_schema field of the table's row in the geometry_columns table.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a geometry column like any other table column using `ALTER TABLE`

## Examples

    			SELECT DropGeometryColumn ('my_schema','my_spatial_table','geom');
    			----RESULT output ---
    			                  dropgeometrycolumn
    ------------------------------------------------------
     my_schema.my_spatial_table.geom effectively removed.

    -- In PostGIS 2.0+ the above is also equivalent to the standard
    -- the standard alter table.  Both will deregister from geometry_columns
    ALTER TABLE my_schema.my_spatial_table DROP column geom;

## See Also

AddGeometryColumn, DropGeometryTable, Section 4.6.2, “GEOMETRY_COLUMNS View”

## Name

DropGeometryTable — Drops a table and all its references in geometry_columns.

## Synopsis

`boolean DropGeometryTable(` varchar table_name`)`;

`boolean DropGeometryTable(` varchar schema_name, varchar table_name`)`;

`boolean DropGeometryTable(` varchar catalog_name, varchar schema_name, varchar table_name`)`;

## Description

Drops a table and all its references in geometry_columns. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a table with geometry columns like any other table using `DROP TABLE`

## Examples

    SELECT DropGeometryTable ('my_schema','my_spatial_table');
    ----RESULT output ---
    my_schema.my_spatial_table dropped.

    -- The above is now equivalent to --
    DROP TABLE my_schema.my_spatial_table;

## See Also

AddGeometryColumn, DropGeometryColumn, Section 4.6.2, “GEOMETRY_COLUMNS View”

## Name

Find_SRID — Returns the SRID defined for a geometry column.

## Synopsis

`integer Find_SRID(` varchar a_schema_name, varchar a_table_name, varchar a_geomfield_name`)`;

## Description

Returns the integer SRID of the specified geometry column by searching through the GEOMETRY_COLUMNS table. If the geometry column has not been properly added (e.g. with the AddGeometryColumn function), this function will not work.

## Examples

     SELECT Find_SRID('public', 'tiger_us_state_2007', 'geom_4269');
    find_srid
    ----------
    4269

## See Also

ST_SRID

## Name

Populate_Geometry_Columns — Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.

## Synopsis

`text Populate_Geometry_Columns(` boolean use_typmod=true`)`;

`int Populate_Geometry_Columns(` oid relation_oid, boolean use_typmod=true`)`;

## Description

Ensures geometry columns have appropriate type modifiers or spatial constraints to ensure they are registered correctly in the `geometry_columns` view. By default will convert all geometry columns with no type modifier to ones with type modifiers.

For backwards compatibility and for spatial needs such as table inheritance where each child table may have different geometry type, the old check constraint behavior is still supported. If you need the old behavior, you need to pass in the new optional argument as false `use_typmod=false`. When this is done geometry columns will be created with no type modifiers but will have 3 constraints defined. In particular, this means that every geometry column belonging to a table has at least three constraints:

- `enforce_dims_geom` - ensures every geometry has the same dimension (see ST_NDims)

- `enforce_geotype_geom` - ensures every geometry is of the same type (see GeometryType)

- `enforce_srid_geom` - ensures every geometry is in the same projection (see ST_SRID)

If a table `oid` is provided, this function tries to determine the srid, dimension, and geometry type of all geometry columns in the table, adding constraints as necessary. If successful, an appropriate row is inserted into the geometry_columns table, otherwise, the exception is caught and an error notice is raised describing the problem.

If the `oid` of a view is provided, as with a table oid, this function tries to determine the srid, dimension, and type of all the geometries in the view, inserting appropriate entries into the `geometry_columns` table, but nothing is done to enforce constraints.

The parameterless variant is a simple wrapper for the parameterized variant that first truncates and repopulates the geometry_columns table for every spatial table and view in the database, adding spatial constraints to tables where appropriate. It returns a summary of the number of geometry columns detected in the database and the number that were inserted into the `geometry_columns` table. The parameterized version simply returns the number of rows inserted into the `geometry_columns` table.

Availability: 1.4.0

Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still use check constraint behavior instead by using the new `use_typmod` and setting it to false.

Enhanced: 2.0.0 `use_typmod` optional argument was introduced that allows controlling if columns are created with typmodifiers or with check constraints.

## Examples

    CREATE TABLE public.myspatial_table(gid serial, geom geometry);
    INSERT INTO myspatial_table(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
    -- This will now use typ modifiers.  For this to work, there must exist data
    SELECT Populate_Geometry_Columns('public.myspatial_table'::regclass);

    populate_geometry_columns
    --------------------------
                            1

    \d myspatial_table

                                       Table "public.myspatial_table"
     Column |           Type            |                           Modifiers
    --------+---------------------------+---------------------------------------------------------------
     gid    | integer                   | not null default nextval('myspatial_table_gid_seq'::regclass)
     geom   | geometry(LineString,4326) |

    -- This will change the geometry columns to use constraints if they are not typmod or have constraints already.
    --For this to work, there must exist data
    CREATE TABLE public.myspatial_table_cs(gid serial, geom geometry);
    INSERT INTO myspatial_table_cs(geom) VALUES(ST_GeomFromText('LINESTRING(1 2, 3 4)',4326) );
    SELECT Populate_Geometry_Columns('public.myspatial_table_cs'::regclass, false);
    populate_geometry_columns
    --------------------------
                            1
    \d myspatial_table_cs

                              Table "public.myspatial_table_cs"
     Column |   Type   |                            Modifiers
    --------+----------+------------------------------------------------------------------
     gid    | integer  | not null default nextval('myspatial_table_cs_gid_seq'::regclass)
     geom   | geometry |
    Check constraints:
        "enforce_dims_geom" CHECK (st_ndims(geom) = 2)
        "enforce_geotype_geom" CHECK (geometrytype(geom) = 'LINESTRING'::text OR geom IS NULL)
        "enforce_srid_geom" CHECK (st_srid(geom) = 4326)

## Name

UpdateGeometrySRID — Updates the SRID of all features in a geometry column, and the table metadata.

## Synopsis

`text UpdateGeometrySRID(` varchar table_name, varchar column_name, integer srid`)`;

`text UpdateGeometrySRID(` varchar schema_name, varchar table_name, varchar column_name, integer srid`)`;

`text UpdateGeometrySRID(` varchar catalog_name, varchar schema_name, varchar table_name, varchar column_name, integer srid`)`;

## Description

Updates the SRID of all features in a geometry column, updating constraints and reference in geometry_columns. If the column was enforced by a type definition, the type definition will be changed. Note: uses current_schema() on schema-aware pgsql installations if schema is not provided.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

Insert geometries into roads table with a SRID set already using EWKT format:

    COPY roads (geom) FROM STDIN;
    SRID=4326;LINESTRING(0 0, 10 10)
    SRID=4326;LINESTRING(10 10, 15 0)
    \.

This will change the srid of the roads table to 4326 from whatever it was before:

    SELECT UpdateGeometrySRID('roads','geom',4326);

The prior example is equivalent to this DDL statement:

    ALTER TABLE roads
      ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 4326)
        USING ST_SetSRID(geom,4326);

If you got the projection wrong (or brought it in as unknown) in load and you wanted to transform to web mercator all in one shot you can do this with DDL but there is no equivalent PostGIS management function to do so in one go.

    ALTER TABLE roads
     ALTER COLUMN geom TYPE geometry(MULTILINESTRING, 3857) USING ST_Transform(ST_SetSRID(geom,4326),3857) ;

## See Also

UpdateRasterSRID, ST_SetSRID, ST_Transform, ST_GeomFromEWKT

## 7.3. Geometry Constructors

## Name

ST_Collect — Creates a GeometryCollection or Multi* geometry from a set of geometries.

## Synopsis

`geometry ST_Collect(` geometry g1, geometry g2`)`;

`geometry ST_Collect(` geometry[] g1_array`)`;

`geometry ST_Collect(` geometry set g1field`)`;

## Description

Collects geometries into a geometry collection. The result is either a Multi* or a GeometryCollection, depending on whether the input geometries have the same or different types (homogeneous or heterogeneous). The input geometries are left unchanged within the collection.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries.

If any of the input geometries are collections (Multi* or GeometryCollection) ST_Collect returns a GeometryCollection (since that is the only type which can contain nested collections). To prevent this, use ST_Dump in a subquery to expand the input collections to their atomic elements (see example below).

ST_Collect and ST_Union appear similar, but in fact operate quite differently. ST_Collect aggregates geometries into a collection without changing them in any way. ST_Union geometrically merges geometries where they overlap, and splits linestrings at intersections. It may return single geometries when it dissolves boundaries.

Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples - Two-input variant

Collect 2D points.

    SELECT ST_AsText( ST_Collect( ST_GeomFromText('POINT(1 2)'),
    	ST_GeomFromText('POINT(-2 3)') ));

    st_astext
    ----------
    MULTIPOINT((1 2),(-2 3))

Collect 3D points.

    SELECT ST_AsEWKT( ST_Collect( ST_GeomFromEWKT('POINT(1 2 3)'),
    		ST_GeomFromEWKT('POINT(1 2 4)') ) );

    		st_asewkt
    -------------------------
     MULTIPOINT(1 2 3,1 2 4)

Collect curves.

    SELECT ST_AsText( ST_Collect( 'CIRCULARSTRING(220268 150415,220227 150505,220227 150406)',
    		'CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));

    		st_astext
    ------------------------------------------------------------------------------------
    MULTICURVE(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),
     CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))

## Examples - Array variant

Using an array constructor for a subquery.

    SELECT ST_Collect( ARRAY( SELECT geom FROM sometable ) );

Using an array constructor for values.

    SELECT ST_AsText(  ST_Collect(
    		ARRAY[ ST_GeomFromText('LINESTRING(1 2, 3 4)'),
    			ST_GeomFromText('LINESTRING(3 4, 4 5)') ] )) As wktcollect;

    --wkt collect --
    MULTILINESTRING((1 2,3 4),(3 4,4 5))

## Examples - Aggregate variant

Creating multiple collections by grouping geometries in a table.

    SELECT stusps, ST_Collect(f.geom) as geom
    	 FROM (SELECT stusps, (ST_Dump(geom)).geom As geom
    				FROM
    				somestatetable ) As f
    	GROUP BY stusps

## See Also

ST_Dump, ST_Union

## Name

ST_LineFromMultiPoint — Creates a LineString from a MultiPoint geometry.

## Synopsis

`geometry ST_LineFromMultiPoint(` geometry aMultiPoint`)`;

## Description

Creates a LineString from a MultiPoint geometry.

Use ST_MakeLine to create lines from Point or LineString inputs.

This function supports 3d and will not drop the z-index.

## Examples

Create a 3D line string from a 3D MultiPoint

    SELECT ST_AsEWKT(  ST_LineFromMultiPoint('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')  ));

    --result--
    LINESTRING(1 2 3,4 5 6,7 8 9)

## See Also

ST_AsEWKT, ST_MakeLine

## Name

ST_MakeEnvelope — Creates a rectangular Polygon from minimum and maximum coordinates.

## Synopsis

`geometry ST_MakeEnvelope(` float xmin, float ymin, float xmax, float ymax, integer srid=unknown`)`;

## Description

Creates a rectangular Polygon from the minimum and maximum values for X and Y. Input values must be in the spatial reference system specified by the SRID. If no SRID is specified the unknown spatial reference system (SRID 0) is used.

Availability: 1.5

Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.

## Example: Building a bounding box polygon

    SELECT ST_AsText( ST_MakeEnvelope(10, 10, 11, 11, 4326) );

    st_asewkt
    -----------
    POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))

## See Also

ST_MakePoint, ST_MakeLine, ST_MakePolygon, ST_TileEnvelope

## Name

ST_MakeLine — Creates a LineString from Point, MultiPoint, or LineString geometries.

## Synopsis

`geometry ST_MakeLine(` geometry geom1, geometry geom2`)`;

`geometry ST_MakeLine(` geometry[] geoms_array`)`;

`geometry ST_MakeLine(` geometry set geoms`)`;

## Description

Creates a LineString containing the points of Point, MultiPoint, or LineString geometries. Other geometry types cause an error.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries. To ensure the order of the input geometries use `ORDER BY` in the function call, or a subquery with an `ORDER BY` clause.

Repeated nodes at the beginning of input LineStrings are collapsed to a single point. Repeated points in Point and MultiPoint inputs are not collapsed. ST_RemoveRepeatedPoints can be used to collapse repeated points from the output LineString.

This function supports 3d and will not drop the z-index.

Availability: 2.3.0 - Support for MultiPoint input elements was introduced

Availability: 2.0.0 - Support for LineString input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

## Examples: Two-input variant

Create a line composed of two points.

    SELECT ST_AsText( ST_MakeLine(ST_Point(1,2), ST_Point(3,4)) );

    	  st_astext
    ---------------------
     LINESTRING(1 2,3 4)

Create a 3D line from two 3D points.

    SELECT ST_AsEWKT( ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5) ));

    		st_asewkt
    -------------------------
     LINESTRING(1 2 3,3 4 5)

Create a line from two disjoint LineStrings.

     select ST_AsText( ST_MakeLine( 'LINESTRING(0 0, 1 1)', 'LINESTRING(2 2, 3 3)' ) );

              st_astext
    -----------------------------
     LINESTRING(0 0,1 1,2 2,3 3)

## Examples: Array variant

Create a line from an array formed by a subquery with ordering.

    SELECT ST_MakeLine( ARRAY( SELECT ST_Centroid(geom) FROM visit_locations ORDER BY visit_time) );

Create a 3D line from an array of 3D points

    SELECT ST_AsEWKT( ST_MakeLine(
              ARRAY[ ST_MakePoint(1,2,3), ST_MakePoint(3,4,5), ST_MakePoint(6,6,6) ]  ));

    		st_asewkt
    -------------------------
    LINESTRING(1 2 3,3 4 5,6 6 6)

## Examples: Aggregate variant

This example queries time-based sequences of GPS points from a set of tracks and creates one record for each track. The result geometries are LineStrings composed of the GPS track points in the order of travel.

Using aggregate `ORDER BY` provides a correctly-ordered LineString.

    SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) As geom
    	FROM gps_points As gps
    	GROUP BY track_id;

Prior to PostgreSQL 9, ordering in a subquery can be used. However, sometimes the query plan may not respect the order of the subquery.

    SELECT gps.track_id, ST_MakeLine(gps.geom) As geom
    	FROM ( SELECT track_id, gps_time, geom
    			FROM gps_points ORDER BY track_id, gps_time ) As gps
    	GROUP BY track_id;

## See Also

ST_RemoveRepeatedPoints, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_MakePoint, ST_Point

## Name

ST_MakePoint — Creates a 2D, 3DZ or 4D Point.

## Synopsis

`geometry ST_MakePoint(` float x, float y`)`;

`geometry ST_MakePoint(` float x, float y, float z`)`;

`geometry ST_MakePoint(` float x, float y, float z, float m`)`;

## Description

Creates a 2D XY, 3D XYZ or 4D XYZM Point geometry. Use ST_MakePointM to make points with XYM coordinates.

Use ST_SetSRID to specify a SRID for the created point.

While not OGC-compliant, `ST_MakePoint` is faster and more precise than ST_GeomFromText and ST_PointFromText. It is also easier to use for numeric coordinate values.

For geodetic coordinates, `X` is longitude and `Y` is latitude

The functions ST_Point, ST_PointZ, ST_PointM, and ST_PointZM can be used to create points with a given SRID.

This function supports 3d and will not drop the z-index.

## Examples

    -- Create a point with unknown SRID
    SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

    -- Create a point in the WGS 84 geodetic CRS
    SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

    -- Create a 3D point (e.g. has altitude)
    SELECT ST_MakePoint(1, 2,1.5);

    -- Get z of point
    SELECT ST_Z(ST_MakePoint(1, 2,1.5));
    result
    -------
    1.5

## See Also

ST_GeomFromText, ST_PointFromText, ST_SetSRID, ST_MakePointM, ST_Point, ST_PointZ, ST_PointM, ST_PointZM

## Name

ST_MakePointM — Creates a Point from X, Y and M values.

## Synopsis

`geometry ST_MakePointM(` float x, float y, float m`)`;

## Description

Creates a point with X, Y and M (measure) ordinates. Use ST_MakePoint to make points with XY, XYZ, or XYZM coordinates.

Use ST_SetSRID to specify a SRID for the created point.

For geodetic coordinates, `X` is longitude and `Y` is latitude

The functions ST_PointM, and ST_PointZM can be used to create points with an M value and a given SRID.

## Examples

ST_AsEWKT is used for text output because ST_AsText does not support M values.

Create point with unknown SRID.

    SELECT ST_AsEWKT(  ST_MakePointM(-71.1043443253471, 42.3150676015829, 10)  );

    				   st_asewkt
    -----------------------------------------------
     POINTM(-71.1043443253471 42.3150676015829 10)

Create point with a measure in the WGS 84 geodetic coordinate system.

    SELECT ST_AsEWKT( ST_SetSRID(  ST_MakePointM(-71.104, 42.315, 10),  4326));

    						st_asewkt
    ---------------------------------------------------------
    SRID=4326;POINTM(-71.104 42.315 10)

Get measure of created point.

    SELECT ST_M(  ST_MakePointM(-71.104, 42.315, 10)  );

    result
    -------
    10

## See Also

ST_MakePoint, ST_SetSRID, ST_PointM, ST_PointZM

## Name

ST_MakePolygon — Creates a Polygon from a shell and optional list of holes.

## Synopsis

`geometry ST_MakePolygon(` geometry linestring`)`;

`geometry ST_MakePolygon(` geometry outerlinestring, geometry[] interiorlinestrings`)`;

## Description

Creates a Polygon formed by the given shell and optional array of holes. Input geometries must be closed LineStrings (rings).

Variant 1: Accepts one shell LineString.

Variant 2: Accepts a shell LineString and an array of inner (hole) LineStrings. A geometry array can be constructed using the PostgreSQL array_agg(), ARRAY[] or ARRAY() constructs.

This function does not accept MultiLineStrings. Use ST_LineMerge to generate a LineString, or ST_Dump to extract LineStrings.

This function supports 3d and will not drop the z-index.

## Examples: Single input variant

Create a Polygon from a 2D LineString.

    SELECT ST_MakePolygon( ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)'));

Create a Polygon from an open LineString, using ST_StartPoint and ST_AddPoint to close it.

    SELECT ST_MakePolygon( ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)) )
    FROM (
      SELECT ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)') As open_line) As foo;

Create a Polygon from a 3D LineString

    SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

    st_asewkt
    -----------
    POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))

Create a Polygon from a LineString with measures

    SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)' ));

    st_asewkt
    ----------
    POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))

## Examples: Outer shell with inner holes variant

Create a donut Polygon with an extra hole

    SELECT ST_MakePolygon( ST_ExteriorRing( ST_Buffer(ring.line,10)),
    	ARRAY[  ST_Translate(ring.line, 1, 1),
    		ST_ExteriorRing(ST_Buffer(ST_Point(20,20),1)) ]
    	)
    FROM (SELECT ST_ExteriorRing(
    	ST_Buffer(ST_Point(10,10),10,10)) AS line ) AS ring;

Create a set of province boundaries with holes representing lakes. The input is a table of province Polygons/MultiPolygons and a table of water linestrings. Lines forming lakes are determined by using ST_IsClosed. The province linework is extracted by using ST_Boundary. As required by `ST_MakePolygon`, the boundary is forced to be a single LineString by using ST_LineMerge. (However, note that if a province has more than one region or has islands this will produce an invalid polygon.) Using a LEFT JOIN ensures all provinces are included even if they have no lakes.

The CASE construct is used because passing a null array into ST_MakePolygon results in a NULL return value.

    SELECT p.gid, p.province_name,
    	CASE WHEN array_agg(w.geom) IS NULL
    	THEN p.geom
    	ELSE  ST_MakePolygon( ST_LineMerge(ST_Boundary(p.geom)),
                            array_agg(w.geom)) END
    FROM
    	provinces p LEFT JOIN waterlines w
    		ON (ST_Within(w.geom, p.geom) AND ST_IsClosed(w.geom))
    GROUP BY p.gid, p.province_name, p.geom;

Another technique is to utilize a correlated subquery and the ARRAY() constructor that converts a row set to an array.

    SELECT p.gid,  p.province_name,
        CASE WHEN EXISTS( SELECT w.geom
            FROM waterlines w
            WHERE ST_Within(w.geom, p.geom)
            AND ST_IsClosed(w.geom))
        THEN ST_MakePolygon(
            ST_LineMerge(ST_Boundary(p.geom)),
            ARRAY( SELECT w.geom
                FROM waterlines w
                WHERE ST_Within(w.geom, p.geom)
                AND ST_IsClosed(w.geom)))
        ELSE p.geom
        END AS geom
    FROM provinces p;

## See Also

ST_BuildArea ST_Polygon

## Name

ST_Point — Creates a Point with X, Y and SRID values.

## Synopsis

`geometry ST_Point(` float x, float y`)`;

`geometry ST_Point(` float x, float y, integer srid=unknown`)`;

## Description

Returns a Point with the given X and Y coordinate values. This is the SQL-MM equivalent for ST_MakePoint that takes just X and Y.

For geodetic coordinates, `X` is longitude and `Y` is latitude

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.2

## Examples: Geometry

    SELECT ST_Point( -71.104, 42.315);

Creating a point with SRID specified:

    SELECT ST_Point( -71.104, 42.315, 4326);

Alternative way of specifying SRID:

    SELECT ST_SetSRID( ST_Point( -71.104, 42.315), 4326);

## Examples: Geography

Create geography points using the `::` cast syntax:

    SELECT ST_Point( -71.104, 42.315, 4326)::geography;

Pre-PostGIS 3.2 code, using `CAST`:

    SELECT CAST( ST_SetSRID(ST_Point( -71.104, 42.315), 4326) AS geography);

If the point coordinates are not in a geodetic coordinate system (such as WGS84), then they must be reprojected before casting to a geography. In this example a point in Pennsylvania State Plane feet (SRID 2273) is projected to WGS84 (SRID 4326).

    SELECT ST_Transform( ST_Point( 3637510, 3014852, 2273), 4326)::geography;

## See Also

ST_MakePoint, ST_PointZ, ST_PointM, ST_PointZM, ST_SetSRID, ST_Transform

## Name

ST_PointZ — Creates a Point with X, Y, Z and SRID values.

## Synopsis

`geometry ST_PointZ(` float x, float y, float z, integer srid=unknown`)`;

## Description

Returns an Point with the given X, Y and Z coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

## Examples

    SELECT ST_PointZ(-71.104, 42.315, 3.4, 4326)

    SELECT ST_PointZ(-71.104, 42.315, 3.4, srid => 4326)

    SELECT ST_PointZ(-71.104, 42.315, 3.4)

## See Also

ST_MakePoint, ST_Point, ST_PointM, ST_PointZM

## Name

ST_PointM — Creates a Point with X, Y, M and SRID values.

## Synopsis

`geometry ST_PointM(` float x, float y, float m, integer srid=unknown`)`;

## Description

Returns an Point with the given X, Y and M coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

## Examples

    SELECT ST_PointM(-71.104, 42.315, 3.4, 4326)

    SELECT ST_PointM(-71.104, 42.315, 3.4, srid => 4326)

    SELECT ST_PointM(-71.104, 42.315, 3.4)

## See Also

ST_MakePoint, ST_Point, ST_PointZ, ST_PointZM

## Name

ST_PointZM — Creates a Point with X, Y, Z, M and SRID values.

## Synopsis

`geometry ST_PointZM(` float x, float y, float z, float m, integer srid=unknown`)`;

## Description

Returns an Point with the given X, Y, Z and M coordinate values, and optionally an SRID number.

Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.

## Examples

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, 4326)

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, srid => 4326)

    SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5)

## See Also

ST_MakePoint, ST_Point, ST_PointM, ST_PointZ, ST_SetSRID

## Name

ST_Polygon — Creates a Polygon from a LineString with a specified SRID.

## Synopsis

`geometry ST_Polygon(` geometry lineString, integer srid`)`;

## Description

Returns a polygon built from the given LineString and sets the spatial reference system from the `srid`.

ST_Polygon is similar to ST_MakePolygon Variant 1 with the addition of setting the SRID.

To create polygons with holes use ST_MakePolygon Variant 2 and then ST_SetSRID.

This function does not accept MultiLineStrings. Use ST_LineMerge to generate a LineString, or ST_Dump to extract LineStrings.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.3.2

This function supports 3d and will not drop the z-index.

## Examples

Create a 2D polygon.

    SELECT ST_AsText( ST_Polygon('LINESTRING(75 29, 77 29, 77 29, 75 29)'::geometry, 4326) );

    -- result --
    POLYGON((75 29, 77 29, 77 29, 75 29))

Create a 3D polygon.

    SELECT ST_AsEWKT( ST_Polygon( ST_GeomFromEWKT('LINESTRING(75 29 1, 77 29 2, 77 29 3, 75 29 1)'), 4326) );

    -- result --
    SRID=4326;POLYGON((75 29 1, 77 29 2, 77 29 3, 75 29 1))

## See Also

ST_AsEWKT, ST_AsText, ST_GeomFromEWKT, ST_GeomFromText, ST_LineMerge, ST_MakePolygon

## Name

ST_TileEnvelope — Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.

## Synopsis

`geometry ST_TileEnvelope(` integer tileZoom, integer tileX, integer tileY, geometry bounds=SRID=3857;LINESTRING(-20037508.342789 -20037508.342789,20037508.342789 20037508.342789), float margin=0.0`)`;

## Description

Creates a rectangular Polygon giving the extent of a tile in the XYZ tile system. The tile is specified by the zoom level Z and the XY index of the tile in the grid at that level. Can be used to define the tile bounds required by ST_AsMVTGeom to convert geometry into the MVT tile coordinate space.

By default, the tile envelope is in the Web Mercator coordinate system (SRID:3857) using the standard range of the Web Mercator system (-20037508.342789, 20037508.342789). This is the most common coordinate system used for MVT tiles. The optional `bounds` parameter can be used to generate tiles in any coordinate system. It is a geometry that has the SRID and extent of the "Zoom Level zero" square within which the XYZ tile system is inscribed.

The optional `margin` parameter can be used to expand a tile by the given percentage. E.g. `margin=0.125` expands the tile by 12.5%, which is equivalent to buffer=512 when the tile extent size is 4096, as used in ST_AsMVTGeom. This is useful to create a tile buffer to include data lying outside of the tile's visible area, but whose existence affects the tile rendering. For example, a city name (a point) could be near an edge of a tile, so its label should be rendered on two tiles, even though the point is located in the visible area of just one tile. Using expanded tiles in a query will include the city point in both tiles. Use a negative value to shrink the tile instead. Values less than -0.5 are prohibited because that would eliminate the tile completely. Do not specify a margin when using with `ST_AsMVTGeom`. See the example for ST_AsMVT.

Enhanced: 3.1.0 Added margin parameter.

Availability: 3.0.0

## Example: Building a tile envelope

    SELECT ST_AsText( ST_TileEnvelope(2, 1, 1) );

     st_astext
    ------------------------------
     POLYGON((-10018754.1713945 0,-10018754.1713945 10018754.1713945,0 10018754.1713945,0 0,-10018754.1713945 0))

    SELECT ST_AsText( ST_TileEnvelope(3, 1, 1, ST_MakeEnvelope(-180, -90, 180, 90, 4326) ) );

                          st_astext
    ------------------------------------------------------
     POLYGON((-135 45,-135 67.5,-90 67.5,-90 45,-135 45))

## See Also

ST_MakeEnvelope

## Name

ST_HexagonGrid — Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.

## Synopsis

`setof record ST_HexagonGrid(` float8 size, geometry bounds`)`;

## Description

Starts with the concept of a hexagon tiling of the plane. (Not a hexagon tiling of the globe, this is not the H3 tiling scheme.) For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique hexagonal tiling of the plane, Tiling(SRS, Size). This function answers the question: what hexagons in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output hexagons is the SRS provided by the bounds geometry.

Doubling or tripling the edge size of the hexagon generates a new parent tiling that fits with the origin tiling. Unfortunately, it is not possible to generate parent hexagon tilings that the child tiles perfectly fit inside.

Availability: 3.1.0

## Example: Counting points in hexagons

To do a point summary against a hexagonal tiling, generate a hexagon grid using the extent of the points as the bounds, then spatially join to that grid.

    SELECT COUNT(*), hexes.geom
    FROM
        ST_HexagonGrid(
            10000,
            ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
        ) AS hexes
        INNER JOIN
        pointtable AS pts
        ON ST_Intersects(pts.geom, hexes.geom)
    GROUP BY hexes.geom;

## Example: Generating hex coverage of polygons

If we generate a set of hexagons for each polygon boundary and filter out those that do not intersect their hexagons, we end up with a tiling for each polygon.

Tiling states results in a hexagon coverage of each state, and multiple hexagons overlapping at the borders between states.

The LATERAL keyword is implied for set-returning functions when referring to a prior table in the FROM list. So CROSS JOIN LATERAL, CROSS JOIN, or just plain , are equivalent constructs for this example.

    SELECT admin1.gid, hex.geom
    FROM
        admin1
        CROSS JOIN
        ST_HexagonGrid(100000, admin1.geom) AS hex
    WHERE
        adm0_a3 = 'USA'
        AND
        ST_Intersects(admin1.geom, hex.geom)

## See Also

ST_EstimatedExtent, ST_SetSRID, ST_SquareGrid, ST_TileEnvelope

## Name

ST_Hexagon — Returns a single hexagon, using the provided edge size and cell coordinate within the hexagon grid space.

## Synopsis

`geometry ST_Hexagon(` float8 size, integer cell_i, integer cell_j, geometry origin`)`;

## Description

Uses the same hexagon tiling concept as ST_HexagonGrid, but generates just one hexagon at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Hexagons are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Availability: 3.1.0

## Example: Creating a hexagon at the origin

    SELECT ST_AsText(ST_SetSRID(ST_Hexagon(1.0, 0, 0), 3857));

    POLYGON((-1 0,-0.5
             -0.866025403784439,0.5
             -0.866025403784439,1
             0,0.5
             0.866025403784439,-0.5
             0.866025403784439,-1 0))

## See Also

ST_TileEnvelope, ST_HexagonGrid, ST_Square

## Name

ST_SquareGrid — Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.

## Synopsis

`setof record ST_SquareGrid(` float8 size, geometry bounds`)`;

## Description

Starts with the concept of a square tiling of the plane. For a given planar SRS, and a given edge size, starting at the origin of the SRS, there is one unique square tiling of the plane, Tiling(SRS, Size). This function answers the question: what grids in a given Tiling(SRS, Size) overlap with a given bounds.

The SRS for the output squares is the SRS provided by the bounds geometry.

Doubling or edge size of the square generates a new parent tiling that perfectly fits with the original tiling. Standard web map tilings in mercator are just powers-of-two square grids in the mercator plane.

Availability: 3.1.0

## Example: Generating a 1 degree grid for a country

The grid will fill the whole bounds of the country, so if you want just squares that touch the country you will have to filter afterwards with ST_Intersects.

    WITH grid AS (
    SELECT (ST_SquareGrid(1, ST_Transform(geom,4326))).*
    FROM admin0 WHERE name = 'Canada'
    )
      SELEcT ST_AsText(geom)
      FROM grid

## Example: Counting points in squares (using single chopped grid)

To do a point summary against a square tiling, generate a square grid using the extent of the points as the bounds, then spatially join to that grid. Note the estimated extent might be off from actual extent, so be cautious and at very least make sure you've analyzed your table.

    SELECT COUNT(*), squares.geom
        FROM
        pointtable AS pts
        INNER JOIN
        ST_SquareGrid(
            1000,
            ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
        ) AS squares
        ON ST_Intersects(pts.geom, squares.geom)
        GROUP BY squares.geom

## Example: Counting points in squares using set of grid per point

This yields the same result as the first example but will be slower for a large number of points

    SELECT COUNT(*), squares.geom
        FROM
        pointtable AS pts
        INNER JOIN
        ST_SquareGrid(
            1000,
           pts.geom
        ) AS squares
        ON ST_Intersects(pts.geom, squares.geom)
        GROUP BY squares.geom

## See Also

ST_TileEnvelope, ST_HexagonGrid , ST_EstimatedExtent , ST_SetSRID

## Name

ST_Square — Returns a single square, using the provided edge size and cell coordinate within the square grid space.

## Synopsis

`geometry ST_Square(` float8 size, integer cell_i, integer cell_j, geometry origin`)`;

## Description

Uses the same square tiling concept as ST_SquareGrid, but generates just one square at the desired cell coordinate. Optionally, can adjust origin coordinate of the tiling, the default origin is at 0,0.

Squares are generated with no SRID set, so use ST_SetSRID to set the SRID to the one you expect.

Availability: 3.1.0

## Example: Creating a square at the origin

    SELECT ST_AsText(ST_SetSRID(ST_Square(1.0, 0, 0), 3857));

     POLYGON((0 0,0 1,1 1,1 0,0 0))

## See Also

ST_TileEnvelope, ST_SquareGrid, ST_Hexagon

## Name

ST_Letters — Returns the input letters rendered as geometry with a default start position at the origin and default text height of 100.

## Synopsis

`geometry ST_Letters(` text letters, json font`)`;

## Description

Uses a built-in font to render out a string as a multipolygon geometry. The default text height is 100.0, the distance from the bottom of a descender to the top of a capital. The default start position places the start of the baseline at the origin. Over-riding the font involves passing in a json map, with a character as the key, and base64 encoded TWKB for the font shape, with the fonts having a height of 1000 units from the bottom of the descenders to the tops of the capitals.

The text is generated at the origin by default, so to reposition and resize the text, first apply the `ST_Scale` function and then apply the `ST_Translate` function.

Availability: 3.3.0

## Example: Generating the word 'Yo'

    SELECT ST_AsText(ST_Letters('Yo'), 1);

Letters generated by ST_Letters

## Example: Scaling and moving words

    SELECT ST_Translate(ST_Scale(ST_Letters('Yo'), 10, 10), 100,100);

## See Also

ST_AsTWKB, ST_Scale, ST_Translate

## 7.4. Geometry Accessors

## Name

GeometryType — Returns the type of a geometry as text.

## Synopsis

`text GeometryType(` geometry geomA`)`;

## Description

Returns the type of the geometry as a string. Eg: 'LINESTRING', 'POLYGON', 'MULTIPOINT', etc.

OGC SPEC s2.1.1.1 - Returns the name of the instantiable subtype of Geometry of which this Geometry instance is a member. The name of the instantiable subtype of Geometry is returned as a string.

This function also indicates if the geometry is measured, by returning a string of the form 'POINTM'.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
     geometrytype
    --------------
     LINESTRING

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			POLYHEDRALSURFACE

    SELECT GeometryType(geom) as result
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
     result
    --------
     TIN

## See Also

ST_GeometryType

## Name

ST_Boundary — Returns the boundary of a geometry.

## Synopsis

`geometry ST_Boundary(` geometry geomA`)`;

## Description

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Performed by the GEOS module

Prior to 2.0.0, this function throws an exception if used with `GEOMETRYCOLLECTION`. From 2.0.0 up it will return NULL instead (unsupported input).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1.17

This function supports 3d and will not drop the z-index.

Enhanced: 2.1.0 support for Triangle was introduced

Changed: 3.2.0 support for TIN, does not use geos, does not linearize curves

## Examples

Linestring with boundary points overlaid
    SELECT ST_Boundary(geom)
    FROM (SELECT 'LINESTRING(100 150,50 60, 70 80, 160 170)'::geometry As geom) As f;
    ST_AsText output

    MULTIPOINT((100 150),(160 170))
| polygon holes with boundary multilinestring
    SELECT ST_Boundary(geom)
    FROM (SELECT
    'POLYGON (( 10 130, 50 190, 110 190, 140 150, 150 80, 100 10, 20 40, 10 130 ),
    	( 70 40, 100 50, 120 80, 80 110, 50 90, 70 40 ))'::geometry As geom) As f;
    ST_AsText output

    MULTILINESTRING((10 130,50 190,110 190,140 150,150 80,100 10,20 40,10 130),
    	(70 40,100 50,120 80,80 110,50 90,70 40))

    SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)')));
    st_astext
    -----------
    MULTIPOINT((1 1),(-1 1))

    SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))')));
    st_astext
    ----------
    LINESTRING(1 1,0 0,-1 1,1 1)

    --Using a 3d polygon
    SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))')));

    st_asewkt
    -----------------------------------
    LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

    --Using a 3d multilinestring
    SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )')));

    st_asewkt
    ----------
    MULTIPOINT((-1 1 1),(1 1 0.75))

## See Also

ST_AsText, ST_ExteriorRing, ST_MakePolygon

## Name

ST_BoundingDiagonal — Returns the diagonal of a geometry's bounding box.

## Synopsis

`geometry ST_BoundingDiagonal(` geometry geom, boolean fits=false`)`;

## Description

Returns the diagonal of the supplied geometry's bounding box as a LineString. The diagonal is a 2-point LineString with the minimum values of each dimension in its start point and the maximum values in its end point. If the input geometry is empty, the diagonal line is a LINESTRING EMPTY.

The optional `fits` parameter specifies if the best fit is needed. If false, the diagonal of a somewhat larger bounding box can be accepted (which is faster to compute for geometries with many vertices). In either case, the bounding box of the returned diagonal line always covers the input geometry.

The returned geometry retains the SRID and dimensionality (Z and M presence) of the input geometry.

In degenerate cases (i.e. a single vertex in input) the returned linestring will be formally invalid (no interior). The result is still topologically valid.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

    -- Get the minimum X in a buffer around a point
    SELECT ST_X(ST_StartPoint(ST_BoundingDiagonal(
      ST_Buffer(ST_Point(0,0),10)
    )));
     st_x
    ------
      -10

## See Also

ST_StartPoint, ST_EndPoint, ST_X, ST_Y, ST_Z, ST_M, ST_Envelope

## Name

ST_CoordDim — Return the coordinate dimension of a geometry.

## Synopsis

`integer ST_CoordDim(` geometry geomA`)`;

## Description

Return the coordinate dimension of the ST_Geometry value.

This is the MM compliant alias name for ST_NDims

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.3

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_CoordDim('CIRCULARSTRING(1 2 3, 1 3 4, 5 6 7, 8 9 10, 11 12 13)');
    			---result--
    				3

    				SELECT ST_CoordDim(ST_Point(1,2));
    			--result--
    				2

## See Also

ST_NDims

## Name

ST_Dimension — Returns the topological dimension of a geometry.

## Synopsis

`integer ST_Dimension(` geometry g`)`;

## Description

Return the topological dimension of this Geometry object, which must be less than or equal to the coordinate dimension. OGC SPEC s2.1.1.1 - returns 0 for `POINT`, 1 for `LINESTRING`, 2 for `POLYGON`, and the largest dimension of the components of a `GEOMETRYCOLLECTION`. If the dimension is unknown (e.g. for an empty `GEOMETRYCOLLECTION`) 0 is returned.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.2

Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry.

Prior to 2.0.0, this function throws an exception if used with empty geometry.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_Dimension('GEOMETRYCOLLECTION(LINESTRING(1 1,0 0),POINT(0 0))');
    ST_Dimension
    -----------
    1

## See Also

ST_NDims

## Name

ST_Dump — Returns a set of `geometry_dump` rows for the components of a geometry.

## Synopsis

`geometry_dump[] ST_Dump(` geometry g1`)`;

## Description

A set-returning function (SRF) that extracts the components of a geometry. It returns a set of geometry_dump rows, each containing a geometry (`geom` field) and an array of integers (`path` field).

For an atomic geometry type (POINT,LINESTRING,POLYGON) a single record is returned with an empty `path` array and the input geometry as `geom`. For a collection or multi-geometry a record is returned for each of the collection components, and the `path` denotes the position of the component inside the collection.

ST_Dump is useful for expanding geometries. It is the inverse of a ST_Collect / GROUP BY, in that it creates new rows. For example it can be use to expand MULTIPOLYGONS into POLYGONS.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: PostGIS 1.0.0RC1. Requires PostgreSQL 7.3 or higher.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Standard Examples

    SELECT sometable.field1, sometable.field1,
          (ST_Dump(sometable.geom)).geom AS geom
    FROM sometable;

    -- Break a compound curve into its constituent linestrings and circularstrings
    SELECT ST_AsEWKT(a.geom), ST_HasArc(a.geom)
      FROM ( SELECT (ST_Dump(p_geom)).geom AS geom
             FROM (SELECT ST_GeomFromEWKT('COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 0 1))') AS p_geom) AS b
            ) AS a;
              st_asewkt          | st_hasarc
    -----------------------------+----------
     CIRCULARSTRING(0 0,1 1,1 0) | t
     LINESTRING(1 0,0 1)         | f
    (2 rows)

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface example
    -- Break a Polyhedral surface into its faces
    SELECT (a.p_geom).path[1] As path, ST_AsEWKT((a.p_geom).geom) As geom_ewkt
      FROM (SELECT ST_Dump(ST_GeomFromEWKT('POLYHEDRALSURFACE(
    ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),  ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),  ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )') ) AS p_geom )  AS a;

     path |                geom_ewkt
    ------+------------------------------------------
        1 | POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0))
        2 | POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))
        3 | POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))
        4 | POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0))
        5 | POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0))
        6 | POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))

    -- TIN --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_Dump( ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )') ) AS gdump
        ) AS g;
    -- result --
     path |                 wkt
    ------+-------------------------------------
     {1}  | TRIANGLE((0 0 0,0 0 1,0 1 0,0 0 0))
     {2}  | TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

## See Also

geometry_dump, Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Collect, ST_GeometryN

## Name

ST_DumpPoints — Returns a set of `geometry_dump` rows for the coordinates in a geometry.

## Synopsis

`geometry_dump[] ST_DumpPoints(` geometry geom`)`;

## Description

A set-returning function (SRF) that extracts the coordinates (vertices) of a geometry. It returns a set of geometry_dump rows, each containing a geometry (`geom` field) and an array of integers (`path` field).

- the `geom` field `POINT`s represent the coordinates of the supplied geometry.

- the `path` field (an `integer[]`) is an index enumerating the coordinate positions in the elements of the supplied geometry. The indices are 1-based. For example, for a `LINESTRING` the paths are `{i}` where `i` is the `nth` coordinate in the `LINESTRING`. For a `POLYGON` the paths are `{i,j}` where `i` is the ring number (1 is outer; inner rings follow) and `j` is the coordinate position in the ring.

To obtain a single geometry containing the coordinates use ST_Points.

Enhanced: 2.1.0 Faster speed. Reimplemented as native-C.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.5.0

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Classic Explode a Table of LineStrings into nodes

    SELECT edge_id, (dp).path[1] As index, ST_AsText((dp).geom) As wktnode
    FROM (SELECT 1 As edge_id
    	, ST_DumpPoints(ST_GeomFromText('LINESTRING(1 2, 3 4, 10 10)')) AS dp
         UNION ALL
         SELECT 2 As edge_id
    	, ST_DumpPoints(ST_GeomFromText('LINESTRING(3 5, 5 6, 9 10)')) AS dp
       ) As foo;
     edge_id | index |    wktnode
    ---------+-------+--------------
           1 |     1 | POINT(1 2)
           1 |     2 | POINT(3 4)
           1 |     3 | POINT(10 10)
           2 |     1 | POINT(3 5)
           2 |     2 | POINT(5 6)
           2 |     3 | POINT(9 10)

## Standard Geometry Examples

    SELECT path, ST_AsText(geom)
    FROM (
      SELECT (ST_DumpPoints(g.geom)).*
      FROM
        (SELECT
           'GEOMETRYCOLLECTION(
              POINT ( 0 1 ),
              LINESTRING ( 0 3, 3 4 ),
              POLYGON (( 2 0, 2 3, 0 2, 2 0 )),
              POLYGON (( 3 0, 3 3, 6 3, 6 0, 3 0 ),
                       ( 5 1, 4 2, 5 2, 5 1 )),
              MULTIPOLYGON (
                      (( 0 5, 0 8, 4 8, 4 5, 0 5 ),
                       ( 1 6, 3 6, 2 7, 1 6 )),
                      (( 5 4, 5 8, 6 7, 5 4 ))
              )
            )'::geometry AS geom
        ) AS g
      ) j;

       path    | st_astext
    -----------+------------
     {1,1}     | POINT(0 1)
     {2,1}     | POINT(0 3)
     {2,2}     | POINT(3 4)
     {3,1,1}   | POINT(2 0)
     {3,1,2}   | POINT(2 3)
     {3,1,3}   | POINT(0 2)
     {3,1,4}   | POINT(2 0)
     {4,1,1}   | POINT(3 0)
     {4,1,2}   | POINT(3 3)
     {4,1,3}   | POINT(6 3)
     {4,1,4}   | POINT(6 0)
     {4,1,5}   | POINT(3 0)
     {4,2,1}   | POINT(5 1)
     {4,2,2}   | POINT(4 2)
     {4,2,3}   | POINT(5 2)
     {4,2,4}   | POINT(5 1)
     {5,1,1,1} | POINT(0 5)
     {5,1,1,2} | POINT(0 8)
     {5,1,1,3} | POINT(4 8)
     {5,1,1,4} | POINT(4 5)
     {5,1,1,5} | POINT(0 5)
     {5,1,2,1} | POINT(1 6)
     {5,1,2,2} | POINT(3 6)
     {5,1,2,3} | POINT(2 7)
     {5,1,2,4} | POINT(1 6)
     {5,2,1,1} | POINT(5 4)
     {5,2,1,2} | POINT(5 8)
     {5,2,1,3} | POINT(6 7)
     {5,2,1,4} | POINT(5 4)
    (29 rows)

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface cube --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )') ) AS gdump
        ) AS g;
    -- result --
      path   |     wkt
    ---------+--------------
     {1,1,1} | POINT(0 0 0)
     {1,1,2} | POINT(0 0 1)
     {1,1,3} | POINT(0 1 1)
     {1,1,4} | POINT(0 1 0)
     {1,1,5} | POINT(0 0 0)
     {2,1,1} | POINT(0 0 0)
     {2,1,2} | POINT(0 1 0)
     {2,1,3} | POINT(1 1 0)
     {2,1,4} | POINT(1 0 0)
     {2,1,5} | POINT(0 0 0)
     {3,1,1} | POINT(0 0 0)
     {3,1,2} | POINT(1 0 0)
     {3,1,3} | POINT(1 0 1)
     {3,1,4} | POINT(0 0 1)
     {3,1,5} | POINT(0 0 0)
     {4,1,1} | POINT(1 1 0)
     {4,1,2} | POINT(1 1 1)
     {4,1,3} | POINT(1 0 1)
     {4,1,4} | POINT(1 0 0)
     {4,1,5} | POINT(1 1 0)
     {5,1,1} | POINT(0 1 0)
     {5,1,2} | POINT(0 1 1)
     {5,1,3} | POINT(1 1 1)
     {5,1,4} | POINT(1 1 0)
     {5,1,5} | POINT(0 1 0)
     {6,1,1} | POINT(0 0 1)
     {6,1,2} | POINT(1 0 1)
     {6,1,3} | POINT(1 1 1)
     {6,1,4} | POINT(0 1 1)
     {6,1,5} | POINT(0 0 1)
    (30 rows)

    -- Triangle --
    SELECT (g.gdump).path, ST_AsText((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints( ST_GeomFromEWKT('TRIANGLE ((
                    0 0,
                    0 9,
                    9 0,
                    0 0
                ))') ) AS gdump
        ) AS g;
    -- result --
     path |    wkt
    ------+------------
     {1}  | POINT(0 0)
     {2}  | POINT(0 9)
     {3}  | POINT(9 0)
     {4}  | POINT(0 0)

    -- TIN --
    SELECT (g.gdump).path, ST_AsEWKT((g.gdump).geom) as wkt
      FROM
        (SELECT
           ST_DumpPoints( ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )') ) AS gdump
        ) AS g;
    -- result --
      path   |     wkt
    ---------+--------------
     {1,1,1} | POINT(0 0 0)
     {1,1,2} | POINT(0 0 1)
     {1,1,3} | POINT(0 1 0)
     {1,1,4} | POINT(0 0 0)
     {2,1,1} | POINT(0 0 0)
     {2,1,2} | POINT(0 1 0)
     {2,1,3} | POINT(1 1 0)
     {2,1,4} | POINT(0 0 0)
    (8 rows)

## See Also

geometry_dump, Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Dump, ST_DumpRings, ST_Points

## Name

ST_DumpSegments — Returns a set of `geometry_dump` rows for the segments in a geometry.

## Synopsis

`geometry_dump[] ST_DumpSegments(` geometry geom`)`;

## Description

A set-returning function (SRF) that extracts the segments of a geometry. It returns a set of geometry_dump rows, each containing a geometry (`geom` field) and an array of integers (`path` field).

- the `geom` field `LINESTRING`s represent the linear segments of the supplied geometry, while the `CIRCULARSTRING`s represent the arc segments.

- the `path` field (an `integer[]`) is an index enumerating the segment start point positions in the elements of the supplied geometry. The indices are 1-based. For example, for a `LINESTRING` the paths are `{i}` where `i` is the `nth` segment start point in the `LINESTRING`. For a `POLYGON` the paths are `{i,j}` where `i` is the ring number (1 is outer; inner rings follow) and `j` is the segment start point position in the ring.

Availability: 3.2.0

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Standard Geometry Examples

    SELECT path, ST_AsText(geom)
    FROM (
        SELECT (ST_DumpSegments(g.geom)).*
        FROM (SELECT 'GEOMETRYCOLLECTION(
        LINESTRING(1 1, 3 3, 4 4),
        POLYGON((5 5, 6 6, 7 7, 5 5))
    )'::geometry AS geom
            ) AS g
    ) j;

      path   │      st_astext
    ---------------------------------
     {1,1}   │ LINESTRING(1 1,3 3)
     {1,2}   │ LINESTRING(3 3,4 4)
     {2,1,1} │ LINESTRING(5 5,6 6)
     {2,1,2} │ LINESTRING(6 6,7 7)
     {2,1,3} │ LINESTRING(7 7,5 5)
    (5 rows)

## TIN and Triangle Examples

    -- Triangle --
    SELECT path, ST_AsText(geom)
    FROM (
        SELECT (ST_DumpSegments(g.geom)).*
        FROM (SELECT 'TRIANGLE((
            0 0,
            0 9,
            9 0,
            0 0
        ))'::geometry AS geom
            ) AS g
    ) j;

     path  │      st_astext
     ---------------------------------
     {1,1} │ LINESTRING(0 0,0 9)
     {1,2} │ LINESTRING(0 9,9 0)
     {1,3} │ LINESTRING(9 0,0 0)
    (3 rows)

    -- TIN --
    SELECT path, ST_AsEWKT(geom)
    FROM (
        SELECT (ST_DumpSegments(g.geom)).*
        FROM (SELECT 'TIN(((
            0 0 0,
            0 0 1,
            0 1 0,
            0 0 0
        )), ((
            0 0 0,
            0 1 0,
            1 1 0,
            0 0 0
        ))
        )'::geometry AS geom
            ) AS g
    ) j;

      path   │        st_asewkt
      ---------------------------------
     {1,1,1} │ LINESTRING(0 0 0,0 0 1)
     {1,1,2} │ LINESTRING(0 0 1,0 1 0)
     {1,1,3} │ LINESTRING(0 1 0,0 0 0)
     {2,1,1} │ LINESTRING(0 0 0,0 1 0)
     {2,1,2} │ LINESTRING(0 1 0,1 1 0)
     {2,1,3} │ LINESTRING(1 1 0,0 0 0)
    (6 rows)

## See Also

geometry_dump, Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Dump, ST_DumpRings

## Name

ST_DumpRings — Returns a set of `geometry_dump` rows for the exterior and interior rings of a Polygon.

## Synopsis

`geometry_dump[] ST_DumpRings(` geometry a_polygon`)`;

## Description

A set-returning function (SRF) that extracts the rings of a polygon. It returns a set of geometry_dump rows, each containing a geometry (`geom` field) and an array of integers (`path` field).

The `geom` field contains each ring as a POLYGON. The `path` field is an integer array of length 1 containing the polygon ring index. The exterior ring (shell) has index 0. The interior rings (holes) have indices of 1 and higher.

This only works for POLYGON geometries. It does not work for MULTIPOLYGONS

Availability: PostGIS 1.1.3. Requires PostgreSQL 7.3 or higher.

This function supports 3d and will not drop the z-index.

## Examples

General form of query.

    SELECT polyTable.field1, polyTable.field1,
    	  (ST_DumpRings(polyTable.geom)).geom As geom
    FROM polyTable;

A polygon with a single hole.

    SELECT path, ST_AsEWKT(geom) As geom
    	FROM ST_DumpRings(
    		ST_GeomFromEWKT('POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,-8148941 5132466 1,-8148924 5132394 1,
    		-8148903 5132210 1,-8148930 5131967 1,-8148992 5131978 1,-8149237 5132093 1,-8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,
    		-8150305 5132788 1,-8149064 5133092 1),
    		(-8149362 5132394 1,-8149446 5132501 1,-8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))')
    		)  as foo;
     path |                                            geom
    ----------------------------------------------------------------------------------------------------------------
      {0} | POLYGON((-8149064 5133092 1,-8149064 5132986 1,-8148996 5132839 1,-8148972 5132767 1,-8148958 5132508 1,
    	  |          -8148941 5132466 1,-8148924 5132394 1,
    	  |          -8148903 5132210 1,-8148930 5131967 1,
    	  |          -8148992 5131978 1,-8149237 5132093 1,
    	  |          -8149404 5132211 1,-8149647 5132310 1,-8149757 5132394 1,-8150305 5132788 1,-8149064 5133092 1))
      {1} | POLYGON((-8149362 5132394 1,-8149446 5132501 1,
    	  |          -8149548 5132597 1,-8149695 5132675 1,-8149362 5132394 1))

## See Also

geometry_dump, Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”, ST_Dump, ST_ExteriorRing, ST_InteriorRingN

## Name

ST_EndPoint — Returns the last point of a LineString or CircularLineString.

## Synopsis

`geometry ST_EndPoint(` geometry g`)`;

## Description

Returns the last point of a `LINESTRING` or `CIRCULARLINESTRING` geometry as a `POINT`. Returns `NULL` if the input is not a `LINESTRING` or `CIRCULARLINESTRING`.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.4

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Changed: 2.0.0 no longer works with single geometry MultiLineStrings. In older versions of PostGIS a single-line MultiLineString would work with this function and return the end point. In 2.0.0 it returns NULL like any other MultiLineString. The old behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0.0.

## Examples

End point of a LineString

    postgis=# SELECT ST_AsText(ST_EndPoint('LINESTRING(1 1, 2 2, 3 3)'::geometry));
     st_astext
    ------------
     POINT(3 3)

End point of a non-LineString is NULL

    SELECT ST_EndPoint('POINT(1 1)'::geometry) IS NULL AS is_null;
      is_null
    ----------
     t

End point of a 3D LineString

    --3d endpoint
    SELECT ST_AsEWKT(ST_EndPoint('LINESTRING(1 1 2, 1 2 3, 0 0 5)'));
      st_asewkt
    --------------
     POINT(0 0 5)

End point of a CircularString

    SELECT ST_AsText(ST_EndPoint('CIRCULARSTRING(5 2,-3 1.999999, -2 1, -4 2, 6 3)'::geometry));
     st_astext
    ------------
     POINT(6 3)

## See Also

ST_PointN, ST_StartPoint

## Name

ST_Envelope — Returns a geometry representing the bounding box of a geometry.

## Synopsis

`geometry ST_Envelope(` geometry g1`)`;

## Description

Returns the double-precision (float8) minimum bounding box for the supplied geometry, as a geometry. The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MINX`, `MAXY`), (`MAXX`, `MAXY`), (`MAXX`, `MINY`), (`MINX`, `MINY`)). (PostGIS will add a `ZMIN`/`ZMAX` coordinate as well).

Degenerate cases (vertical lines, points) will return a geometry of lower dimension than `POLYGON`, ie. `POINT` or `LINESTRING`.

Availability: 1.5.0 behavior changed to output double precision instead of float4

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.19

## Examples

    SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry));
     st_astext
    ------------
     POINT(1 3)
    (1 row)

    SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry));
    		   st_astext
    --------------------------------
     POLYGON((0 0,0 3,1 3,1 0,0 0))
    (1 row)

    SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry));
    						  st_astext
    --------------------------------------------------------------
     POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
    (1 row)
    SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry));
    						  st_astext
    --------------------------------------------------------------
     POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
    (1 row)

    SELECT Box3D(geom), Box2D(geom), ST_AsText(ST_Envelope(geom)) As envelopewkt
    	FROM (SELECT 'POLYGON((0 0, 0 1000012333334.34545678, 1.0000001 1, 1.0000001 0, 0 0))'::geometry As geom) As foo;

Envelope of a point and linestring.

    SELECT ST_AsText(ST_Envelope(
    		ST_Collect(
    			ST_GeomFromText('LINESTRING(55 75,125 150)'),
    				ST_Point(20, 80))
    				)) As wktenv;
    wktenv
    -----------
    POLYGON((20 75,20 150,125 150,125 75,20 75))

## See Also

Box2D, Box3D, ST_OrientedEnvelope

## Name

ST_ExteriorRing — Returns a LineString representing the exterior ring of a Polygon.

## Synopsis

`geometry ST_ExteriorRing(` geometry a_polygon`)`;

## Description

Returns a LINESTRING representing the exterior ring (shell) of a POLYGON. Returns NULL if the geometry is not a polygon.

This function does not support MULTIPOLYGONs. For MULTIPOLYGONs use in conjunction with ST_GeometryN or ST_Dump

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.2.3, 8.3.3

This function supports 3d and will not drop the z-index.

## Examples

    --If you have a table of polygons
    SELECT gid, ST_ExteriorRing(geom) AS ering
    FROM sometable;

    --If you have a table of MULTIPOLYGONs
    --and want to return a MULTILINESTRING composed of the exterior rings of each polygon
    SELECT gid, ST_Collect(ST_ExteriorRing(geom)) AS erings
    	FROM (SELECT gid, (ST_Dump(geom)).geom As geom
    			FROM sometable) As foo
    GROUP BY gid;

    --3d Example
    SELECT ST_AsEWKT(
    	ST_ExteriorRing(
    	ST_GeomFromEWKT('POLYGON((0 0 1, 1 1 1, 1 2 1, 1 1 1, 0 0 1))')
    	)
    );

    st_asewkt
    ---------
    LINESTRING(0 0 1,1 1 1,1 2 1,1 1 1,0 0 1)

## See Also

ST_InteriorRingN, ST_Boundary, ST_NumInteriorRings

## Name

ST_GeometryN — Return an element of a geometry collection.

## Synopsis

`geometry ST_GeometryN(` geometry geomA, integer n`)`;

## Description

Return the 1-based Nth element geometry of an input geometry which is a GEOMETRYCOLLECTION, MULTIPOINT, MULTILINESTRING, MULTICURVE, MULTI)POLYGON, or POLYHEDRALSURFACE. Otherwise, returns NULL.

Index is 1-based as for OGC specs since version 0.8.0. Previous versions implemented this as 0-based instead.

To extract all elements of a geometry, ST_Dump is more efficient and works for atomic geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Standard Examples

    --Extracting a subset of points from a 3d multipoint
    SELECT n, ST_AsEWKT(ST_GeometryN(geom, n)) As geomewkt
    FROM (
    VALUES (ST_GeomFromEWKT('MULTIPOINT((1 2 7), (3 4 7), (5 6 7), (8 9 10))') ),
    ( ST_GeomFromEWKT('MULTICURVE(CIRCULARSTRING(2.5 2.5,4.5 2.5, 3.5 3.5), (10 11, 12 11))') )
    	)As foo(geom)
    	CROSS JOIN generate_series(1,100) n
    WHERE n <= ST_NumGeometries(geom);

     n |               geomewkt
    ---+-----------------------------------------
     1 | POINT(1 2 7)
     2 | POINT(3 4 7)
     3 | POINT(5 6 7)
     4 | POINT(8 9 10)
     1 | CIRCULARSTRING(2.5 2.5,4.5 2.5,3.5 3.5)
     2 | LINESTRING(10 11,12 11)

    --Extracting all geometries (useful when you want to assign an id)
    SELECT gid, n, ST_GeometryN(geom, n)
    FROM sometable CROSS JOIN generate_series(1,100) n
    WHERE n <= ST_NumGeometries(geom);

## Polyhedral Surfaces, TIN and Triangle Examples

    -- Polyhedral surface example
    -- Break a Polyhedral surface into its faces
    SELECT ST_AsEWKT(ST_GeometryN(p_geom,3)) As geom_ewkt
      FROM (SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
    ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
    ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
    ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )')  AS p_geom )  AS a;

                    geom_ewkt
    ------------------------------------------
     POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0))

    -- TIN --
    SELECT ST_AsEWKT(ST_GeometryN(geom,2)) as wkt
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
    -- result --
                     wkt
    -------------------------------------
     TRIANGLE((0 0 0,0 1 0,1 1 0,0 0 0))

## See Also

ST_Dump, ST_NumGeometries

## Name

ST_GeometryType — Returns the SQL-MM type of a geometry as text.

## Synopsis

`text ST_GeometryType(` geometry g1`)`;

## Description

Returns the type of the geometry as a string. EG: 'ST_LineString', 'ST_Polygon','ST_MultiPolygon' etc. This function differs from GeometryType(geometry) in the case of the string and ST in front that is returned, as well as the fact that it will not indicate whether the geometry is measured.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_GeometryType(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    			--result
    			ST_LineString

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			ST_PolyhedralSurface

    SELECT ST_GeometryType(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    			--result
    			ST_PolyhedralSurface

    SELECT ST_GeometryType(geom) as result
      FROM
        (SELECT
           ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')  AS geom
        ) AS g;
     result
    --------
     ST_Tin

## See Also

GeometryType

## Name

ST_HasArc — Tests if a geometry contains a circular arc

## Synopsis

`boolean ST_HasArc(` geometry geomA`)`;

## Description

Returns true if a geometry or geometry collection contains a circular string

Availability: 1.2.3?

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_HasArc(ST_Collect('LINESTRING(1 2, 3 4, 5 6)', 'CIRCULARSTRING(1 1, 2 3, 4 5, 6 7, 5 6)'));
    		st_hasarc
    		--------
    		t

## See Also

ST_CurveToLine, ST_LineToCurve

## Name

ST_InteriorRingN — Returns the Nth interior ring (hole) of a Polygon.

## Synopsis

`geometry ST_InteriorRingN(` geometry a_polygon, integer n`)`;

## Description

Returns the Nth interior ring (hole) of a POLYGON geometry as a LINESTRING. The index starts at 1. Returns NULL if the geometry is not a polygon or the index is out of range.

This function does not support MULTIPOLYGONs. For MULTIPOLYGONs use in conjunction with ST_GeometryN or ST_Dump

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_InteriorRingN(geom, 1)) As geom
    FROM (SELECT ST_BuildArea(
    		ST_Collect(ST_Buffer(ST_Point(1,2), 20,3),
    			ST_Buffer(ST_Point(1, 2), 10,3))) As geom
    		)  as foo;

## See Also

ST_ExteriorRing, ST_BuildArea, ST_Collect, ST_Dump, ST_NumInteriorRing, ST_NumInteriorRings

## Name

ST_NumCurves — Return the number of component curves in a CompoundCurve.

## Synopsis

`integer ST_NumCurves(` geometry a_compoundcurve`)`;

## Description

Return the number of component curves in a CompoundCurve, zero for an empty CompoundCurve, or NULL for a non-CompoundCurve input.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

## Examples

    -- Returns 3
    SELECT ST_NumCurves('COMPOUNDCURVE(
        (2 2, 2.5 2.5),
        CIRCULARSTRING(2.5 2.5, 4.5 2.5, 3.5 3.5),
        (3.5 3.5, 2.5 4.5, 3 5, 2 2)
      )');

    -- Returns 0
    SELECT ST_NumCurves('COMPOUNDCURVE EMPTY');

## See Also

ST_CurveN, ST_Dump, ST_ExteriorRing, ST_NumInteriorRings, ST_NumGeometries

## Name

ST_CurveN — Returns the Nth component curve geometry of a CompoundCurve.

## Synopsis

`geometry ST_CurveN(` geometry a_compoundcurve, integer index`)`;

## Description

Returns the Nth component curve geometry of a CompoundCurve. The index starts at 1. Returns NULL if the geometry is not a CompoundCurve or the index is out of range.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_CurveN('COMPOUNDCURVE(
        (2 2, 2.5 2.5),
        CIRCULARSTRING(2.5 2.5, 4.5 2.5, 3.5 3.5),
        (3.5 3.5, 2.5 4.5, 3 5, 2 2)
      )', 1));

## See Also

ST_NumCurves, ST_Dump, ST_ExteriorRing, ST_NumInteriorRings, ST_NumGeometries

## Name

ST_IsClosed — Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).

## Synopsis

`boolean ST_IsClosed(` geometry g`)`;

## Description

Returns `TRUE` if the `LINESTRING`'s start and end points are coincident. For Polyhedral Surfaces, reports if the surface is areal (open) or volumetric (closed).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.5, 9.3.3

SQL-MM defines the result of `ST_IsClosed(NULL)` to be 0, while PostGIS returns `NULL`.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports Polyhedral surfaces.

## Line String and Point Examples

    postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 1 1)'::geometry);
     st_isclosed
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsClosed('LINESTRING(0 0, 0 1, 1 1, 0 0)'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsClosed('MULTILINESTRING((0 0, 0 1, 1 1, 0 0),(0 0, 1 1))'::geometry);
     st_isclosed
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsClosed('POINT(0 0)'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsClosed('MULTIPOINT((0 0), (1 1))'::geometry);
     st_isclosed
    -------------
     t
    (1 row)

## Polyhedral Surface Examples

    		-- A cube --
    		SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));

     st_isclosed
    -------------
     t

     -- Same as cube but missing a side --
     SELECT ST_IsClosed(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)) )'));

     st_isclosed
    -------------
     f

## See Also

ST_IsRing

## Name

ST_IsCollection — Tests if a geometry is a geometry collection type.

## Synopsis

`boolean ST_IsCollection(` geometry g`)`;

## Description

Returns `TRUE` if the geometry type of the argument a geometry collection type. Collection types are the following:

- GEOMETRYCOLLECTION

- MULTI{POINT,POLYGON,LINESTRING,CURVE,SURFACE}

- COMPOUNDCURVE

This function analyzes the type of the geometry. This means that it will return `TRUE` on collections that are empty or that contain a single element.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    postgis=# SELECT ST_IsCollection('LINESTRING(0 0, 1 1)'::geometry);
     st_iscollection
    -------------
     f
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT EMPTY'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('MULTIPOINT((0 0), (42 42))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

    postgis=# SELECT ST_IsCollection('GEOMETRYCOLLECTION(POINT(0 0))'::geometry);
     st_iscollection
    -------------
     t
    (1 row)

## See Also

ST_NumGeometries

## Name

ST_IsEmpty — Tests if a geometry is empty.

## Synopsis

`boolean ST_IsEmpty(` geometry geomA`)`;

## Description

Returns true if this Geometry is an empty geometry. If true, then this Geometry represents an empty geometry collection, polygon, point etc.

SQL-MM defines the result of ST_IsEmpty(NULL) to be 0, while PostGIS returns NULL.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.7

This method supports Circular Strings and Curves.

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards

## Examples

    SELECT ST_IsEmpty(ST_GeomFromText('GEOMETRYCOLLECTION EMPTY'));
     st_isempty
    ------------
     t
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('POLYGON EMPTY'));
     st_isempty
    ------------
     t
    (1 row)

    SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));

     st_isempty
    ------------
     f
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))')) = false;
     ?column?
    ----------
     t
    (1 row)

     SELECT ST_IsEmpty(ST_GeomFromText('CIRCULARSTRING EMPTY'));
      st_isempty
    ------------
     t
    (1 row)

## Name

ST_IsPolygonCCW — Tests if Polygons have exterior rings oriented counter-clockwise and interior rings oriented clockwise.

## Synopsis

`boolean ST_IsPolygonCCW (` geometry geom `)`;

## Description

Returns true if all polygonal components of the input geometry use a counter-clockwise orientation for their exterior ring, and a clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

Availability: 2.4.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## See Also

ST_ForcePolygonCW , ST_ForcePolygonCCW , ST_IsPolygonCW

## Name

ST_IsPolygonCW — Tests if Polygons have exterior rings oriented clockwise and interior rings oriented counter-clockwise.

## Synopsis

`boolean ST_IsPolygonCW (` geometry geom `)`;

## Description

Returns true if all polygonal components of the input geometry use a clockwise orientation for their exterior ring, and a counter-clockwise direction for all interior rings.

Returns true if the geometry has no polygonal components.

Closed linestrings are not considered polygonal components, so you would still get a true return by passing a single closed linestring no matter its orientation.

If a polygonal geometry does not use reversed orientation for interior rings (i.e., if one or more interior rings are oriented in the same direction as an exterior ring) then both ST_IsPolygonCW and ST_IsPolygonCCW will return false.

Availability: 2.4.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## See Also

ST_ForcePolygonCW , ST_ForcePolygonCCW , ST_IsPolygonCW

## Name

ST_IsRing — Tests if a LineString is closed and simple.

## Synopsis

`boolean ST_IsRing(` geometry g`)`;

## Description

Returns `TRUE` if this `LINESTRING` is both ST_IsClosed (`ST_StartPoint(g) ~= ST_Endpoint(g)`) and ST_IsSimple (does not self intersect).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.6

SQL-MM defines the result of `ST_IsRing(NULL)` to be 0, while PostGIS returns `NULL`.

## Examples

    SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom)
    FROM (SELECT 'LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)'::geometry AS geom) AS foo;
     st_isring | st_isclosed | st_issimple
    -----------+-------------+-------------
     t         | t           | t
    (1 row)

    SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom)
    FROM (SELECT 'LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)'::geometry AS geom) AS foo;
     st_isring | st_isclosed | st_issimple
    -----------+-------------+-------------
     f         | t           | f
    (1 row)

## See Also

ST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint

## Name

ST_IsSimple — Tests if a geometry has no points of self-intersection or self-tangency.

## Synopsis

`boolean ST_IsSimple(` geometry geomA`)`;

## Description

Returns true if this Geometry has no anomalous geometric points, such as self-intersection or self-tangency. For more information on the OGC's definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliance of geometries"

SQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.8

This function supports 3d and will not drop the z-index.

## Examples

     SELECT ST_IsSimple(ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))'));
     st_issimple
    -------------
     f
    (1 row)

     SELECT ST_IsSimple(ST_GeomFromText('LINESTRING(1 1,2 2,2 3.5,1 3,1 2,2 1)'));
     st_issimple
    -------------
     f
    (1 row)

## See Also

ST_IsValid

## Name

ST_M — Returns the M coordinate of a Point.

## Synopsis

`float ST_M(` geometry a_point`)`;

## Description

Return the M coordinate of a Point, or NULL if not available. Input must be a Point.

This is not (yet) part of the OGC spec, but is listed here to complete the point coordinate extractor function list.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_M(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_m
    ------
    	4
    (1 row)

## See Also

ST_GeomFromEWKT, ST_X, ST_Y, ST_Z

## Name

ST_MemSize — Returns the amount of memory space a geometry takes.

## Synopsis

`integer ST_MemSize(` geometry geomA`)`;

## Description

Returns the amount of memory space (in bytes) the geometry takes.

This complements the PostgreSQL built-in database object functions pg_column_size, pg_size_pretty, pg_relation_size, pg_total_relation_size.

pg_relation_size which gives the byte size of a table may return byte size lower than ST_MemSize. This is because pg_relation_size does not add toasted table contribution and large geometries are stored in TOAST tables. pg_total_relation_size - includes, the table, the toasted tables, and the indexes. pg_column_size returns how much space a geometry would take in a column considering compression, so may be lower than ST_MemSize

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Changed: 2.2.0 name changed to ST_MemSize to follow naming convention.

## Examples

    --Return how much byte space Boston takes up  in our Mass data set
    SELECT pg_size_pretty(SUM(ST_MemSize(geom))) as totgeomsum,
    pg_size_pretty(SUM(CASE WHEN town = 'BOSTON' THEN ST_MemSize(geom) ELSE 0 END)) As bossum,
    CAST(SUM(CASE WHEN town = 'BOSTON' THEN ST_MemSize(geom) ELSE 0 END)*1.00 /
    		SUM(ST_MemSize(geom))*100 As numeric(10,2)) As perbos
    FROM towns;

    totgeomsum	bossum	perbos
    ----------	------	------
    1522 kB		30 kB	1.99

    SELECT ST_MemSize(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));

    ---
    73

    --What percentage of our table is taken up by just the geometry
    SELECT pg_total_relation_size('public.neighborhoods') As fulltable_size, sum(ST_MemSize(geom)) As geomsize,
    sum(ST_MemSize(geom))*1.00/pg_total_relation_size('public.neighborhoods')*100 As pergeom
    FROM neighborhoods;
    fulltable_size geomsize  pergeom
    ------------------------------------------------
    262144         96238	 36.71188354492187500000

## Name

ST_NDims — Returns the coordinate dimension of a geometry.

## Synopsis

`integer ST_NDims(` geometry g1`)`;

## Description

Returns the coordinate dimension of the geometry. PostGIS supports 2 - (x,y) , 3 - (x,y,z) or 2D with measure - x,y,m, and 4 - 3D with measure space x,y,z,m

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_NDims(ST_GeomFromText('POINT(1 1)')) As d2point,
    	ST_NDims(ST_GeomFromEWKT('POINT(1 1 2)')) As d3point,
    	ST_NDims(ST_GeomFromEWKT('POINTM(1 1 0.5)')) As d2pointm;

    	 d2point | d3point | d2pointm
    ---------+---------+----------
    	   2 |       3 |        3

## See Also

ST_CoordDim, ST_Dimension, ST_GeomFromEWKT

## Name

ST_NPoints — Returns the number of points (vertices) in a geometry.

## Synopsis

`integer ST_NPoints(` geometry g1`)`;

## Description

Return the number of points in a geometry. Works for all geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_NPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    --result
    4

    --Polygon in 3D space
    SELECT ST_NPoints(ST_GeomFromEWKT('LINESTRING(77.29 29.07 1,77.42 29.26 0,77.27 29.31 -1,77.29 29.07 3)'))
    --result
    4

## See Also

ST_NumPoints

## Name

ST_NRings — Returns the number of rings in a polygonal geometry.

## Synopsis

`integer ST_NRings(` geometry geomA`)`;

## Description

If the geometry is a polygon or multi-polygon returns the number of rings. Unlike NumInteriorRings, it counts the outer rings as well.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_NRings(geom) As Nrings, ST_NumInteriorRings(geom) As ninterrings
    					FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As geom) As foo;
    	 nrings | ninterrings
    --------+-------------
    	  1 |           0
    (1 row)

## See Also

ST_NumInteriorRings

## Name

ST_NumGeometries — Returns the number of elements in a geometry collection.

## Synopsis

`integer ST_NumGeometries(` geometry geom`)`;

## Description

Returns the number of elements in a geometry collection (GEOMETRYCOLLECTION or MULTI*). For non-empty atomic geometries returns 1. For empty geometries returns 0.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT.

This method implements the SQL/MM specification. SQL-MM 3: 9.1.4

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Prior versions would have returned NULL for this -- in 2.0.0 this returns 1
    SELECT ST_NumGeometries(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    --result
    1

    --Geometry Collection Example - multis count as one geom in a collection
    SELECT ST_NumGeometries(ST_GeomFromEWKT('GEOMETRYCOLLECTION(MULTIPOINT((-2 3),(-2 2)),
    LINESTRING(5 5 ,10 10),
    POLYGON((-7 4.2,-7.1 5,-7.1 4.3,-7 4.2)))'));
    --result
    3

## See Also

ST_GeometryN, ST_Multi

## Name

ST_NumInteriorRings — Returns the number of interior rings (holes) of a Polygon.

## Synopsis

`integer ST_NumInteriorRings(` geometry a_polygon`)`;

## Description

Return the number of interior rings of a polygon geometry. Return NULL if the geometry is not a polygon.

This method implements the SQL/MM specification. SQL-MM 3: 8.2.5

Changed: 2.0.0 - in prior versions it would allow passing a MULTIPOLYGON, returning the number of interior rings of first POLYGON.

## Examples

    --If you have a regular polygon
    SELECT gid, field1, field2, ST_NumInteriorRings(geom) AS numholes
    FROM sometable;

    --If you have multipolygons
    --And you want to know the total number of interior rings in the MULTIPOLYGON
    SELECT gid, field1, field2, SUM(ST_NumInteriorRings(geom)) AS numholes
    FROM (SELECT gid, field1, field2, (ST_Dump(geom)).geom As geom
    	FROM sometable) As foo
    GROUP BY gid, field1,field2;

## See Also

ST_NumInteriorRing, ST_InteriorRingN

## Name

ST_NumInteriorRing — Returns the number of interior rings (holes) of a Polygon. Aias for ST_NumInteriorRings

## Synopsis

`integer ST_NumInteriorRing(` geometry a_polygon`)`;

## See Also

ST_NumInteriorRings, ST_InteriorRingN

## Name

ST_NumPatches — Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.

## Synopsis

`integer ST_NumPatches(` geometry g1`)`;

## Description

Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries. This is an alias for ST_NumGeometries to support MM naming. Faster to use ST_NumGeometries if you don't care about MM convention.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3: 8.5

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_NumPatches(ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    		((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    		((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    		((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    		--result
    		6

## See Also

ST_GeomFromEWKT, ST_NumGeometries

## Name

ST_NumPoints — Returns the number of points in a LineString or CircularString.

## Synopsis

`integer ST_NumPoints(` geometry g1`)`;

## Description

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertices for not just linestrings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.4

## Examples

    SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(77.29 29.07,77.42 29.26,77.27 29.31,77.29 29.07)'));
    		--result
    		4

## See Also

ST_NPoints

## Name

ST_PatchN — Returns the Nth geometry (face) of a PolyhedralSurface.

## Synopsis

`geometry ST_PatchN(` geometry geomA, integer n`)`;

## Description

Returns the 1-based Nth geometry (face) if the geometry is a POLYHEDRALSURFACE or POLYHEDRALSURFACEM. Otherwise, returns NULL. This returns the same answer as ST_GeometryN for PolyhedralSurfaces. Using ST_GeometryN is faster.

Index is 1-based.

If you want to extract all elements of a geometry ST_Dump is more efficient.

Availability: 2.0.0

This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3: 8.5

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    --Extract the 2nd face of the polyhedral surface
    SELECT ST_AsEWKT(ST_PatchN(geom, 2)) As geomewkt
    FROM (
    VALUES (ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ) As foo(geom);

                  geomewkt
    ---+-----------------------------------------
     POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0))

## See Also

ST_AsEWKT, ST_GeomFromEWKT, ST_Dump, ST_GeometryN, ST_NumGeometries

## Name

ST_PointN — Returns the Nth point in the first LineString or circular LineString in a geometry.

## Synopsis

`geometry ST_PointN(` geometry a_linestring, integer n`)`;

## Description

Return the Nth point in a single linestring or circular linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry.

Index is 1-based as for OGC specs since version 0.8.0. Backward indexing (negative index) is not in OGC Previous versions implemented this as 0-based instead.

If you want to get the Nth point of each LineString in a MultiLineString, use in conjunction with ST_Dump

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.5, 7.3.5

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. Changed: 2.3.0 : negative indexing available (-1 is last point)

## Examples

    -- Extract all POINTs from a LINESTRING
    SELECT ST_AsText(
       ST_PointN(
    	  column1,
    	  generate_series(1, ST_NPoints(column1))
       ))
    FROM ( VALUES ('LINESTRING(0 0, 1 1, 2 2)'::geometry) ) AS foo;

     st_astext
    ------------
     POINT(0 0)
     POINT(1 1)
     POINT(2 2)
    (3 rows)

    --Example circular string
    SELECT ST_AsText(ST_PointN(ST_GeomFromText('CIRCULARSTRING(1 2, 3 2, 1 2)'), 2));

     st_astext
    ------------
     POINT(3 2)
    (1 row)

    SELECT ST_AsText(f)
    FROM ST_GeomFromText('LINESTRING(0 0 0, 1 1 1, 2 2 2)') AS g
      ,ST_PointN(g, -2) AS f; -- 1 based index

        st_astext
    -----------------
     POINT Z (1 1 1)
    (1 row)

## See Also

ST_NPoints

## Name

ST_Points — Returns a MultiPoint containing the coordinates of a geometry.

## Synopsis

`geometry ST_Points(` geometry geom `)`;

## Description

Returns a MultiPoint containing all the coordinates of a geometry. Duplicate points are preserved, including the start and end points of ring geometries. (If desired, duplicate points can be removed by calling ST_RemoveRepeatedPoints on the result).

To obtain information about the position of each coordinate in the parent geometry use ST_DumpPoints.

M and Z coordinates are preserved if present.

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

Availability: 2.3.0

## Examples

    SELECT ST_AsText(ST_Points('POLYGON Z ((30 10 4,10 30 5,40 40 6, 30 10))'));

    --result
    MULTIPOINT Z ((30 10 4),(10 30 5),(40 40 6),(30 10 4))

## See Also

ST_RemoveRepeatedPoints, ST_DumpPoints

## Name

ST_StartPoint — Returns the first point of a LineString.

## Synopsis

`geometry ST_StartPoint(` geometry geomA`)`;

## Description

Returns the first point of a `LINESTRING` or `CIRCULARLINESTRING` geometry as a `POINT`. Returns `NULL` if the input is not a `LINESTRING` or `CIRCULARLINESTRING`.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.3

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

Enhanced: 3.2.0 returns a point for all geometries. Prior behavior returns NULLs if input was not a LineString. Changed: 2.0.0 no longer works with single geometry MultiLineStrings. In older versions of PostGIS a single-line MultiLineString would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other MultiLineString. The old behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0.0.

## Examples

Start point of a LineString

    SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry));
     st_astext
    ------------
     POINT(0 1)

Start point of a non-LineString is NULL

    SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
      is_null
    ----------
     t

Start point of a 3D LineString

    SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry));
     st_asewkt
    ------------
     POINT(0 1 1)

Start point of a CircularString

    SELECT ST_AsText(ST_StartPoint('CIRCULARSTRING(5 2,-3 1.999999, -2 1, -4 2, 6 3)'::geometry));
     st_astext
    ------------
     POINT(5 2)

## See Also

ST_EndPoint, ST_PointN

## Name

ST_Summary — Returns a text summary of the contents of a geometry.

## Synopsis

`text ST_Summary(` geometry g`)`;

`text ST_Summary(` geography g`)`;

## Description

Returns a text summary of the contents of the geometry.

Flags shown square brackets after the geometry type have the following meaning:

- M: has M coordinate

- Z: has Z coordinate

- B: has a cached bounding box

- G: is geodetic (geography)

- S: has spatial reference system

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Availability: 1.2.2

Enhanced: 2.0.0 added support for geography

Enhanced: 2.1.0 S flag to denote if has a known spatial reference system

Enhanced: 2.2.0 Added support for TIN and Curves

## Examples

    =# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom,
            ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog;
                geom             |          geog
    -----------------------------+--------------------------
     LineString[B] with 2 points | Polygon[BGS] with 1 rings
                                 | ring 0 has 5 points
                                 :
    (1 row)

    =# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line,
            ST_Summary(ST_GeomFromText('SRID=4326;POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly;
    ;
               geog_line             |        geom_poly
    -------------------------------- +--------------------------
     LineString[ZBGS] with 2 points | Polygon[ZBS] with 1 rings
                                    :    ring 0 has 5 points
                                    :
    (1 row)

## See Also

PostGIS_DropBBox, PostGIS_AddBBox, ST_Force3DM, ST_Force3DZ, ST_Force2D, geography

ST_IsValid, ST_IsValid, ST_IsValidReason, ST_IsValidDetail

## Name

ST_X — Returns the X coordinate of a Point.

## Synopsis

`float ST_X(` geometry a_point`)`;

## Description

Return the X coordinate of the point, or NULL if not available. Input must be a point.

To get the minimum and maximum X value of geometry coordinates use the functions ST_XMin and ST_XMax.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.3

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_X(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_x
    ------
    	1
    (1 row)

    SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
     st_y
    ------
      1.5
    (1 row)

## See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_XMax, ST_XMin, ST_Y, ST_Z

## Name

ST_Y — Returns the Y coordinate of a Point.

## Synopsis

`float ST_Y(` geometry a_point`)`;

## Description

Return the Y coordinate of the point, or NULL if not available. Input must be a point.

To get the minimum and maximum Y value of geometry coordinates use the functions ST_YMin and ST_YMax.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.4

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_Y(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_y
    ------
    	2
    (1 row)

    SELECT ST_Y(ST_Centroid(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)')));
     st_y
    ------
      1.5
    (1 row)

## See Also

ST_Centroid, ST_GeomFromEWKT, ST_M, ST_X, ST_YMax, ST_YMin, ST_Z

## Name

ST_Z — Returns the Z coordinate of a Point.

## Synopsis

`float ST_Z(` geometry a_point`)`;

## Description

Return the Z coordinate of the point, or NULL if not available. Input must be a point.

To get the minimum and maximum Z value of geometry coordinates use the functions ST_ZMin and ST_ZMax.

This method implements the SQL/MM specification.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_Z(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_z
    ------
    	3
    (1 row)

## See Also

ST_GeomFromEWKT, ST_M, ST_X, ST_Y, ST_ZMax, ST_ZMin

## Name

ST_Zmflag — Returns a code indicating the ZM coordinate dimension of a geometry.

## Synopsis

`smallint ST_Zmflag(` geometry geomA`)`;

## Description

Returns a code indicating the ZM coordinate dimension of a geometry.

Values are: 0 = 2D, 1 = 3D-M, 2 = 3D-Z, 3 = 4D.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRING(1 2, 3 4)'));
     st_zmflag
    -----------
    		 0

    SELECT ST_Zmflag(ST_GeomFromEWKT('LINESTRINGM(1 2 3, 3 4 3)'));
     st_zmflag
    -----------
    		 1

    SELECT ST_Zmflag(ST_GeomFromEWKT('CIRCULARSTRING(1 2 3, 3 4 3, 5 6 3)'));
     st_zmflag
    -----------
    		 2
    SELECT ST_Zmflag(ST_GeomFromEWKT('POINT(1 2 3 4)'));
     st_zmflag
    -----------
    		 3

## See Also

ST_CoordDim, ST_NDims, ST_Dimension

## Name

ST_HasZ — Checks if a geometry has a Z dimension.

## Synopsis

`boolean ST_HasZ(` geometry geom`)`;

## Description

Checks if the input geometry has a Z dimension and returns a boolean value. If the geometry has a Z dimension, it returns true; otherwise, it returns false.

Geometry objects with a Z dimension typically represent three-dimensional (3D) geometries, while those without it are two-dimensional (2D) geometries.

This function is useful for determining if a geometry has elevation or height information.

Availability: 3.5.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

    SELECT ST_HasZ(ST_GeomFromText('POINT(1 2 3)'));
     --result
     true

    SELECT ST_HasZ(ST_GeomFromText('LINESTRING(0 0, 1 1)'));
     --result
     false

## See Also

ST_Zmflag

ST_HasM

## Name

ST_HasM — Checks if a geometry has an M (measure) dimension.

## Synopsis

`boolean ST_HasM(` geometry geom`)`;

## Description

Checks if the input geometry has an M (measure) dimension and returns a boolean value. If the geometry has an M dimension, it returns true; otherwise, it returns false.

Geometry objects with an M dimension typically represent measurements or additional data associated with spatial features.

This function is useful for determining if a geometry includes measure information.

Availability: 3.5.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

    SELECT ST_HasM(ST_GeomFromText('POINTM(1 2 3)'));
     --result
     true

    SELECT ST_HasM(ST_GeomFromText('LINESTRING(0 0, 1 1)'));
     --result
     false

## See Also

ST_Zmflag

ST_HasZ

## 7.5. Geometry Editors

Abstract

These functions create modified geometries by changing type, structure or vertices.

## Name

ST_AddPoint — Add a point to a LineString.

## Synopsis

`geometry ST_AddPoint(` geometry linestring, geometry point`)`;

`geometry ST_AddPoint(` geometry linestring, geometry point, integer position = -1`)`;

## Description

Adds a point to a LineString before the index `position` (using a 0-based index). If the `position` parameter is omitted or is -1 the point is appended to the end of the LineString.

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

Add a point to the end of a 3D line

    SELECT ST_AsEWKT(ST_AddPoint('LINESTRING(0 0 1, 1 1 1)', ST_MakePoint(1, 2, 3)));

        st_asewkt
        ----------
        LINESTRING(0 0 1,1 1 1,1 2 3)

Guarantee all lines in a table are closed by adding the start point of each line to the end of the line only for those that are not closed.

    UPDATE sometable
    SET geom = ST_AddPoint(geom, ST_StartPoint(geom))
    FROM sometable
    WHERE ST_IsClosed(geom) = false;

## See Also

ST_RemovePoint, ST_SetPoint

## Name

ST_CollectionExtract — Given a geometry collection, returns a multi-geometry containing only elements of a specified type.

## Synopsis

`geometry ST_CollectionExtract(` geometry collection`)`;

`geometry ST_CollectionExtract(` geometry collection, integer type`)`;

## Description

Given a geometry collection, returns a homogeneous multi-geometry.

If the `type` is not specified, returns a multi-geometry containing only geometries of the highest dimension. So polygons are preferred over lines, which are preferred over points.

If the `type` is specified, returns a multi-geometry containing only that type. If there are no sub-geometries of the right type, an EMPTY geometry is returned. Only points, lines and polygons are supported. The type numbers are:

- 1 == POINT

- 2 == LINESTRING

- 3 == POLYGON

For atomic geometry inputs, the geometry is returned unchanged if the input type matches the requested type. Otherwise, the result is an EMPTY geometry of the specified type. If required, these can be converted to multi-geometries using ST_Multi.

MultiPolygon results are not checked for validity. If the polygon components are adjacent or overlapping the result will be invalid. (For example, this can occur when applying this function to an ST_Split result.) This situation can be checked with ST_IsValid and repaired with ST_MakeValid.

Availability: 1.5.0

Prior to 1.5.3 this function returned atomic inputs unchanged, no matter type. In 1.5.3 non-matching single geometries returned a NULL result. In 2.0.0 non-matching single geometries return an EMPTY result of the requested type.

## Examples

Extract highest-dimension type:

    SELECT ST_AsText(ST_CollectionExtract(
            'GEOMETRYCOLLECTION( POINT(0 0), LINESTRING(1 1, 2 2) )'));
        st_astext
        ---------------
        MULTILINESTRING((1 1, 2 2))

Extract points (type 1 == POINT):

    SELECT ST_AsText(ST_CollectionExtract(
            'GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(POINT(0 0)))',
            1 ));
        st_astext
        ---------------
        MULTIPOINT((0 0))

Extract lines (type 2 == LINESTRING):

    SELECT ST_AsText(ST_CollectionExtract(
            'GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING(0 0, 1 1)),LINESTRING(2 2, 3 3))',
            2 ));
        st_astext
        ---------------
        MULTILINESTRING((0 0, 1 1), (2 2, 3 3))

## See Also

ST_CollectionHomogenize, ST_Multi, ST_IsValid, ST_MakeValid

## Name

ST_CollectionHomogenize — Returns the simplest representation of a geometry collection.

## Synopsis

`geometry ST_CollectionHomogenize(` geometry collection`)`;

## Description

Given a geometry collection, returns the "simplest" representation of the contents.

- Homogeneous (uniform) collections are returned as the appropriate multi-geometry.

- Heterogeneous (mixed) collections are flattened into a single GeometryCollection.

- Collections containing a single atomic element are returned as that element.

- Atomic geometries are returned unchanged. If required, these can be converted to a multi-geometry using ST_Multi.

This function does not ensure that the result is valid. In particular, a collection containing adjacent or overlapping Polygons will create an invalid MultiPolygon. This situation can be checked with ST_IsValid and repaired with ST_MakeValid.

Availability: 2.0.0

## Examples

Single-element collection converted to an atomic geometry

      SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0))'));

    	st_astext
    	------------
    	POINT(0 0)

Nested single-element collection converted to an atomic geometry:

    SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(MULTIPOINT((0 0)))'));

    	st_astext
    	------------
    	POINT(0 0)

Collection converted to a multi-geometry:

    SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0),POINT(1 1))'));

    	st_astext
    	---------------------
    	MULTIPOINT((0 0),(1 1))

Nested heterogeneous collection flattened to a GeometryCollection:

    SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION(POINT(0 0), GEOMETRYCOLLECTION( LINESTRING(1 1, 2 2)))'));

    	st_astext
    	---------------------
    	GEOMETRYCOLLECTION(POINT(0 0),LINESTRING(1 1,2 2))

Collection of Polygons converted to an (invalid) MultiPolygon:

    SELECT ST_AsText(ST_CollectionHomogenize('GEOMETRYCOLLECTION (POLYGON ((10 50, 50 50, 50 10, 10 10, 10 50)), POLYGON ((90 50, 90 10, 50 10, 50 50, 90 50)))'));

    	st_astext
    	---------------------
    	MULTIPOLYGON(((10 50,50 50,50 10,10 10,10 50)),((90 50,90 10,50 10,50 50,90 50)))

## See Also

ST_CollectionExtract, ST_Multi, ST_IsValid, ST_MakeValid

## Name

ST_CurveToLine — Converts a geometry containing curves to a linear geometry.

## Synopsis

`geometry ST_CurveToLine(` geometry curveGeom, float tolerance, integer tolerance_type, integer flags`)`;

## Description

Converts a CIRCULAR STRING to regular LINESTRING or CURVEPOLYGON to POLYGON or MULTISURFACE to MULTIPOLYGON. Useful for outputting to devices that can't support CIRCULARSTRING geometry types

Converts a given geometry to a linear geometry. Each curved geometry or segment is converted into a linear approximation using the given `tolerance` and options (32 segments per quadrant and no options by default).

The 'tolerance_type' argument determines interpretation of the `tolerance` argument. It can take the following values:

- 0 (default): Tolerance is max segments per quadrant.

- 1: Tolerance is max-deviation of line from curve, in source units.

- 2: Tolerance is max-angle, in radians, between generating radii.

The 'flags' argument is a bitfield. 0 by default. Supported bits are:

- 1: Symmetric (orientation idependent) output.

- 2: Retain angle, avoids reducing angles (segment lengths) when producing symmetric output. Has no effect when Symmetric flag is off.

Availability: 1.3.0

Enhanced: 2.4.0 added support for max-deviation and max-angle tolerance, and for symmetric output.

Enhanced: 3.0.0 implemented a minimum number of segments per linearized arc to prevent topological collapse.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.7

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)')));

    --Result --
     LINESTRING(220268 150415,220269.95064912 150416.539364228,220271.823415575 150418.17258804,220273.613787707 150419.895736857,
     220275.317452352 150421.704659462,220276.930305234 150423.594998003,220278.448460847 150425.562198489,
     220279.868261823 150427.60152176,220281.186287736 150429.708054909,220282.399363347 150431.876723113,
     220283.50456625 150434.10230186,220284.499233914 150436.379429536,220285.380970099 150438.702620341,220286.147650624 150441.066277505,
     220286.797428488 150443.464706771,220287.328738321 150445.892130112,220287.740300149 150448.342699654,
     220288.031122486 150450.810511759,220288.200504713 150453.289621251,220288.248038775 150455.77405574,
     220288.173610157 150458.257830005,220287.977398166 150460.734960415,220287.659875492 150463.199479347,
     220287.221807076 150465.64544956,220286.664248262 150468.066978495,220285.988542259 150470.458232479,220285.196316903 150472.81345077,
     220284.289480732 150475.126959442,220283.270218395 150477.39318505,220282.140985384 150479.606668057,
     220280.90450212 150481.762075989,220279.5637474 150483.85421628,220278.12195122 150485.87804878,
     220276.582586992 150487.828697901,220274.949363179 150489.701464356,220273.226214362 150491.491836488,
     220271.417291757 150493.195501133,220269.526953216 150494.808354014,220267.559752731 150496.326509628,
     220265.520429459 150497.746310603,220263.41389631 150499.064336517,220261.245228106 150500.277412127,
     220259.019649359 150501.38261503,220256.742521683 150502.377282695,220254.419330878 150503.259018879,
     220252.055673714 150504.025699404,220249.657244448 150504.675477269,220247.229821107 150505.206787101,
     220244.779251566 150505.61834893,220242.311439461 150505.909171266,220239.832329968 150506.078553494,
     220237.347895479 150506.126087555,220234.864121215 150506.051658938,220232.386990804 150505.855446946,
     220229.922471872 150505.537924272,220227.47650166 150505.099855856,220225.054972724 150504.542297043,
     220222.663718741 150503.86659104,220220.308500449 150503.074365683,
     220217.994991777 150502.167529512,220215.72876617 150501.148267175,
     220213.515283163 150500.019034164,220211.35987523 150498.7825509,
     220209.267734939 150497.441796181,220207.243902439 150496,
     220205.293253319 150494.460635772,220203.420486864 150492.82741196,220201.630114732 150491.104263143,
     220199.926450087 150489.295340538,220198.313597205 150487.405001997,220196.795441592 150485.437801511,
     220195.375640616 150483.39847824,220194.057614703 150481.291945091,220192.844539092 150479.123276887,220191.739336189 150476.89769814,
     220190.744668525 150474.620570464,220189.86293234 150472.297379659,220189.096251815 150469.933722495,
     220188.446473951 150467.535293229,220187.915164118 150465.107869888,220187.50360229 150462.657300346,
     220187.212779953 150460.189488241,220187.043397726 150457.710378749,220186.995863664 150455.22594426,
     220187.070292282 150452.742169995,220187.266504273 150450.265039585,220187.584026947 150447.800520653,
     220188.022095363 150445.35455044,220188.579654177 150442.933021505,220189.25536018 150440.541767521,
     220190.047585536 150438.18654923,220190.954421707 150435.873040558,220191.973684044 150433.60681495,
     220193.102917055 150431.393331943,220194.339400319 150429.237924011,220195.680155039 150427.14578372,220197.12195122 150425.12195122,
     220198.661315447 150423.171302099,220200.29453926 150421.298535644,220202.017688077 150419.508163512,220203.826610682 150417.804498867,
     220205.716949223 150416.191645986,220207.684149708 150414.673490372,220209.72347298 150413.253689397,220211.830006129 150411.935663483,
     220213.998674333 150410.722587873,220216.22425308 150409.61738497,220218.501380756 150408.622717305,220220.824571561 150407.740981121,
     220223.188228725 150406.974300596,220225.586657991 150406.324522731,220227 150406)

    --3d example
    SELECT ST_AsEWKT(ST_CurveToLine(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)')));
    Output
    ------
     LINESTRING(220268 150415 1,220269.95064912 150416.539364228 1.0181172856673,
     220271.823415575 150418.17258804 1.03623457133459,220273.613787707 150419.895736857 1.05435185700189,....AD INFINITUM ....
        220225.586657991 150406.324522731 1.32611114201132,220227 150406 3)

    --use only 2 segments to approximate quarter circle
    SELECT ST_AsText(ST_CurveToLine(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'),2));
    st_astext
    ------------------------------
     LINESTRING(220268 150415,220287.740300149 150448.342699654,220278.12195122 150485.87804878,
     220244.779251566 150505.61834893,220207.243902439 150496,220187.50360229 150462.657300346,
     220197.12195122 150425.12195122,220227 150406)

    -- Ensure approximated line is no further than 20 units away from
    -- original curve, and make the result direction-neutral
    SELECT ST_AsText(ST_CurveToLine(
     'CIRCULARSTRING(0 0,100 -100,200 0)'::geometry,
        20, -- Tolerance
        1, -- Above is max distance between curve and line
        1  -- Symmetric flag
    ));
    st_astext
    -------------------------------------------------------------------------------------------
     LINESTRING(0 0,50 -86.6025403784438,150 -86.6025403784439,200 -1.1331077795296e-13,200 0)

## See Also

ST_LineToCurve

## Name

ST_Scroll — Change start point of a closed LineString.

## Synopsis

`geometry ST_Scroll(` geometry linestring, geometry point`)`;

## Description

Changes the start/end point of a closed LineString to the given vertex `point`.

Availability: 3.2.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

Make e closed line start at its 3rd vertex

    SELECT ST_AsEWKT(ST_Scroll('SRID=4326;LINESTRING(0 0 0 1, 10 0 2 0, 5 5 4 2,0 0 0 1)', 'POINT(5 5 4 2)'));

    st_asewkt
    ----------
    SRID=4326;LINESTRING(5 5 4 2,0 0 0 1,10 0 2 0,5 5 4 2)

## See Also

ST_Normalize

## Name

ST_FlipCoordinates — Returns a version of a geometry with X and Y axis flipped.

## Synopsis

`geometry ST_FlipCoordinates(` geometry geom`)`;

## Description

Returns a version of the given geometry with X and Y axis flipped. Useful for fixing geometries which contain coordinates expressed as latitude/longitude (Y,X).

Availability: 2.0.0

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Example

    SELECT ST_AsEWKT(ST_FlipCoordinates(GeomFromEWKT('POINT(1 2)')));
     st_asewkt
    ------------
    POINT(2 1)

## See Also

ST_SwapOrdinates

## Name

ST_Force2D — Force the geometries into a "2-dimensional mode".

## Synopsis

`geometry ST_Force2D(` geometry geomA`)`;

## Description

Forces the geometries into a "2-dimensional mode" so that all output representations will only have the X and Y coordinates. This is useful for force OGC-compliant output (since OGC only specifies 2-D geometries).

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_2D.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsEWKT(ST_Force2D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    		st_asewkt
    -------------------------------------
    CIRCULARSTRING(1 1,2 3,4 5,6 7,5 6)

    SELECT  ST_AsEWKT(ST_Force2D('POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))'));

    				  st_asewkt
    ----------------------------------------------
     POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))

## See Also

ST_Force3D

## Name

ST_Force3D — Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.

## Synopsis

`geometry ST_Force3D(` geometry geomA, float Zvalue = 0.0`)`;

## Description

Forces the geometries into XYZ mode. This is an alias for ST_Force3DZ. If a geometry has no Z component, then a `Zvalue` Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3D.

Changed: 3.1.0. Added support for supplying a non-zero Z value.

This function supports Polyhedral surfaces.

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

## Examples

    		--Nothing happens to an already 3D geometry
    		SELECT ST_AsEWKT(ST_Force3D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force3D('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force2D, ST_Force3DM, ST_Force3DZ

## Name

ST_Force3DZ — Force the geometries into XYZ mode.

## Synopsis

`geometry ST_Force3DZ(` geometry geomA, float Zvalue = 0.0`)`;

## Description

Forces the geometries into XYZ mode. If a geometry has no Z component, then a `Zvalue` Z coordinate is tacked on.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DZ.

Changed: 3.1.0. Added support for supplying a non-zero Z value.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force3DZ(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    -----------------------------------------------
     CIRCULARSTRING(1 1 2,2 3 2,4 5 2,6 7 2,5 6 2)

    SELECT  ST_AsEWKT(ST_Force3DZ('POLYGON((0 0,0 5,5 0,0 0),(1 1,3 1,1 3,1 1))'));

    						 st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force2D, ST_Force3DM, ST_Force3D

## Name

ST_Force3DM — Force the geometries into XYM mode.

## Synopsis

`geometry ST_Force3DM(` geometry geomA, float Mvalue = 0.0`)`;

## Description

Forces the geometries into XYM mode. If a geometry has no M component, then a `Mvalue` M coordinate is tacked on. If it has a Z component, then Z is removed

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DM.

Changed: 3.1.0. Added support for supplying a non-zero M value.

This method supports Circular Strings and Curves.

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    				   st_asewkt
    ------------------------------------------------
     CIRCULARSTRINGM(1 1 0,2 3 0,4 5 0,6 7 0,5 6 0)

    SELECT  ST_AsEWKT(ST_Force3DM('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    						  st_asewkt
    ---------------------------------------------------------------
     POLYGONM((0 0 0,0 5 0,5 0 0,0 0 0),(1 1 0,3 1 0,1 3 0,1 1 0))

## See Also

ST_AsEWKT, ST_Force2D, ST_Force3DM, ST_Force3D, ST_GeomFromEWKT

## Name

ST_Force4D — Force the geometries into XYZM mode.

## Synopsis

`geometry ST_Force4D(` geometry geomA, float Zvalue = 0.0, float Mvalue = 0.0`)`;

## Description

Forces the geometries into XYZM mode. `Zvalue` and `Mvalue` is tacked on for missing Z and M dimensions, respectively.

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_4D.

Changed: 3.1.0. Added support for supplying non-zero Z and M values.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    --Nothing happens to an already 3D geometry
    SELECT ST_AsEWKT(ST_Force4D(ST_GeomFromEWKT('CIRCULARSTRING(1 1 2, 2 3 2, 4 5 2, 6 7 2, 5 6 2)')));
    						st_asewkt
    ---------------------------------------------------------
     CIRCULARSTRING(1 1 2 0,2 3 2 0,4 5 2 0,6 7 2 0,5 6 2 0)

    SELECT  ST_AsEWKT(ST_Force4D('MULTILINESTRINGM((0 0 1,0 5 2,5 0 3,0 0 4),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    									  st_asewkt
    --------------------------------------------------------------------------------------
     MULTILINESTRING((0 0 0 1,0 5 0 2,5 0 0 3,0 0 0 4),(1 1 0 1,3 1 0 1,1 3 0 1,1 1 0 1))

## See Also

ST_AsEWKT, ST_Force2D, ST_Force3DM, ST_Force3D

## Name

ST_ForceCollection — Convert the geometry into a GEOMETRYCOLLECTION.

## Synopsis

`geometry ST_ForceCollection(` geometry geomA`)`;

## Description

Converts the geometry into a GEOMETRYCOLLECTION. This is useful for simplifying the WKB representation.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.2.2, prior to 1.3.4 this function will crash with Curves. This is fixed in 1.3.4+

Changed: 2.1.0. Up to 2.0.x this was called ST_Force_Collection.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT  ST_AsEWKT(ST_ForceCollection('POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1))'));

    								   st_asewkt
    ----------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0 1,0 5 1,5 0 1,0 0 1),(1 1 1,3 1 1,1 3 1,1 1 1)))

      SELECT ST_AsText(ST_ForceCollection('CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));
    								   st_astext
    --------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
    (1 row)

    -- POLYHEDRAL example --
    SELECT ST_AsEWKT(ST_ForceCollection('POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
     ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
     ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
     ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
     ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
     ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))'))

    								   st_asewkt
    ----------------------------------------------------------------------------------
    GEOMETRYCOLLECTION(
      POLYGON((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
      POLYGON((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
      POLYGON((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
      POLYGON((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
      POLYGON((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
      POLYGON((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1))
    )

## See Also

ST_AsEWKT, ST_Force2D, ST_Force3DM, ST_Force3D, ST_GeomFromEWKT

## Name

ST_ForceCurve — Upcast a geometry into its curved type, if applicable.

## Synopsis

`geometry ST_ForceCurve(` geometry g`)`;

## Description

Turns a geometry into its curved representation, if applicable: lines become compoundcurves, multilines become multicurves polygons become curvepolygons multipolygons become multisurfaces. If the geometry input is already a curved representation returns back same as input.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsText(
      ST_ForceCurve(
    	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'::geometry
      )
    );
                                  st_astext
    ----------------------------------------------------------------------
     CURVEPOLYGON Z ((0 0 2,5 0 2,0 5 2,0 0 2),(1 1 2,1 3 2,3 1 2,1 1 2))
    (1 row)

## See Also

ST_LineToCurve

## Name

ST_ForcePolygonCCW — Orients all exterior rings counter-clockwise and all interior rings clockwise.

## Synopsis

`geometry ST_ForcePolygonCCW (` geometry geom `)`;

## Description

Forces (Multi)Polygons to use a counter-clockwise orientation for their exterior ring, and a clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Availability: 2.4.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## See Also

ST_ForcePolygonCW , ST_IsPolygonCCW , ST_IsPolygonCW

## Name

ST_ForcePolygonCW — Orients all exterior rings clockwise and all interior rings counter-clockwise.

## Synopsis

`geometry ST_ForcePolygonCW (` geometry geom `)`;

## Description

Forces (Multi)Polygons to use a clockwise orientation for their exterior ring, and a counter-clockwise orientation for their interior rings. Non-polygonal geometries are returned unchanged.

Availability: 2.4.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## See Also

ST_ForcePolygonCCW , ST_IsPolygonCCW , ST_IsPolygonCW

## Name

ST_ForceSFS — Force the geometries to use SFS 1.1 geometry types only.

## Synopsis

`geometry ST_ForceSFS(` geometry geomA`)`;

`geometry ST_ForceSFS(` geometry geomA, text version`)`;

## Description

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

## Name

ST_ForceRHR — Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.

## Synopsis

`geometry ST_ForceRHR(` geometry g`)`;

## Description

Forces the orientation of the vertices in a polygon to follow a Right-Hand-Rule, in which the area that is bounded by the polygon is to the right of the boundary. In particular, the exterior ring is orientated in a clockwise direction and the interior rings in a counter-clockwise direction. This function is a synonym for ST_ForcePolygonCW

The above definition of the Right-Hand-Rule conflicts with definitions used in other contexts. To avoid confusion, it is recommended to use ST_ForcePolygonCW.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_AsEWKT(
      ST_ForceRHR(
    	'POLYGON((0 0 2, 5 0 2, 0 5 2, 0 0 2),(1 1 2, 1 3 2, 3 1 2, 1 1 2))'
      )
    );
    						  st_asewkt
    --------------------------------------------------------------
     POLYGON((0 0 2,0 5 2,5 0 2,0 0 2),(1 1 2,3 1 2,1 3 2,1 1 2))
    (1 row)

## See Also

ST_ForcePolygonCCW , ST_ForcePolygonCW , ST_IsPolygonCCW , ST_IsPolygonCW , ST_BuildArea, ST_Polygonize, ST_Reverse

## Name

ST_LineExtend — Returns a line extended forwards and backwards by specified distances.

## Synopsis

`geometry ST_LineExtend(` geometry line, float distance_forward, float distance_backward=0.0`)`;

## Description

Returns a line extended forwards and backwards by adding new start (and end) points at the given distance(s). A distance of zero does not add a point. Only non-negative distances are allowed. The direction(s) of the added point(s) is determined by the first (and last) two distinct points of the line. Duplicate points are ignored.

Availability: 3.4.0

## Example: Extends a line 5 units forward and 6 units backward

    SELECT ST_AsText(ST_LineExtend('LINESTRING(0 0, 0 10)'::geometry, 5, 6));
    --------------------------------------------
    LINESTRING(0 -6,0 0,0 10,0 15)

## See Also

ST_LineSubstring, ST_LocateAlong, ST_Project

## Name

ST_LineToCurve — Converts a linear geometry to a curved geometry.

## Synopsis

`geometry ST_LineToCurve(` geometry geomANoncircular`)`;

## Description

Converts plain LINESTRING/POLYGON to CIRCULAR STRINGs and Curved Polygons. Note much fewer points are needed to describe the curved equivalent.

If the input LINESTRING/POLYGON is not curved enough to clearly represent a curve, the function will return the same input geometry.

Availability: 1.3.0

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

     -- 2D Example
    SELECT ST_AsText(ST_LineToCurve(foo.geom)) As curvedastext,ST_AsText(foo.geom) As non_curvedastext
        FROM (SELECT ST_Buffer('POINT(1 3)'::geometry, 3) As geom) As foo;

    curvedatext                                                            non_curvedastext
    --------------------------------------------------------------------|-----------------------------------------------------------------
    CURVEPOLYGON(CIRCULARSTRING(4 3,3.12132034355964 0.878679656440359, | POLYGON((4 3,3.94235584120969 2.41472903395162,3.77163859753386 1.85194970290473,
    1 0,-1.12132034355965 5.12132034355963,4 3))                        |  3.49440883690764 1.33328930094119,3.12132034355964 0.878679656440359,
                                                                        |  2.66671069905881 0.505591163092366,2.14805029709527 0.228361402466141,
                                                                        |  1.58527096604839 0.0576441587903094,1 0,
                                                                        |  0.414729033951621 0.0576441587903077,-0.148050297095264 0.228361402466137,
                                                                        |  -0.666710699058802 0.505591163092361,-1.12132034355964 0.878679656440353,
                                                                        |  -1.49440883690763 1.33328930094119,-1.77163859753386 1.85194970290472
                                                                        |  --ETC-- ,3.94235584120969 3.58527096604839,4 3))

    --3D example
    SELECT ST_AsText(ST_LineToCurve(geom)) As curved, ST_AsText(geom) AS not_curved
    FROM (SELECT ST_Translate(ST_Force3D(ST_Boundary(ST_Buffer(ST_Point(1,3), 2,2))),0,0,3) AS geom) AS foo;

                            curved                        |               not_curved
    ------------------------------------------------------+---------------------------------------------------------------------
     CIRCULARSTRING Z (3 3 3,-1 2.99999999999999 3,3 3 3) | LINESTRING Z (3 3 3,2.4142135623731 1.58578643762691 3,1 1 3,
                                                          | -0.414213562373092 1.5857864376269 3,-1 2.99999999999999 3,
                                                          | -0.414213562373101 4.41421356237309 3,
                                                          | 0.999999999999991 5 3,2.41421356237309 4.4142135623731 3,3 3 3)
    (1 row)

## See Also

ST_CurveToLine

## Name

ST_Multi — Return the geometry as a MULTI* geometry.

## Synopsis

`geometry ST_Multi(` geometry geom`)`;

## Description

Returns the geometry as a MULTI* geometry collection. If the geometry is already a collection, it is returned unchanged.

## Examples

    SELECT ST_AsText(ST_Multi('POLYGON ((10 30, 30 30, 30 10, 10 10, 10 30))'));
                        st_astext
        -------------------------------------------------
        MULTIPOLYGON(((10 30,30 30,30 10,10 10,10 30)))

## See Also

ST_AsText

## Name

ST_Normalize — Return the geometry in its canonical form.

## Synopsis

`geometry ST_Normalize(` geometry geom`)`;

## Description

Returns the geometry in its normalized/canonical form. May reorder vertices in polygon rings, rings in a polygon, elements in a multi-geometry complex.

Mostly only useful for testing purposes (comparing expected and obtained results).

Availability: 2.3.0

## Examples

    SELECT ST_AsText(ST_Normalize(ST_GeomFromText(
      'GEOMETRYCOLLECTION(
        POINT(2 3),
        MULTILINESTRING((0 0, 1 1),(2 2, 3 3)),
        POLYGON(
          (0 10,0 0,10 0,10 10,0 10),
          (4 2,2 2,2 4,4 4,4 2),
          (6 8,8 8,8 6,6 6,6 8)
        )
      )'
    )));
                                                                         st_astext
    ----------------------------------------------------------------------------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0,0 10,10 10,10 0,0 0),(6 6,8 6,8 8,6 8,6 6),(2 2,4 2,4 4,2 4,2 2)),MULTILINESTRING((2 2,3 3),(0 0,1 1)),POINT(2 3))
    (1 row)

## See Also

ST_Equals,

## Name

ST_Project — Returns a point projected from a start point by a distance and bearing (azimuth).

## Synopsis

`geometry ST_Project(` geometry g1, float distance, float azimuth`)`;

`geometry ST_Project(` geometry g1, geometry g2, float distance`)`;

`geography ST_Project(` geography g1, float distance, float azimuth`)`;

`geography ST_Project(` geography g1, geography g2, float distance`)`;

## Description

Returns a point projected from a point along a geodesic using a given distance and azimuth (bearing). This is known as the direct geodesic problem.

The two-point version uses the path from the first to the second point to implicitly define the azimuth and uses the distance as before.

The distance is given in meters. Negative values are supported.

The azimuth (also known as heading or bearing) is given in radians. It is measured clockwise from true north.

- North is azimuth zero (0 degrees)

- East is azimuth π/2 (90 degrees)

- South is azimuth π (180 degrees)

- West is azimuth 3π/2 (270 degrees)

Negative azimuth values and values greater than 2π (360 degrees) are supported.

Availability: 2.0.0

Enhanced: 2.4.0 Allow negative distance and non-normalized azimuth.

Enhanced: 3.4.0 Allow geometry arguments and two-point form omitting azimuth.

## Example: Projected point at 100,000 meters and bearing 45 degrees

    SELECT ST_AsText(ST_Project('POINT(0 0)'::geography, 100000, radians(45.0)));
    --------------------------------------------
     POINT(0.635231029125537 0.639472334729198)

## See Also

ST_Azimuth, ST_Distance, PostgreSQL function radians()

## Name

ST_QuantizeCoordinates — Sets least significant bits of coordinates to zero

## Synopsis

`geometry ST_QuantizeCoordinates (` geometry g , int prec_x , int prec_y , int prec_z , int prec_m `)`;

## Description

`ST_QuantizeCoordinates` determines the number of bits (`N`) required to represent a coordinate value with a specified number of digits after the decimal point, and then sets all but the `N` most significant bits to zero. The resulting coordinate value will still round to the original value, but will have improved compressiblity. This can result in a significant disk usage reduction provided that the geometry column is using a compressible storage type. The function allows specification of a different number of digits after the decimal point in each dimension; unspecified dimensions are assumed to have the precision of the `x` dimension. Negative digits are interpreted to refer digits to the left of the decimal point, (i.e., `prec_x=-2` will preserve coordinate values to the nearest 100.

The coordinates produced by `ST_QuantizeCoordinates` are independent of the geometry that contains those coordinates and the relative position of those coordinates within the geometry. As a result, existing topological relationships between geometries are unaffected by use of this function. The function may produce invalid geometry when it is called with a number of digits lower than the intrinsic precision of the geometry.

Availability: 2.5.0

## Technical Background

PostGIS stores all coordinate values as double-precision floating point integers, which can reliably represent 15 significant digits. However, PostGIS may be used to manage data that intrinsically has fewer than 15 significant digits. An example is TIGER data, which is provided as geographic coordinates with six digits of precision after the decimal point (thus requiring only nine significant digits of longitude and eight significant digits of latitude.)

When 15 significant digits are available, there are many possible representations of a number with 9 significant digits. A double precision floating point number uses 52 explicit bits to represent the significand (mantissa) of the coordinate. Only 30 bits are needed to represent a mantissa with 9 significant digits, leaving 22 insignificant bits; we can set their value to anything we like and still end up with a number that rounds to our input value. For example, the value 100.123456 can be represented by the floating point numbers closest to 100.123456000000, 100.123456000001, and 100.123456432199. All are equally valid, in that `ST_AsText(geom, 6)` will return the same result with any of these inputs. As we can set these bits to any value, `ST_QuantizeCoordinates` sets the 22 insignificant bits to zero. For a long coordinate sequence this creates a pattern of blocks of consecutive zeros that is compressed by PostgreSQL more efficiently.

Only the on-disk size of the geometry is potentially affected by `ST_QuantizeCoordinates`. ST_MemSize, which reports the in-memory usage of the geometry, will return the the same value regardless of the disk space used by a geometry.

## Examples

    SELECT ST_AsText(ST_QuantizeCoordinates('POINT (100.123456 0)'::geometry, 4));
    st_astext
    -------------------------
    POINT(100.123455047607 0)

    WITH test AS (SELECT 'POINT (123.456789123456 123.456789123456)'::geometry AS geom)
    SELECT
      digits,
      encode(ST_QuantizeCoordinates(geom, digits), 'hex'),
      ST_AsText(ST_QuantizeCoordinates(geom, digits))
    FROM test, generate_series(15, -15, -1) AS digits;

    digits  |                   encode                   |                st_astext
    --------+--------------------------------------------+------------------------------------------
    15      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    14      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    13      | 01010000005f9a72083cdd5e405f9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    12      | 01010000005c9a72083cdd5e405c9a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    11      | 0101000000409a72083cdd5e40409a72083cdd5e40 | POINT(123.456789123456 123.456789123456)
    10      | 0101000000009a72083cdd5e40009a72083cdd5e40 | POINT(123.456789123455 123.456789123455)
    9       | 0101000000009072083cdd5e40009072083cdd5e40 | POINT(123.456789123418 123.456789123418)
    8       | 0101000000008072083cdd5e40008072083cdd5e40 | POINT(123.45678912336 123.45678912336)
    7       | 0101000000000070083cdd5e40000070083cdd5e40 | POINT(123.456789121032 123.456789121032)
    6       | 0101000000000040083cdd5e40000040083cdd5e40 | POINT(123.456789076328 123.456789076328)
    5       | 0101000000000000083cdd5e40000000083cdd5e40 | POINT(123.456789016724 123.456789016724)
    4       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
    3       | 0101000000000000003cdd5e40000000003cdd5e40 | POINT(123.456787109375 123.456787109375)
    2       | 01010000000000000038dd5e400000000038dd5e40 | POINT(123.45654296875 123.45654296875)
    1       | 01010000000000000000dd5e400000000000dd5e40 | POINT(123.453125 123.453125)
    0       | 01010000000000000000dc5e400000000000dc5e40 | POINT(123.4375 123.4375)
    -1      | 01010000000000000000c05e400000000000c05e40 | POINT(123 123)
    -2      | 01010000000000000000005e400000000000005e40 | POINT(120 120)
    -3      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -4      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -5      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -6      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -7      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -8      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -9      | 010100000000000000000058400000000000005840 | POINT(96 96)
    -10     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -11     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -12     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -13     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -14     | 010100000000000000000058400000000000005840 | POINT(96 96)
    -15     | 010100000000000000000058400000000000005840 | POINT(96 96)

## See Also

ST_SnapToGrid

## Name

ST_RemovePoint — Remove a point from a linestring.

## Synopsis

`geometry ST_RemovePoint(` geometry linestring, integer offset`)`;

## Description

Removes a point from a LineString, given its index (0-based). Useful for turning a closed line (ring) into an open linestring.

Enhanced: 3.2.0

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

Guarantees no lines are closed by removing the end point of closed lines (rings). Assumes geom is of type LINESTRING

    UPDATE sometable
    	SET geom = ST_RemovePoint(geom, ST_NPoints(geom) - 1)
    	FROM sometable
    	WHERE ST_IsClosed(geom);

## See Also

ST_AddPoint, ST_NPoints, ST_NumPoints

## Name

ST_RemoveRepeatedPoints — Returns a version of a geometry with duplicate points removed.

## Synopsis

`geometry ST_RemoveRepeatedPoints(` geometry geom, float8 tolerance`)`;

## Description

Returns a version of the given geometry with duplicate consecutive points removed. The function processes only (Multi)LineStrings, (Multi)Polygons and MultiPoints but it can be called with any kind of geometry. Elements of GeometryCollections are processed individually. The endpoints of LineStrings are preserved.

If the `tolerance` parameter is provided, vertices within the tolerance distance of one another are considered to be duplicates.

Enhanced: 3.2.0

Availability: 2.2.0

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText( ST_RemoveRepeatedPoints( 'MULTIPOINT ((1 1), (2 2), (3 3), (2 2))'));
    -------------------------
     MULTIPOINT(1 1,2 2,3 3)

    SELECT ST_AsText( ST_RemoveRepeatedPoints( 'LINESTRING (0 0, 0 0, 1 1, 0 0, 1 1, 2 2)'));
    ---------------------------------
     LINESTRING(0 0,1 1,0 0,1 1,2 2)

Example: Collection elements are processed individually.

    SELECT ST_AsText( ST_RemoveRepeatedPoints( 'GEOMETRYCOLLECTION (LINESTRING (1 1, 2 2, 2 2, 3 3), POINT (4 4), POINT (4 4), POINT (5 5))'));
    ------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(LINESTRING(1 1,2 2,3 3),POINT(4 4),POINT(4 4),POINT(5 5))

Example: Repeated point removal with a distance tolerance.

    SELECT ST_AsText( ST_RemoveRepeatedPoints( 'LINESTRING (0 0, 0 0, 1 1, 5 5, 1 1, 2 2)', 2));
    -------------------------
     LINESTRING(0 0,5 5,2 2)

## See Also

ST_Simplify

## Name

ST_RemoveIrrelevantPointsForView — Removes points that are irrelevant for rendering a specific rectangluar view of a geometry.

## Synopsis

`geometry ST_RemoveIrrelevantPointsForView(` geometry geom, box2d bounds, boolean cartesian_hint = false`)`;

## Description

Returns a geometry without points being irrelevant for rendering the geometry within a given rectangluar view.

This function can be used to quickly preprocess geometries that should be rendered only within certain bounds.

Only geometries of type (MULTI)POLYGON and (MULTI)LINESTRING are evaluated. Other geometries keep unchanged.

In contrast to `ST_ClipByBox2D()` this function

- sorts out points without computing new intersection points which avoids rounding errors and usually increases performance,

- returns a geometry with equal or similar point number,

- leads to the same rendering result within the specified view, and

- may introduce self-intersections which would make the resulting geometry invalid (see example below).

If `cartesian_hint` is set to `true`, the algorithm applies additional optimizations involving cartesian math to further reduce the resulting point number. Please note that using this option might introduce rendering artifacts if the resulting coordinates are projected into another (non-cartesian) coordinate system before rendering.

For polygons, this function does currently not ensure that the result is valid. This situation can be checked with ST_IsValid and repaired with ST_MakeValid.

Example: ST_RemoveIrrelevantPointsForView() applied to a polygon. Blue points remain, the rendering result (light-blue area) within the grey view box remains as well.

Example: Due to the fact that points are just sorted out and no new points are computed, the result of ST_RemoveIrrelevantPointsForView() may contain self-intersections.

Availability: 3.5.0

## Examples

    			SELECT ST_AsText(
    			ST_RemoveIrrelevantPointsForView(
    			ST_GeomFromText('MULTIPOLYGON(((10 10, 20 10, 30 10, 40 10, 20 20, 10 20, 10 10)),((10 10, 20 10, 20 20, 10 20, 10 10)))'),
    			ST_MakeEnvelope(12,12,18,18), true));

    		st_astext
    		---------
    		    MULTIPOLYGON(((10 10,40 10,20 20,10 20,10 10)),((10 10,20 10,20 20,10 20,10 10)))

    			SELECT ST_AsText(
    			ST_RemoveIrrelevantPointsForView(
    			ST_GeomFromText('MULTILINESTRING((0 0, 10 0,20 0,30 0), (0 15, 5 15, 10 15, 15 15, 20 15, 25 15, 30 15, 40 15), (13 13,15 15,17 17))'),
    			ST_MakeEnvelope(12,12,18,18), true));

    		st_astext
    		---------
    			MULTILINESTRING((10 15,15 15,20 15),(13 13,15 15,17 17))

    			SELECT ST_AsText(
    			ST_RemoveIrrelevantPointsForView(
    			ST_GeomFromText('LINESTRING(0 0, 10 0,20 0,30 0)'),
    			ST_MakeEnvelope(12,12,18,18), true));

    		st_astext
    		---------
    		    LINESTRING EMPTY

    			SELECT ST_AsText(
    			ST_RemoveIrrelevantPointsForView(
    			ST_GeomFromText('POLYGON((0 30, 15 30, 30 30, 30 0, 0 0, 0 30))'),
    			ST_MakeEnvelope(12,12,18,18), true));

    		st_astext
    		---------
    		    POLYGON((15 30,30 0,0 0,15 30))

    			SELECT ST_AsText(
    			ST_RemoveIrrelevantPointsForView(
    			ST_GeomFromText('POLYGON((0 30, 15 30, 30 30, 30 0, 0 0, 0 30))'),
    			ST_MakeEnvelope(12,12,18,18)));

    		st_astext
    		---------
    		    POLYGON((0 30,30 30,30 0,0 0,0 30))

## See Also

ST_ClipByBox2D, ST_Intersection

## Name

ST_RemoveSmallParts — Removes small parts (polygon rings or linestrings) of a geometry.

## Synopsis

`geometry ST_RemoveSmallParts(` geometry geom, double precision minSizeX, double precision minSizeY`)`;

## Description

Returns a geometry without small parts (exterior or interior polygon rings, or linestrings).

This function can be used as preprocessing step for creating simplified maps, e. g. to remove small islands or holes.

It evaluates only geometries of type (MULTI)POLYGON and (MULTI)LINESTRING. Other geometries remain unchanged.

If `minSizeX` is greater than 0, parts are sorted out if their width is smaller than `minSizeX`.

If `minSizeY` is greater than 0, parts are sorted out if their height is smaller than `minSizeY`.

Both `minSizeX` and `minSizeY` are measured in coordinate system units of the geometry.

For polygon types, evaluation is done separately for each ring which can lead to one of the following results:

- the original geometry,

- a POLYGON with all rings with less vertices,

- a POLYGON with a reduced number of interior rings (having possibly less vertices),

- a POLYGON EMPTY, or

- a MULTIPOLYGON with a reduced number of polygons (having possibly less interior rings or vertices), or

- a MULTIPOLYGON EMPTY.

For linestring types, evaluation is done for each linestring which can lead to one of the following results:

- the original geometry,

- a LINESTRING with a reduced number of vertices,

- a LINESTRING EMPTY,

- a MULTILINESTRING with a reduced number of linestrings (having possibly less vertices), or

- a MULTILINESTRING EMPTY.

Example: ST_RemoveSmallParts() applied to a multi-polygon. Blue parts remain.

Availability: 3.5.0

## Examples

    			SELECT ST_AsText(
    			ST_RemoveSmallParts(
    			ST_GeomFromText('MULTIPOLYGON(
    				((60 160, 120 160, 120 220, 60 220, 60 160), (70 170, 70 210, 110 210, 110 170, 70 170)),
    				((85 75, 155 75, 155 145, 85 145, 85 75)),
    				((50 110, 70 110, 70 130, 50 130, 50 110)))'),
    				50, 50));

    		st_astext
    		---------
    			MULTIPOLYGON(((60 160,120 160,120 220,60 220,60 160)),((85 75,155 75,155 145,85 145,85 75)))

    			SELECT ST_AsText(
    			ST_RemoveSmallParts(
    			ST_GeomFromText('LINESTRING(10 10, 20 20)'),
    				50, 50));

    		st_astext
    		---------
    			LINESTRING EMPTY

## Name

ST_Reverse — Return the geometry with vertex order reversed.

## Synopsis

`geometry ST_Reverse(` geometry g1`)`;

## Description

Can be used on any geometry and reverses the order of the vertices.

Enhanced: 2.4.0 support for curves was introduced.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_AsText(geom) as line, ST_AsText(ST_Reverse(geom)) As reverseline
    FROM
    (SELECT ST_MakeLine(ST_Point(1,2),
    		ST_Point(1,10)) As geom) as foo;
    --result
    		line         |     reverseline
    ---------------------+----------------------
    LINESTRING(1 2,1 10) | LINESTRING(1 10,1 2)

## Name

ST_Segmentize — Returns a modified geometry/geography having no segment longer than a given distance.

## Synopsis

`geometry ST_Segmentize(` geometry geom, float max_segment_length`)`;

`geography ST_Segmentize(` geography geog, float max_segment_length`)`;

## Description

Returns a modified geometry/geography having no segment longer than `max_segment_length`. Length is computed in 2D. Segments are always split into equal-length subsegments.

- For geometry, the maximum length is in the units of the spatial reference system.

- For geography, the maximum length is in meters. Distances are computed on the sphere. Added vertices are created along the spherical great-circle arcs defined by segment endpoints.

This only shortens long segments. It does not lengthen segments shorter than the maximum length.

For inputs containing long segments, specifying a relatively short `max_segment_length` can cause a very large number of vertices to be added. This can happen unintentionally if the argument is specified accidentally as a number of segments, rather than a maximum length.

Availability: 1.2.2

Enhanced: 3.0.0 Segmentize geometry now produces equal-length subsegments

Enhanced: 2.3.0 Segmentize geography now produces equal-length subsegments

Enhanced: 2.1.0 support for geography was introduced.

Changed: 2.1.0 As a result of the introduction of geography support, the usage `ST_Segmentize('LINESTRING(1 2, 3 4)', 0.5)` causes an ambiguous function error. The input needs to be properly typed as a geometry or geography. Use ST_GeomFromText, ST_GeogFromText or a cast to the required type (e.g. `ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry, 0.5) )`

## Examples

Segmentizing a line. Long segments are split evenly, and short segments are not split.

    SELECT ST_AsText(ST_Segmentize(
        'MULTILINESTRING((0 0, 0 1, 0 9),(1 10, 1 18))'::geometry,
    	5 ) );
    ---------------------------------------------------
    MULTILINESTRING((0 0,0 1,0 5,0 9),(1 10,1 14,1 18))

Segmentizing a polygon:

    SELECT ST_AsText(
            ST_Segmentize(('POLYGON((0 0, 0 8, 30 0, 0 0))'::geometry), 10));
    -------------------------------------------------------
    POLYGON((0 0,0 8,7.5 6,15 4,22.5 2,30 0,20 0,10 0,0 0))

Segmentizing a geographic line, using a maximum segment length of 2000 kilometers. Vertices are added along the great-circle arc connecting the endpoints.

    SELECT ST_AsText(
            ST_Segmentize(('LINESTRING (0 0, 60 60)'::geography), 2000000));
    -------------------------------------------------------------
    LINESTRING(0 0,4.252632294621186 8.43596525986862,8.69579947419404 16.824093489701564,13.550465473227048 25.107950473646188,19.1066053508691 33.21091076089908,25.779290201459894 41.01711439406505,34.188839517966954 48.337222885886,45.238153936612264 54.84733442373889,60 60)

A geographic line segmentized along a great circle arc

## See Also

ST_LineSubstring

## Name

ST_SetPoint — Replace point of a linestring with a given point.

## Synopsis

`geometry ST_SetPoint(` geometry linestring, integer zerobasedposition, geometry point`)`;

## Description

Replace point N of linestring with given point. Index is 0-based.Negative index are counted backwards, so that -1 is last point. This is especially useful in triggers when trying to maintain relationship of joints when one vertex moves.

Availability: 1.1.0

Updated 2.3.0 : negative indexing

This function supports 3d and will not drop the z-index.

## Examples

    --Change first point in line string from -1 3 to -1 1
    SELECT ST_AsText(ST_SetPoint('LINESTRING(-1 2,-1 3)', 0, 'POINT(-1 1)'));
    	   st_astext
    -----------------------
     LINESTRING(-1 1,-1 3)

    ---Change last point in a line string (lets play with 3d linestring this time)
    SELECT ST_AsEWKT(ST_SetPoint(foo.geom, ST_NumPoints(foo.geom) - 1, ST_GeomFromEWKT('POINT(-1 1 3)')))
    FROM (SELECT ST_GeomFromEWKT('LINESTRING(-1 2 3,-1 3 4, 5 6 7)') As geom) As foo;
    	   st_asewkt
    -----------------------
    LINESTRING(-1 2 3,-1 3 4,-1 1 3)

    SELECT ST_AsText(ST_SetPoint(g, -3, p))
    FROM ST_GEomFromText('LINESTRING(0 0, 1 1, 2 2, 3 3, 4 4)') AS g
    	, ST_PointN(g,1) as p;
    	   st_astext
    -----------------------
    LINESTRING(0 0,1 1,0 0,3 3,4 4)

## See Also

ST_AddPoint, ST_NPoints, ST_NumPoints, ST_PointN, ST_RemovePoint

## Name

ST_ShiftLongitude — Shifts the longitude coordinates of a geometry between -180..180 and 0..360.

## Synopsis

`geometry ST_ShiftLongitude(` geometry geom`)`;

## Description

Reads every point/vertex in a geometry, and shifts its longitude coordinate from -180..0 to 180..360 and vice versa if between these ranges. This function is symmetrical so the result is a 0..360 representation of a -180..180 data and a -180..180 representation of a 0..360 data.

This is only useful for data with coordinates in longitude/latitude; e.g. SRID 4326 (WGS 84 geographic)

Pre-1.3.4 bug prevented this from working for MULTIPOINT. 1.3.4+ works with MULTIPOINT as well.

This function supports 3d and will not drop the z-index.

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

NOTE: this function was renamed from "ST_Shift_Longitude" in 2.2.0

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --single point forward transformation
    SELECT ST_AsText(ST_ShiftLongitude('SRID=4326;POINT(270 0)'::geometry))

    st_astext
    ----------
    POINT(-90 0)

    --single point reverse transformation
    SELECT ST_AsText(ST_ShiftLongitude('SRID=4326;POINT(-90 0)'::geometry))

    st_astext
    ----------
    POINT(270 0)

    --for linestrings the functions affects only to the sufficient coordinates
    SELECT ST_AsText(ST_ShiftLongitude('SRID=4326;LINESTRING(174 12, 182 13)'::geometry))

    st_astext
    ----------
    LINESTRING(174 12,-178 13)

## See Also

ST_WrapX

## Name

ST_WrapX — Wrap a geometry around an X value.

## Synopsis

`geometry ST_WrapX(` geometry geom, float8 wrap, float8 move`)`;

## Description

This function splits the input geometries and then moves every resulting component falling on the right (for negative 'move') or on the left (for positive 'move') of given 'wrap' line in the direction specified by the 'move' parameter, finally re-unioning the pieces together.

This is useful to "recenter" long-lat input to have features of interest not spawned from one side to the other.

Availability: 2.3.0 requires GEOS

This function supports 3d and will not drop the z-index.

## Examples

    -- Move all components of the given geometries whose bounding box
    -- falls completely on the left of x=0 to +360
    select ST_WrapX(geom, 0, 360);

    -- Move all components of the given geometries whose bounding box
    -- falls completely on the left of x=-30 to +360
    select ST_WrapX(geom, -30, 360);

## See Also

ST_ShiftLongitude

## Name

ST_SnapToGrid — Snap all points of the input geometry to a regular grid.

## Synopsis

`geometry ST_SnapToGrid(` geometry geomA, float originX, float originY, float sizeX, float sizeY`)`;

`geometry ST_SnapToGrid(` geometry geomA, float sizeX, float sizeY`)`;

`geometry ST_SnapToGrid(` geometry geomA, float size`)`;

`geometry ST_SnapToGrid(` geometry geomA, geometry pointOrigin, float sizeX, float sizeY, float sizeZ, float sizeM`)`;

## Description

Variant 1,2,3: Snap all points of the input geometry to the grid defined by its origin and cell size. Remove consecutive points falling on the same cell, eventually returning NULL if output points are not enough to define a geometry of the given type. Collapsed geometries in a collection are stripped from it. Useful for reducing precision.

Variant 4: Introduced 1.1.0 - Snap all points of the input geometry to the grid defined by its origin (the second argument, must be a point) and cell sizes. Specify 0 as size for any dimension you don't want to snap to a grid.

The returned geometry might lose its simplicity (see ST_IsSimple).

Before release 1.1.0 this function always returned a 2d geometry. Starting at 1.1.0 the returned geometry will have same dimensionality as the input one with higher dimension values untouched. Use the version taking a second geometry argument to define all grid dimensions.

Availability: 1.0.0RC1

Availability: 1.1.0 - Z and M support

This function supports 3d and will not drop the z-index.

## Examples

    --Snap your geometries to a precision grid of 10^-3
    UPDATE mytable
       SET geom = ST_SnapToGrid(geom, 0.001);

    SELECT ST_AsText(ST_SnapToGrid(
    			ST_GeomFromText('LINESTRING(1.1115678 2.123, 4.111111 3.2374897, 4.11112 3.23748667)'),
    			0.001)
    		);
    			  st_astext
    -------------------------------------
     LINESTRING(1.112 2.123,4.111 3.237)
     --Snap a 4d geometry
    SELECT ST_AsEWKT(ST_SnapToGrid(
    	ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 2.3456 1.11111,
    		4.111111 3.2374897 3.1234 1.1111, -1.11111112 2.123 2.3456 1.1111112)'),
     ST_GeomFromEWKT('POINT(1.12 2.22 3.2 4.4444)'),
     0.1, 0.1, 0.1, 0.01) );
    								  st_asewkt
    ------------------------------------------------------------------------------
     LINESTRING(-1.08 2.12 2.3 1.1144,4.12 3.22 3.1 1.1144,-1.08 2.12 2.3 1.1144)

    --With a 4d geometry - the ST_SnapToGrid(geom,size) only touches x and y coords but keeps m and z the same
    SELECT ST_AsEWKT(ST_SnapToGrid(ST_GeomFromEWKT('LINESTRING(-1.1115678 2.123 3 2.3456,
    		4.111111 3.2374897 3.1234 1.1111)'),
    	   0.01)      );
    						st_asewkt
    ---------------------------------------------------------
     LINESTRING(-1.11 2.12 3 2.3456,4.11 3.24 3.1234 1.1111)

## See Also

ST_Snap, ST_AsEWKT, ST_AsText, ST_GeomFromText, ST_GeomFromEWKT, ST_Simplify

## Name

ST_Snap — Snap segments and vertices of input geometry to vertices of a reference geometry.

## Synopsis

`geometry ST_Snap(` geometry input, geometry reference, float tolerance`)`;

## Description

Snaps the vertices and segments of a geometry to another Geometry's vertices. A snap distance tolerance is used to control where snapping is performed. The result geometry is the input geometry with the vertices snapped. If no snapping occurs then the input geometry is returned unchanged.

Snapping one geometry to another can improve robustness for overlay operations by eliminating nearly-coincident edges (which cause problems during noding and intersection calculation).

Too much snapping can result in invalid topology being created, so the number and location of snapped vertices is decided using heuristics to determine when it is safe to snap. This can result in some potential snaps being omitted, however.

The returned geometry might lose its simplicity (see ST_IsSimple) and validity (see ST_IsValid).

Performed by the GEOS module.

Availability: 2.0.0

## Examples

A multipolygon shown with a linestring (before any snapping)
A multipolygon snapped to linestring to tolerance: 1.01 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(ST_Snap(poly,line, ST_Distance(poly,line)*1.01)) AS polysnapped
    FROM (SELECT
       ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
     MULTIPOLYGON(((26 125,26 200,126 200,126 125,101 100,26 125),
     (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
| A multipolygon snapped to linestring to tolerance: 1.25 of distance. The new multipolygon is shown with reference linestring
    SELECT ST_AsText(
        ST_Snap(poly,line, ST_Distance(poly,line)*1.25)
      ) AS polysnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
        (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          ( 51 150, 101 150, 76 175, 51 150 )),
          (( 151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                                 polysnapped
    ---------------------------------------------------------------------
    MULTIPOLYGON(((5 107,26 200,126 200,126 125,101 100,54 84,5 107),
    (51 150,101 150,76 175,51 150)),((151 100,151 200,176 175,151 100)))
The linestring snapped to the original multipolygon at tolerance 1.01 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
       ST_Snap(line, poly, ST_Distance(poly,line)*1.01)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         ((26 125, 26 200, 126 200, 126 125, 26 125),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100)))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;

                  linesnapped
    ----------------------------------------
     LINESTRING(5 107,26 125,54 84,101 100)
| The linestring snapped to the original multipolygon at tolerance 1.25 of distance. The new linestring is shown with reference multipolygon
    SELECT ST_AsText(
     ST_Snap(line, poly, ST_Distance(poly,line)*1.25)
      ) AS linesnapped
    FROM (SELECT
      ST_GeomFromText('MULTIPOLYGON(
         (( 26 125, 26 200, 126 200, 126 125, 26 125 ),
          (51 150, 101 150, 76 175, 51 150 )),
          ((151 100, 151 200, 176 175, 151 100 )))') As poly,
           ST_GeomFromText('LINESTRING (5 107, 54 84, 101 100)') As line
    	) As foo;
                  linesnapped
    ---------------------------------------
    LINESTRING(26 125,54 84,101 100)

## See Also

ST_SnapToGrid

## Name

ST_SwapOrdinates — Returns a version of the given geometry with given ordinate values swapped.

## Synopsis

`geometry ST_SwapOrdinates(` geometry geom, cstring ords`)`;

## Description

Returns a version of the given geometry with given ordinates swapped.

The `ords` parameter is a 2-characters string naming the ordinates to swap. Valid names are: x,y,z and m.

Availability: 2.2.0

This method supports Circular Strings and Curves.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Example

    -- Scale M value by 2
    SELECT ST_AsText(
      ST_SwapOrdinates(
        ST_Scale(
          ST_SwapOrdinates(g,'xm'),
          2, 1
        ),
      'xm')
    ) FROM ( SELECT 'POINT ZM (0 0 0 2)'::geometry g ) foo;
         st_astext
    --------------------
     POINT ZM (0 0 0 4)

## See Also

ST_FlipCoordinates

## 7.6. Geometry Validation

Abstract

These functions test whether geometries are valid according to the OGC SFS standard. They also provide information about the nature and location of invalidity. There is also a function to create a valid geometry out of an invalid one.

## Name

ST_IsValid — Tests if a geometry is well-formed in 2D.

## Synopsis

`boolean ST_IsValid(` geometry g`)`;

`boolean ST_IsValid(` geometry g, integer flags`)`;

## Description

Tests if an ST_Geometry value is well-formed and valid in 2D according to the OGC rules. For geometries with 3 and 4 dimensions, the validity is still only tested in 2 dimensions. For geometries that are invalid, a PostgreSQL NOTICE is emitted providing details of why it is not valid.

For the version with the `flags` parameter, supported values are documented in ST_IsValidDetail This version does not print a NOTICE explaining invalidity.

For more information on the definition of geometry validity, refer to Section 4.4, “Geometry Validation”

SQL-MM defines the result of ST_IsValid(NULL) to be 0, while PostGIS returns NULL.

Performed by the GEOS module.

The version accepting flags is available starting with 2.0.0.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.9

Neither OGC-SFS nor SQL-MM specifications include a flag argument for ST_IsValid. The flag is a PostGIS extension.

## Examples

    SELECT ST_IsValid(ST_GeomFromText('LINESTRING(0 0, 1 1)')) As good_line,
    	ST_IsValid(ST_GeomFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) As bad_poly
    --results
    NOTICE:  Self-intersection at or near point 0 0
     good_line | bad_poly
    -----------+----------
     t         | f

## See Also

ST_IsSimple, ST_IsValidReason, ST_IsValidDetail,

## Name

ST_IsValidDetail — Returns a `valid_detail` row stating if a geometry is valid or if not a reason and a location.

## Synopsis

`valid_detail ST_IsValidDetail(` geometry geom, integer flags`)`;

## Description

Returns a `valid_detail` row, containing a boolean (`valid`) stating if a geometry is valid, a varchar (`reason`) stating a reason why it is invalid and a geometry (`location`) pointing out where it is invalid.

Useful to improve on the combination of ST_IsValid and ST_IsValidReason to generate a detailed report of invalid geometries.

The optional `flags` parameter is a bitfield. It can have the following values:

- 0: Use usual OGC SFS validity semantics.

- 1: Consider certain kinds of self-touching rings (inverted shells and exverted holes) as valid. This is also known as "the ESRI flag", since this is the validity model used by those tools. Note that this is invalid under the OGC model.

Performed by the GEOS module.

Availability: 2.0.0

## Examples

    --First 3 Rejects from a successful quintuplet experiment
    SELECT gid, reason(ST_IsValidDetail(geom)), ST_AsText(location(ST_IsValidDetail(geom))) as location
    FROM
    (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), array_agg(f.line)) As geom, gid
    FROM (SELECT ST_Buffer(ST_Point(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
    	FROM generate_series(-4,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,8) z1
    	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
    	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_Point(x1*10,y1), z1)),y1*1, z1*2) As line
    	FROM generate_series(-3,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,10) z1
    	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
    ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
    GROUP BY gid, e.buff) As quintuplet_experiment
    WHERE ST_IsValid(geom) = false
    ORDER BY gid
    LIMIT 3;

     gid  |      reason       |  location
    ------+-------------------+-------------
     5330 | Self-intersection | POINT(32 5)
     5340 | Self-intersection | POINT(42 5)
     5350 | Self-intersection | POINT(52 5)

     --simple example
    SELECT * FROM ST_IsValidDetail('LINESTRING(220227 150406,2220227 150407,222020 150410)');

     valid | reason | location
    -------+--------+----------
     t     |        |

## See Also

ST_IsValid, ST_IsValidReason

## Name

ST_IsValidReason — Returns text stating if a geometry is valid, or a reason for invalidity.

## Synopsis

`text ST_IsValidReason(` geometry geomA`)`;

`text ST_IsValidReason(` geometry geomA, integer flags`)`;

## Description

Returns text stating if a geometry is valid, or if invalid a reason why.

Useful in combination with ST_IsValid to generate a detailed report of invalid geometries and reasons.

Allowed `flags` are documented in ST_IsValidDetail.

Performed by the GEOS module.

Availability: 1.4

Availability: 2.0 version taking flags.

## Examples

    -- invalid bow-tie polygon
    SELECT ST_IsValidReason(
        'POLYGON ((100 200, 100 100, 200 200,
         200 100, 100 200))'::geometry) as validity_info;
    validity_info
    --------------------------
    Self-intersection[150 150]

    --First 3 Rejects from a successful quintuplet experiment
    SELECT gid, ST_IsValidReason(geom) as validity_info
    FROM
    (SELECT ST_MakePolygon(ST_ExteriorRing(e.buff), array_agg(f.line)) As geom, gid
    FROM (SELECT ST_Buffer(ST_Point(x1*10,y1), z1) As buff, x1*10 + y1*100 + z1*1000 As gid
    	FROM generate_series(-4,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,8) z1
    	WHERE x1 > y1*0.5 AND z1 < x1*y1) As e
    	INNER JOIN (SELECT ST_Translate(ST_ExteriorRing(ST_Buffer(ST_Point(x1*10,y1), z1)),y1*1, z1*2) As line
    	FROM generate_series(-3,6) x1
    	CROSS JOIN generate_series(2,5) y1
    	CROSS JOIN generate_series(1,10) z1
    	WHERE x1 > y1*0.75 AND z1 < x1*y1) As f
    ON (ST_Area(e.buff) > 78 AND ST_Contains(e.buff, f.line))
    GROUP BY gid, e.buff) As quintuplet_experiment
    WHERE ST_IsValid(geom) = false
    ORDER BY gid
    LIMIT 3;

     gid  |      validity_info
    ------+--------------------------
     5330 | Self-intersection [32 5]
     5340 | Self-intersection [42 5]
     5350 | Self-intersection [52 5]

     --simple example
    SELECT ST_IsValidReason('LINESTRING(220227 150406,2220227 150407,222020 150410)');

     st_isvalidreason
    ------------------
     Valid Geometry

## See Also

ST_IsValid, ST_Summary

## Name

ST_MakeValid — Attempts to make an invalid geometry valid without losing vertices.

## Synopsis

`geometry ST_MakeValid(` geometry input`)`;

`geometry ST_MakeValid(` geometry input, text params`)`;

## Description

The function attempts to create a valid representation of a given invalid geometry without losing any of the input vertices. Valid geometries are returned unchanged.

Supported inputs are: POINTS, MULTIPOINTS, LINESTRINGS, MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS and GEOMETRYCOLLECTIONS containing any mix of them.

In case of full or partial dimensional collapses, the output geometry may be a collection of lower-to-equal dimension geometries, or a geometry of lower dimension.

Single polygons may become multi-geometries in case of self-intersections.

The `params` argument can be used to supply an options string to select the method to use for building valid geometry. The options string is in the format "method=linework|structure keepcollapsed=true|false". If no "params" argument is provided, the "linework" algorithm will be used as the default.

The "method" key has two values.

- "linework" is the original algorithm, and builds valid geometries by first extracting all lines, noding that linework together, then building a value output from the linework.

- "structure" is an algorithm that distinguishes between interior and exterior rings, building new geometry by unioning exterior rings, and then differencing all interior rings.

The "keepcollapsed" key is only valid for the "structure" algorithm, and takes a value of "true" or "false". When set to "false", geometry components that collapse to a lower dimensionality, for example a one-point linestring would be dropped.

Performed by the GEOS module.

Availability: 2.0.0

Enhanced: 2.0.1, speed improvements

Enhanced: 2.1.0, added support for GEOMETRYCOLLECTION and MULTIPOINT.

Enhanced: 3.1.0, added removal of Coordinates with NaN values.

Enhanced: 3.2.0, added algorithm options, 'linework' and 'structure' which requires GEOS >= 3.10.0.

This function supports 3d and will not drop the z-index.

## Examples

before_geom: MULTIPOLYGON of 2 overlapping polygons after_geom: MULTIPOLYGON of 4 non-overlapping polygons after_geom_structure: MULTIPOLYGON of 1 non-overlapping polygon
    SELECT f.geom AS before_geom, ST_MakeValid(f.geom) AS after_geom, ST_MakeValid(f.geom, 'method=structure') AS after_geom_structure
    FROM (SELECT 'MULTIPOLYGON(((186 194,187 194,188 195,189 195,190 195,
    191 195,192 195,193 194,194 194,194 193,195 192,195 191,
    195 190,195 189,195 188,194 187,194 186,14 6,13 6,12 5,11 5,
    10 5,9 5,8 5,7 6,6 6,6 7,5 8,5 9,5 10,5 11,5 12,6 13,6 14,186 194)),
    ((150 90,149 80,146 71,142 62,135 55,128 48,119 44,110 41,100 40,
    90 41,81 44,72 48,65 55,58 62,54 71,51 80,50 90,51 100,
    54 109,58 118,65 125,72 132,81 136,90 139,100 140,110 139,
    119 136,128 132,135 125,142 118,146 109,149 100,150 90)))'::geometry AS geom) AS f;
before_geom: MULTIPOLYGON of 6 overlapping polygons after_geom: MULTIPOLYGON of 14 Non-overlapping polygons after_geom_structure: MULTIPOLYGON of 1 Non-overlapping polygon
    SELECT c.geom AS before_geom,
                        ST_MakeValid(c.geom) AS after_geom,
                        ST_MakeValid(c.geom, 'method=structure') AS after_geom_structure
    	FROM (SELECT 'MULTIPOLYGON(((91 50,79 22,51 10,23 22,11 50,23 78,51 90,79 78,91 50)),
    		  ((91 100,79 72,51 60,23 72,11 100,23 128,51 140,79 128,91 100)),
    		  ((91 150,79 122,51 110,23 122,11 150,23 178,51 190,79 178,91 150)),
    		  ((141 50,129 22,101 10,73 22,61 50,73 78,101 90,129 78,141 50)),
    		  ((141 100,129 72,101 60,73 72,61 100,73 128,101 140,129 128,141 100)),
    		  ((141 150,129 122,101 110,73 122,61 150,73 178,101 190,129 178,141 150)))'::geometry AS geom) AS c;

## Examples

    SELECT ST_AsText(ST_MakeValid(
        'LINESTRING(0 0, 0 0)',
        'method=structure keepcollapsed=true'
        ));

     st_astext
    ------------
     POINT(0 0)

    SELECT ST_AsText(ST_MakeValid(
        'LINESTRING(0 0, 0 0)',
        'method=structure keepcollapsed=false'
        ));

        st_astext
    ------------------
     LINESTRING EMPTY

## See Also

ST_IsValid, ST_Collect, ST_CollectionExtract

## 7.7. Spatial Reference System Functions

Abstract

These functions work with the Spatial Reference System of geometries as defined in the `spatial_ref_sys` table.

## Name

ST_InverseTransformPipeline — Return a new geometry with coordinates transformed to a different spatial reference system using the inverse of a defined coordinate transformation pipeline.

## Synopsis

`geometry ST_InverseTransformPipeline(` geometry geom, text pipeline, integer to_srid`)`;

## Description

Return a new geometry with coordinates transformed to a different spatial reference system using a defined coordinate transformation pipeline to go in the inverse direction.

Refer to ST_TransformPipeline for details on writing a transformation pipeline.

Availability: 3.4.0

The SRID of the input geometry is ignored, and the SRID of the output geometry will be set to zero unless a value is provided via the optional `to_srid` parameter. When using ST_TransformPipeline the pipeline is executed in a forward direction. Using `ST_InverseTransformPipeline()` the pipeline is executed in the inverse direction.

Transforms using pipelines are a specialised version of ST_Transform. In most cases `ST_Transform` will choose the correct operations to convert between coordinate systems, and should be preferred.

## Examples

Change WGS 84 long lat to UTM 31N using the EPSG:16031 conversion

    -- Inverse direction
    SELECT ST_AsText(ST_InverseTransformPipeline('POINT(426857.9877165967 5427937.523342293)'::geometry,
      'urn:ogc:def:coordinateOperation:EPSG::16031')) AS wgs_geom;

              wgs_geom
    ----------------------------
     POINT(2 48.99999999999999)
    (1 row)

GDA2020 example.

    -- using ST_Transform with automatic selection of a conversion pipeline.
    SELECT ST_AsText(ST_Transform('SRID=4939;POINT(143.0 -37.0)'::geometry, 7844)) AS gda2020_auto;

                     gda2020_auto
    -----------------------------------------------
     POINT(143.00000635638918 -36.999986706128176)
    (1 row)

## See Also

ST_Transform, ST_TransformPipeline

## Name

ST_SetSRID — Set the SRID on a geometry.

## Synopsis

`geometry ST_SetSRID(` geometry geom, integer srid`)`;

## Description

Sets the SRID on a geometry to a particular integer value. Useful in constructing bounding boxes for queries.

This function does not transform the geometry coordinates in any way - it simply sets the meta data defining the spatial reference system the geometry is assumed to be in. Use ST_Transform if you want to transform the geometry into a new projection.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method supports Circular Strings and Curves.

## Examples

-- Mark a point as WGS 84 long lat --

    SELECT ST_SetSRID(ST_Point(-123.365556, 48.428611),4326) As wgs84long_lat;
    -- the ewkt representation (wrap with ST_AsEWKT) -
    SRID=4326;POINT(-123.365556 48.428611)

-- Mark a point as WGS 84 long lat and then transform to web mercator (Spherical Mercator) --

    SELECT ST_Transform(ST_SetSRID(ST_Point(-123.365556, 48.428611),4326),3785) As spere_merc;
    -- the ewkt representation (wrap with ST_AsEWKT) -
    SRID=3785;POINT(-13732990.8753491 6178458.96425423)

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SRID, ST_Transform, UpdateGeometrySRID

## Name

ST_SRID — Returns the spatial reference identifier for a geometry.

## Synopsis

`integer ST_SRID(` geometry g1`)`;

## Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.5, “Spatial Reference Systems”

spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.5

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326));
        --result
        4326

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SetSRID, ST_Transform, ST_SRID, ST_SRID

## Name

ST_Transform — Return a new geometry with coordinates transformed to a different spatial reference system.

## Synopsis

`geometry ST_Transform(` geometry g1, integer srid`)`;

`geometry ST_Transform(` geometry geom, text to_proj`)`;

`geometry ST_Transform(` geometry geom, text from_proj, text to_proj`)`;

`geometry ST_Transform(` geometry geom, text from_proj, integer to_srid`)`;

## Description

Returns a new geometry with its coordinates transformed to a different spatial reference system. The destination spatial reference `to_srid` may be identified by a valid SRID integer parameter (i.e. it must exist in the `spatial_ref_sys` table). Alternatively, a spatial reference defined as a PROJ.4 string can be used for `to_proj` and/or `from_proj`, however these methods are not optimized. If the destination spatial reference system is expressed with a PROJ.4 string instead of an SRID, the SRID of the output geometry will be set to zero. With the exception of functions with `from_proj`, input geometries must have a defined SRID.

ST_Transform is often confused with ST_SetSRID. ST_Transform actually changes the coordinates of a geometry from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the geometry.

ST_Transform automatically selects a suitable conversion pipeline given the source and target spatial reference systems. To use a specific conversion method, use ST_TransformPipeline.

Requires PostGIS be compiled with PROJ support. Use PostGIS_Full_Version to confirm you have PROJ support compiled in.

If using more than one transformation, it is useful to have a functional index on the commonly used transformations to take advantage of index usage.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Enhanced: 2.3.0 support for direct PROJ.4 text was introduced.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.6

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

Change Massachusetts state plane US feet geometry to WGS 84 long lat

    SELECT ST_AsText(ST_Transform(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,
      743265 2967450,743265.625 2967416,743238 2967416))',2249),4326)) As wgs_geom;

     wgs_geom
    ---------------------------
     POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
    -71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.177684
    8522251 42.3902896512902));
    (1 row)

    --3D Circular String example
    SELECT ST_AsEWKT(ST_Transform(ST_GeomFromEWKT('SRID=2249;CIRCULARSTRING(743238 2967416 1,743238 2967450 2,743265 2967450 3,743265.625 2967416 3,743238 2967416 4)'),4326));

             st_asewkt
    --------------------------------------------------------------------------------------
     SRID=4326;CIRCULARSTRING(-71.1776848522251 42.3902896512902 1,-71.1776843766326 42.3903829478009 2,
     -71.1775844305465 42.3903826677917 3,
     -71.1775825927231 42.3902893647987 3,-71.1776848522251 42.3902896512902 4)

Example of creating a partial functional index. For tables where you are not sure all the geometries will be filled in, its best to use a partial index that leaves out null geometries which will both conserve space and make your index smaller and more efficient.

    CREATE INDEX idx_geom_26986_parcels
      ON parcels
      USING gist
      (ST_Transform(geom, 26986))
      WHERE geom IS NOT NULL;

Examples of using PROJ.4 text to transform with custom spatial references.

    -- Find intersection of two polygons near the North pole, using a custom Gnomic projection
    -- See http://boundlessgeo.com/2012/02/flattening-the-peel/
     WITH data AS (
       SELECT
         ST_GeomFromText('POLYGON((170 50,170 72,-130 72,-130 50,170 50))', 4326) AS p1,
         ST_GeomFromText('POLYGON((-170 68,-170 90,-141 90,-141 68,-170 68))', 4326) AS p2,
         '+proj=gnom +ellps=WGS84 +lat_0=70 +lon_0=-160 +no_defs'::text AS gnom
     )
     SELECT ST_AsText(
       ST_Transform(
         ST_Intersection(ST_Transform(p1, gnom), ST_Transform(p2, gnom)),
       gnom, 4326))
     FROM data;
                                              st_astext
     --------------------------------------------------------------------------------
      POLYGON((-170 74.053793645338,-141 73.4268621378904,-141 68,-170 68,-170 74.053793645338))

## Configuring transformation behavior

Sometimes coordinate transformation involving a grid-shift can fail, for example if PROJ.4 has not been built with grid-shift files or the coordinate does not lie within the range for which the grid shift is defined. By default, PostGIS will throw an error if a grid shift file is not present, but this behavior can be configured on a per-SRID basis either by testing different `to_proj` values of PROJ.4 text, or altering the `proj4text` value within the `spatial_ref_sys` table.

For example, the proj4text parameter +datum=NAD87 is a shorthand form for the following +nadgrids parameter:

    +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat

The @ prefix means no error is reported if the files are not present, but if the end of the list is reached with no file having been appropriate (ie. found and overlapping) then an error is issued.

If, conversely, you wanted to ensure that at least the standard files were present, but that if all files were scanned without a hit a null transformation is applied you could use:

    +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null

The null grid shift file is a valid grid shift file covering the whole world and applying no shift. So for a complete example, if you wanted to alter PostGIS so that transformations to SRID 4267 that didn't lie within the correct range did not throw an ERROR, you would use the following:

    UPDATE spatial_ref_sys SET proj4text = '+proj=longlat +ellps=clrk66 +nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat,null +no_defs' WHERE srid = 4267;

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SetSRID, ST_SRID, UpdateGeometrySRID, ST_TransformPipeline

## Name

ST_TransformPipeline — Return a new geometry with coordinates transformed to a different spatial reference system using a defined coordinate transformation pipeline.

## Synopsis

`geometry ST_TransformPipeline(` geometry g1, text pipeline, integer to_srid`)`;

## Description

Return a new geometry with coordinates transformed to a different spatial reference system using a defined coordinate transformation pipeline.

Transformation pipelines are defined using any of the following string formats:

- `urn:ogc:def:coordinateOperation:AUTHORITY::CODE`. Note that a simple `EPSG:CODE` string does not uniquely identify a coordinate operation: the same EPSG code can be used for a CRS definition.

- A PROJ pipeline string of the form: `+proj=pipeline ...`. Automatic axis normalisation will not be applied, and if necessary the caller will need to add an additional pipeline step, or remove `axisswap` steps.

- Concatenated operations of the form: `urn:ogc:def:coordinateOperation,coordinateOperation:EPSG::3895,coordinateOperation:EPSG::1618`.

Availability: 3.4.0

The SRID of the input geometry is ignored, and the SRID of the output geometry will be set to zero unless a value is provided via the optional `to_srid` parameter. When using `ST_TransformPipeline()` the pipeline is executed in a forward direction. Using ST_InverseTransformPipeline the pipeline is executed in the inverse direction.

Transforms using pipelines are a specialised version of ST_Transform. In most cases `ST_Transform` will choose the correct operations to convert between coordinate systems, and should be preferred.

## Examples

Change WGS 84 long lat to UTM 31N using the EPSG:16031 conversion

    -- Forward direction
    SELECT ST_AsText(ST_TransformPipeline('SRID=4326;POINT(2 49)'::geometry,
      'urn:ogc:def:coordinateOperation:EPSG::16031')) AS utm_geom;

                      utm_geom
    --------------------------------------------
     POINT(426857.9877165967 5427937.523342293)
    (1 row)

    -- Inverse direction
    SELECT ST_AsText(ST_InverseTransformPipeline('POINT(426857.9877165967 5427937.523342293)'::geometry,
      'urn:ogc:def:coordinateOperation:EPSG::16031')) AS wgs_geom;

              wgs_geom
    ----------------------------
     POINT(2 48.99999999999999)
    (1 row)

GDA2020 example.

    -- using ST_Transform with automatic selection of a conversion pipeline.
    SELECT ST_AsText(ST_Transform('SRID=4939;POINT(143.0 -37.0)'::geometry, 7844)) AS gda2020_auto;

                     gda2020_auto
    -----------------------------------------------
     POINT(143.00000635638918 -36.999986706128176)
    (1 row)

    -- using a defined conversion (EPSG:8447)
    SELECT ST_AsText(ST_TransformPipeline('SRID=4939;POINT(143.0 -37.0)'::geometry,
      'urn:ogc:def:coordinateOperation:EPSG::8447')) AS gda2020_code;

                       gda2020_code
    ----------------------------------------------
     POINT(143.0000063280214 -36.999986718287545)
    (1 row)

    -- using a PROJ pipeline definition matching EPSG:8447, as returned from
    -- 'projinfo -s EPSG:4939 -t EPSG:7844'.
    -- NOTE: any 'axisswap' steps must be removed.
    SELECT ST_AsText(ST_TransformPipeline('SRID=4939;POINT(143.0 -37.0)'::geometry,
      '+proj=pipeline
       +step +proj=unitconvert +xy_in=deg +xy_out=rad
       +step +proj=hgridshift +grids=au_icsm_GDA94_GDA2020_conformal_and_distortion.tif
       +step +proj=unitconvert +xy_in=rad +xy_out=deg')) AS gda2020_pipeline;

                       gda2020_pipeline
    ----------------------------------------------
     POINT(143.0000063280214 -36.999986718287545)
    (1 row)

## See Also

ST_Transform, ST_InverseTransformPipeline

## Name

postgis_srs_codes — Return the list of SRS codes associated with the given authority.

## Synopsis

`setof text postgis_srs_codes(` text auth_name`)`;

## Description

Returns a set of all `auth_srid` for the given `auth_name`.

Availability: 3.4.0

Proj version 6+

## Examples

List the first ten codes associated with the EPSG authority.

    SELECT * FROM postgis_srs_codes('EPSG') LIMIT 10;

     postgis_srs_codes
    -------------------
     2000
     20004
     20005
     20006
     20007
     20008
     20009
     2001
     20010
     20011

## See Also

postgis_srs, postgis_srs_all, postgis_srs_search

## Name

postgis_srs — Return a metadata record for the requested authority and srid.

## Synopsis

`setof record postgis_srs(` text auth_name, text auth_srid`)`;

## Description

Returns a metadata record for the requested `auth_srid` for the given `auth_name`. The record will have the `auth_name`, `auth_srid`, `srname`, `srtext`, `proj4text`, and the corners of the area of usage, `point_sw` and `point_ne`.

Availability: 3.4.0

Proj version 6+

## Examples

Get the metadata for EPSG:3005.

    SELECT * FROM postgis_srs('EPSG', '3005');

    auth_name | EPSG
    auth_srid | 3005
    srname    | NAD83 / BC Albers
    srtext    | PROJCS["NAD83 / BC Albers", ... ]]
    proj4text | +proj=aea +lat_0=45 +lon_0=-126 +lat_1=50 +lat_2=58.5 +x_0=1000000 +y_0=0 +datum=NAD83 +units=m +no_defs +type=crs
    point_sw  | 0101000020E6100000E17A14AE476161C00000000000204840
    point_ne  | 0101000020E610000085EB51B81E855CC0E17A14AE47014E40

## See Also

postgis_srs_codes, postgis_srs_all, postgis_srs_search

## Name

postgis_srs_all — Return metadata records for every spatial reference system in the underlying Proj database.

## Synopsis

`setof record postgis_srs_all(` `void)`;

## Description

Returns a set of all metadata records in the underlying Proj database. The records will have the `auth_name`, `auth_srid`, `srname`, `srtext`, `proj4text`, and the corners of the area of usage, `point_sw` and `point_ne`.

Availability: 3.4.0

Proj version 6+

## Examples

Get the first 10 metadata records from the Proj database.

    SELECT auth_name, auth_srid, srname FROM postgis_srs_all() LIMIT 10;

     auth_name | auth_srid |                  srname
    -----------+-----------+------------------------------------------
     EPSG      | 2000      | Anguilla 1957 / British West Indies Grid
     EPSG      | 20004     | Pulkovo 1995 / Gauss-Kruger zone 4
     EPSG      | 20005     | Pulkovo 1995 / Gauss-Kruger zone 5
     EPSG      | 20006     | Pulkovo 1995 / Gauss-Kruger zone 6
     EPSG      | 20007     | Pulkovo 1995 / Gauss-Kruger zone 7
     EPSG      | 20008     | Pulkovo 1995 / Gauss-Kruger zone 8
     EPSG      | 20009     | Pulkovo 1995 / Gauss-Kruger zone 9
     EPSG      | 2001      | Antigua 1943 / British West Indies Grid
     EPSG      | 20010     | Pulkovo 1995 / Gauss-Kruger zone 10
     EPSG      | 20011     | Pulkovo 1995 / Gauss-Kruger zone 11

## See Also

postgis_srs_codes, postgis_srs, postgis_srs_search

## Name

postgis_srs_search — Return metadata records for projected coordinate systems that have areas of usage that fully contain the bounds parameter.

## Synopsis

`setof record postgis_srs_search(` geometry bounds, text auth_name=EPSG`)`;

## Description

Return a set of metadata records for projected coordinate systems that have areas of usage that fully contain the bounds parameter. Each record will have the `auth_name`, `auth_srid`, `srname`, `srtext`, `proj4text`, and the corners of the area of usage, `point_sw` and `point_ne`.

The search only looks for projected coordinate systems, and is intended for users to explore the possible systems that work for the extent of their data.

Availability: 3.4.0

Proj version 6+

## Examples

Search for projected coordinate systems in Louisiana.

    SELECT auth_name, auth_srid, srname,
      ST_AsText(point_sw) AS point_sw,
      ST_AsText(point_ne) AS point_ne
    FROM postgis_srs_search('SRID=4326;LINESTRING(-90 30, -91 31)')
    LIMIT 3;

     auth_name | auth_srid |                srname                |      point_sw       |      point_ne
    -----------+-----------+--------------------------------------+---------------------+---------------------
     EPSG      | 2801      | NAD83(HARN) / Louisiana South        | POINT(-93.94 28.85) | POINT(-88.75 31.07)
     EPSG      | 3452      | NAD83 / Louisiana South (ftUS)       | POINT(-93.94 28.85) | POINT(-88.75 31.07)
     EPSG      | 3457      | NAD83(HARN) / Louisiana South (ftUS) | POINT(-93.94 28.85) | POINT(-88.75 31.07)

Scan a table for max extent and find projected coordinate systems that might suit.

    WITH ext AS (
      SELECT ST_Extent(geom) AS geom, Max(ST_SRID(geom)) AS srid
      FROM foo
    )
    SELECT auth_name, auth_srid, srname,
      ST_AsText(point_sw) AS point_sw,
      ST_AsText(point_ne) AS point_ne
    FROM ext
    CROSS JOIN postgis_srs_search(ST_SetSRID(ext.geom, ext.srid))
    LIMIT 3;

## See Also

postgis_srs_codes, postgis_srs_all, postgis_srs

## 7.8. Geometry Input

Abstract

These functions create geometry objects from various textual or binary formats.

### 7.8.1. Well-Known Text (WKT)

## Name

ST_BdPolyFromText — Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

## Synopsis

`geometry ST_BdPolyFromText(` text WKT, integer srid`)`;

## Description

Construct a Polygon given an arbitrary collection of closed linestrings as a MultiLineString Well-Known text representation.

Throws an error if WKT is not a MULTILINESTRING. Throws an error if output is a MULTIPOLYGON; use ST_BdMPolyFromText in that case, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Performed by the GEOS module.

Availability: 1.1.0

## See Also

ST_BuildArea, ST_BdMPolyFromText

## Name

ST_BdMPolyFromText — Construct a MultiPolygon given an arbitrary collection of closed linestrings as a MultiLineString text representation Well-Known text representation.

## Synopsis

`geometry ST_BdMPolyFromText(` text WKT, integer srid`)`;

## Description

Construct a Polygon given an arbitrary collection of closed linestrings, polygons, MultiLineStrings as Well-Known text representation.

Throws an error if WKT is not a MULTILINESTRING. Forces MULTIPOLYGON output even when result is really only composed by a single POLYGON; use ST_BdPolyFromText if you're sure a single POLYGON will result from operation, or see ST_BuildArea() for a postgis-specific approach.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

Performed by the GEOS module.

Availability: 1.1.0

## See Also

ST_BuildArea, ST_BdPolyFromText

## Name

ST_GeogFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

## Synopsis

`geography ST_GeogFromText(` text EWKT`)`;

## Description

Returns a geography object from the well-known text or extended well-known representation. SRID 4326 is assumed if unspecified. This is an alias for ST_GeographyFromText. Points are always expressed in long lat form.

## Examples

    --- converting lon lat coords to geography
    ALTER TABLE sometable ADD COLUMN geog geography(POINT,4326);
    UPDATE sometable SET geog = ST_GeogFromText('SRID=4326;POINT(' || lon || ' ' || lat || ')');

    --- specify a geography point using EPSG:4267, NAD27
    SELECT ST_AsEWKT(ST_GeogFromText('SRID=4267;POINT(-77.0092 38.889588)'));

## See Also

ST_AsText, ST_GeographyFromText

## Name

ST_GeographyFromText — Return a specified geography value from Well-Known Text representation or extended (WKT).

## Synopsis

`geography ST_GeographyFromText(` text EWKT`)`;

## Description

Returns a geography object from the well-known text representation. SRID 4326 is assumed if unspecified.

## See Also

ST_GeogFromText, ST_AsText

## Name

ST_GeomCollFromText — Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.

## Synopsis

`geometry ST_GeomCollFromText(` text WKT, integer srid`)`;

`geometry ST_GeomCollFromText(` text WKT`)`;

## Description

Makes a collection Geometry from the Well-Known-Text (WKT) representation with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a GEOMETRYCOLLECTION

If you are absolutely sure all your WKT geometries are collections, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification.

## Examples

    SELECT ST_GeomCollFromText('GEOMETRYCOLLECTION(POINT(1 2),LINESTRING(1 2, 3 4))');

## See Also

ST_GeomFromText, ST_SRID

## Name

ST_GeomFromEWKT — Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).

## Synopsis

`geometry ST_GeomFromEWKT(` text EWKT`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known text (EWKT) representation.

The EWKT format is not an OGC standard, but an PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_GeomFromEWKT('SRID=4269;LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
    SELECT ST_GeomFromEWKT('SRID=4269;MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

    SELECT ST_GeomFromEWKT('SRID=4269;POINT(-71.064544 42.28787)');

    SELECT ST_GeomFromEWKT('SRID=4269;POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

    SELECT ST_GeomFromEWKT('SRID=4269;MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
    -71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
    -71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
    -71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
    -71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
    -71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
    -71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
    -71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
    -71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
    -71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
    -71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
    -71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
    -71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
    -71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
    -71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
    -71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
    -71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
    -71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
    -71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
    -71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
    -71.1031880899493 42.3152774590236)),
    ((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
    -71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))');

    --3d circular string
    SELECT ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)');

    --Polyhedral Surface example
    SELECT ST_GeomFromEWKT('POLYHEDRALSURFACE(
    	((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    	((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
    	((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    	((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    	((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
    	((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1))
    )');

## See Also

ST_AsEWKT, ST_GeomFromText

## Name

ST_GeomFromMARC21 — Takes MARC21/XML geographic data as input and returns a PostGIS geometry object.

## Synopsis

`geometry ST_GeomFromMARC21 (` text marcxml `)`;

## Description

This function creates a PostGIS geometry from a MARC21/XML record, which can contain a `POINT` or a `POLYGON`. In case of multiple geographic data entries in the same MARC21/XML record, a `MULTIPOINT` or `MULTIPOLYGON` will be returned. If the record contains mixed geometry types, a `GEOMETRYCOLLECTION` will be returned. It returns NULL if the MARC21/XML record does not contain any geographic data (datafield:034).

LOC MARC21/XML versions supported:

- MARC21/XML 1.1

Availability: 3.3.0, requires libxml2 2.6+

The MARC21/XML Coded Cartographic Mathematical Data currently does not provide any means to describe the Spatial Reference System of the encoded coordinates, so this function will always return a geometry with `SRID 0`.

Returned `POLYGON` geometries will always be clockwise oriented.

## Examples

Converting MARC21/XML geographic data containing a single `POINT` encoded as `hddd.dddddd`

                    SELECT
                    ST_AsText(
                        ST_GeomFromMARC21('
                            <record xmlns="http://www.loc.gov/MARC21/slim">
                                <leader>00000nz a2200000nc 4500</leader>
                                <controlfield tag="001">040277569</controlfield>
                                <datafield tag="034" ind1=" " ind2=" ">
                                    <subfield code="d">W004.500000</subfield>
                                    <subfield code="e">W004.500000</subfield>
                                    <subfield code="f">N054.250000</subfield>
                                    <subfield code="g">N054.250000</subfield>
                                </datafield>
                            </record>'));

                    st_astext
                    -------------------
                    POINT(-4.5 54.25)
                    (1 row)

Converting MARC21/XML geographic data containing a single `POLYGON` encoded as `hdddmmss`

                    SELECT
                    ST_AsText(
                        ST_GeomFromMARC21('
                            <record xmlns="http://www.loc.gov/MARC21/slim">
                                <leader>01062cem a2200241 a 4500</leader>
                                <controlfield tag="001">   84696781 </controlfield>
                                <datafield tag="034" ind1="1" ind2=" ">
                                    <subfield code="a">a</subfield>
                                    <subfield code="b">50000</subfield>
                                    <subfield code="d">E0130600</subfield>
                                    <subfield code="e">E0133100</subfield>
                                    <subfield code="f">N0523900</subfield>
                                    <subfield code="g">N0522300</subfield>
                                </datafield>
                            </record>'));

                    st_astext
                    -----------------------------------------------------------------------------------------------------------------------
                    POLYGON((13.1 52.65,13.516666666666667 52.65,13.516666666666667 52.38333333333333,13.1 52.38333333333333,13.1 52.65))
                    (1 row)

Converting MARC21/XML geographic data containing a `POLYGON` and a `POINT`:

                    SELECT
                    ST_AsText(
                        ST_GeomFromMARC21('
                    <record xmlns="http://www.loc.gov/MARC21/slim">
                        <datafield tag="034" ind1="1" ind2=" ">
                            <subfield code="a">a</subfield>
                            <subfield code="b">50000</subfield>
                            <subfield code="d">E0130600</subfield>
                            <subfield code="e">E0133100</subfield>
                            <subfield code="f">N0523900</subfield>
                            <subfield code="g">N0522300</subfield>
                        </datafield>
                        <datafield tag="034" ind1=" " ind2=" ">
                            <subfield code="d">W004.500000</subfield>
                            <subfield code="e">W004.500000</subfield>
                            <subfield code="f">N054.250000</subfield>
                            <subfield code="g">N054.250000</subfield>
                        </datafield>
                    </record>'));
                                                                                            st_astext
                    -------------------------------------------------------------------------------------------------------------------------------------------------------------
                    GEOMETRYCOLLECTION(POLYGON((13.1 52.65,13.516666666666667 52.65,13.516666666666667 52.38333333333333,13.1 52.38333333333333,13.1 52.65)),POINT(-4.5 54.25))
                    (1 row)

## See Also

ST_AsMARC21

## Name

ST_GeometryFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

## Synopsis

`geometry ST_GeometryFromText(` text WKT`)`;

`geometry ST_GeometryFromText(` text WKT, integer srid`)`;

## Description

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

## See Also

ST_GeomFromText

## Name

ST_GeomFromText — Return a specified ST_Geometry value from Well-Known Text representation (WKT).

## Synopsis

`geometry ST_GeomFromText(` text WKT`)`;

`geometry ST_GeomFromText(` text WKT, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Well-Known text representation.

There are two variants of ST_GeomFromText function. The first takes no SRID and returns a geometry with no defined spatial reference system (SRID=0). The second takes a SRID as the second argument and returns a geometry that includes this SRID as part of its metadata.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.40

This method supports Circular Strings and Curves.

While not OGC-compliant, ST_MakePoint is faster than ST_GeomFromText and ST_PointFromText. It is also easier to use for numeric coordinate values. ST_Point is another option similar in speed to ST_MakePoint and is OGC-compliant, but doesn't support anything but 2D points.

Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY')

## Examples

    SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)');
    SELECT ST_GeomFromText('LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932)',4269);

    SELECT ST_GeomFromText('MULTILINESTRING((-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932))');

    SELECT ST_GeomFromText('POINT(-71.064544 42.28787)');

    SELECT ST_GeomFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');

    SELECT ST_GeomFromText('MULTIPOLYGON(((-71.1031880899493 42.3152774590236,
    -71.1031627617667 42.3152960829043,-71.102923838298 42.3149156848307,
    -71.1023097974109 42.3151969047397,-71.1019285062273 42.3147384934248,
    -71.102505233663 42.3144722937587,-71.10277487471 42.3141658254797,
    -71.103113945163 42.3142739188902,-71.10324876416 42.31402489987,
    -71.1033002961013 42.3140393340215,-71.1033488797549 42.3139495090772,
    -71.103396240451 42.3138632439557,-71.1041521907712 42.3141153348029,
    -71.1041411411543 42.3141545014533,-71.1041287795912 42.3142114839058,
    -71.1041188134329 42.3142693656241,-71.1041112482575 42.3143272556118,
    -71.1041072845732 42.3143851580048,-71.1041057218871 42.3144430686681,
    -71.1041065602059 42.3145009876017,-71.1041097995362 42.3145589148055,
    -71.1041166403905 42.3146168544148,-71.1041258822717 42.3146748022936,
    -71.1041375307579 42.3147318674446,-71.1041492906949 42.3147711126569,
    -71.1041598612795 42.314808571739,-71.1042515013869 42.3151287620809,
    -71.1041173835118 42.3150739481917,-71.1040809891419 42.3151344119048,
    -71.1040438678912 42.3151191367447,-71.1040194562988 42.3151832057859,
    -71.1038734225584 42.3151140942995,-71.1038446938243 42.3151006300338,
    -71.1038315271889 42.315094347535,-71.1037393329282 42.315054824985,
    -71.1035447555574 42.3152608696313,-71.1033436658644 42.3151648370544,
    -71.1032580383161 42.3152269126061,-71.103223066939 42.3152517403219,
    -71.1031880899493 42.3152774590236)),
    ((-71.1043632495873 42.315113108546,-71.1043583974082 42.3151211109857,
    -71.1043443253471 42.3150676015829,-71.1043850704575 42.3150793250568,-71.1043632495873 42.315113108546)))',4326);

    SELECT ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)');

## See Also

ST_GeomFromEWKT, ST_GeomFromWKB, ST_SRID

## Name

ST_LineFromText — Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.

## Synopsis

`geometry ST_LineFromText(` text WKT`)`;

`geometry ST_LineFromText(` text WKT, integer srid`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. If WKT passed in is not a LINESTRING, then null is returned.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

If you know all your geometries are LINESTRINGS, its more efficient to just use ST_GeomFromText. This just calls ST_GeomFromText and adds additional validation that it returns a linestring.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.8

## Examples

    SELECT ST_LineFromText('LINESTRING(1 2, 3 4)') AS aline, ST_LineFromText('POINT(1 2)') AS null_return;
    aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromText

## Name

ST_MLineFromText — Return a specified ST_MultiLineString value from WKT representation.

## Synopsis

`geometry ST_MLineFromText(` text WKT, integer srid`)`;

`geometry ST_MLineFromText(` text WKT`)`;

## Description

Makes a Geometry from Well-Known-Text (WKT) with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTILINESTRING

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.4.4

## Examples

    SELECT ST_MLineFromText('MULTILINESTRING((1 2, 3 4), (4 5, 6 7))');

## See Also

ST_GeomFromText

## Name

ST_MPointFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

## Synopsis

`geometry ST_MPointFromText(` text WKT, integer srid`)`;

`geometry ST_MPointFromText(` text WKT`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Returns null if the WKT is not a MULTIPOINT

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. 3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.2.4

## Examples

    SELECT ST_MPointFromText('MULTIPOINT((1 2),(3 4))');
    SELECT ST_MPointFromText('MULTIPOINT((-70.9590 42.1180),(-70.9611 42.1223))', 4326);

## See Also

ST_GeomFromText

## Name

ST_MPolyFromText — Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

## Synopsis

`geometry ST_MPolyFromText(` text WKT, integer srid`)`;

`geometry ST_MPolyFromText(` text WKT`)`;

## Description

Makes a MultiPolygon from WKT with the given SRID. If SRID is not given, it defaults to 0.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

Throws an error if the WKT is not a MULTIPOLYGON

If you are absolutely sure all your WKT geometries are multipolygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 9.6.4

## Examples

    SELECT ST_MPolyFromText('MULTIPOLYGON(((0 0 1,20 0 1,20 20 1,0 20 1,0 0 1),(5 5 3,5 7 3,7 7 3,7 5 3,5 5 3)))');
    SELECt ST_MPolyFromText('MULTIPOLYGON(((-70.916 42.1002,-70.9468 42.0946,-70.9765 42.0872,-70.9754 42.0875,-70.9749 42.0879,-70.9752 42.0881,-70.9754 42.0891,-70.9758 42.0894,-70.9759 42.0897,-70.9759 42.0899,-70.9754 42.0902,-70.9756 42.0906,-70.9753 42.0907,-70.9753 42.0917,-70.9757 42.0924,-70.9755 42.0928,-70.9755 42.0942,-70.9751 42.0948,-70.9755 42.0953,-70.9751 42.0958,-70.9751 42.0962,-70.9759 42.0983,-70.9767 42.0987,-70.9768 42.0991,-70.9771 42.0997,-70.9771 42.1003,-70.9768 42.1005,-70.977 42.1011,-70.9766 42.1019,-70.9768 42.1026,-70.9769 42.1033,-70.9775 42.1042,-70.9773 42.1043,-70.9776 42.1043,-70.9778 42.1048,-70.9773 42.1058,-70.9774 42.1061,-70.9779 42.1065,-70.9782 42.1078,-70.9788 42.1085,-70.9798 42.1087,-70.9806 42.109,-70.9807 42.1093,-70.9806 42.1099,-70.9809 42.1109,-70.9808 42.1112,-70.9798 42.1116,-70.9792 42.1127,-70.979 42.1129,-70.9787 42.1134,-70.979 42.1139,-70.9791 42.1141,-70.9987 42.1116,-71.0022 42.1273,
    	-70.9408 42.1513,-70.9315 42.1165,-70.916 42.1002)))',4326);

## See Also

ST_GeomFromText, ST_SRID

## Name

ST_PointFromText — Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.

## Synopsis

`geometry ST_PointFromText(` text WKT`)`;

`geometry ST_PointFromText(` text WKT, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry point object from the OGC Well-Known text representation. If SRID is not given, it defaults to unknown (currently 0). If geometry is not a WKT point representation, returns null. If completely invalid WKT, then throws an error.

There are 2 variants of ST_PointFromText function, the first takes no SRID and returns a geometry with no defined spatial reference system. The second takes a spatial reference id as the second argument and returns an ST_Geometry that includes this srid as part of its meta-data. The srid must be defined in the spatial_ref_sys table.

If you are absolutely sure all your WKT geometries are points, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step. If you are building points from long lat coordinates and care more about performance and accuracy than OGC compliance, use ST_MakePoint or OGC compliant alias ST_Point.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2 - option SRID is from the conformance suite.

This method implements the SQL/MM specification. SQL-MM 3: 6.1.8

## Examples

    SELECT ST_PointFromText('POINT(-71.064544 42.28787)');
    SELECT ST_PointFromText('POINT(-71.064544 42.28787)', 4326);

## See Also

ST_GeomFromText, ST_MakePoint, ST_Point, ST_SRID

## Name

ST_PolygonFromText — Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.

## Synopsis

`geometry ST_PolygonFromText(` text WKT`)`;

`geometry ST_PolygonFromText(` text WKT, integer srid`)`;

## Description

Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0. Returns null if WKT is not a polygon.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite

If you are absolutely sure all your WKT geometries are polygons, don't use this function. It is slower than ST_GeomFromText since it adds an additional validation step.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 8.3.6

## Examples

    SELECT ST_PolygonFromText('POLYGON((-71.1776585052917 42.3902909739571,-71.1776820268866 42.3903701743239,
    -71.1776063012595 42.3903825660754,-71.1775826583081 42.3903033653531,-71.1776585052917 42.3902909739571))');
    st_polygonfromtext
    ------------------
    010300000001000000050000006...

    SELECT ST_PolygonFromText('POINT(1 2)') IS NULL as point_is_notpoly;

    point_is_not_poly
    ----------
    t

## See Also

ST_GeomFromText

## Name

ST_WKTToSQL — Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText

## Synopsis

`geometry ST_WKTToSQL(` text WKT`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.34

## See Also

ST_GeomFromText

### 7.8.2. Well-Known Binary (WKB)

## Name

ST_GeogFromWKB — Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).

## Synopsis

`geography ST_GeogFromWKB(` bytea wkb`)`;

## Description

The `ST_GeogFromWKB` function, takes a well-known binary representation (WKB) of a geometry or PostGIS Extended WKB and creates an instance of the appropriate geography type. This function plays the role of the Geometry Factory in SQL.

If SRID is not specified, it defaults to 4326 (WGS 84 long lat).

This method supports Circular Strings and Curves.

## Examples

    --Although bytea rep contains single \, these need to be escaped when inserting into a table
    SELECT ST_AsText(
    ST_GeogFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@')
    );
    					  st_astext
    ------------------------------------------------------
     LINESTRING(-113.98 39.198,-113.981 39.195)
    (1 row)

## See Also

ST_GeogFromText, ST_AsBinary

## Name

ST_GeomFromEWKB — Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).

## Synopsis

`geometry ST_GeomFromEWKB(` bytea EWKB`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC Extended Well-Known binary (EWKT) representation.

The EWKB format is not an OGC standard, but a PostGIS specific format that includes the spatial reference system (SRID) identifier

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

line string binary rep 0f LINESTRING(-71.160281 42.258729,-71.160837 42.259113,-71.161144 42.25932) in NAD 83 long lat (4269).

NOTE: Even though byte arrays are delimited with \ and may have ', we need to escape both out with \ and '' if standard_conforming_strings is off. So it does not look exactly like its AsEWKB representation.

    SELECT ST_GeomFromEWKB(E'\\001\\002\\000\\000 \\255\\020\\000\\000\\003\\000\\000\\000\\344J=
    \\013B\\312Q\\300n\\303(\\010\\036!E@''\\277E''K
    \\312Q\\300\\366{b\\235*!E@\\225|\\354.P\\312Q
    \\300p\\231\\323e1!E@');

In PostgreSQL 9.1+ - standard_conforming_strings is set to on by default, where as in past versions it was set to off. You can change defaults as needed for a single query or at the database or server level. Below is how you would do it with standard_conforming_strings = on. In this case we escape the ' with standard ansi ', but slashes are not escaped

    	    set standard_conforming_strings = on;
    SELECT ST_GeomFromEWKB('\001\002\000\000 \255\020\000\000\003\000\000\000\344J=\012\013B
        \312Q\300n\303(\010\036!E@''\277E''K\012\312Q\300\366{b\235*!E@\225|\354.P\312Q\012\300p\231\323e1')

## See Also

ST_AsBinary, ST_AsEWKB, ST_GeomFromWKB

## Name

ST_GeomFromWKB — Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.

## Synopsis

`geometry ST_GeomFromWKB(` bytea geom`)`;

`geometry ST_GeomFromWKB(` bytea geom, integer srid`)`;

## Description

The `ST_GeomFromWKB` function, takes a well-known binary representation of a geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type. This function plays the role of the Geometry Factory in SQL. This is an alternate name for ST_WKBToSQL.

If SRID is not specified, it defaults to 0 (Unknown).

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.7.2 - the optional SRID is from the conformance suite

This method implements the SQL/MM specification. SQL-MM 3: 5.1.41

This method supports Circular Strings and Curves.

## Examples

    --Although bytea rep contains single \, these need to be escaped when inserting into a table
    		-- unless standard_conforming_strings is set to on.
    SELECT ST_AsEWKT(
    ST_GeomFromWKB(E'\\001\\002\\000\\000\\000\\002\\000\\000\\000\\037\\205\\353Q\\270~\\\\\\300\\323Mb\\020X\\231C@\\020X9\\264\\310~\\\\\\300)\\\\\\217\\302\\365\\230C@',4326)
    );
    					  st_asewkt
    ------------------------------------------------------
     SRID=4326;LINESTRING(-113.98 39.198,-113.981 39.195)
    (1 row)

    SELECT
      ST_AsText(
    	ST_GeomFromWKB(
    	  ST_AsEWKB('POINT(2 5)'::geometry)
    	)
      );
     st_astext
    ------------
     POINT(2 5)
    (1 row)

## See Also

ST_WKBToSQL, ST_AsBinary, ST_GeomFromEWKB

## Name

ST_LineFromWKB — Makes a `LINESTRING` from WKB with the given SRID

## Synopsis

`geometry ST_LineFromWKB(` bytea WKB`)`;

`geometry ST_LineFromWKB(` bytea WKB, integer srid`)`;

## Description

The `ST_LineFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `LINESTRING` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. `NULL` is returned if the input `bytea` does not represent a `LINESTRING`.

OGC SPEC 3.2.6.2 - option SRID is from the conformance suite.

If you know all your geometries are `LINESTRING`s, its more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a linestring.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

## Examples

    SELECT ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))) AS aline,
    		ST_LineFromWKB(ST_AsBinary(ST_GeomFromText('POINT(1 2)'))) IS NULL AS null_return;
    aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromWKB, ST_LinestringFromWKB

## Name

ST_LinestringFromWKB — Makes a geometry from WKB with the given SRID.

## Synopsis

`geometry ST_LinestringFromWKB(` bytea WKB`)`;

`geometry ST_LinestringFromWKB(` bytea WKB, integer srid`)`;

## Description

The `ST_LinestringFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `LINESTRING` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. `NULL` is returned if the input `bytea` does not represent a `LINESTRING` geometry. This an alias for ST_LineFromWKB.

OGC SPEC 3.2.6.2 - optional SRID is from the conformance suite.

If you know all your geometries are `LINESTRING`s, it's more efficient to just use ST_GeomFromWKB. This function just calls ST_GeomFromWKB and adds additional validation that it returns a `LINESTRING`.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.6.2

This method implements the SQL/MM specification. SQL-MM 3: 7.2.9

## Examples

    SELECT
      ST_LineStringFromWKB(
    	ST_AsBinary(ST_GeomFromText('LINESTRING(1 2, 3 4)'))
      ) AS aline,
      ST_LinestringFromWKB(
    	ST_AsBinary(ST_GeomFromText('POINT(1 2)'))
      ) IS NULL AS null_return;
       aline                            | null_return
    ------------------------------------------------
    010200000002000000000000000000F ... | t

## See Also

ST_GeomFromWKB, ST_LineFromWKB

## Name

ST_PointFromWKB — Makes a geometry from WKB with the given SRID

## Synopsis

`geometry ST_GeomFromWKB(` bytea geom`)`;

`geometry ST_GeomFromWKB(` bytea geom, integer srid`)`;

## Description

The `ST_PointFromWKB` function, takes a well-known binary representation of geometry and a Spatial Reference System ID (`SRID`) and creates an instance of the appropriate geometry type - in this case, a `POINT` geometry. This function plays the role of the Geometry Factory in SQL.

If an SRID is not specified, it defaults to 0. `NULL` is returned if the input `bytea` does not represent a `POINT` geometry.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.7.2

This method implements the SQL/MM specification. SQL-MM 3: 6.1.9

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT
      ST_AsText(
    	ST_PointFromWKB(
    	  ST_AsEWKB('POINT(2 5)'::geometry)
    	)
      );
     st_astext
    ------------
     POINT(2 5)
    (1 row)

    SELECT
      ST_AsText(
    	ST_PointFromWKB(
    	  ST_AsEWKB('LINESTRING(2 5, 2 6)'::geometry)
    	)
      );
     st_astext
    -----------

    (1 row)

## See Also

ST_GeomFromWKB, ST_LineFromWKB

## Name

ST_WKBToSQL — Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid

## Synopsis

`geometry ST_WKBToSQL(` bytea WKB`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.36

## See Also

ST_GeomFromWKB

### 7.8.3. Other Formats

## Name

ST_Box2dFromGeoHash — Return a BOX2D from a GeoHash string.

## Synopsis

`box2d ST_Box2dFromGeoHash(` text geohash, integer precision=full_precision_of_geohash`)`;

## Description

Return a BOX2D from a GeoHash string.

If no `precision` is specified ST_Box2dFromGeoHash returns a BOX2D based on full precision of the input GeoHash string.

If `precision` is specified ST_Box2dFromGeoHash will use that many characters from the GeoHash to create the BOX2D. Lower precision values results in larger BOX2Ds and larger values increase the precision.

Availability: 2.1.0

## Examples

    SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0');

                    st_geomfromgeohash
    --------------------------------------------------
     BOX(-115.172816 36.114646,-115.172816 36.114646)

    SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 0);

     st_box2dfromgeohash
    ----------------------
     BOX(-180 -90,180 90)

     SELECT ST_Box2dFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10);
                                st_box2dfromgeohash
    ---------------------------------------------------------------------------
     BOX(-115.17282128334 36.1146408319473,-115.172810554504 36.1146461963654)

## See Also

ST_GeoHash, ST_GeomFromGeoHash, ST_PointFromGeoHash

## Name

ST_GeomFromGeoHash — Return a geometry from a GeoHash string.

## Synopsis

`geometry ST_GeomFromGeoHash(` text geohash, integer precision=full_precision_of_geohash`)`;

## Description

Return a geometry from a GeoHash string. The geometry will be a polygon representing the GeoHash bounds.

If no `precision` is specified ST_GeomFromGeoHash returns a polygon based on full precision of the input GeoHash string.

If `precision` is specified ST_GeomFromGeoHash will use that many characters from the GeoHash to create the polygon.

Availability: 2.1.0

## Examples

    SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
                                                            st_astext
    --------------------------------------------------------------------------------------------------------------------------
     POLYGON((-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646,-115.172816 36.114646))

    SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
                                                              st_astext
    ------------------------------------------------------------------------------------------------------------------------------
     POLYGON((-115.3125 36.03515625,-115.3125 36.2109375,-114.9609375 36.2109375,-114.9609375 36.03515625,-115.3125 36.03515625))

    SELECT ST_AsText(ST_GeomFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                                                                                           st_astext
    ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
     POLYGON((-115.17282128334 36.1146408319473,-115.17282128334 36.1146461963654,-115.172810554504 36.1146461963654,-115.172810554504 36.1146408319473,-115.17282128334 36.1146408319473))

## See Also

ST_GeoHash,ST_Box2dFromGeoHash, ST_PointFromGeoHash

## Name

ST_GeomFromGML — Takes as input GML representation of geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromGML(` text geomgml`)`;

`geometry ST_GeomFromGML(` text geomgml, integer srid`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC GML representation.

ST_GeomFromGML works only for GML Geometry fragments. It throws an error if you try to use it on a whole GML document.

OGC GML versions supported:

- GML 3.2.1 Namespace

- GML 3.1.1 Simple Features profile SF-2 (with GML 3.1.0 and 3.0.0 backward compatibility)

- GML 2.1.2

OGC GML standards, cf: http://www.opengeospatial.org/standards/gml:

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

GML allow mixed dimensions (2D and 3D inside the same MultiGeometry for instance). As PostGIS geometries don't, ST_GeomFromGML convert the whole geometry to 2D if a missing Z dimension is found once.

GML support mixed SRS inside the same MultiGeometry. As PostGIS geometries don't, ST_GeomFromGML, in this case, reproject all subgeometries to the SRS root node. If no srsName attribute available for the GML root node, the function throw an error.

ST_GeomFromGML function is not pedantic about an explicit GML namespace. You could avoid to mention it explicitly for common usages. But you need it if you want to use XLink feature inside GML.

ST_GeomFromGML function not support SQL/MM curves geometries.

## Examples - A single geometry with srsName

    SELECT ST_GeomFromGML($$
        <gml:LineString xmlns:gml="http://www.opengis.net/gml"
    			srsName="EPSG:4269">
            <gml:coordinates>
                -71.16028,42.258729 -71.160837,42.259112 -71.161143,42.25932
            </gml:coordinates>
        </gml:LineString>
    $$);

## Examples - XLink usage

    SELECT ST_GeomFromGML($$
        <gml:LineString xmlns:gml="http://www.opengis.net/gml"
                xmlns:xlink="http://www.w3.org/1999/xlink"
                srsName="urn:ogc:def:crs:EPSG::4269">
            <gml:pointProperty>
                <gml:Point gml:id="p1"><gml:pos>42.258729 -71.16028</gml:pos></gml:Point>
            </gml:pointProperty>
            <gml:pos>42.259112 -71.160837</gml:pos>
            <gml:pointProperty>
                <gml:Point xlink:type="simple" xlink:href="#p1"/>
            </gml:pointProperty>
        </gml:LineString>
    $$);

## Examples - Polyhedral Surface

    SELECT ST_AsEWKT(ST_GeomFromGML('
    <gml:PolyhedralSurface xmlns:gml="http://www.opengis.net/gml">
    <gml:polygonPatches>
      <gml:PolygonPatch>
        <gml:exterior>
          <gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
    	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
    	<gml:LinearRing><gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
    	<gml:LinearRing><gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
    	<gml:LinearRing><gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
      <gml:PolygonPatch>
        <gml:exterior>
    	<gml:LinearRing><gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList></gml:LinearRing>
        </gml:exterior>
      </gml:PolygonPatch>
    </gml:polygonPatches>
    </gml:PolyhedralSurface>'));

    -- result --
     POLYHEDRALSURFACE(((0 0 0,0 0 1,0 1 1,0 1 0,0 0 0)),
     ((0 0 0,0 1 0,1 1 0,1 0 0,0 0 0)),
     ((0 0 0,1 0 0,1 0 1,0 0 1,0 0 0)),
     ((1 1 0,1 1 1,1 0 1,1 0 0,1 1 0)),
     ((0 1 0,0 1 1,1 1 1,1 1 0,0 1 0)),
     ((0 0 1,1 0 1,1 1 1,0 1 1,0 0 1)))

## See Also

Section 2.2.3, “Build configuration”, ST_AsGML, ST_GMLToSQL

## Name

ST_GeomFromGeoJSON — Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromGeoJSON(` text geomjson`)`;

`geometry ST_GeomFromGeoJSON(` json geomjson`)`;

`geometry ST_GeomFromGeoJSON(` jsonb geomjson`)`;

## Description

Constructs a PostGIS geometry object from the GeoJSON representation.

ST_GeomFromGeoJSON works only for JSON Geometry fragments. It throws an error if you try to use it on a whole JSON document.

Enhanced: 3.0.0 parsed geometry defaults to SRID=4326 if not specified otherwise.

Enhanced: 2.5.0 can now accept json and jsonb as inputs.

Availability: 2.0.0 requires - JSON-C >= 0.9

If you do not have JSON-C enabled, support you will get an error notice instead of seeing an output. To enable JSON-C, run configure --with-jsondir=/path/to/json-c. See Section 2.2.3, “Build configuration” for details.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"Point","coordinates":[-48.23456,20.12345]}')) As wkt;
    wkt
    ------
    POINT(-48.23456 20.12345)

    -- a 3D linestring
    SELECT ST_AsText(ST_GeomFromGeoJSON('{"type":"LineString","coordinates":[[1,2,3],[4,5,6],[7,8,9]]}')) As wkt;

    wkt
    -------------------
    LINESTRING(1 2,4 5,7 8)

## See Also

ST_AsText, ST_AsGeoJSON, Section 2.2.3, “Build configuration”

## Name

ST_GeomFromKML — Takes as input KML representation of geometry and outputs a PostGIS geometry object

## Synopsis

`geometry ST_GeomFromKML(` text geomkml`)`;

## Description

Constructs a PostGIS ST_Geometry object from the OGC KML representation.

ST_GeomFromKML works only for KML Geometry fragments. It throws an error if you try to use it on a whole KML document.

OGC KML versions supported:

- KML 2.2.0 Namespace

OGC KML standards, cf: http://www.opengeospatial.org/standards/kml:

Availability: 1.5, requires libxml2 2.6+

This function supports 3d and will not drop the z-index.

ST_GeomFromKML function not support SQL/MM curves geometries.

## Examples - A single geometry with srsName

    SELECT ST_GeomFromKML($$
        <LineString>
            <coordinates>-71.1663,42.2614
                -71.1667,42.2616</coordinates>
        </LineString>
    $$);

## See Also

Section 2.2.3, “Build configuration”, ST_AsKML

## Name

ST_GeomFromTWKB — Creates a geometry instance from a TWKB ("Tiny Well-Known Binary") geometry representation.

## Synopsis

`geometry ST_GeomFromTWKB(` bytea twkb`)`;

## Description

The `ST_GeomFromTWKB` function, takes a a TWKB ("Tiny Well-Known Binary") geometry representation (WKB) and creates an instance of the appropriate geometry type.

## Examples

    SELECT ST_AsText(ST_GeomFromTWKB(ST_AsTWKB('LINESTRING(126 34, 127 35)'::geometry)));

             st_astext
    -----------------------------
     LINESTRING(126 34, 127 35)
    (1 row)

    SELECT ST_AsEWKT(
      ST_GeomFromTWKB(E'\\x620002f7f40dbce4040105')
    );
    					  st_asewkt
    ------------------------------------------------------
    LINESTRING(-113.98 39.198,-113.981 39.195)
    (1 row)

## See Also

ST_AsTWKB

## Name

ST_GMLToSQL — Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML

## Synopsis

`geometry ST_GMLToSQL(` text geomgml`)`;

`geometry ST_GMLToSQL(` text geomgml, integer srid`)`;

## Description

This method implements the SQL/MM specification. SQL-MM 3: 5.1.50 (except for curves support).

Availability: 1.5, requires libxml2 1.6+

Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced.

Enhanced: 2.0.0 default srid optional parameter added.

## See Also

Section 2.2.3, “Build configuration”, ST_GeomFromGML, ST_AsGML

## Name

ST_LineFromEncodedPolyline — Creates a LineString from an Encoded Polyline.

## Synopsis

`geometry ST_LineFromEncodedPolyline(` text polyline, integer precision=5`)`;

## Description

Creates a LineString from an Encoded Polyline string.

Optional `precision` specifies how many decimal places will be preserved in Encoded Polyline. Value should be the same on encoding and decoding, or coordinates will be incorrect.

See http://developers.google.com/maps/documentation/utilities/polylinealgorithm

Availability: 2.2.0

## Examples

    -- Create a line string from a polyline
    SELECT ST_AsEWKT(ST_LineFromEncodedPolyline('_p~iF~ps|U_ulLnnqC_mqNvxq`@'));
    -- result --
    SRID=4326;LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)

    -- Select different precision that was used for polyline encoding
    SELECT ST_AsEWKT(ST_LineFromEncodedPolyline('_p~iF~ps|U_ulLnnqC_mqNvxq`@',6));
    -- result --
    SRID=4326;LINESTRING(-12.02 3.85,-12.095 4.07,-12.6453 4.3252)

## See Also

ST_AsEncodedPolyline

## Name

ST_PointFromGeoHash — Return a point from a GeoHash string.

## Synopsis

`point ST_PointFromGeoHash(` text geohash, integer precision=full_precision_of_geohash`)`;

## Description

Return a point from a GeoHash string. The point represents the center point of the GeoHash.

If no `precision` is specified ST_PointFromGeoHash returns a point based on full precision of the input GeoHash string.

If `precision` is specified ST_PointFromGeoHash will use that many characters from the GeoHash to create the point.

Availability: 2.1.0

## Examples

    SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0'));
              st_astext
    ------------------------------
     POINT(-115.172816 36.114646)

    SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 4));
                 st_astext
    -----------------------------------
     POINT(-115.13671875 36.123046875)

    SELECT ST_AsText(ST_PointFromGeoHash('9qqj7nmxncgyy4d0dbxqz0', 10));
                     st_astext
    -------------------------------------------
     POINT(-115.172815918922 36.1146435141563)

## See Also

ST_GeoHash, ST_Box2dFromGeoHash, ST_GeomFromGeoHash

## Name

ST_FromFlatGeobufToTable — Creates a table based on the structure of FlatGeobuf data.

## Synopsis

`void ST_FromFlatGeobufToTable(` text schemaname, text tablename, bytea FlatGeobuf input data`)`;

## Description

Creates a table based on the structure of FlatGeobuf data. (http://flatgeobuf.org).

`schema` Schema name.

`table` Table name.

`data` Input FlatGeobuf data.

Availability: 3.2.0

## Name

ST_FromFlatGeobuf — Reads FlatGeobuf data.

## Synopsis

`setof anyelement ST_FromFlatGeobuf(` anyelement Table reference, bytea FlatGeobuf input data`)`;

## Description

Reads FlatGeobuf data (http://flatgeobuf.org). NOTE: PostgreSQL bytea cannot exceed 1GB.

`tabletype` reference to a table type.

`data` input FlatGeobuf data.

Availability: 3.2.0

## 7.9. Geometry Output

Abstract

These functions convert geometry objects into various textual or binary formats.

### 7.9.1. Well-Known Text (WKT)

## Name

ST_AsEWKT — Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.

## Synopsis

`text ST_AsEWKT(` geometry g1`)`;

`text ST_AsEWKT(` geometry g1, integer maxdecimaldigits=15`)`;

`text ST_AsEWKT(` geography g1`)`;

`text ST_AsEWKT(` geography g1, integer maxdecimaldigits=15`)`;

## Description

Returns the Well-Known Text representation of the geometry prefixed with the SRID. The optional `maxdecimaldigits` argument may be used to reduce the maximum number of decimal digits after floating point used in output (defaults to 15).

To perform the inverse conversion of EWKT representation to PostGIS geometry use ST_GeomFromEWKT.

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

The WKT spec does not include the SRID. To get the OGC WKT format use ST_AsText.

WKT format does not maintain precision so to prevent floating truncation, use ST_AsBinary or ST_AsEWKB format for transport.

Enhanced: 3.1.0 support for optional precision parameter.

Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsEWKT('0103000020E61000000100000005000000000000
    			000000000000000000000000000000000000000000000000000000
    			F03F000000000000F03F000000000000F03F000000000000F03
    			F000000000000000000000000000000000000000000000000'::geometry);

    		   st_asewkt
    --------------------------------
    SRID=4326;POLYGON((0 0,0 1,1 1,1 0,0 0))
    (1 row)

    SELECT ST_AsEWKT('0108000080030000000000000060E30A4100000000785C0241000000000000F03F0000000018
    E20A4100000000485F024100000000000000400000000018
    E20A4100000000305C02410000000000000840')

    --st_asewkt---
    CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)

## See Also

ST_AsBinary, ST_AsEWKB, ST_AsText, ST_GeomFromEWKT

## Name

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

## Synopsis

`text ST_AsText(` geometry g1`)`;

`text ST_AsText(` geometry g1, integer maxdecimaldigits = 15`)`;

`text ST_AsText(` geography g1`)`;

`text ST_AsText(` geography g1, integer maxdecimaldigits = 15`)`;

## Description

Returns the OGC Well-Known Text (WKT) representation of the geometry/geography. The optional `maxdecimaldigits` argument may be used to limit the number of digits after the decimal point in output ordinates (defaults to 15).

To perform the inverse conversion of WKT representation to PostGIS geometry use ST_GeomFromText.

The standard OGC WKT representation does not include the SRID. To include the SRID as part of the output representation, use the non-standard PostGIS function ST_AsEWKT

The textual representation of numbers in WKT may not maintain full floating-point precision. To ensure full accuracy for data storage or transport it is best to use Well-Known Binary (WKB) format (see ST_AsBinary and `maxdecimaldigits`).

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

Availability: 1.5 - support for geography was introduced.

Enhanced: 2.5 - optional parameter precision introduced.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsText('01030000000100000005000000000000000000
    000000000000000000000000000000000000000000000000
    F03F000000000000F03F000000000000F03F000000000000F03
    F000000000000000000000000000000000000000000000000');

        st_astext
    --------------------------------
     POLYGON((0 0,0 1,1 1,1 0,0 0))

Full precision output is the default.

    SELECT ST_AsText('POINT(111.1111111 1.1111111)'));
        st_astext
    ------------------------------
     POINT(111.1111111 1.1111111)

The `maxdecimaldigits` argument can be used to limit output precision.

    SELECT ST_AsText('POINT(111.1111111 1.1111111)'), 2);
        st_astext
    --------------------
     POINT(111.11 1.11)

## See Also

ST_AsBinary, ST_AsEWKB, ST_AsEWKT, ST_GeomFromText

### 7.9.2. Well-Known Binary (WKB)

## Name

ST_AsBinary — Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.

## Synopsis

`bytea ST_AsBinary(` geometry g1`)`;

`bytea ST_AsBinary(` geometry g1, text NDR_or_XDR`)`;

`bytea ST_AsBinary(` geography g1`)`;

`bytea ST_AsBinary(` geography g1, text NDR_or_XDR`)`;

## Description

Returns the OGC/ISO Well-Known Binary (WKB) representation of the geometry. The first function variant defaults to encoding using server machine endian. The second function variant takes a text argument specifying the endian encoding, either little-endian ('NDR') or big-endian ('XDR').

WKB format is useful to read geometry data from the database and maintaining full numeric precision. This avoids the precision rounding that can happen with text formats such as WKT.

To perform the inverse conversion of WKB to PostGIS geometry use ST_GeomFromWKB.

The OGC/ISO WKB format does not include the SRID. To get the EWKB format which does include the SRID use ST_AsEWKB

The default behavior in PostgreSQL 9.0 has been changed to output bytea in hex encoding. If your GUI tools require the old behavior, then SET bytea_output='escape' in your database.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 support for higher coordinate dimensions was introduced.

Enhanced: 2.0.0 support for specifying endian with geography was introduced.

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 Inputs to this function can not be unknown -- must be geometry. Constructs such as `ST_AsBinary('POINT(1 2)')` are no longer valid and you will get an `n st_asbinary(unknown) is not unique error`. Code like that needs to be changed to `ST_AsBinary('POINT(1 2)'::geometry);`. If that is not possible, then install `legacy.sql`.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.1

This method implements the SQL/MM specification. SQL-MM 3: 5.1.37

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		   st_asbinary
    --------------------------------
    \x01030000000100000005000000000000000000000000000000000000000000000000000000000000
    000000f03f000000000000f03f000000000000f03f000000000000f03f0000000000000000000000
    00000000000000000000000000

    SELECT ST_AsBinary(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
    		   st_asbinary
    --------------------------------
    \x000000000300000001000000050000000000000000000000000000000000000000000000003ff000
    00000000003ff00000000000003ff00000000000003ff00000000000000000000000000000000000
    00000000000000000000000000

## See Also

ST_GeomFromWKB, ST_AsEWKB, ST_AsTWKB, ST_AsText,

## Name

ST_AsEWKB — Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.

## Synopsis

`bytea ST_AsEWKB(` geometry g1`)`;

`bytea ST_AsEWKB(` geometry g1, text NDR_or_XDR`)`;

## Description

Returns the Extended Well-Known Binary (EWKB) representation of the geometry with SRID metadata. The first function variant defaults to encoding using server machine endian. The second function variant takes a text argument specifying the endian encoding, either little-endian ('NDR') or big-endian ('XDR').

WKB format is useful to read geometry data from the database and maintaining full numeric precision. This avoids the precision rounding that can happen with text formats such as WKT.

To perform the inverse conversion of EWKB to PostGIS geometry use ST_GeomFromEWKB.

To get the OGC/ISO WKB format use ST_AsBinary. Note that OGC/ISO WKB format does not include the SRID.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		   st_asewkb
    --------------------------------
    \x0103000020e610000001000000050000000000000000000000000000000000000000000000000000
    00000000000000f03f000000000000f03f000000000000f03f000000000000f03f00000000000000
    0000000000000000000000000000000000

    			SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326), 'XDR');
    		   st_asewkb
    --------------------------------
    \x0020000003000010e600000001000000050000000000000000000000000000000000000000000000
    003ff00000000000003ff00000000000003ff00000000000003ff000000000000000000000000000
    0000000000000000000000000000000000

## See Also

ST_AsBinary, ST_GeomFromEWKB, ST_SRID

## Name

ST_AsHEXEWKB — Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.

## Synopsis

`text ST_AsHEXEWKB(` geometry g1, text NDRorXDR`)`;

`text ST_AsHEXEWKB(` geometry g1`)`;

## Description

Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding. If no encoding is specified, then NDR is used.

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsHEXEWKB(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
    		which gives same answer as

    		SELECT ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326)::text;

    		st_ashexewkb
    		--------
    		0103000020E6100000010000000500
    		00000000000000000000000000000000
    		00000000000000000000000000000000F03F
    		000000000000F03F000000000000F03F000000000000F03
    		F000000000000000000000000000000000000000000000000

### 7.9.3. Other Formats

## Name

ST_AsEncodedPolyline — Returns an Encoded Polyline from a LineString geometry.

## Synopsis

`text ST_AsEncodedPolyline(` geometry geom, integer precision=5`)`;

## Description

Returns the geometry as an Encoded Polyline. This format is used by Google Maps with precision=5 and by Open Source Routing Machine with precision=5 and 6.

Optional `precision` specifies how many decimal places will be preserved in Encoded Polyline. Value should be the same on encoding and decoding, or coordinates will be incorrect.

Availability: 2.2.0

## Examples

Basic

    	SELECT ST_AsEncodedPolyline(GeomFromEWKT('SRID=4326;LINESTRING(-120.2 38.5,-120.95 40.7,-126.453 43.252)'));
    	--result--
    	|_p~iF~ps|U_ulLnnqC_mqNvxq`@

Use in conjunction with geography linestring and geography segmentize, and put on google maps

    -- the SQL for Boston to San Francisco, segments every 100 KM
    	SELECT ST_AsEncodedPolyline(
    		ST_Segmentize(
    			ST_GeogFromText('LINESTRING(-71.0519 42.4935,-122.4483 37.64)'),
    				100000)::geometry) As encodedFlightPath;

javascript will look something like this where $ variable you replace with query result

    <script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?libraries=geometry"></script>
    <script type="text/javascript">
    	 flightPath = new google.maps.Polyline({
    			path:  google.maps.geometry.encoding.decodePath("$encodedFlightPath"),
    			map: map,
    			strokeColor: '#0000CC',
    			strokeOpacity: 1.0,
    			strokeWeight: 4
    		});
    </script>

## See Also

ST_LineFromEncodedPolyline, ST_Segmentize

## Name

ST_AsFlatGeobuf — Return a FlatGeobuf representation of a set of rows.

## Synopsis

`bytea ST_AsFlatGeobuf(` anyelement set row`)`;

`bytea ST_AsFlatGeobuf(` anyelement row, bool index`)`;

`bytea ST_AsFlatGeobuf(` anyelement row, bool index, text geom_name`)`;

## Description

Return a FlatGeobuf representation (http://flatgeobuf.org) of a set of rows corresponding to a FeatureCollection. NOTE: PostgreSQL bytea cannot exceed 1GB.

`row` row data with at least a geometry column.

`index` toggle spatial index creation. Default is false.

`geom_name` is the name of the geometry column in the row data. If NULL it will default to the first found geometry column.

Availability: 3.2.0

## Name

ST_AsGeobuf — Return a Geobuf representation of a set of rows.

## Synopsis

`bytea ST_AsGeobuf(` anyelement set row`)`;

`bytea ST_AsGeobuf(` anyelement row, text geom_name`)`;

## Description

Return a Geobuf representation (https://github.com/mapbox/geobuf) of a set of rows corresponding to a FeatureCollection. Every input geometry is analyzed to determine maximum precision for optimal storage. Note that Geobuf in its current form cannot be streamed so the full output will be assembled in memory.

`row` row data with at least a geometry column.

`geom_name` is the name of the geometry column in the row data. If NULL it will default to the first found geometry column.

Availability: 2.4.0

## Examples

    SELECT encode(ST_AsGeobuf(q, 'geom'), 'base64')
        FROM (SELECT ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))') AS geom) AS q;
     st_asgeobuf
    ----------------------------------
     GAAiEAoOCgwIBBoIAAAAAgIAAAE=

## Name

ST_AsGeoJSON — Return a geometry or feature in GeoJSON format.

## Synopsis

`text ST_AsGeoJSON(` record feature, text geom_column="", integer maxdecimaldigits=9, boolean pretty_bool=false, text id_column=''`)`;

`text ST_AsGeoJSON(` geometry geom, integer maxdecimaldigits=9, integer options=8`)`;

`text ST_AsGeoJSON(` geography geog, integer maxdecimaldigits=9, integer options=0`)`;

## Description

Returns a geometry as a GeoJSON "geometry" object, or a row as a GeoJSON "feature" object.

The resulting GeoJSON geometry and feature representations conform with the GeoJSON specifications RFC 7946, except when the parsed geometries are referenced with a CRS other than WGS84 longitude and latitude (EPSG:4326, urn:ogc:def:crs:OGC::CRS84); the GeoJSON geometry object will then have a short CRS SRID identifier attached by default. 2D and 3D Geometries are both supported. GeoJSON only supports SFS 1.1 geometry types (no curve support for example).

The `geom_column` parameter is used to distinguish between multiple geometry columns. If omitted, the first geometry column in the record will be determined. Conversely, passing the parameter will save column type lookups.

The `maxdecimaldigits` argument may be used to reduce the maximum number of decimal places used in output (defaults to 9). If you are using EPSG:4326 and are outputting the geometry only for display, `maxdecimaldigits`=6 can be a good choice for many maps.

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

The `options` argument can be used to add BBOX or CRS in GeoJSON output:

- 0: means no option

- 1: GeoJSON BBOX

- 2: GeoJSON Short CRS (e.g EPSG:4326)

- 4: GeoJSON Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

- 8: GeoJSON Short CRS if not EPSG:4326 (default)

The `id_column` parameter is used to set the "id" member of the returned GeoJSON features. As per GeoJSON RFC, this SHOULD be used whenever a feature has a commonly used identifier, such as a primary key. When not specified, the produced features will not get an "id" member and any columns other than the geometry, including any potential keys, will just end up inside the feature’s "properties" member.

The GeoJSON specification states that polygons are oriented using the Right-Hand Rule, and some clients require this orientation. This can be ensured by using ST_ForcePolygonCCW . The specification also requires that geometry be in the WGS84 coordinate system (SRID = 4326). If necessary geometry can be projected into WGS84 using ST_Transform: `ST_Transform( geom, 4326 )`.

GeoJSON can be tested and viewed online at geojson.io and geojsonlint.com. It is widely supported by web mapping frameworks:

- OpenLayers GeoJSON Example

- Leaflet GeoJSON Example

- Mapbox GL GeoJSON Example

Availability: 1.3.4

Availability: 1.5.0 geography support was introduced.

Changed: 2.0.0 support default args and named args.

Changed: 3.0.0 support records as input

Changed: 3.0.0 output SRID if not EPSG:4326.

Changed: 3.5.0 allow specifying the column containing the feature id

This function supports 3d and will not drop the z-index.

## Examples

Generate a FeatureCollection:

    SELECT json_build_object(
        'type', 'FeatureCollection',
        'features', json_agg(ST_AsGeoJSON(t.*, id_column => 'id')::json)
        )
    FROM ( VALUES (1, 'one', 'POINT(1 1)'::geometry),
                  (2, 'two', 'POINT(2 2)'),
                  (3, 'three', 'POINT(3 3)')
         ) as t(id, name, geom);

    {"type" : "FeatureCollection", "features" : [{"type": "Feature", "geometry": {"type":"Point","coordinates":[1,1]}, "id": 1, "properties": {"name": "one"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[2,2]}, "id": 2, "properties": {"name": "two"}}, {"type": "Feature", "geometry": {"type":"Point","coordinates":[3,3]}, "id": 3, "properties": {"name": "three"}}]}

Generate a Feature:

    SELECT ST_AsGeoJSON(t.*, id_column => 'id')
    FROM (VALUES (1, 'one', 'POINT(1 1)'::geometry)) AS t(id, name, geom);

                                                      st_asgeojson
    -----------------------------------------------------------------------------------------------------------------
     {"type": "Feature", "geometry": {"type":"Point","coordinates":[1,1]}, "id": 1, "properties": {"name": "one"}}

Don't forget to transform your data to WGS84 longitude, latitude to conform with the GeoJSON specification:

    SELECT ST_AsGeoJSON(ST_Transform(geom,4326)) from fe_edges limit 1;

    					   st_asgeojson
    -----------------------------------------------------------------------------------------------------------

    {"type":"MultiLineString","coordinates":[[[-89.734634999999997,31.492072000000000],
    [-89.734955999999997,31.492237999999997]]]}

3D geometries are supported:

    SELECT ST_AsGeoJSON('LINESTRING(1 2 3, 4 5 6)');

    {"type":"LineString","coordinates":[[1,2,3],[4,5,6]]}

Options argument can be used to add BBOX and CRS in GeoJSON output:

     SELECT ST_AsGeoJSON(ST_SetSRID('POINT(1 1)'::geometry, 4326), 9, 4|1);

      {"type":"Point","crs":{"type":"name","properties":{"name":"urn:ogc:def:crs:EPSG::4326"}},"bbox":[1.000000000,1.000000000,1.000000000,1.000000000],"coordinates":[1,1]}

## See Also

ST_GeomFromGeoJSON, ST_ForcePolygonCCW , ST_Transform

## Name

ST_AsGML — Return the geometry as a GML version 2 or 3 element.

## Synopsis

`text ST_AsGML(` geometry geom, integer maxdecimaldigits=15, integer options=0`)`;

`text ST_AsGML(` geography geog, integer maxdecimaldigits=15, integer options=0, text nprefix=null, text id=null`)`;

`text ST_AsGML(` integer version, geometry geom, integer maxdecimaldigits=15, integer options=0, text nprefix=null, text id=null`)`;

`text ST_AsGML(` integer version, geography geog, integer maxdecimaldigits=15, integer options=0, text nprefix=null, text id=null`)`;

## Description

Return the geometry as a Geography Markup Language (GML) element. The version parameter, if specified, may be either 2 or 3. If no version parameter is specified then the default is assumed to be 2. The `maxdecimaldigits` argument may be used to reduce the maximum number of decimal places used in output (defaults to 15).

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

GML 2 refer to 2.1.2 version, GML 3 to 3.1.1 version

The 'options' argument is a bitfield. It could be used to define CRS output type in GML output, and to declare data as lat/lon:

- 0: GML Short CRS (e.g EPSG:4326), default value

- 1: GML Long CRS (e.g urn:ogc:def:crs:EPSG::4326)

- 2: For GML 3 only, remove srsDimension attribute from output.

- 4: For GML 3 only, use <LineString> rather than <Curve> tag for lines.

- 16: Declare that data are lat/lon (e.g srid=4326). Default is to assume that data are planars. This option is useful for GML 3.1.1 output only, related to axis order. So if you set it, it will swap the coordinates so order is lat lon instead of database lon lat.

- 32: Output the box of the geometry (envelope).

The 'namespace prefix' argument may be used to specify a custom namespace prefix or no prefix (if empty). If null or omitted 'gml' prefix is used

Availability: 1.3.2

Availability: 1.5.0 geography support was introduced.

Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curve tag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box.

Changed: 2.0.0 use default named args

Enhanced: 2.1.0 id support was introduced, for GML 3.

Only version 3+ of ST_AsGML supports Polyhedral Surfaces and TINS.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 17.2

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples: Version 2

    SELECT ST_AsGML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));
    		st_asgml
    		--------
    		<gml:Polygon srsName="EPSG:4326"><gml:outerBoundaryIs><gml:LinearRing><gml:coordinates>0,0 0,1 1,1 1,0 0,0</gml:coordinates></gml:LinearRing></gml:outerBoundaryIs></gml:Polygon>

## Examples: Version 3

    -- Flip coordinates and output extended EPSG (16 | 1)--
    SELECT ST_AsGML(3, ST_GeomFromText('POINT(5.234234233242 6.34534534534)',4326), 5, 17);
    			st_asgml
    			--------
    		<gml:Point srsName="urn:ogc:def:crs:EPSG::4326"><gml:pos>6.34535 5.23423</gml:pos></gml:Point>

    -- Output the envelope (32) --
    SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 32);
    		st_asgml
    		--------
    	<gml:Envelope srsName="EPSG:4326">
    		<gml:lowerCorner>1 2</gml:lowerCorner>
    		<gml:upperCorner>10 20</gml:upperCorner>
    	</gml:Envelope>

    -- Output the envelope (32) , reverse (lat lon instead of lon lat) (16), long srs (1)= 32 | 16 | 1 = 49 --
    SELECT ST_AsGML(3, ST_GeomFromText('LINESTRING(1 2, 3 4, 10 20)',4326), 5, 49);
    	st_asgml
    	--------
    <gml:Envelope srsName="urn:ogc:def:crs:EPSG::4326">
    	<gml:lowerCorner>2 1</gml:lowerCorner>
    	<gml:upperCorner>20 10</gml:upperCorner>
    </gml:Envelope>

    -- Polyhedral Example --
    SELECT ST_AsGML(3, ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
    	st_asgml
    	--------
     <gml:PolyhedralSurface>
    <gml:polygonPatches>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 0 0 1 0 1 1 0 1 0 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 0 1 0 1 1 0 1 0 0 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 0 1 0 0 1 0 1 0 0 1 0 0 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">1 1 0 1 1 1 1 0 1 1 0 0 1 1 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 1 0 0 1 1 1 1 1 1 1 0 0 1 0</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
       <gml:PolygonPatch>
    		<gml:exterior>
    			  <gml:LinearRing>
    				   <gml:posList srsDimension="3">0 0 1 1 0 1 1 1 1 0 1 1 0 0 1</gml:posList>
    			  </gml:LinearRing>
    		</gml:exterior>
       </gml:PolygonPatch>
    </gml:polygonPatches>
    </gml:PolyhedralSurface>

## See Also

ST_GeomFromGML

## Name

ST_AsKML — Return the geometry as a KML element.

## Synopsis

`text ST_AsKML(` geometry geom, integer maxdecimaldigits=15, text nprefix=NULL`)`;

`text ST_AsKML(` geography geog, integer maxdecimaldigits=15, text nprefix=NULL`)`;

## Description

Return the geometry as a Keyhole Markup Language (KML) element. default maximum number of decimal places is 15, default namespace is no prefix.

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

Requires PostGIS be compiled with Proj support. Use PostGIS_Full_Version to confirm you have proj support compiled in.

Availability: 1.2.2 - later variants that include version param came in 1.3.2

Enhanced: 2.0.0 - Add prefix namespace, use default and named args

Changed: 3.0.0 - Removed the "versioned" variant signature

AsKML output will not work with geometries that do not have an SRID

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsKML(ST_GeomFromText('POLYGON((0 0,0 1,1 1,1 0,0 0))',4326));

    		st_askml
    		--------
    		<Polygon><outerBoundaryIs><LinearRing><coordinates>0,0 0,1 1,1 1,0 0,0</coordinates></LinearRing></outerBoundaryIs></Polygon>

    		--3d linestring
    		SELECT ST_AsKML('SRID=4326;LINESTRING(1 2 3, 4 5 6)');
    		<LineString><coordinates>1,2,3 4,5,6</coordinates></LineString>

## See Also

ST_AsSVG, ST_AsGML

## Name

ST_AsLatLonText — Return the Degrees, Minutes, Seconds representation of the given point.

## Synopsis

`text ST_AsLatLonText(` geometry pt, text format=''`)`;

## Description

Returns the Degrees, Minutes, Seconds representation of the point.

It is assumed the point is in a lat/lon projection. The X (lon) and Y (lat) coordinates are normalized in the output to the "normal" range (-180 to +180 for lon, -90 to +90 for lat).

The text parameter is a format string containing the format for the resulting text, similar to a date format string. Valid tokens are "D" for degrees, "M" for minutes, "S" for seconds, and "C" for cardinal direction (NSEW). DMS tokens may be repeated to indicate desired width and precision ("SSS.SSSS" means " 1.0023").

"M", "S", and "C" are optional. If "C" is omitted, degrees are shown with a "-" sign if south or west. If "S" is omitted, minutes will be shown as decimal with as many digits of precision as you specify. If "M" is also omitted, degrees are shown as decimal with as many digits precision as you specify.

If the format string is omitted (or zero-length) a default format will be used.

Availability: 2.0

## Examples

Default format.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)'));
          st_aslatlontext
    ----------------------------
     2°19'29.928"S 3°14'3.243"W

Providing a format (same as the default).

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"C'));
          st_aslatlontext
    ----------------------------
     2°19'29.928"S 3°14'3.243"W

Characters other than D, M, S, C and . are just passed through.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D degrees, M minutes, S seconds to the C'));
                                       st_aslatlontext
    --------------------------------------------------------------------------------------
     2 degrees, 19 minutes, 30 seconds to the S 3 degrees, 14 minutes, 3 seconds to the W

Signed degrees instead of cardinal directions.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D°M''S.SSS"'));
          st_aslatlontext
    ----------------------------
     -2°19'29.928" -3°14'3.243"

Decimal degrees.

    SELECT (ST_AsLatLonText('POINT (-3.2342342 -2.32498)', 'D.DDDD degrees C'));
              st_aslatlontext
    -----------------------------------
     2.3250 degrees S 3.2342 degrees W

Excessively large values are normalized.

    SELECT (ST_AsLatLonText('POINT (-302.2342342 -792.32498)'));
            st_aslatlontext
    -------------------------------
     72°19'29.928"S 57°45'56.757"E

## Name

ST_AsMARC21 — Returns geometry as a MARC21/XML record with a geographic datafield (034).

## Synopsis

`text ST_AsMARC21 (` geometry geom , text format='hdddmmss' `)`;

## Description

This function returns a MARC21/XML record with Coded Cartographic Mathematical Data representing the bounding box of a given geometry. The `format` parameter allows to encode the coordinates in subfields `$d`,`$e`,`$f` and `$g` in all formats supported by the MARC21/XML standard. Valid formats are:

- cardinal direction, degrees, minutes and seconds (default): `hdddmmss`

- decimal degrees with cardinal direction: `hddd.dddddd`

- decimal degrees without cardinal direction: `ddd.dddddd`

- decimal minutes with cardinal direction: `hdddmm.mmmm`

- decimal minutes without cardinal direction: `dddmm.mmmm`

- decimal seconds with cardinal direction: `hdddmmss.sss`

The decimal sign may be also a comma, e.g. `hdddmm,mmmm`.

The precision of decimal formats can be limited by the number of characters after the decimal sign, e.g. `hdddmm.mm` for decimal minutes with a precision of two decimals.

This function ignores the Z and M dimensions.

LOC MARC21/XML versions supported:

- MARC21/XML 1.1

Availability: 3.3.0

This function does not support non lon/lat geometries, as they are not supported by the MARC21/XML standard (Coded Cartographic Mathematical Data).

The MARC21/XML Standard does not provide any means to annotate the spatial reference system for Coded Cartographic Mathematical Data, which means that this information will be lost after conversion to MARC21/XML.

## Examples

Converting a `POINT` to MARC21/XML formatted as hdddmmss (default)

                    SELECT ST_AsMARC21('SRID=4326;POINT(-4.504289 54.253312)'::geometry);

                                    st_asmarc21
                    -------------------------------------------------
                    <record xmlns="http://www.loc.gov/MARC21/slim">
                        <datafield tag="034" ind1="1" ind2=" ">
                            <subfield code="a">a</subfield>
                            <subfield code="d">W0043015</subfield>
                            <subfield code="e">W0043015</subfield>
                            <subfield code="f">N0541512</subfield>
                            <subfield code="g">N0541512</subfield>
                        </datafield>
                    </record>

Converting a `POLYGON` to MARC21/XML formatted in decimal degrees

                    SELECT ST_AsMARC21('SRID=4326;POLYGON((-4.5792388916015625 54.18172660239091,-4.56756591796875 54.196993557130355,-4.546623229980469 54.18313300502024,-4.5792388916015625 54.18172660239091))'::geometry,'hddd.dddd');

                    <record xmlns="http://www.loc.gov/MARC21/slim">
                        <datafield tag="034" ind1="1" ind2=" ">
                            <subfield code="a">a</subfield>
                            <subfield code="d">W004.5792</subfield>
                            <subfield code="e">W004.5466</subfield>
                            <subfield code="f">N054.1970</subfield>
                            <subfield code="g">N054.1817</subfield>
                        </datafield>
                    </record>

Converting a `GEOMETRYCOLLECTION` to MARC21/XML formatted in decimal minutes. The geometries order in the MARC21/XML output correspond to their order in the collection.

                    SELECT ST_AsMARC21('SRID=4326;GEOMETRYCOLLECTION(POLYGON((13.1 52.65,13.516666666666667 52.65,13.516666666666667 52.38333333333333,13.1 52.38333333333333,13.1 52.65)),POINT(-4.5 54.25))'::geometry,'hdddmm.mmmm');

                                    st_asmarc21
                    -------------------------------------------------
                    <record xmlns="http://www.loc.gov/MARC21/slim">
                        <datafield tag="034" ind1="1" ind2=" ">
                            <subfield code="a">a</subfield>
                            <subfield code="d">E01307.0000</subfield>
                            <subfield code="e">E01331.0000</subfield>
                            <subfield code="f">N05240.0000</subfield>
                            <subfield code="g">N05224.0000</subfield>
                        </datafield>
                        <datafield tag="034" ind1="1" ind2=" ">
                            <subfield code="a">a</subfield>
                            <subfield code="d">W00430.0000</subfield>
                            <subfield code="e">W00430.0000</subfield>
                            <subfield code="f">N05415.0000</subfield>
                            <subfield code="g">N05415.0000</subfield>
                        </datafield>
                    </record>

## See Also

ST_GeomFromMARC21

## Name

ST_AsMVTGeom — Transforms a geometry into the coordinate space of a MVT tile.

## Synopsis

`geometry ST_AsMVTGeom(` geometry geom, box2d bounds, integer extent=4096, integer buffer=256, boolean clip_geom=true`)`;

## Description

Transforms a geometry into the coordinate space of a MVT (Mapbox Vector Tile) tile, clipping it to the tile bounds if required. The geometry must be in the coordinate system of the target map (using ST_Transform if needed). Commonly this is Web Mercator (SRID:3857).

The function attempts to preserve geometry validity, and corrects it if needed. This may cause the result geometry to collapse to a lower dimension.

The rectangular bounds of the tile in the target map coordinate space must be provided, so the geometry can be transformed, and clipped if required. The bounds can be generated using ST_TileEnvelope.

This function is used to convert geometry into the tile coordinate space required by ST_AsMVT.

`geom` is the geometry to transform, in the coordinate system of the target map.

`bounds` is the rectangular bounds of the tile in map coordinate space, with no buffer.

`extent` is the tile extent size in tile coordinate space as defined by the MVT specification. Defaults to 4096.

`buffer` is the buffer size in tile coordinate space for geometry clippig. Defaults to 256.

`clip_geom` is a boolean to control if geometries are clipped or encoded as-is. Defaults to true.

Availability: 2.4.0

From 3.0, Wagyu can be chosen at configure time to clip and validate MVT polygons. This library is faster and produces more correct results than the GEOS default, but it might drop small polygons.

## Examples

    SELECT ST_AsText(ST_AsMVTGeom(
    	ST_GeomFromText('POLYGON ((0 0, 10 0, 10 5, 0 -5, 0 0))'),
    	ST_MakeBox2D(ST_Point(0, 0), ST_Point(4096, 4096)),
    	4096, 0, false));
                                  st_astext
    --------------------------------------------------------------------
     MULTIPOLYGON(((5 4096,10 4091,10 4096,5 4096)),((5 4096,0 4101,0 4096,5 4096)))

Canonical example for a Web Mercator tile using a computed tile bounds to query and clip geometry. This assumes the data.geom column has srid of 4326.

    SELECT ST_AsMVTGeom(
                ST_Transform( geom, 3857 ),
                ST_TileEnvelope(12, 513, 412), extent => 4096, buffer => 64) AS geom
      FROM data
      WHERE geom && ST_Transform(ST_TileEnvelope(12, 513, 412, margin => (64.0 / 4096)),4326)

## See Also

ST_AsMVT, ST_TileEnvelope, PostGIS_Wagyu_Version

## Name

ST_AsMVT — Aggregate function returning a MVT representation of a set of rows.

## Synopsis

`bytea ST_AsMVT(` anyelement set row`)`;

`bytea ST_AsMVT(` anyelement row, text name`)`;

`bytea ST_AsMVT(` anyelement row, text name, integer extent`)`;

`bytea ST_AsMVT(` anyelement row, text name, integer extent, text geom_name`)`;

`bytea ST_AsMVT(` anyelement row, text name, integer extent, text geom_name, text feature_id_name`)`;

## Description

An aggregate function which returns a binary Mapbox Vector Tile representation of a set of rows corresponding to a tile layer. The rows must contain a geometry column which will be encoded as a feature geometry. The geometry must be in tile coordinate space and valid as per the MVT specification. ST_AsMVTGeom can be used to transform geometry into tile coordinate space. Other row columns are encoded as feature attributes.

The Mapbox Vector Tile format can store features with varying sets of attributes. To use this capability supply a JSONB column in the row data containing Json objects one level deep. The keys and values in the JSONB values will be encoded as feature attributes.

Tiles with multiple layers can be created by concatenating multiple calls to this function using `||` or `STRING_AGG`.

Do not call with a `GEOMETRYCOLLECTION` as an element in the row. However you can use ST_AsMVTGeom to prepare a geometry collection for inclusion.

`row` row data with at least a geometry column.

`name` is the name of the layer. Default is the string "default".

`extent` is the tile extent in screen space as defined by the specification. Default is 4096.

`geom_name` is the name of the geometry column in the row data. Default is the first geometry column. Note that PostgreSQL by default automatically folds unquoted identifiers to lower case, which means that unless the geometry column is quoted, e.g. `"MyMVTGeom"`, this parameter must be provided as lowercase.

`feature_id_name` is the name of the Feature ID column in the row data. If NULL or negative the Feature ID is not set. The first column matching name and valid type (smallint, integer, bigint) will be used as Feature ID, and any subsequent column will be added as a property. JSON properties are not supported.

Enhanced: 3.0 - added support for Feature ID.

Enhanced: 2.5.0 - added support parallel query.

Availability: 2.4.0

## Examples

    WITH mvtgeom AS
    (
      SELECT ST_AsMVTGeom(geom, ST_TileEnvelope(12, 513, 412), extent => 4096, buffer => 64) AS geom, name, description
      FROM points_of_interest
      WHERE geom && ST_TileEnvelope(12, 513, 412, margin => (64.0 / 4096))
    )
    SELECT ST_AsMVT(mvtgeom.*)
    FROM mvtgeom;

## See Also

ST_AsMVTGeom, ST_TileEnvelope

## Name

ST_AsSVG — Returns SVG path data for a geometry.

## Synopsis

`text ST_AsSVG(` geometry geom, integer rel=0, integer maxdecimaldigits=15`)`;

`text ST_AsSVG(` geography geog, integer rel=0, integer maxdecimaldigits=15`)`;

## Description

Return the geometry as Scalar Vector Graphics (SVG) path data. Use 1 as second argument to have the path data implemented in terms of relative moves, the default (or 0) uses absolute moves. Third argument may be used to reduce the maximum number of decimal digits used in output (defaults to 15). Point geometries will be rendered as cx/cy when 'rel' arg is 0, x/y when 'rel' is 1. Multipoint geometries are delimited by commas (","), GeometryCollection geometries are delimited by semicolons (";").

For working with PostGIS SVG graphics, checkout pg_svg library which provides plpgsql functions for working with outputs from ST_AsSVG.

Enhanced: 3.4.0 to support all curve types

Changed: 2.0.0 to use default args and support named args

Availability: 1.2.2. Availability: 1.4.0 Changed in PostGIS 1.4.0 to include L command in absolute path to conform to http://www.w3.org/TR/SVG/paths.html#PathDataBNF

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsSVG('POLYGON((0 0,0 1,1 1,1 0,0 0))'::geometry);

    st_assvg
    --------
    M 0 0 L 0 -1 1 -1 1 0 Z

Circular string

    SELECT ST_AsSVG( ST_GeomFromText('CIRCULARSTRING(-2 0,0 2,2 0,0 2,2 4)') );

    st_assvg
    --------
    M -2 0 A 2 2 0 0 1 2 0 A 2 2 0 0 1 2 -4

Multi-curve

    SELECT ST_AsSVG('MULTICURVE((5 5,3 5,3 3,0 3),
     CIRCULARSTRING(0 0,2 1,2 2))'::geometry, 0, 0);
     st_assvg
    ------------------------------------------------
     M 5 -5 L 3 -5 3 -3 0 -3 M 0 0 A 2 2 0 0 0 2 -2

Multi-surface

    SELECT ST_AsSVG('MULTISURFACE(
    CURVEPOLYGON(CIRCULARSTRING(-2 0,-1 -1,0 0,1 -1,2 0,0 2,-2 0),
        (-1 0,0 0.5,1 0,0 1,-1 0)),
    ((7 8,10 10,6 14,4 11,7 8)))'::geometry, 0, 2);

    st_assvg
    ---------------------------------------------------------
    M -2 0 A 1 1 0 0 0 0 0 A 1 1 0 0 0 2 0 A 2 2 0 0 0 -2 0 Z
    M -1 0 L 0 -0.5 1 0 0 -1 -1 0 Z
    M 7 -8 L 10 -10 6 -14 4 -11 Z

## Name

ST_AsTWKB — Returns the geometry as TWKB, aka "Tiny Well-Known Binary"

## Synopsis

`bytea ST_AsTWKB(` geometry geom, integer prec=0, integer prec_z=0, integer prec_m=0, boolean with_sizes=false, boolean with_boxes=false`)`;

`bytea ST_AsTWKB(` geometry[] geom, bigint[] ids, integer prec=0, integer prec_z=0, integer prec_m=0, boolean with_sizes=false, boolean with_boxes=false`)`;

## Description

Returns the geometry in TWKB (Tiny Well-Known Binary) format. TWKB is a compressed binary format with a focus on minimizing the size of the output.

The decimal digits parameters control how much precision is stored in the output. By default, values are rounded to the nearest unit before encoding. If you want to transfer more precision, increase the number. For example, a value of 1 implies that the first digit to the right of the decimal point will be preserved.

The sizes and bounding boxes parameters control whether optional information about the encoded length of the object and the bounds of the object are included in the output. By default they are not. Do not turn them on unless your client software has a use for them, as they just use up space (and saving space is the point of TWKB).

The array-input form of the function is used to convert a collection of geometries and unique identifiers into a TWKB collection that preserves the identifiers. This is useful for clients that expect to unpack a collection and then access further information about the objects inside. You can create the arrays using the array_agg function. The other parameters operate the same as for the simple form of the function.

The format specification is available online at https://github.com/TWKB/Specification, and code for building a JavaScript client can be found at https://github.com/TWKB/twkb.js.

Enhanced: 2.4.0 memory and speed improvements.

Availability: 2.2.0

## Examples

    SELECT ST_AsTWKB('LINESTRING(1 1,5 5)'::geometry);
                     st_astwkb
    --------------------------------------------
    \x02000202020808

To create an aggregate TWKB object including identifiers aggregate the desired geometries and objects first, using "array_agg()", then call the appropriate TWKB function.

    SELECT ST_AsTWKB(array_agg(geom), array_agg(gid)) FROM mytable;
                     st_astwkb
    --------------------------------------------
    \x040402020400000202

## See Also

ST_GeomFromTWKB, ST_AsBinary, ST_AsEWKB, ST_AsEWKT, ST_GeomFromText

## Name

ST_AsX3D — Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML

## Synopsis

`text ST_AsX3D(` geometry g1, integer maxdecimaldigits=15, integer options=0`)`;

## Description

Returns a geometry as an X3D xml formatted node element http://www.web3d.org/standards/number/19776-1. If `maxdecimaldigits` (precision) is not specified then defaults to 15.

There are various options for translating PostGIS geometries to X3D since X3D geometry types don't map directly to PostGIS geometry types and some newer X3D types that might be better mappings we have avoided since most rendering tools don't currently support them. These are the mappings we have settled on. Feel free to post a bug ticket if you have thoughts on the idea or ways we can allow people to denote their preferred mappings. Below is how we currently map PostGIS 2D/3D types to X3D types

The 'options' argument is a bitfield. For PostGIS 2.2+, this is used to denote whether to represent coordinates with X3D GeoCoordinates Geospatial node and also whether to flip the x/y axis. By default, `ST_AsX3D` outputs in database form (long,lat or X,Y), but X3D default of lat/lon, y/x may be preferred.

- 0: X/Y in database order (e.g. long/lat = X,Y is standard database order), default value, and non-spatial coordinates (just regular old Coordinate tag).

- 1: Flip X and Y. If used in conjunction with the GeoCoordinate option switch, then output will be default "latitude_first" and coordinates will be flipped as well.

- 2: Output coordinates in GeoSpatial GeoCoordinates. This option will throw an error if geometries are not in WGS 84 long lat (srid: 4326). This is currently the only GeoCoordinate type supported. Refer to X3D specs specifying a spatial reference system.. Default output will be `GeoCoordinate geoSystem='"GD" "WE" "longitude_first"'`. If you prefer the X3D default of `GeoCoordinate geoSystem='"GD" "WE" "latitude_first"'` use `(2 + 1)` = `3`

PostGIS Type | 2D X3D Type | 3D X3D Type
--- | --- | ---
LINESTRING | not yet implemented - will be PolyLine2D | LineSet
MULTILINESTRING | not yet implemented - will be PolyLine2D | IndexedLineSet
MULTIPOINT | Polypoint2D | PointSet
POINT | outputs the space delimited coordinates | outputs the space delimited coordinates
(MULTI) POLYGON, POLYHEDRALSURFACE | Invalid X3D markup | IndexedFaceSet (inner rings currently output as another faceset)
TIN | TriangleSet2D (Not Yet Implemented) | IndexedTriangleSet

2D geometry support not yet complete. Inner rings currently just drawn as separate polygons. We are working on these.

Lots of advancements happening in 3D space particularly with X3D Integration with HTML5

There is also a nice open source X3D viewer you can use to view rendered geometries. Free Wrl http://freewrl.sourceforge.net/ binaries available for Mac, Linux, and Windows. Use the FreeWRL_Launcher packaged to view the geometries.

Also check out PostGIS minimalist X3D viewer that utilizes this function and x3dDom html/js open source toolkit.

Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML

Enhanced: 2.2.0: Support for GeoCoordinates and axis (x/y, long/lat) flipping. Look at options for details.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Example: Create a fully functional X3D document - This will generate a cube that is viewable in FreeWrl and other X3D viewers.

    SELECT '<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
    <X3D>
      <Scene>
        <Transform>
          <Shape>
           <Appearance>
                <Material emissiveColor=''0 0 1''/>
           </Appearance> ' ||
           ST_AsX3D( ST_GeomFromEWKT('POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )')) ||
          '</Shape>
        </Transform>
      </Scene>
    </X3D>' As x3ddoc;

    		x3ddoc
    		--------
    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE X3D PUBLIC "ISO//Web3D//DTD X3D 3.0//EN" "http://www.web3d.org/specifications/x3d-3.0.dtd">
    <X3D>
      <Scene>
        <Transform>
          <Shape>
           <Appearance>
                <Material emissiveColor='0 0 1'/>
           </Appearance>
           <IndexedFaceSet  coordIndex='0 1 2 3 -1 4 5 6 7 -1 8 9 10 11 -1 12 13 14 15 -1 16 17 18 19 -1 20 21 22 23'>
                <Coordinate point='0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 0 0 1 1 1 0 1 1 1 1 0 1 1 0 0 0 1 0 0 1 1 1 1 1 1 1 0 0 0 1 1 0 1 1 1 1 0 1 1' />
          </IndexedFaceSet>
          </Shape>
        </Transform>
      </Scene>
    </X3D>

## PostGIS buildings

Copy and paste the output of this query to x3d scene viewer and click Show

    SELECT string_agg('<Shape>' || ST_AsX3D(ST_Extrude(geom, 0,0, i*0.5)) ||
        '<Appearance>
              <Material diffuseColor="' || (0.01*i)::text || ' 0.8 0.2" specularColor="' || (0.05*i)::text || ' 0 0.5"/>
            </Appearance>
        </Shape>', '')
    FROM ST_Subdivide(ST_Letters('PostGIS'),20) WITH ORDINALITY AS f(geom,i);

Buildings formed by subdividing PostGIS and extrusion

## Example: An Octagon elevated 3 Units and decimal precision of 6

    SELECT ST_AsX3D(
    ST_Translate(
        ST_Force_3d(
            ST_Buffer(ST_Point(10,10),5, 'quad_segs=2')), 0,0,
        3)
      ,6) As x3dfrag;

    x3dfrag
    --------
    <IndexedFaceSet coordIndex="0 1 2 3 4 5 6 7">
        <Coordinate point="15 10 3 13.535534 6.464466 3 10 5 3 6.464466 6.464466 3 5 10 3 6.464466 13.535534 3 10 15 3 13.535534 13.535534 3 " />
    </IndexedFaceSet>

## Example: TIN

    SELECT ST_AsX3D(ST_GeomFromEWKT('TIN (((
                    0 0 0,
                    0 0 1,
                    0 1 0,
                    0 0 0
                )), ((
                    0 0 0,
                    0 1 0,
                    1 1 0,
                    0 0 0
                ))
                )')) As x3dfrag;

    		x3dfrag
    		--------
    <IndexedTriangleSet  index='0 1 2 3 4 5'><Coordinate point='0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 1 0'/></IndexedTriangleSet>

## Example: Closed multilinestring (the boundary of a polygon with holes)

    SELECT ST_AsX3D(
    		    ST_GeomFromEWKT('MULTILINESTRING((20 0 10,16 -12 10,0 -16 10,-12 -12 10,-20 0 10,-12 16 10,0 24 10,16 16 10,20 0 10),
      (12 0 10,8 8 10,0 12 10,-8 8 10,-8 0 10,-8 -4 10,0 -8 10,8 -4 10,12 0 10))')
    ) As x3dfrag;

    		x3dfrag
    		--------
    <IndexedLineSet  coordIndex='0 1 2 3 4 5 6 7 0 -1 8 9 10 11 12 13 14 15 8'>
        <Coordinate point='20 0 10 16 -12 10 0 -16 10 -12 -12 10 -20 0 10 -12 16 10 0 24 10 16 16 10 12 0 10 8 8 10 0 12 10 -8 8 10 -8 0 10 -8 -4 10 0 -8 10 8 -4 10 ' />
     </IndexedLineSet>

## Name

ST_GeoHash — Return a GeoHash representation of the geometry.

## Synopsis

`text ST_GeoHash(` geometry geom, integer maxchars=full_precision_of_point`)`;

## Description

Computes a GeoHash representation of a geometry. A GeoHash encodes a geographic Point into a text form that is sortable and searchable based on prefixing. A shorter GeoHash is a less precise representation of a point. It can be thought of as a box that contains the point.

Non-point geometry values with non-zero extent can also be mapped to GeoHash codes. The precision of the code depends on the geographic extent of the geometry.

If `maxchars` is not specified, the returned GeoHash code is for the smallest cell containing the input geometry. Points return a GeoHash with 20 characters of precision (about enough to hold the full double precision of the input). Other geometric types may return a GeoHash with less precision, depending on the extent of the geometry. Larger geometries are represented with less precision, smaller ones with more precision. The box determined by the GeoHash code always contains the input feature.

If `maxchars` is specified the returned GeoHash code has at most that many characters. It maps to a (possibly) lower precision representation of the input geometry. For non-points, the starting point of the calculation is the center of the bounding box of the geometry.

Availability: 1.4.0

ST_GeoHash requires input geometry to be in geographic (lon/lat) coordinates.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_GeoHash( ST_Point(-126,48) );

    	 st_geohash
    ----------------------
     c0w3hf1s70w3hf1s70w3

    SELECT ST_GeoHash( ST_Point(-126,48), 5);

     st_geohash
    ------------
     c0w3h

    -- This line contains the point, so the GeoHash is a prefix of the point code
    SELECT ST_GeoHash('LINESTRING(-126 48, -126.1 48.1)'::geometry);

     st_geohash
    ------------
     c0w3

## See Also

ST_GeomFromGeoHash, ST_PointFromGeoHash, ST_Box2dFromGeoHash

## 7.10. Operators

### 7.10.1. Bounding Box Operators

## Name

&& — Returns `TRUE` if A's 2D bounding box intersects B's 2D bounding box.

## Synopsis

`boolean &&(` geometry A , geometry B `)`;

`boolean &&(` geography A , geography B `)`;

## Description

The `&&` operator returns `TRUE` if the 2D bounding box of geometry A intersects the 2D bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces was introduced.

Availability: 1.5.0 support for geography was introduced.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 && tbl2.column2 AS overlaps
    FROM ( VALUES
    	(1, 'LINESTRING(0 0, 3 3)'::geometry),
    	(2, 'LINESTRING(0 1, 0 5)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overlaps
    ---------+---------+----------
    	   1 |       3 | t
    	   2 |       3 | f
    (2 rows)

## See Also

ST_Intersects, ST_Extent, |&>, &>, &<|, &<, ~, @

## Name

&&(geometry,box2df) — Returns `TRUE` if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).

## Synopsis

`boolean &&(` geometry A , box2df B `)`;

## Description

The `&&` operator returns `TRUE` if the cached 2D bounding box of geometry A intersects the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_Point(1,1) && ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

&&(box2df,geometry) — Returns `TRUE` if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.

## Synopsis

`boolean &&(` box2df A , geometry B `)`;

## Description

The `&&` operator returns `TRUE` if the 2D bounding box A intersects the cached 2D bounding box of geometry B, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) && ST_Point(1,1) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

&&(box2df,box2df) — Returns `TRUE` if two 2D float precision bounding boxes (BOX2DF) intersect each other.

## Synopsis

`boolean &&(` box2df A , box2df B `)`;

## Description

The `&&` operator returns `TRUE` if two 2D bounding boxes A and B intersect each other, using float precision. This means that if A (or B) is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) && ST_MakeBox2D(ST_Point(1,1), ST_Point(3,3)) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

&&& — Returns `TRUE` if A's n-D bounding box intersects B's n-D bounding box.

## Synopsis

`boolean &&&(` geometry A , geometry B `)`;

## Description

The `&&&` operator returns `TRUE` if the n-D bounding box of geometry A intersects the n-D bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

Availability: 2.0.0

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples: 3D LineStrings

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3d,
    			            tbl1.column2 && tbl2.column2 AS overlaps_2d
    FROM ( VALUES
    	(1, 'LINESTRING Z(0 0 1, 3 3 2)'::geometry),
    	(2, 'LINESTRING Z(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING Z(1 2 1, 4 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overlaps_3d | overlaps_2d
    ---------+---------+-------------+-------------
           1 |       3 | t           | t
           2 |       3 | f           | t

## Examples: 3M LineStrings

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &&& tbl2.column2 AS overlaps_3zm,
    			            tbl1.column2 && tbl2.column2 AS overlaps_2d
    FROM ( VALUES
    	(1, 'LINESTRING M(0 0 1, 3 3 2)'::geometry),
    	(2, 'LINESTRING M(1 2 0, 0 5 -1)'::geometry)) AS tbl1,
    ( VALUES
    	(3, 'LINESTRING M(1 2 1, 4 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overlaps_3zm | overlaps_2d
    ---------+---------+-------------+-------------
           1 |       3 | t           | t
           2 |       3 | f           | t

## See Also

&&

## Name

&&&(geometry,gidx) — Returns `TRUE` if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).

## Synopsis

`boolean &&&(` geometry A , gidx B `)`;

## Description

The `&&&` operator returns `TRUE` if the cached n-D bounding box of geometry A intersects the n-D bounding box B, using float precision. This means that if B is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_MakePoint(1,1,1) &&& ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&&(gidx,geometry), &&&(gidx,gidx)

## Name

&&&(gidx,geometry) — Returns `TRUE` if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.

## Synopsis

`boolean &&&(` gidx A , geometry B `)`;

## Description

The `&&&` operator returns `TRUE` if the n-D bounding box A intersects the cached n-D bounding box of geometry B, using float precision. This means that if A is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) &&& ST_MakePoint(1,1,1) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&&(geometry,gidx), &&&(gidx,gidx)

## Name

&&&(gidx,gidx) — Returns `TRUE` if two n-D float precision bounding boxes (GIDX) intersect each other.

## Synopsis

`boolean &&&(` gidx A , gidx B `)`;

## Description

The `&&&` operator returns `TRUE` if two n-D bounding boxes A and B intersect each other, using float precision. This means that if A (or B) is a (double precision) box3d, it will be internally converted to a float precision 3D bounding box (GIDX)

This operator is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_3DMakeBox(ST_MakePoint(0,0,0), ST_MakePoint(2,2,2)) &&& ST_3DMakeBox(ST_MakePoint(1,1,1), ST_MakePoint(3,3,3)) AS overlaps;

     overlaps
    ----------
     t
    (1 row)

## See Also

&&&(geometry,gidx), &&&(gidx,geometry)

## Name

&< — Returns `TRUE` if A's bounding box overlaps or is to the left of B's.

## Synopsis

`boolean &<(` geometry A , geometry B `)`;

## Description

The `&<` operator returns `TRUE` if the bounding box of geometry A overlaps or is to the left of the bounding box of geometry B, or more accurately, overlaps or is NOT to the right of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &< tbl2.column2 AS overleft
    FROM
      ( VALUES
    	(1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overleft
    ---------+---------+----------
    	   1 |       2 | f
    	   1 |       3 | f
    	   1 |       4 | t
    (3 rows)

## See Also

&&, |&>, &>, &<|

## Name

&<| — Returns `TRUE` if A's bounding box overlaps or is below B's.

## Synopsis

`boolean &<|(` geometry A , geometry B `)`;

## Description

The `&<|` operator returns `TRUE` if the bounding box of geometry A overlaps or is below of the bounding box of geometry B, or more accurately, overlaps or is NOT above the bounding box of geometry B.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &<| tbl2.column2 AS overbelow
    FROM
      ( VALUES
    	(1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overbelow
    ---------+---------+-----------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

&&, |&>, &>, &<

## Name

&> — Returns `TRUE` if A' bounding box overlaps or is to the right of B's.

## Synopsis

`boolean &>(` geometry A , geometry B `)`;

## Description

The `&>` operator returns `TRUE` if the bounding box of geometry A overlaps or is to the right of the bounding box of geometry B, or more accurately, overlaps or is NOT to the left of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 &> tbl2.column2 AS overright
    FROM
      ( VALUES
    	(1, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(6 0, 6 1)'::geometry)) AS tbl2;

     column1 | column1 | overright
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | t
    	   1 |       4 | f
    (3 rows)

## See Also

&&, |&>, &<|, &<

## Name

<< — Returns `TRUE` if A's bounding box is strictly to the left of B's.

## Synopsis

`boolean <<(` geometry A , geometry B `)`;

## Description

The `<<` operator returns `TRUE` if the bounding box of geometry A is strictly to the left of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 << tbl2.column2 AS left
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 2, 1 5)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 3)'::geometry),
    	(3, 'LINESTRING (6 0, 6 5)'::geometry),
    	(4, 'LINESTRING (2 2, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | left
    ---------+---------+------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

>>, |>>, <<|

## Name

<<| — Returns `TRUE` if A's bounding box is strictly below B's.

## Synopsis

`boolean <<|(` geometry A , geometry B `)`;

## Description

The `<<|` operator returns `TRUE` if the bounding box of geometry A is strictly below the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 <<| tbl2.column2 AS below
    FROM
      ( VALUES
    	(1, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (1 4, 1 7)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | below
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, >>, |>>

## Name

= — Returns `TRUE` if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.

## Synopsis

`boolean =(` geometry A , geometry B `)`;

`boolean =(` geography A , geography B `)`;

## Description

The `=` operator returns `TRUE` if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B. PostgreSQL uses the =, <, and > operators defined for geometries to perform internal orderings and comparison of geometries (ie. in a GROUP BY or ORDER BY clause).

Only geometry/geography that are exactly equal in all respects, with the same coordinates, in the same order, are considered equal by this operator. For "spatial equality", that ignores things like coordinate order, and can detect features that cover the same spatial area with different representations, use ST_OrderingEquals or ST_Equals

This operand will NOT make use of any indexes that may be available on the geometries. For an index assisted exact equality test, combine = with &&.

Changed: 2.4.0, in prior versions this was bounding box equality not a geometric equality. If you need bounding box equality, use ~= instead.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT 'LINESTRING(0 0, 0 1, 1 0)'::geometry = 'LINESTRING(1 1, 0 0)'::geometry;
     ?column?
    ----------
     f
    (1 row)

    SELECT ST_AsText(column1)
    FROM ( VALUES
    	('LINESTRING(0 0, 1 1)'::geometry),
    	('LINESTRING(1 1, 0 0)'::geometry)) AS foo;
    	  st_astext
    ---------------------
     LINESTRING(0 0,1 1)
     LINESTRING(1 1,0 0)
    (2 rows)

    -- Note: the GROUP BY uses the "=" to compare for geometry equivalency.
    SELECT ST_AsText(column1)
    FROM ( VALUES
    	('LINESTRING(0 0, 1 1)'::geometry),
    	('LINESTRING(1 1, 0 0)'::geometry)) AS foo
    GROUP BY column1;
          st_astext
    ---------------------
     LINESTRING(0 0,1 1)
     LINESTRING(1 1,0 0)
    (2 rows)

    -- In versions prior to 2.0, this used to return true --
     SELECT ST_GeomFromText('POINT(1707296.37 4820536.77)') =
    	ST_GeomFromText('POINT(1707296.27 4820536.87)') As pt_intersect;

    --pt_intersect --
    f

## See Also

ST_Equals, ST_OrderingEquals, ~=

## Name

>> — Returns `TRUE` if A's bounding box is strictly to the right of B's.

## Synopsis

`boolean >>(` geometry A , geometry B `)`;

## Description

The `>>` operator returns `TRUE` if the bounding box of geometry A is strictly to the right of the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 >> tbl2.column2 AS right
    FROM
      ( VALUES
    	(1, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (1 4, 1 7)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (0 0, 4 3)'::geometry)) AS tbl2;

     column1 | column1 | right
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, |>>, <<|

## Name

@ — Returns `TRUE` if A's bounding box is contained by B's.

## Synopsis

`boolean @(` geometry A , geometry B `)`;

## Description

The `@` operator returns `TRUE` if the bounding box of geometry A is completely contained by the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 @ tbl2.column2 AS contained
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 4)'::geometry),
    	(3, 'LINESTRING (2 2, 4 4)'::geometry),
    	(4, 'LINESTRING (1 1, 3 3)'::geometry)) AS tbl2;

     column1 | column1 | contained
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | t
    (3 rows)

## See Also

~, &&

## Name

@(geometry,box2df) — Returns `TRUE` if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).

## Synopsis

`boolean @(` geometry A , box2df B `)`;

## Description

The `@` operator returns `TRUE` if the A geometry's 2D bounding box is contained the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_Buffer(ST_GeomFromText('POINT(2 2)'), 1) @ ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) AS is_contained;

     is_contained
    --------------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

@(box2df,geometry) — Returns `TRUE` if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.

## Synopsis

`boolean @(` box2df A , geometry B `)`;

## Description

The `@` operator returns `TRUE` if the 2D bounding box A is contained into the B geometry's 2D bounding box, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) @ ST_Buffer(ST_GeomFromText('POINT(1 1)'), 10) AS is_contained;

     is_contained
    --------------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,box2df)

## Name

@(box2df,box2df) — Returns `TRUE` if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.

## Synopsis

`boolean @(` box2df A , box2df B `)`;

## Description

The `@` operator returns `TRUE` if the 2D bounding box A is contained into the 2D bounding box B, using float precision. This means that if A (or B) is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) @ ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) AS is_contained;

     is_contained
    --------------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry)

## Name

|&> — Returns `TRUE` if A's bounding box overlaps or is above B's.

## Synopsis

`boolean |&>(` geometry A , geometry B `)`;

## Description

The `|&>` operator returns `TRUE` if the bounding box of geometry A overlaps or is above the bounding box of geometry B, or more accurately, overlaps or is NOT below the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 |&> tbl2.column2 AS overabove
    FROM
      ( VALUES
    	(1, 'LINESTRING(6 0, 6 4)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING(0 0, 3 3)'::geometry),
    	(3, 'LINESTRING(0 1, 0 5)'::geometry),
    	(4, 'LINESTRING(1 2, 4 6)'::geometry)) AS tbl2;

     column1 | column1 | overabove
    ---------+---------+-----------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

&&, &>, &<|, &<

## Name

|>> — Returns `TRUE` if A's bounding box is strictly above B's.

## Synopsis

`boolean |>>(` geometry A , geometry B `)`;

## Description

The `|>>` operator returns `TRUE` if the bounding box of geometry A is strictly above the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 |>> tbl2.column2 AS above
    FROM
      ( VALUES
    	(1, 'LINESTRING (1 4, 1 7)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 2)'::geometry),
    	(3, 'LINESTRING (6 1, 6 5)'::geometry),
    	(4, 'LINESTRING (2 3, 5 6)'::geometry)) AS tbl2;

     column1 | column1 | above
    ---------+---------+-------
    	   1 |       2 | t
    	   1 |       3 | f
    	   1 |       4 | f
    (3 rows)

## See Also

<<, >>, <<|

## Name

~ — Returns `TRUE` if A's bounding box contains B's.

## Synopsis

`boolean ~(` geometry A , geometry B `)`;

## Description

The `~` operator returns `TRUE` if the bounding box of geometry A completely contains the bounding box of geometry B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT tbl1.column1, tbl2.column1, tbl1.column2 ~ tbl2.column2 AS contains
    FROM
      ( VALUES
    	(1, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl1,
      ( VALUES
    	(2, 'LINESTRING (0 0, 4 4)'::geometry),
    	(3, 'LINESTRING (1 1, 2 2)'::geometry),
    	(4, 'LINESTRING (0 0, 3 3)'::geometry)) AS tbl2;

     column1 | column1 | contains
    ---------+---------+----------
    	   1 |       2 | f
    	   1 |       3 | t
    	   1 |       4 | t
    (3 rows)

## See Also

@, &&

## Name

~(geometry,box2df) — Returns `TRUE` if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).

## Synopsis

`boolean ~(` geometry A , box2df B `)`;

## Description

The `~` operator returns `TRUE` if the 2D bounding box of a geometry A contains the 2D bounding box B, using float precision. This means that if B is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_Buffer(ST_GeomFromText('POINT(1 1)'), 10) ~ ST_MakeBox2D(ST_Point(0,0), ST_Point(2,2)) AS contains;

     contains
    ----------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(box2df,geometry), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

~(box2df,geometry) — Returns `TRUE` if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.

## Synopsis

`boolean ~(` box2df A , geometry B `)`;

## Description

The `~` operator returns `TRUE` if the 2D bounding box A contains the B geometry's bounding box, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) ~ ST_Buffer(ST_GeomFromText('POINT(2 2)'), 1) AS contains;

     contains
    ----------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,box2df), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

~(box2df,box2df) — Returns `TRUE` if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).

## Synopsis

`boolean ~(` box2df A , box2df B `)`;

## Description

The `~` operator returns `TRUE` if the 2D bounding box A contains the 2D bounding box B, using float precision. This means that if A is a (double precision) box2d, it will be internally converted to a float precision 2D bounding box (BOX2DF)

This operand is intended to be used internally by BRIN indexes, more than by users.

Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

## Examples

    SELECT ST_MakeBox2D(ST_Point(0,0), ST_Point(5,5)) ~ ST_MakeBox2D(ST_Point(2,2), ST_Point(3,3)) AS contains;

     contains
    ----------
     t
    (1 row)

## See Also

&&(geometry,box2df), &&(box2df,geometry), &&(box2df,box2df), ~(geometry,box2df), ~(box2df,geometry), @(geometry,box2df), @(box2df,geometry), @(box2df,box2df)

## Name

~= — Returns `TRUE` if A's bounding box is the same as B's.

## Synopsis

`boolean ~=(` geometry A , geometry B `)`;

## Description

The `~=` operator returns `TRUE` if the bounding box of geometry/geography A is the same as the bounding box of geometry/geography B.

This operand will make use of any indexes that may be available on the geometries.

Availability: 1.5.0 changed behavior

This function supports Polyhedral surfaces.

This operator has changed behavior in PostGIS 1.5 from testing for actual geometric equality to only checking for bounding box equality. To complicate things it also depends on if you have done a hard or soft upgrade which behavior your database has. To find out which behavior your database has you can run the query below. To check for true equality use ST_OrderingEquals or ST_Equals.

## Examples

    select 'LINESTRING(0 0, 1 1)'::geometry ~= 'LINESTRING(0 1, 1 0)'::geometry as equality;
     equality   |
    -----------------+
              t    |

## See Also

ST_Equals, ST_OrderingEquals, =

### 7.10.2. Distance Operators

## Name

<-> — Returns the 2D distance between A and B.

## Synopsis

`double precision <->(` geometry A , geometry B `)`;

`double precision <->(` geography A , geography B `)`;

## Description

The `<->` operator returns the 2D distance between two geometries. Used in the "ORDER BY" clause provides index-assisted nearest-neighbor result sets. For PostgreSQL below 9.5 only gives centroid distance of bounding boxes and for PostgreSQL 9.5+, does true KNN distance search giving true distance between geometries, and distance sphere for geographies.

This operand will make use of 2D GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;POINT(1011102 450541)'::geometry instead of a.geom

Refer to PostGIS workshop: Nearest-Neighbor Searching for a detailed example.

Enhanced: 2.2.0 -- True KNN ("K nearest neighbor") behavior for geometry and geography for PostgreSQL 9.5+. Note for geography KNN is based on sphere rather than spheroid. For PostgreSQL 9.4 and below, geography support is new but only supports centroid box.

Changed: 2.2.0 -- For PostgreSQL 9.5 users, old Hybrid syntax may be slower, so you'll want to get rid of that hack if you are running your code only on PostGIS 2.2+ 9.5+. See examples below.

Availability: 2.0.0 -- Weak KNN provides nearest neighbors based on geometry centroid distances instead of true distances. Exact results for points, inexact for all other types. Available for PostgreSQL 9.1+

## Examples

    SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
    FROM va2005
    ORDER BY d limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5541.57712511724 | ALQ    | 129A
     5579.67450712005 | ALQ    | 001
      6083.4207708641 | ALQ    | 131
      7691.2205404848 | ALQ    | 003
     7900.75451037313 | ALQ    | 122
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      12089.665931705 | ALQ    | 127
     18472.5531479404 | ALQ    | 002
    (10 rows)

Then the KNN raw answer:

    SELECT st_distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
    FROM va2005
    ORDER BY geom <-> 'SRID=3005;POINT(1011102 450541)'::geometry limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5541.57712511724 | ALQ    | 129A
     5579.67450712005 | ALQ    | 001
      6083.4207708641 | ALQ    | 131
      7691.2205404848 | ALQ    | 003
     7900.75451037313 | ALQ    | 122
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      12089.665931705 | ALQ    | 127
     18472.5531479404 | ALQ    | 002
    (10 rows)

If you run "EXPLAIN ANALYZE" on the two queries you would see a performance improvement for the second.

For users running with PostgreSQL < 9.5, use a hybrid query to find the true nearest neighbors. First a CTE query using the index-assisted KNN, then an exact query to get correct ordering:

    WITH index_query AS (
      SELECT ST_Distance(geom, 'SRID=3005;POINT(1011102 450541)'::geometry) as d,edabbr, vaabbr
    	FROM va2005
      ORDER BY geom <-> 'SRID=3005;POINT(1011102 450541)'::geometry LIMIT 100)
      SELECT *
    	FROM index_query
      ORDER BY d limit 10;

            d         | edabbr | vaabbr
    ------------------+--------+--------
                    0 | ALQ    | 128
     5541.57712511724 | ALQ    | 129A
     5579.67450712005 | ALQ    | 001
      6083.4207708641 | ALQ    | 131
      7691.2205404848 | ALQ    | 003
     7900.75451037313 | ALQ    | 122
     8694.20710669982 | ALQ    | 129B
     9564.24289057111 | ALQ    | 130
      12089.665931705 | ALQ    | 127
     18472.5531479404 | ALQ    | 002
    (10 rows)

## See Also

ST_DWithin, ST_Distance, <#>

## Name

|=| — Returns the distance between A and B trajectories at their closest point of approach.

## Synopsis

`double precision |=|(` geometry A , geometry B `)`;

## Description

The `|=|` operator returns the 3D distance between two trajectories (See ST_IsValidTrajectory). This is the same as ST_DistanceCPA but as an operator it can be used for doing nearest neighbor searches using an N-dimensional index (requires PostgreSQL 9.5.0 or higher).

This operand will make use of ND GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;LINESTRINGM(0 0 0,0 0 1)'::geometry instead of a.geom

Availability: 2.2.0. Index-supported only available for PostgreSQL 9.5+

## Examples

    -- Save a literal query trajectory in a psql variable...
    \set qt 'ST_AddMeasure(ST_MakeLine(ST_MakePointM(-350,300,0),ST_MakePointM(-410,490,0)),10,20)'
    -- Run the query !
    SELECT track_id, dist FROM (
      SELECT track_id, ST_DistanceCPA(tr,:qt) dist
      FROM trajectories
      ORDER BY tr |=| :qt
      LIMIT 5
    ) foo;
     track_id        dist
    ----------+-------------------
          395 | 0.576496831518066
          380 |  5.06797130410151
          390 |  7.72262293958322
          385 |   9.8004461358071
          405 |  10.9534397988433
    (5 rows)

## See Also

ST_DistanceCPA, ST_ClosestPointOfApproach, ST_IsValidTrajectory

## Name

<#> — Returns the 2D distance between A and B bounding boxes.

## Synopsis

`double precision <#>(` geometry A , geometry B `)`;

## Description

The `<#>` operator returns distance between two floating point bounding boxes, possibly reading them from a spatial index (PostgreSQL 9.1+ required). Useful for doing nearest neighbor approximate distance ordering.

This operand will make use of any indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant e.g. ORDER BY (ST_GeomFromText('POINT(1 2)') <#> geom) instead of g1.geom <#>.

Availability: 2.0.0 -- KNN only available for PostgreSQL 9.1+

## Examples

    SELECT *
    FROM (
    SELECT b.tlid, b.mtfcc,
    	b.geom <#> ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
    		745787 2948499,745740 2948468,745712 2948438,
    		745690 2948384,745677 2948319)',2249) As b_dist,
    		ST_Distance(b.geom, ST_GeomFromText('LINESTRING(746149 2948672,745954 2948576,
    		745787 2948499,745740 2948468,745712 2948438,
    		745690 2948384,745677 2948319)',2249)) As act_dist
        FROM bos_roads As b
        ORDER BY b_dist, b.tlid
        LIMIT 100) As foo
        ORDER BY act_dist, tlid LIMIT 10;

       tlid    | mtfcc |      b_dist      |     act_dist
    -----------+-------+------------------+------------------
      85732027 | S1400 |                0 |                0
      85732029 | S1400 |                0 |                0
      85732031 | S1400 |                0 |                0
      85734335 | S1400 |                0 |                0
      85736037 | S1400 |                0 |                0
     624683742 | S1400 |                0 | 128.528874268666
      85719343 | S1400 | 260.839270432962 | 260.839270432962
      85741826 | S1400 | 164.759294123275 | 260.839270432962
      85732032 | S1400 |           277.75 | 311.830282365264
      85735592 | S1400 |           222.25 | 311.830282365264
    (10 rows)

## See Also

ST_DWithin, ST_Distance, <->

## Name

<<->> — Returns the n-D distance between the A and B geometries or bounding boxes

## Synopsis

`double precision <<->>(` geometry A , geometry B `)`;

## Description

The `<<->>` operator returns the n-D (euclidean) distance between the centroids of the bounding boxes of two geometries. Useful for doing nearest neighbor approximate distance ordering.

This operand will make use of n-D GiST indexes that may be available on the geometries. It is different from other operators that use spatial indexes in that the spatial index is only used when the operator is in the ORDER BY clause.

Index only kicks in if one of the geometries is a constant (not in a subquery/cte). e.g. 'SRID=3005;POINT(1011102 450541)'::geometry instead of a.geom

Availability: 2.2.0 -- KNN only available for PostgreSQL 9.1+

## See Also

<->

## 7.11. Spatial Relationships

Abstract

These functions determine spatial relationships between geometries.

### 7.11.1. Topological Relationships

## Name

ST_3DIntersects — Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)

## Synopsis

`boolean ST_3DIntersects(` geometry geomA , geometry geomB `)`;

## Description

Overlaps, Touches, Within all imply spatial intersection. If any of the aforementioned returns true, then the geometries also spatially intersect. Disjoint implies false for spatial intersection.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Because of floating robustness failures, geometries don't always intersect as you'd expect them to after geometric processing. For example the closest point on a linestring to a geometry may not lie on the linestring. For these kind of issues where a distance of a centimeter you want to just consider as intersecting, use ST_3DDWithin.

Changed: 3.0.0 SFCGAL backend removed, GEOS backend supports TINs.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

## Geometry Examples

    SELECT ST_3DIntersects(pt, line), ST_Intersects(pt, line)
      FROM (SELECT 'POINT(0 0 2)'::geometry As pt, 'LINESTRING (0 0 1, 0 2 3)'::geometry As line) As foo;
     st_3dintersects | st_intersects
    -----------------+---------------
     f               | t
    (1 row)

## TIN Examples

    SELECT ST_3DIntersects('TIN(((0 0 0,1 0 0,0 1 0,0 0 0)))'::geometry, 'POINT(.1 .1 0)'::geometry);
     st_3dintersects
    -----------------
     t

## See Also

ST_3DDWithin, ST_Intersects

## Name

ST_Contains — Tests if every point of B lies in A, and their interiors have a point in common

## Synopsis

`boolean ST_Contains(` geometry geomA, geometry geomB`)`;

## Description

Returns TRUE if geometry A contains geometry B. A contains B if and only if all points of B lie inside (i.e. in the interior or boundary of) A (or equivalently, no points of B lie in the exterior of A), and the interiors of A and B have at least one point in common.

In mathematical terms: ST_Contains(A, B) ⇔ (A ⋂ B = B) ∧ (Int(A) ⋂ Int(B) ≠ ∅)

The contains relationship is reflexive: every geometry contains itself. (In contrast, in the ST_ContainsProperly predicate a geometry does not properly contain itself.) The relationship is antisymmetric: if `ST_Contains(A,B) = true` and `ST_Contains(B,A) = true`, then the two geometries must be topologically equal (`ST_Equals(A,B) = true`).

ST_Contains is the converse of ST_Within. So, `ST_Contains(A,B) = ST_Within(B,A)`.

Because the interiors must have a common point, a subtlety of the definition is that polygons and lines do not contain lines and points lying fully in their boundary. For further details see Subtleties of OGC Covers, Contains, Within. The ST_Covers predicate provides a more inclusive relationship.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_Contains`.

Performed by the GEOS module

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - same as within(geometry B, geometry A)

This method implements the SQL/MM specification. SQL-MM 3: 5.1.31

## Examples

`ST_Contains` returns `TRUE` in the following situations:

`LINESTRING` / `MULTIPOINT` | `POLYGON` / `POINT`
`POLYGON` / `LINESTRING` | `POLYGON` / `POLYGON`

`ST_Contains` returns `FALSE` in the following situations:

`POLYGON` / `MULTIPOINT` | `POLYGON` / `LINESTRING`

Due to the interior intersection condition `ST_Contains` returns `FALSE` in the following situations (whereas `ST_Covers` returns `TRUE`):

`LINESTRING` / `POINT` | `POLYGON` / `LINESTRING`

    -- A circle within a circle
    SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
         ST_Contains(bigc,smallc) As bigcontainssmall,
         ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
         ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
         ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
         ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
           ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;

    -- Result
      smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                | t                | t                | t          | t        | f

    -- Example demonstrating difference between contains and contains properly
    SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
       ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
    FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
           ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
           ( ST_Point(1,1) )
        ) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

## See Also

ST_Boundary, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Equals, ST_Within

## Name

ST_ContainsProperly — Tests if every point of B lies in the interior of A

## Synopsis

`boolean ST_ContainsProperly(` geometry geomA, geometry geomB`)`;

## Description

Returns `true` if every point of B lies in the interior of A (or equivalently, no point of B lies in the the boundary or exterior of A).

In mathematical terms: ST_ContainsProperly(A, B) ⇔ Int(A) ⋂ B = B

A contains B properly if the DE-9IM Intersection Matrix for the two geometries matches [T**FF*FF*]

A does not properly contain itself, but does contain itself.

A use for this predicate is computing the intersections of a set of geometries with a large polygonal geometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out test geometries which lie fully inside the area. In these cases the intersection is known a priori to be exactly the original test geometry.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_ContainsProperly`.

The advantage of this predicate over ST_Contains and ST_Intersects is that it can be computed more efficiently, with no need to compute topology at individual points.

Performed by the GEOS module.

Availability: 1.4.0

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

## Examples

      --a circle within a circle
      SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
      ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
      ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
      ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
      ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
      ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
      FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
      ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
      --Result
      smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
    ------------------+------------------+------------------+------------+-------------------+---------------------
     f                     | t                    | f                    | t          | t                 | f

     --example demonstrating difference between contains and contains properly
     SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
     ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
     FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
          ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
          ( ST_Point(1,1) )
      ) As foo(geomA);

      geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
    --------------+------------+----------------+-------------+-----------------
    ST_Polygon    | t          | f              | f           | f
    ST_LineString | t          | f              | f           | f
    ST_Point      | t          | t              | f           | f

## See Also

ST_GeometryType, ST_Boundary, ST_Contains, ST_Covers, ST_CoveredBy, ST_Equals, ST_Relate, ST_Within

## Name

ST_CoveredBy — Tests if every point of A lies in B

## Synopsis

`boolean ST_CoveredBy(` geometry geomA, geometry geomB`)`;

`boolean ST_CoveredBy(` geography geogA, geography geogB`)`;

## Description

Returns `true` if every point in Geometry/Geography A lies inside (i.e. intersects the interior or boundary of) Geometry/Geography B. Equivalently, tests that no point of A lies outside (in the exterior of) B.

In mathematical terms: ST_CoveredBy(A, B) ⇔ A ⋂ B = A

ST_CoveredBy is the converse of ST_Covers. So, `ST_CoveredBy(A,B) = ST_Covers(B,A)`.

Generally this function should be used instead of ST_Within, since it has a simpler definition which does not have the quirk that "boundaries are not within their geometry".

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_CoveredBy`.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

Performed by the GEOS module

Availability: 1.2.2

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

## Examples

      --a circle coveredby a circle
    SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
      ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
      ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
      ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
      ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
      --Result
     smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
    --------------+-------------------+----------------------+------------------
     t            | t                 | t                    | f
    (1 row)

## See Also

ST_Contains, ST_Covers, ST_ExteriorRing, ST_Within

## Name

ST_Covers — Tests if every point of B lies in A

## Synopsis

`boolean ST_Covers(` geometry geomA, geometry geomB`)`;

`boolean ST_Covers(` geography geogpolyA, geography geogpointB`)`;

## Description

Returns `true` if every point in Geometry/Geography B lies inside (i.e. intersects the interior or boundary of) Geometry/Geography A. Equivalently, tests that no point of B lies outside (in the exterior of) A.

In mathematical terms: ST_Covers(A, B) ⇔ A ⋂ B = B

ST_Covers is the converse of ST_CoveredBy. So, `ST_Covers(A,B) = ST_CoveredBy(B,A)`.

Generally this function should be used instead of ST_Contains, since it has a simpler definition which does not have the quirk that "geometries do not contain their boundary".

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_Covers`.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

Performed by the GEOS module

Enhanced: 2.4.0 Support for polygon in polygon and line in polygon added for geography type

Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Availability: 1.5 - support for geography was introduced.

Availability: 1.2.2

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Not an OGC standard, but Oracle has it too.

## Examples

Geometry example

      --a circle covering a circle
    SELECT ST_Covers(smallc,smallc) As smallinsmall,
      ST_Covers(smallc, bigc) As smallcoversbig,
      ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
      ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
    FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
      ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
      --Result
     smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior
    --------------+----------------+-------------------+---------------------
     t            | f              | t                 | f
    (1 row)

Geeography Example

    -- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer
    SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,
      ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent
      FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly,
            ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo;

     poly_covers_pt | buff_10m_covers_cent
    ----------------+------------------
     f              | t

## See Also

ST_Contains, ST_CoveredBy, ST_Within

## Name

ST_Crosses — Tests if two geometries have some, but not all, interior points in common

## Synopsis

`boolean ST_Crosses(` geometry g1, geometry g2`)`;

## Description

Compares two geometry objects and returns `true` if their intersection "spatially crosses"; that is, the geometries have some, but not all interior points in common. The intersection of the interiors of the geometries must be non-empty and must have dimension less than the maximum dimension of the two input geometries, and the intersection of the two geometries must not equal either geometry. Otherwise, it returns `false`. The crosses relation is symmetric and irreflexive.

In mathematical terms: ST_Crosses(A, B) ⇔ (dim( Int(A) ⋂ Int(B) ) < max( dim( Int(A) ), dim( Int(B) ) )) ∧ (A ⋂ B ≠ A) ∧ (A ⋂ B ≠ B)

Geometries cross if their DE-9IM Intersection Matrix matches:

- `T*T******` for Point/Line, Point/Area, and Line/Area situations

- `T*****T**` for Line/Point, Area/Point, and Area/Line situations

- `0********` for Line/Line situations

- the result is `false` for Point/Point and Area/Area situations

The OpenGIS Simple Features Specification defines this predicate only for Point/Line, Point/Area, Line/Line, and Line/Area situations. JTS / GEOS extends the definition to apply to Line/Point, Area/Point and Area/Line situations as well. This makes the relation symmetric.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.29

## Examples

The following situations all return `true`.

`MULTIPOINT` / `LINESTRING` | `MULTIPOINT` / `POLYGON`
`LINESTRING` / `POLYGON` | `LINESTRING` / `LINESTRING`

Consider a situation where a user has two tables: a table of roads and a table of highways.

    CREATE TABLE roads (
      id serial NOT NULL,
      geom geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );
    CREATE TABLE highways (
      id serial NOT NULL,
      the_gem geometry,
      CONSTRAINT roads_pkey PRIMARY KEY (road_id)
    );

To determine a list of roads that cross a highway, use a query similar to:

    SELECT roads.id
    FROM roads, highways
    WHERE ST_Crosses(roads.geom, highways.geom);

## See Also

ST_Contains, ST_Overlaps

## Name

ST_Disjoint — Tests if two geometries have no points in common

## Synopsis

`boolean ST_Disjoint(` geometry A , geometry B `)`;

## Description

Returns `true` if two geometries are disjoint. Geometries are disjoint if they have no point in common.

If any other spatial relationship is true for a pair of geometries, they are not disjoint. Disjoint implies that ST_Intersects is false.

In mathematical terms: ST_Disjoint(A, B) ⇔ A ⋂ B = ∅

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Performed by the GEOS module

This function call does not use indexes. A negated ST_Intersects predicate can be used as a more performant alternative that uses indexes: `ST_Disjoint(A,B) = NOT ST_Intersects(A,B)`

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - a.Relate(b, 'FF*FF****')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.26

## Examples

    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     t
    (1 row)
    SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_disjoint
    ---------------
     f
    (1 row)

## See Also

ST_Intersects

## Name

ST_Equals — Tests if two geometries include the same set of points

## Synopsis

`boolean ST_Equals(` geometry A, geometry B`)`;

## Description

Returns `true` if the given geometries are "topologically equal". Use this for a 'better' answer than '='. Topological equality means that the geometries have the same dimension, and their point-sets occupy the same space. This means that the order of vertices may be different in topologically equal geometries. To verify the order of points is consistent use ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of points are the same).

In mathematical terms: ST_Equals(A, B) ⇔ A = B

The following relation holds: ST_Equals(A, B) ⇔ ST_Within(A,B) ∧ ST_Within(B,A)

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2

This method implements the SQL/MM specification. SQL-MM 3: 5.1.24

Changed: 2.2.0 Returns true even for invalid geometries if they are binary equal

## Examples

    SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
        ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

    SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
        ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_equals
    -----------
     t
    (1 row)

## See Also

ST_IsValid, ST_OrderingEquals, ST_Reverse, ST_Within

## Name

ST_Intersects — Tests if two geometries intersect (they have at least one point in common)

## Synopsis

`boolean ST_Intersects(` geometry geomA , geometry geomB `)`;

`boolean ST_Intersects(` geography geogA , geography geogB `)`;

## Description

Returns `true` if two geometries intersect. Geometries intersect if they have any point in common.

For geography, a distance tolerance of 0.00001 meters is used (so points that are very close are considered to intersect).

In mathematical terms: ST_Intersects(A, B) ⇔ A ⋂ B ≠ ∅

Geometries intersect if their DE-9IM Intersection Matrix matches one of:

- `T********`

- `*T*******`

- `***T*****`

- `****T****`

Spatial intersection is implied by all the other spatial relationship tests, except ST_Disjoint, which tests that geometries do NOT intersect.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Changed: 3.0.0 SFCGAL version removed and native support for 2D TINS added.

Enhanced: 2.5.0 Supports GEOMETRYCOLLECTION.

Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Performed by the GEOS module (for geometry), geography is native

Availability: 1.5 support for geography was introduced.

For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather than spheroid calculation.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 //s2.1.13.3 - ST_Intersects(g1, g2 ) --> Not (ST_Disjoint(g1, g2 ))

This method implements the SQL/MM specification. SQL-MM 3: 5.1.27

This method supports Circular Strings and Curves.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     f
    (1 row)
    SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
     st_intersects
    ---------------
     t
    (1 row)

    -- Look up in table. Make sure table has a GiST index on geometry column for faster lookup.
    SELECT id, name FROM cities WHERE ST_Intersects(geom, 'SRID=4326;POLYGON((28 53,27.707 52.293,27 52,26.293 52.293,26 53,26.293 53.707,27 54,27.707 53.707,28 53))');
     id | name
    ----+-------
      2 | Minsk
    (1 row)

## Geography Examples

    SELECT ST_Intersects(
        'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'::geography,
        'SRID=4326;POINT(-43.23456 72.4567772)'::geography
        );

     st_intersects
    ---------------
    t

## See Also

&&, ST_3DIntersects, ST_Disjoint

## Name

ST_LineCrossingDirection — Returns a number indicating the crossing behavior of two LineStrings

## Synopsis

`integer ST_LineCrossingDirection(` geometry linestringA, geometry linestringB`)`;

## Description

Given two linestrings returns an integer between -3 and 3 indicating what kind of crossing behavior exists between them. 0 indicates no crossing. This is only supported for `LINESTRING`s.

The crossing number has the following meaning:

- 0: LINE NO CROSS

- -1: LINE CROSS LEFT

- 1: LINE CROSS RIGHT

- -2: LINE MULTICROSS END LEFT

- 2: LINE MULTICROSS END RIGHT

- -3: LINE MULTICROSS END SAME FIRST LEFT

- 3: LINE MULTICROSS END SAME FIRST RIGHT

Availability: 1.4

## Examples

Example: LINE CROSS LEFT and LINE CROSS RIGHT

Blue: Line A; Green: Line B

    SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
           ST_LineCrossingDirection(lineB, lineA) As B_cross_A
    FROM (SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
      ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As lineB
      ) As foo;

     A_cross_B | B_cross_A
    -----------+-----------
            -1 |         1

Example: LINE MULTICROSS END SAME FIRST LEFT and LINE MULTICROSS END SAME FIRST RIGHT

Blue: Line A; Green: Line B

    SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
           ST_LineCrossingDirection(lineB, lineA) As B_cross_A
    FROM (SELECT
     ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
     ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As lineB
      ) As foo;

     A_cross_B | B_cross_A
    -----------+-----------
             3 |        -3

Example: LINE MULTICROSS END LEFT and LINE MULTICROSS END RIGHT

Blue: Line A; Green: Line B

    SELECT ST_LineCrossingDirection(lineA, lineB) As A_cross_B,
           ST_LineCrossingDirection(lineB, lineA) As B_cross_A
    FROM (SELECT
      ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As lineA,
      ST_GeomFromText('LINESTRING(5 90, 71 74, 20 140, 171 154)') As lineB
      ) As foo;

     A_cross_B | B_cross_A
    -----------+-----------
            -2 |         2

Example: Finds all streets that cross

    SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.geom, s2.geom)
      FROM streets s1 CROSS JOIN streets s2
             ON (s1.gid != s2.gid AND s1.geom && s2.geom )
    WHERE ST_LineCrossingDirection(s1.geom, s2.geom) > 0;

## See Also

ST_Crosses

## Name

ST_OrderingEquals — Tests if two geometries represent the same geometry and have points in the same directional order

## Synopsis

`boolean ST_OrderingEquals(` geometry A, geometry B`)`;

## Description

ST_OrderingEquals compares two geometries and returns t (TRUE) if the geometries are equal and the coordinates are in the same order; otherwise it returns f (FALSE).

This function is implemented as per the ArcSDE SQL specification rather than SQL-MM. http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals

This method implements the SQL/MM specification. SQL-MM 3: 5.1.43

## Examples

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
        ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

    SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
        ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     t
    (1 row)

    SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
        ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
     st_orderingequals
    -----------
     f
    (1 row)

## See Also

&&, ST_Equals, ST_Reverse

## Name

ST_Overlaps — Tests if two geometries have the same dimension and intersect, but each has at least one point not in the other

## Synopsis

`boolean ST_Overlaps(` geometry A, geometry B`)`;

## Description

Returns TRUE if geometry A and B "spatially overlap". Two geometries overlap if they have the same dimension, their interiors intersect in that dimension. and each has at least one point inside the other (or equivalently, neither one covers the other). The overlaps relation is symmetric and irreflexive.

In mathematical terms: ST_Overlaps(A, B) ⇔ ( dim(A) = dim(B) = dim( Int(A) ⋂ Int(B) )) ∧ (A ⋂ B ≠ A) ∧ (A ⋂ B ≠ B)

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_Overlaps`.

Performed by the GEOS module

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.32

## Examples

`ST_Overlaps` returns `TRUE` in the following situations:

`MULTIPOINT` / `MULTIPOINT` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POLYGON`

A Point on a LineString is contained, but since it has lower dimension it does not overlap or cross.

    SELECT ST_Overlaps(a,b) AS overlaps,       ST_Crosses(a,b) AS crosses,
           ST_Intersects(a, b) AS intersects,  ST_Contains(b,a) AS b_contains_a
    FROM (SELECT ST_GeomFromText('POINT (100 100)') As a,
                 ST_GeomFromText('LINESTRING (30 50, 40 160, 160 40, 180 160)')  AS b) AS t

    overlaps | crosses | intersects | b_contains_a
    ---------+----------------------+--------------
    f        | f       | t          | t

A LineString that partly covers a Polygon intersects and crosses, but does not overlap since it has different dimension.

    SELECT ST_Overlaps(a,b) AS overlaps,        ST_Crosses(a,b) AS crosses,
           ST_Intersects(a, b) AS intersects,   ST_Contains(a,b) AS contains
    FROM (SELECT ST_GeomFromText('POLYGON ((40 170, 90 30, 180 100, 40 170))') AS a,
                 ST_GeomFromText('LINESTRING(10 10, 190 190)') AS b) AS t;

     overlap | crosses | intersects | contains
    ---------+---------+------------+--------------
     f       | t       | t          | f

Two Polygons that intersect but with neither contained by the other overlap, but do not cross because their intersection has the same dimension.

    SELECT ST_Overlaps(a,b) AS overlaps,       ST_Crosses(a,b) AS crosses,
           ST_Intersects(a, b) AS intersects,  ST_Contains(b, a) AS b_contains_a,
           ST_Dimension(a) AS dim_a, ST_Dimension(b) AS dim_b,
           ST_Dimension(ST_Intersection(a,b)) AS dim_int
    FROM (SELECT ST_GeomFromText('POLYGON ((40 170, 90 30, 180 100, 40 170))') AS a,
                 ST_GeomFromText('POLYGON ((110 180, 20 60, 130 90, 110 180))') AS b) As t;

     overlaps | crosses | intersects | b_contains_a | dim_a | dim_b | dim_int
    ----------+---------+------------+--------------+-------+-------+-----------
     t        | f       | t          | f            |     2 |     2 |       2

## See Also

ST_Contains, ST_Crosses, ST_Dimension, ST_Intersects

## Name

ST_Relate — Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix

## Synopsis

`boolean ST_Relate(` geometry geomA, geometry geomB, text intersectionMatrixPattern`)`;

`text ST_Relate(` geometry geomA, geometry geomB`)`;

`text ST_Relate(` geometry geomA, geometry geomB, integer boundaryNodeRule`)`;

## Description

These functions allow testing and evaluating the spatial (topological) relationship between two geometries, as defined by the Dimensionally Extended 9-Intersection Model (DE-9IM).

The DE-9IM is specified as a 9-element matrix indicating the dimension of the intersections between the Interior, Boundary and Exterior of two geometries. It is represented by a 9-character text string using the symbols 'F', '0', '1', '2' (e.g. `'FF1FF0102'`).

A specific kind of spatial relationship can be tested by matching the intersection matrix to an intersection matrix pattern. Patterns can include the additional symbols 'T' (meaning "intersection is non-empty") and '*' (meaning "any value"). Common spatial relationships are provided by the named functions ST_Contains, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, and ST_Within. Using an explicit pattern allows testing multiple conditions of intersects, crosses, etc in one step. It also allows testing spatial relationships which do not have a named spatial relationship function. For example, the relationship "Interior-Intersects" has the DE-9IM pattern `T********`, which is not evaluated by any named predicate.

For more information refer to Section 5.1, “Determining Spatial Relationships”.

Variant 1: Tests if two geometries are spatially related according to the given `intersectionMatrixPattern`.

Unlike most of the named spatial relationship predicates, this does NOT automatically include an index call. The reason is that some relationships are true for geometries which do NOT intersect (e.g. Disjoint). If you are using a relationship pattern that requires intersection, then include the && index call.

It is better to use a named relationship function if available, since they automatically use a spatial index where one exists. Also, they may implement performance optimizations which are not available with full relate evaluation.

Variant 2: Returns the DE-9IM matrix string for the spatial relationship between the two input geometries. The matrix string can be tested for matching a DE-9IM pattern using ST_RelateMatch.

Variant 3: Like variant 2, but allows specifying a Boundary Node Rule. A boundary node rule allows finer control over whether the endpoints of MultiLineStrings are considered to lie in the DE-9IM Interior or Boundary. The `boundaryNodeRule` values are:

- `1`: OGC-Mod2 - line endpoints are in the Boundary if they occur an odd number of times. This is the rule defined by the OGC SFS standard, and is the default for `ST_Relate`.

- `2`: Endpoint - all endpoints are in the Boundary.

- `3`: MultivalentEndpoint - endpoints are in the Boundary if they occur more than once. In other words, the boundary is all the "attached" or "inner" endpoints (but not the "unattached/outer" ones).

- `4`: MonovalentEndpoint - endpoints are in the Boundary if they occur only once. In other words, the boundary is all the "unattached" or "outer" endpoints.

This function is not in the OGC spec, but is implied. see s2.1.13.2

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

Performed by the GEOS module

Enhanced: 2.0.0 - added support for specifying boundary node rule.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

## Examples

Using the boolean-valued function to test spatial relationships.

    SELECT ST_Relate('POINT(1 2)', ST_Buffer( 'POINT(1 2)', 2), '0FFFFF212');
    st_relate
    -----------
    t

    SELECT ST_Relate(POINT(1 2)', ST_Buffer( 'POINT(1 2)', 2), '*FF*FF212');
    st_relate
    -----------
    t

Testing a custom spatial relationship pattern as a query condition, with `&&` to enable using a spatial index.

    -- Find compounds that properly intersect (not just touch) a poly (Interior Intersects)

    SELECT c.* , p.name As poly_name
        FROM polys AS p
        INNER JOIN compounds As c
              ON c.geom && p.geom
                 AND ST_Relate(p.geom, c.geom,'T********');

Computing the intersection matrix for spatial relationships.

    SELECT ST_Relate( 'POINT(1 2)',
                      ST_Buffer( 'POINT(1 2)', 2));
    -----------
    0FFFFF212

    SELECT ST_Relate( 'LINESTRING(1 2, 3 4)',
                      'LINESTRING(5 6, 7 8)' );
    -----------
    FF1FF0102

Using different Boundary Node Rules to compute the spatial relationship between a LineString and a MultiLineString with a duplicate endpoint `(3 3)`:

- Using the OGC-Mod2 rule (1) the duplicate endpoint is in the interior of the MultiLineString, so the DE-9IM matrix entry [aB:bI] is `0` and [aB:bB] is `F`.

- Using the Endpoint rule (2) the duplicate endpoint is in the boundary of the MultiLineString, so the DE-9IM matrix entry [aB:bI] is `F` and [aB:bB] is `0`.

    WITH data AS (SELECT
      'LINESTRING(1 1, 3 3)'::geometry AS a_line,
      'MULTILINESTRING((3 3, 3 5), (3 3, 5 3))':: geometry AS b_multiline
    )
    SELECT ST_Relate( a_line, b_multiline, 1) AS bnr_mod2,
           ST_Relate( a_line, b_multiline, 2) AS bnr_endpoint
        FROM data;

     bnr_mod2  | bnr_endpoint
    -----------+--------------
     FF10F0102 | FF1F00102

## See Also

Section 5.1, “Determining Spatial Relationships”, ST_RelateMatch, ST_Contains, ST_ContainsProperly, ST_Covers, ST_CoveredBy, ST_Crosses, ST_Disjoint, ST_Equals, ST_Intersects, ST_Overlaps, ST_Touches, ST_Within

## Name

ST_RelateMatch — Tests if a DE-9IM Intersection Matrix matches an Intersection Matrix pattern

## Synopsis

`boolean ST_RelateMatch(` text intersectionMatrix, text intersectionMatrixPattern`)`;

## Description

Tests if a Dimensionally Extended 9-Intersection Model (DE-9IM) `intersectionMatrix` value satisfies an `intersectionMatrixPattern`. Intersection matrix values can be computed by ST_Relate.

For more information refer to Section 5.1, “Determining Spatial Relationships”.

Performed by the GEOS module

Availability: 2.0.0

## Examples

    SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
    -- result --
    t

Patterns for common spatial relationships matched against intersection matrix values, for a line in various positions relative to a polygon

    SELECT pat.name AS relationship, pat.val AS pattern,
           mat.name AS position, mat.val AS matrix,
           ST_RelateMatch(mat.val, pat.val) AS match
        FROM (VALUES ( 'Equality', 'T1FF1FFF1' ),
                     ( 'Overlaps', 'T*T***T**' ),
                     ( 'Within',   'T*F**F***' ),
                     ( 'Disjoint', 'FF*FF****' )) AS pat(name,val)
        CROSS JOIN
            (VALUES  ('non-intersecting', 'FF1FF0212'),
                     ('overlapping',      '1010F0212'),
                     ('inside',           '1FF0FF212')) AS mat(name,val);

     relationship |  pattern  |     position     |  matrix   | match
    --------------+-----------+------------------+-----------+-------
     Equality     | T1FF1FFF1 | non-intersecting | FF1FF0212 | f
     Equality     | T1FF1FFF1 | overlapping      | 1010F0212 | f
     Equality     | T1FF1FFF1 | inside           | 1FF0FF212 | f
     Overlaps     | T*T***T** | non-intersecting | FF1FF0212 | f
     Overlaps     | T*T***T** | overlapping      | 1010F0212 | t
     Overlaps     | T*T***T** | inside           | 1FF0FF212 | f
     Within       | T*F**F*** | non-intersecting | FF1FF0212 | f
     Within       | T*F**F*** | overlapping      | 1010F0212 | f
     Within       | T*F**F*** | inside           | 1FF0FF212 | t
     Disjoint     | FF*FF**** | non-intersecting | FF1FF0212 | t
     Disjoint     | FF*FF**** | overlapping      | 1010F0212 | f
     Disjoint     | FF*FF**** | inside           | 1FF0FF212 | f

## See Also

Section 5.1, “Determining Spatial Relationships”, ST_Relate

## Name

ST_Touches — Tests if two geometries have at least one point in common, but their interiors do not intersect

## Synopsis

`boolean ST_Touches(` geometry A, geometry B`)`;

## Description

Returns `TRUE` if A and B intersect, but their interiors do not intersect. Equivalently, A and B have at least one point in common, and the common points lie in at least one boundary. For Point/Point inputs the relationship is always `FALSE`, since points do not have a boundary.

In mathematical terms: ST_Touches(A, B) ⇔ (Int(A) ⋂ Int(B) = ∅) ∧ (A ⋂ B ≠ ∅)

This relationship holds if the DE-9IM Intersection Matrix for the two geometries matches one of:

- FT*******

- F**T*****

- F***T****

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid using an index, use `_ST_Touches` instead.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.28

## Examples

The `ST_Touches` predicate returns `TRUE` in the following examples.

`POLYGON` / `POLYGON` | `POLYGON` / `POLYGON` | `POLYGON` / `LINESTRING`
`LINESTRING` / `LINESTRING` | `LINESTRING` / `LINESTRING` | `POLYGON` / `POINT`

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
     st_touches
    ------------
     f
    (1 row)

    SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
     st_touches
    ------------
     t
    (1 row)

## Name

ST_Within — Tests if every point of A lies in B, and their interiors have a point in common

## Synopsis

`boolean ST_Within(` geometry A, geometry B`)`;

## Description

Returns TRUE if geometry A is within geometry B. A is within B if and only if all points of A lie inside (i.e. in the interior or boundary of) B (or equivalently, no points of A lie in the exterior of B), and the interiors of A and B have at least one point in common.

For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

In mathematical terms: ST_Within(A, B) ⇔ (A ⋂ B = A) ∧ (Int(A) ⋂ Int(B) ≠ ∅)

The within relation is reflexive: every geometry is within itself. The relation is antisymmetric: if `ST_Within(A,B) = true` and `ST_Within(B,A) = true`, then the two geometries must be topologically equal (`ST_Equals(A,B) = true`).

ST_Within is the converse of ST_Contains. So, `ST_Within(A,B) = ST_Contains(B,A)`.

Because the interiors must have a common point, a subtlety of the definition is that lines and points lying fully in the boundary of polygons or lines are not within the geometry. For further details see Subtleties of OGC Covers, Contains, Within. The ST_CoveredBy predicate provides a more inclusive relationship.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries. To avoid index use, use the function `_ST_Within`.

Performed by the GEOS module

Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.

Enhanced: 3.0.0 enabled support for `GEOMETRYCOLLECTION`

Do not use this function with invalid geometries. You will get unexpected results.

NOTE: this is the "allowable" version that returns a boolean, not an integer.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.2 // s2.1.13.3 - a.Relate(b, 'T*F**F***')

This method implements the SQL/MM specification. SQL-MM 3: 5.1.30

## Examples

    --a circle within a circle
    SELECT ST_Within(smallc,smallc) As smallinsmall,
      ST_Within(smallc, bigc) As smallinbig,
      ST_Within(bigc,smallc) As biginsmall,
      ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
      ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
      ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
    FROM
    (
    SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
      ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
    --Result
     smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
    --------------+------------+------------+------------+------------+------------
     t            | t          | f          | t          | t          | t
    (1 row)

## See Also

ST_Contains, ST_CoveredBy, ST_Equals, ST_IsValid

### 7.11.2. Distance Relationships

## Name

ST_3DDWithin — Tests if two 3D geometries are within a given 3D distance

## Synopsis

`boolean ST_3DDWithin(` geometry g1, geometry g2, double precision distance_of_srid`)`;

## Description

Returns true if the 3D distance between two geometry values is no larger than distance `distance_of_srid`. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense the source geometries must be in the same coordinate system (have the same SRID).

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM ?

Availability: 2.0.0

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DDWithin(
          ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
          ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
          126.8
        ) As within_dist_3d,
    ST_DWithin(
          ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
          ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
          126.8
        ) As within_dist_2d;

     within_dist_3d | within_dist_2d
    ----------------+----------------
     f              | t

## See Also

ST_3DDFullyWithin, ST_DWithin, ST_DFullyWithin, ST_3DDistance, ST_Distance, ST_3DMaxDistance, ST_Transform

## Name

ST_3DDFullyWithin — Tests if two 3D geometries are entirely within a given 3D distance

## Synopsis

`boolean ST_3DDFullyWithin(` geometry g1, geometry g2, double precision distance`)`;

## Description

Returns true if the 3D geometries are fully within the specified distance of one another. The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must both be of the same coordinate projection, having the same SRID.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

        -- This compares the difference between fully within and distance within as well
        -- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
        SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
      ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
      ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
        (select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
        ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
     d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
    ------------------+-------------+------------------+------------------
     f                | t           | t                | f

## See Also

ST_3DDWithin, ST_DWithin, ST_DFullyWithin, ST_3DMaxDistance

## Name

ST_DFullyWithin — Tests if a geometry is entirely inside a distance of another

## Synopsis

`boolean ST_DFullyWithin(` geometry g1, geometry g2, double precision distance`)`;

## Description

Returns true if `g2` is entirely within `distance` of `g1`. Visually, the condition is true if `g2` is contained within a `distance` buffer of `g1`. The distance is specified in units defined by the spatial reference system of the geometries.

This function automatically includes a bounding box comparison that makes use of any spatial indexes that are available on the geometries.

Availability: 1.5.0

Changed: 3.5.0 : the logic behind the function now uses a test of containment within a buffer, rather than the ST_MaxDistance algorithm. Results will differ from prior versions, but should be closer to user expectations.

## Examples

    SELECT
        ST_DFullyWithin(geom_a, geom_b, 10) AS DFullyWithin10,
        ST_DWithin(geom_a, geom_b, 10) AS DWithin10,
        ST_DFullyWithin(geom_a, geom_b, 20) AS DFullyWithin20
    FROM (VALUES
        ('POINT(1 1)', 'LINESTRING(1 5, 2 7, 1 9, 14 12)')
        ) AS v(geom_a, geom_b)

     dfullywithin10 | dwithin10 | dfullywithin20
    ----------------+-----------+----------------
     f              | t         | t

## See Also

ST_MaxDistance, ST_DWithin, ST_3DDWithin, ST_3DDFullyWithin

## Name

ST_DWithin — Tests if two geometries are within a given distance

## Synopsis

`boolean ST_DWithin(` geometry g1, geometry g2, double precision distance_of_srid`)`;

`boolean ST_DWithin(` geography gg1, geography gg2, double precision distance_meters, boolean use_spheroid = true`)`;

## Description

Returns true if the geometries are within a given distance

For geometry: The distance is specified in units defined by the spatial reference system of the geometries. For this function to make sense, the source geometries must be in the same coordinate system (have the same SRID).

For geography: units are in meters and distance measurement defaults to `use_spheroid = true`. For faster evaluation use `use_spheroid = false` to measure on the sphere.

Use ST_3DDWithin for 3D geometries.

This function call includes a bounding box comparison that makes use of any indexes that are available on the geometries.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

Availability: 1.5.0 support for geography was introduced

Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.

Enhanced: 2.1.0 support for curved geometries was introduced.

Prior to 1.3, ST_Expand was commonly used in conjunction with && and ST_Distance to test for distance, and in pre-1.3.4 this function used that logic. From 1.3.4, ST_DWithin uses a faster short-circuit distance function.

## Examples

    -- Find the nearest hospital to each school
    -- that is within 3000 units of the school.
    --  We do an ST_DWithin search to utilize indexes to limit our search list
    --  that the non-indexable ST_Distance needs to process
    -- If the units of the spatial reference is meters then units would be meters
    SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.geom, h.hospital_name
      FROM schools s
        LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
      ORDER BY s.gid, ST_Distance(s.geom, h.geom);

    -- The schools with no close hospitals
    -- Find all schools with no hospital within 3000 units
    -- away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
    SELECT s.gid, s.school_name
      FROM schools s
        LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
      WHERE h.gid IS NULL;

    -- Find broadcasting towers that receiver with limited range can receive.
    -- Data is geometry in Spherical Mercator (SRID=3857), ranges are approximate.

    -- Create geometry index that will check proximity limit of user to tower
    CREATE INDEX ON broadcasting_towers using gist (geom);

    -- Create geometry index that will check proximity limit of tower to user
    CREATE INDEX ON broadcasting_towers using gist (ST_Expand(geom, sending_range));

    -- Query towers that 4-kilometer receiver in Minsk Hackerspace can get
    -- Note: two conditions, because shorter LEAST(b.sending_range, 4000) will not use index.
    SELECT b.tower_id, b.geom
      FROM broadcasting_towers b
      WHERE ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', 4000)
        AND ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', b.sending_range);

## See Also

ST_Distance, ST_3DDWithin

## Name

ST_PointInsideCircle — Tests if a point geometry is inside a circle defined by a center and radius

## Synopsis

`boolean ST_PointInsideCircle(` geometry a_point, float center_x, float center_y, float radius`)`;

## Description

Returns true if the geometry is a point and is inside the circle with center `center_x`,`center_y` and radius `radius`.

Does not use spatial indexes. Use ST_DWithin instead.

Availability: 1.2

Changed: 2.2.0 In prior versions this was called ST_Point_Inside_Circle

## Examples

    SELECT ST_PointInsideCircle(ST_Point(1,2), 0.5, 2, 3);
     st_pointinsidecircle
    ------------------------
     t

## See Also

ST_DWithin

## 7.12. Measurement Functions

Abstract

These functions compute measurements of distance, area and angles. There are also functions to compute geometry values determined by measurements.

## Name

ST_Area — Returns the area of a polygonal geometry.

## Synopsis

`float ST_Area(` geometry g1`)`;

`float ST_Area(` geography geog, boolean use_spheroid = true`)`;

## Description

Returns the area of a polygonal geometry. For geometry types a 2D Cartesian (planar) area is computed, with units specified by the SRID. For geography types by default area is determined on a spheroid with units in square meters. To compute the area using the faster but less accurate spherical model use `ST_Area(geog,false)`.

Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced.

Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature.

Changed: 3.0.0 - does not depend on SFCGAL anymore.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.1.2, 9.5.3

This function supports Polyhedral surfaces.

For polyhedral surfaces, only supports 2D polyhedral surfaces (not 2.5D). For 2.5D, may give a non-zero answer, but only for the faces that sit completely in XY plane.

## Examples

Return area in square feet for a plot of Massachusetts land and multiply by conversion to get square meters. Note this is in square feet because EPSG:2249 is Massachusetts State Plane Feet

    select ST_Area(geom) sqft,
        ST_Area(geom) * 0.3048 ^ 2 sqm
    from (
             select 'SRID=2249;POLYGON((743238 2967416,743238 2967450,
    				 743265 2967450,743265.625 2967416,743238 2967416))' :: geometry geom
         ) subquery;
    ┌─────────┬─────────────┐
    │  sqft   │     sqm     │
    ├─────────┼─────────────┤
    │ 928.625 │ 86.27208552 │
    └─────────┴─────────────┘

Return area square feet and transform to Massachusetts state plane meters (EPSG:26986) to get square meters. Note this is in square feet because 2249 is Massachusetts State Plane Feet and transformed area is in square meters since EPSG:26986 is state plane Massachusetts meters

    select ST_Area(geom) sqft,
        ST_Area(ST_Transform(geom, 26986)) As sqm
    from (
             select
                 'SRID=2249;POLYGON((743238 2967416,743238 2967450,
                 743265 2967450,743265.625 2967416,743238 2967416))' :: geometry geom
         ) subquery;
    ┌─────────┬─────────────────┐
    │  sqft   │       sqm       │
    ├─────────┼─────────────────┤
    │ 928.625 │ 86.272430607008 │
    └─────────┴─────────────────┘

Return area square feet and square meters using geography data type. Note that we transform to our geometry to geography (before you can do that make sure your geometry is in WGS 84 long lat 4326). Geography always measures in meters. This is just for demonstration to compare. Normally your table will be stored in geography data type already.

    select ST_Area(geog) / 0.3048 ^ 2 sqft_spheroid,
        ST_Area(geog, false) / 0.3048 ^ 2 sqft_sphere,
        ST_Area(geog) sqm_spheroid
    from (
             select ST_Transform(
                        'SRID=2249;POLYGON((743238 2967416,743238 2967450,743265 2967450,743265.625 2967416,743238 2967416))'::geometry,
                        4326
                 ) :: geography geog
         ) as subquery;
    ┌──────────────────┬──────────────────┬──────────────────┐
    │  sqft_spheroid   │   sqft_sphere    │   sqm_spheroid   │
    ├──────────────────┼──────────────────┼──────────────────┤
    │ 928.684405784452 │ 927.049336105925 │ 86.2776044979692 │
    └──────────────────┴──────────────────┴──────────────────┘

If your data is in geography already:

    select ST_Area(geog) / 0.3048 ^ 2 sqft,
        ST_Area(the_geog) sqm
    from somegeogtable;

## See Also

ST_3DArea, ST_GeomFromText, ST_GeographyFromText, ST_SetSRID, ST_Transform

## Name

ST_Azimuth — Returns the north-based azimuth of a line between two points.

## Synopsis

`float ST_Azimuth(` geometry origin, geometry target`)`;

`float ST_Azimuth(` geography origin, geography target`)`;

## Description

Returns the azimuth in radians of the target point from the origin point, or NULL if the two points are coincident. The azimuth angle is a positive clockwise angle referenced from the positive Y axis (geometry) or the North meridian (geography): North = 0; Northeast = π/4; East = π/2; Southeast = 3π/4; South = π; Southwest 5π/4; West = 3π/2; Northwest = 7π/4.

For the geography type, the azimuth solution is known as the inverse geodesic problem.

The azimuth is a mathematical concept defined as the angle between a reference vector and a point, with angular units in radians. The result value in radians can be converted to degrees using the PostgreSQL function `degrees()`.

Azimuth can be used in conjunction with ST_Translate to shift an object along its perpendicular axis. See the `upgis_lineshift()` function in the PostGIS wiki for an implementation of this.

Availability: 1.1.0

Enhanced: 2.0.0 support for geography was introduced.

Enhanced: 2.2.0 measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature.

## Examples

Geometry Azimuth in degrees

    SELECT degrees(ST_Azimuth( ST_Point(25, 45),  ST_Point(75, 100))) AS degA_B,
           degrees(ST_Azimuth( ST_Point(75, 100), ST_Point(25, 45) )) AS degB_A;

          dega_b       |     degb_a
    ------------------+------------------
     42.2736890060937 | 222.273689006094

Blue: origin Point(25,45); Green: target Point(75, 100); Yellow: Y axis or North; Red: azimuth angle. | Blue: origin Point(75, 100); Green: target Point(25, 45); Yellow: Y axis or North; Red: azimuth angle.

## See Also

ST_Angle, ST_Point, ST_Translate, ST_Project, PostgreSQL Math Functions

## Name

ST_Angle — Returns the angle between two vectors defined by 3 or 4 points, or 2 lines.

## Synopsis

`float ST_Angle(` geometry point1, geometry point2, geometry point3, geometry point4`)`;

`float ST_Angle(` geometry line1, geometry line2`)`;

## Description

Computes the clockwise angle between two vectors.

Variant 1: computes the angle enclosed by the points P1-P2-P3. If a 4th point provided computes the angle points P1-P2 and P3-P4

Variant 2: computes the angle between two vectors S1-E1 and S2-E2, defined by the start and end points of the input lines

The result is a positive angle between 0 and 2π radians. The radian result can be converted to degrees using the PostgreSQL function `degrees()`.

Note that `ST_Angle(P1,P2,P3) = ST_Angle(P2,P1,P2,P3)`.

Availability: 2.5.0

## Examples

Angle between three points

    SELECT degrees( ST_Angle('POINT(0 0)', 'POINT(10 10)', 'POINT(20 0)') );

     degrees
    ---------
         270

Angle between vectors defined by four points

    SELECT degrees( ST_Angle('POINT (10 10)', 'POINT (0 0)', 'POINT(90 90)', 'POINT (100 80)') );

          degrees
    -------------------
     269.9999999999999

Angle between vectors defined by the start and end points of lines

    SELECT degrees( ST_Angle('LINESTRING(0 0, 0.3 0.7, 1 1)', 'LINESTRING(0 0, 0.2 0.5, 1 0)') );

          degrees
    --------------
               45

## See Also

ST_Azimuth

## Name

ST_ClosestPoint — Returns the 2D point on g1 that is closest to g2. This is the first point of the shortest line from one geometry to the other.

## Synopsis

`geometry ST_ClosestPoint(` geometry geom1, geometry geom2`)`;

`geography ST_ClosestPoint(` geography geom1, geography geom2, boolean use_spheroid = true`)`;

## Description

Returns the 2-dimensional point on `geom1` that is closest to `geom2`. This is the first point of the shortest line between the geometries (as computed by ST_ShortestLine).

If you have a 3D Geometry, you may prefer to use ST_3DClosestPoint.

Enhanced: 3.4.0 - Support for geography.

Availability: 1.5.0

## Examples

The closest point for a Point and a LineString is the point itself. The closest point for a LineString and a Point is a point on the line.

    SELECT ST_AsText( ST_ClosestPoint(pt,line)) AS cp_pt_line,
           ST_AsText( ST_ClosestPoint(line,pt)) AS cp_line_pt
        FROM (SELECT 'POINT (160 40)'::geometry AS pt,
                     'LINESTRING (10 30, 50 50, 30 110, 70 90, 180 140, 130 190)'::geometry AS line ) AS t;

       cp_pt_line   |                cp_line_pt
    ----------------+------------------------------------------
     POINT(160 40)  | POINT(125.75342465753425 115.34246575342466)

The closest point on polygon A to polygon B

    SELECT ST_AsText( ST_ClosestPoint(
    		'POLYGON ((190 150, 20 10, 160 70, 190 150))',
    		ST_Buffer('POINT(80 160)', 30)	)) As ptwkt;
    ------------------------------------------
     POINT(131.59149149528952 101.89887534906197)

## See Also

ST_3DClosestPoint, ST_Distance, ST_LongestLine, ST_ShortestLine, ST_MaxDistance

## Name

ST_3DClosestPoint — Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.

## Synopsis

`geometry ST_3DClosestPoint(` geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional point on g1 that is closest to g2. This is the first point of the 3D shortest line. The 3D length of the 3D shortest line is the 3D distance.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Availability: 2.0.0

Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

## Examples

linestring and point -- both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
    		ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

     cp3d_line_pt						|               cp2d_line_pt
    -----------------------------------------------------------+------------------------------------------
     POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(73.0769230769231 115.384615384615)
linestring and multipoint -- both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(line,pt)) AS cp3d_line_pt,
    		ST_AsEWKT(ST_ClosestPoint(line,pt)) As cp2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

                           cp3d_line_pt                        | cp2d_line_pt
    -----------------------------------------------------------+--------------
     POINT(54.6993798867619 128.935022917228 11.5475869506606) | POINT(50 75)
Multilinestring and polygon both 3d and 2d closest point
    SELECT ST_AsEWKT(ST_3DClosestPoint(poly, mline)) As cp3d,
        ST_AsEWKT(ST_ClosestPoint(poly, mline)) As cp2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                       cp3d                    |     cp2d
    -------------------------------------------+--------------
     POINT(39.993580415989 54.1889925532825 5) | POINT(20 40)

## See Also

ST_AsEWKT, ST_ClosestPoint, ST_3DDistance, ST_3DShortestLine

## Name

ST_Distance — Returns the distance between two geometry or geography values.

## Synopsis

`float ST_Distance(` geometry g1, geometry g2`)`;

`float ST_Distance(` geography geog1, geography geog2, boolean use_spheroid = true`)`;

## Description

For geometry types returns the minimum 2D Cartesian (planar) distance between two geometries, in projected units (spatial ref units).

For geography types defaults to return the minimum geodesic distance between two geographies in meters, compute on the spheroid determined by the SRID. If `use_spheroid` is false, a faster spherical calculation is used.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.23

This method supports Circular Strings and Curves.

Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertex geometries

Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details.

Enhanced: 2.1.0 - support for curved geometries was introduced.

Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature.

Changed: 3.0.0 - does not depend on SFCGAL anymore.

## Geometry Examples

Geometry example - units in planar degrees 4326 is WGS 84 long lat, units are degrees.

    SELECT ST_Distance(
        'SRID=4326;POINT(-72.1235 42.3521)'::geometry,
        'SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry );
    -----------------
    0.00150567726382282

Geometry example - units in meters (SRID: 3857, proportional to pixels on popular web maps). Although the value is off, nearby ones can be compared correctly, which makes it a good choice for algorithms like KNN or KMeans.

    SELECT ST_Distance(
        ST_Transform('SRID=4326;POINT(-72.1235 42.3521)'::geometry, 3857),
        ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry, 3857) );
    -----------------
    167.441410065196

Geometry example - units in meters (SRID: 3857 as above, but corrected by cos(lat) to account for distortion)

    SELECT ST_Distance(
        ST_Transform('SRID=4326;POINT(-72.1235 42.3521)'::geometry, 3857),
        ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry, 3857)
    		) * cosd(42.3521);
    -----------------
    123.742351254151

Geometry example - units in meters (SRID: 26986 Massachusetts state plane meters) (most accurate for Massachusetts)

    SELECT ST_Distance(
        ST_Transform('SRID=4326;POINT(-72.1235 42.3521)'::geometry, 26986),
        ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry, 26986) );
    -----------------
    123.797937878454

Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (least accurate)

    SELECT ST_Distance(
        ST_Transform('SRID=4326;POINT(-72.1235 42.3521)'::geometry, 2163),
        ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry, 2163) );
    ------------------
    126.664256056812

## Geography Examples

Same as geometry example but note units in meters - use sphere for slightly faster and less accurate computation.

    SELECT ST_Distance(gg1, gg2) As spheroid_dist, ST_Distance(gg1, gg2, false) As sphere_dist
    FROM (SELECT
        'SRID=4326;POINT(-72.1235 42.3521)'::geography as gg1,
        'SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geography as gg2
    	) As foo  ;

      spheroid_dist   |   sphere_dist
    ------------------+------------------
     123.802076746848 | 123.475736916397

## See Also

ST_3DDistance, ST_DWithin, ST_DistanceSphere, ST_DistanceSpheroid, ST_MaxDistance, ST_HausdorffDistance, ST_FrechetDistance, ST_Transform

## Name

ST_3DDistance — Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.

## Synopsis

`float ST_3DDistance(` geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional minimum cartesian distance between two geometries in projected units (spatial ref units).

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3

Availability: 2.0.0

Changed: 2.2.0 - In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

Changed: 3.0.0 - SFCGAL version removed

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DDistance(
    			ST_Transform('SRID=4326;POINT(-72.1235 42.3521 4)'::geometry,2163),
    			ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'::geometry,2163)
    		) As dist_3d,
    		ST_Distance(
    			ST_Transform('SRID=4326;POINT(-72.1235 42.3521)'::geometry,2163),
    			ST_Transform('SRID=4326;LINESTRING(-72.1260 42.45, -72.123 42.1546)'::geometry,2163)
    		) As dist_2d;

         dist_3d      |     dist_2d
    ------------------+-----------------
     127.295059324629 | 126.66425605671

    -- Multilinestring and polygon both 3d and 2d distance
    -- Same example as 3D closest point example
    SELECT ST_3DDistance(poly, mline) As dist3d,
        ST_Distance(poly, mline) As dist2d
            FROM (SELECT  'POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))'::geometry as poly,
                   'MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1), (1 10 2, 5 20 1))'::geometry as mline) as foo;
          dist3d       | dist2d
    -------------------+--------
     0.716635696066337 |      0

## See Also

ST_Distance, ST_3DClosestPoint, ST_3DDWithin, ST_3DMaxDistance, ST_3DShortestLine, ST_Transform

## Name

ST_DistanceSphere — Returns minimum distance in meters between two lon/lat geometries using a spherical earth model.

## Synopsis

`float ST_DistanceSphere(` geometry geomlonlatA, geometry geomlonlatB, float8 radius=6371008`)`;

## Description

Returns minimum distance in meters between two lon/lat points. Uses a spherical earth and radius derived from the spheroid defined by the SRID. Faster than ST_DistanceSpheroid, but less accurate. PostGIS Versions prior to 1.5 only implemented for points.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

Changed: 2.2.0 In prior versions this used to be called ST_Distance_Sphere

## Examples

    SELECT round(CAST(ST_DistanceSphere(ST_Centroid(geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters,
    round(CAST(ST_Distance(ST_Transform(ST_Centroid(geom),32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters,
    round(CAST(ST_Distance(ST_Centroid(geom), ST_GeomFromText('POINT(-118 38)', 4326)) As numeric),5) As dist_degrees,
    round(CAST(ST_Distance(ST_Transform(geom,32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As min_dist_line_point_meters
    FROM
    	(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As geom) as foo;
    	 dist_meters | dist_utm11_meters | dist_degrees | min_dist_line_point_meters
    	-------------+-------------------+--------------+----------------------------
    		70424.47 |          70438.00 |      0.72900 |                   65871.18

## See Also

ST_Distance, ST_DistanceSpheroid

## Name

ST_DistanceSpheroid — Returns the minimum distance between two lon/lat geometries using a spheroidal earth model.

## Synopsis

`float ST_DistanceSpheroid(` geometry geomlonlatA, geometry geomlonlatB, spheroid measurement_spheroid=WGS84`)`;

## Description

Returns minimum distance in meters between two lon/lat geometries given a particular spheroid. See the explanation of spheroids given for ST_LengthSpheroid.

This function does not look at the SRID of the geometry. It assumes the geometry coordinates are based on the provided spheroid.

Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points.

Changed: 2.2.0 In prior versions this was called ST_Distance_Spheroid

## Examples

    SELECT round(CAST(
    		ST_DistanceSpheroid(ST_Centroid(geom), ST_GeomFromText('POINT(-118 38)',4326), 'SPHEROID["WGS 84",6378137,298.257223563]')
    			As numeric),2) As dist_meters_spheroid,
    		round(CAST(ST_DistanceSphere(ST_Centroid(geom), ST_GeomFromText('POINT(-118 38)',4326)) As numeric),2) As dist_meters_sphere,
    round(CAST(ST_Distance(ST_Transform(ST_Centroid(geom),32611),
    		ST_Transform(ST_GeomFromText('POINT(-118 38)', 4326),32611)) As numeric),2) As dist_utm11_meters
    FROM
    	(SELECT ST_GeomFromText('LINESTRING(-118.584 38.374,-118.583 38.5)', 4326) As geom) as foo;
     dist_meters_spheroid | dist_meters_sphere | dist_utm11_meters
    ----------------------+--------------------+-------------------
    			 70454.92 |           70424.47 |          70438.00

## See Also

ST_Distance, ST_DistanceSphere

## Name

ST_FrechetDistance — Returns the Fréchet distance between two geometries.

## Synopsis

`float ST_FrechetDistance(` geometry g1, geometry g2, float densifyFrac = -1`)`;

## Description

Implements algorithm for computing the Fréchet distance restricted to discrete points for both geometries, based on Computing Discrete Fréchet Distance. The Fréchet distance is a measure of similarity between curves that takes into account the location and ordering of the points along the curves. Therefore it is often better than the Hausdorff distance.

When the optional densifyFrac is specified, this function performs a segment densification before computing the discrete Fréchet distance. The densifyFrac parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction.

Units are in the units of the spatial reference system of the geometries.

The current implementation supports only vertices as the discrete locations. This could be extended to allow an arbitrary density of points to be used.

The smaller densifyFrac we specify, the more accurate Fréchet distance we get. But, the computation time and the memory usage increase with the square of the number of subsegments.

Performed by the GEOS module.

Availability: 2.4.0 - requires GEOS >= 3.7.0

## Examples

    postgres=# SELECT st_frechetdistance('LINESTRING (0 0, 100 0)'::geometry, 'LINESTRING (0 0, 50 50, 100 0)'::geometry);
     st_frechetdistance
    --------------------
       70.7106781186548
    (1 row)

    SELECT st_frechetdistance('LINESTRING (0 0, 100 0)'::geometry, 'LINESTRING (0 0, 50 50, 100 0)'::geometry, 0.5);
     st_frechetdistance
    --------------------
                     50
    (1 row)

## See Also

ST_HausdorffDistance

## Name

ST_HausdorffDistance — Returns the Hausdorff distance between two geometries.

## Synopsis

`float ST_HausdorffDistance(` geometry g1, geometry g2`)`;

`float ST_HausdorffDistance(` geometry g1, geometry g2, float densifyFrac`)`;

## Description

Returns the Hausdorff distance between two geometries. The Hausdorff distance is a measure of how similar or dissimilar 2 geometries are.

The function actually computes the "Discrete Hausdorff Distance". This is the Hausdorff distance computed at discrete points on the geometries. The `densifyFrac` parameter can be specified, to provide a more accurate answer by densifying segments before computing the discrete Hausdorff distance. Each segment is split into a number of equal-length subsegments whose fraction of the segment length is closest to the given fraction.

Units are in the units of the spatial reference system of the geometries.

This algorithm is NOT equivalent to the standard Hausdorff distance. However, it computes an approximation that is correct for a large subset of useful cases. One important case is Linestrings that are roughly parallel to each other, and roughly equal in length. This is a useful metric for line matching.

Availability: 1.5.0

## Examples

Hausdorff distance (red) and distance (yellow) between two lines

    SELECT ST_HausdorffDistance(geomA, geomB),
           ST_Distance(geomA, geomB)
        FROM (SELECT 'LINESTRING (20 70, 70 60, 110 70, 170 70)'::geometry AS geomA,
                     'LINESTRING (20 90, 130 90, 60 100, 190 100)'::geometry AS geomB) AS t;
     st_hausdorffdistance | st_distance
    ----------------------+-------------
        37.26206567625497 |          20

Example: Hausdorff distance with densification.

    SELECT ST_HausdorffDistance(
                'LINESTRING (130 0, 0 0, 0 150)'::geometry,
                'LINESTRING (10 10, 10 150, 130 10)'::geometry,
                0.5);
     ----------------------
              70

Example: For each building, find the parcel that best represents it. First we require that the parcel intersect with the building geometry. `DISTINCT ON` guarantees we get each building listed only once. `ORDER BY .. ST_HausdorffDistance` selects the parcel that is most similar to the building.

    SELECT DISTINCT ON (buildings.gid) buildings.gid, parcels.parcel_id
       FROM buildings
           INNER JOIN parcels
           ON ST_Intersects(buildings.geom, parcels.geom)
       ORDER BY buildings.gid, ST_HausdorffDistance(buildings.geom, parcels.geom);

## See Also

ST_FrechetDistance

## Name

ST_Length — Returns the 2D length of a linear geometry.

## Synopsis

`float ST_Length(` geometry a_2dlinestring`)`;

`float ST_Length(` geography geog, boolean use_spheroid = true`)`;

## Description

For geometry types: returns the 2D Cartesian length of the geometry if it is a LineString, MultiLineString, ST_Curve, ST_MultiCurve. For areal geometries 0 is returned; use ST_Perimeter instead. The units of length is determined by the spatial reference system of the geometry.

For geography types: computation is performed using the inverse geodesic calculation. Units of length are in meters. If PostGIS is compiled with PROJ version 4.8.0 or later, the spheroid is specified by the SRID, otherwise it is exclusive to WGS84. If `use_spheroid = false`, then the calculation is based on a sphere instead of a spheroid.

Currently for geometry this is an alias for ST_Length2D, but this may change to support higher dimensions.

Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon

For geography the calculation defaults to using a spheroidal model. To use the faster but less accurate spherical calculation use ST_Length(gg,false);

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 7.1.2, 9.3.4

Availability: 1.5.0 geography support was introduced in 1.5.

## Geometry Examples

Return length in feet for line string. Note this is in feet because EPSG:2249 is Massachusetts State Plane Feet

    SELECT ST_Length(ST_GeomFromText('LINESTRING(743238 2967416,743238 2967450,743265 2967450,
    743265.625 2967416,743238 2967416)',2249));

    st_length
    ---------
     122.630744000095

    --Transforming WGS 84 LineString to Massachusetts state plane meters
    SELECT ST_Length(
    	ST_Transform(
    		ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)'),
    		26986
    	)
    );

    st_length
    ---------
    34309.4563576191

## Geography Examples

Return length of WGS 84 geography line

    -- the default calculation uses a spheroid
    SELECT ST_Length(the_geog) As length_spheroid,  ST_Length(the_geog,false) As length_sphere
    FROM (SELECT ST_GeographyFromText(
    'SRID=4326;LINESTRING(-72.1260 42.45, -72.1240 42.45666, -72.123 42.1546)') As the_geog)
     As foo;

     length_spheroid  |  length_sphere
    ------------------+------------------
     34310.5703627288 | 34346.2060960742

## See Also

ST_GeographyFromText, ST_GeomFromEWKT, ST_LengthSpheroid, ST_Perimeter, ST_Transform

## Name

ST_Length2D — Returns the 2D length of a linear geometry. Alias for `ST_Length`

## Synopsis

`float ST_Length2D(` geometry a_2dlinestring`)`;

## Description

Returns the 2D length of the geometry if it is a linestring or multi-linestring. This is an alias for `ST_Length`

## See Also

ST_Length, ST_3DLength

## Name

ST_3DLength — Returns the 3D length of a linear geometry.

## Synopsis

`float ST_3DLength(` geometry a_3dlinestring`)`;

## Description

Returns the 3-dimensional or 2-dimensional length of the geometry if it is a LineString or MultiLineString. For 2-d lines it will just return the 2-d length (same as ST_Length and ST_Length2D)

This function supports 3d and will not drop the z-index.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 7.1, 10.3

Changed: 2.0.0 In prior versions this used to be called ST_Length3D

## Examples

Return length in feet for a 3D cable. Note this is in feet because EPSG:2249 is Massachusetts State Plane Feet

    SELECT ST_3DLength(ST_GeomFromText('LINESTRING(743238 2967416 1,743238 2967450 1,743265 2967450 3,
    743265.625 2967416 3,743238 2967416 3)',2249));
    ST_3DLength
    -----------
    122.704716741457

## See Also

ST_Length, ST_Length2D

## Name

ST_LengthSpheroid — Returns the 2D or 3D length/perimeter of a lon/lat geometry on a spheroid.

## Synopsis

`float ST_LengthSpheroid(` geometry a_geometry, spheroid a_spheroid`)`;

## Description

Calculates the length or perimeter of a geometry on an ellipsoid. This is useful if the coordinates of the geometry are in longitude/latitude and a length is desired without reprojection. The spheroid is specified by a text value as follows:

SPHEROID[<NAME>,<SEMI-MAJOR AXIS>,<INVERSE FLATTENING>]

For example:

SPHEROID["GRS_1980",6378137,298.257222101]

Availability: 1.2.2

Changed: 2.2.0 In prior versions this was called ST_Length_Spheroid and had the alias ST_3DLength_Spheroid

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_LengthSpheroid( geometry_column,
    			  'SPHEROID["GRS_1980",6378137,298.257222101]' )
    			  FROM geometry_table;

    SELECT ST_LengthSpheroid( geom, sph_m ) As tot_len,
    ST_LengthSpheroid(ST_GeometryN(geom,1), sph_m) As len_line1,
    ST_LengthSpheroid(ST_GeometryN(geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromText('MULTILINESTRING((-118.584 38.374,-118.583 38.5),
    	(-71.05957 42.3589 , -71.061 43))') As geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;
    	tot_len      |    len_line1     |    len_line2
    ------------------+------------------+------------------
     85204.5207562955 | 13986.8725229309 | 71217.6482333646

     --3D
    SELECT ST_LengthSpheroid( geom, sph_m ) As tot_len,
    ST_LengthSpheroid(ST_GeometryN(geom,1), sph_m) As len_line1,
    ST_LengthSpheroid(ST_GeometryN(geom,2), sph_m) As len_line2
    			  FROM (SELECT ST_GeomFromEWKT('MULTILINESTRING((-118.584 38.374 20,-118.583 38.5 30),
    	(-71.05957 42.3589 75, -71.061 43 90))') As geom,
    CAST('SPHEROID["GRS_1980",6378137,298.257222101]' As spheroid) As sph_m)  as foo;

    	 tot_len      |    len_line1    |    len_line2
    ------------------+-----------------+------------------
     85204.5259107402 | 13986.876097711 | 71217.6498130292

## See Also

ST_GeometryN, ST_Length

## Name

ST_LongestLine — Returns the 2D longest line between two geometries.

## Synopsis

`geometry ST_LongestLine(` geometry g1, geometry g2`)`;

## Description

Returns the 2-dimensional longest line between the points of two geometries. The line returned starts on `g1` and ends on `g2`.

The longest line always occurs between two vertices. The function returns the first longest line if more than one is found. The length of the line is equal to the distance returned by ST_MaxDistance.

If g1 and g2 are the same geometry, returns the line between the two vertices farthest apart in the geometry. The endpoints of the line lie on the circle computed by ST_MinimumBoundingCircle.

Availability: 1.5.0

## Examples

Longest line between a point and a line

    SELECT ST_AsText( ST_LongestLine(
            'POINT (160 40)',
            'LINESTRING (10 30, 50 50, 30 110, 70 90, 180 140, 130 190)' )
    	) AS lline;
    -----------------
    LINESTRING(160 40,130 190)

Longest line between two polygons

    SELECT ST_AsText( ST_LongestLine(
            'POLYGON ((190 150, 20 10, 160 70, 190 150))',
            ST_Buffer('POINT(80 160)', 30)
                ) ) AS llinewkt;
    -----------------
    LINESTRING(20 10,105.3073372946034 186.95518130045156)

Longest line across a single geometry. The length of the line is equal to the Maximum Distance. The endpoints of the line lie on the Minimum Bounding Circle.

    SELECT ST_AsText( ST_LongestLine( geom, geom)) AS llinewkt,
                      ST_MaxDistance( geom, geom) AS max_dist,
                      ST_Length( ST_LongestLine(geom, geom)) AS lenll
    FROM (SELECT 'POLYGON ((40 180, 110 160, 180 180, 180 120, 140 90, 160 40, 80 10, 70 40, 20 50, 40 180),
                  (60 140, 99 77.5, 90 140, 60 140))'::geometry AS geom) AS t;

             llinewkt          |      max_dist      |       lenll
    ---------------------------+--------------------+--------------------
     LINESTRING(20 50,180 180) | 206.15528128088303 | 206.15528128088303

## See Also

ST_MaxDistance, ST_ShortestLine, ST_3DLongestLine, ST_MinimumBoundingCircle

## Name

ST_3DLongestLine — Returns the 3D longest line between two geometries

## Synopsis

`geometry ST_3DLongestLine(` geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional longest line between two geometries. The function returns the first longest line if more than one. The line returned starts in g1 and ends in g2. The 3D length of the line is equal to the distance returned by ST_3DMaxDistance.

Availability: 2.0.0

Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

linestring and point -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

               lol3d_line_pt           |       lol2d_line_pt
    -----------------------------------+----------------------------
     LINESTRING(50 75 1000,100 100 30) | LINESTRING(98 190,100 100)
linestring and multipoint -- both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(line,pt)) AS lol3d_line_pt,
    		ST_AsEWKT(ST_LongestLine(line,pt)) As lol2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

              lol3d_line_pt          |      lol2d_line_pt
    ---------------------------------+--------------------------
     LINESTRING(98 190 1,50 74 1000) | LINESTRING(98 190,50 74)
MultiLineString and Polygon both 3d and 2d longest line
    SELECT ST_AsEWKT(ST_3DLongestLine(poly, mline)) As lol3d,
        ST_AsEWKT(ST_LongestLine(poly, mline)) As lol2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                lol3d             |          lol2d
    ------------------------------+--------------------------
     LINESTRING(175 150 5,1 10 2) | LINESTRING(175 150,1 10)

## See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_3DShortestLine, ST_3DMaxDistance

## Name

ST_MaxDistance — Returns the 2D largest distance between two geometries in projected units.

## Synopsis

`float ST_MaxDistance(` geometry g1, geometry g2`)`;

## Description

Returns the 2-dimensional maximum distance between two geometries, in projected units. The maximum distance always occurs between two vertices. This is the length of the line returned by ST_LongestLine.

If g1 and g2 are the same geometry, returns the distance between the two vertices farthest apart in that geometry.

Availability: 1.5.0

## Examples

Maximum distance between a point and lines.

    SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
    -----------------
     2

    SELECT ST_MaxDistance('POINT(0 0)'::geometry, 'LINESTRING ( 2 2, 2 2 )'::geometry);
    ------------------
     2.82842712474619

Maximum distance between vertices of a single geometry.

    SELECT ST_MaxDistance('POLYGON ((10 10, 10 0, 0 0, 10 10))'::geometry,
                          'POLYGON ((10 10, 10 0, 0 0, 10 10))'::geometry);
    ------------------
     14.142135623730951

## See Also

ST_Distance, ST_LongestLine, ST_DFullyWithin

## Name

ST_3DMaxDistance — Returns the 3D cartesian maximum distance (based on spatial ref) between two geometries in projected units.

## Synopsis

`float ST_3DMaxDistance(` geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional maximum cartesian distance between two geometries in projected units (spatial ref units).

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

Availability: 2.0.0

Changed: 2.2.0 - In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

## Examples

    -- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
    -- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
    SELECT ST_3DMaxDistance(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
    		) As dist_3d,
    		ST_MaxDistance(
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 10000)'),2163),
    			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163)
    		) As dist_2d;

         dist_3d      |     dist_2d
    ------------------+------------------
     24383.7467488441 | 22247.8472107251

## See Also

ST_Distance, ST_3DDWithin, ST_3DMaxDistance, ST_Transform

## Name

ST_MinimumClearance — Returns the minimum clearance of a geometry, a measure of a geometry's robustness.

## Synopsis

`float ST_MinimumClearance(` geometry g`)`;

## Description

It is possible for a geometry to meet the criteria for validity according to ST_IsValid (polygons) or ST_IsSimple (lines), but to become invalid if one of its vertices is moved by a small distance. This can happen due to loss of precision during conversion to text formats (such as WKT, KML, GML, GeoJSON), or binary formats that do not use double-precision floating point coordinates (e.g. MapInfo TAB).

The minimum clearance is a quantitative measure of a geometry's robustness to change in coordinate precision. It is the largest distance by which vertices of the geometry can be moved without creating an invalid geometry. Larger values of minimum clearance indicate greater robustness.

If a geometry has a minimum clearance of `e`, then:

- No two distinct vertices in the geometry are closer than the distance `e`.

- No vertex is closer than `e` to a line segment of which it is not an endpoint.

If no minimum clearance exists for a geometry (e.g. a single point, or a MultiPoint whose points are identical), the return value is `Infinity`.

To avoid validity issues caused by precision loss, ST_ReducePrecision can reduce coordinate precision while ensuring that polygonal geometry remains valid.

Availability: 2.3.0

## Examples

    SELECT ST_MinimumClearance('POLYGON ((0 0, 1 0, 1 1, 0.5 3.2e-4, 0 0))');
     st_minimumclearance
    ---------------------
                 0.00032

## See Also

ST_MinimumClearanceLine, ST_IsSimple, ST_IsValid, ST_ReducePrecision

## Name

ST_MinimumClearanceLine — Returns the two-point LineString spanning a geometry's minimum clearance.

## Synopsis

`Geometry ST_MinimumClearanceLine(` geometry g`)`;

## Description

Returns the two-point LineString spanning a geometry's minimum clearance. If the geometry does not have a minimum clearance, `LINESTRING EMPTY` is returned.

Performed by the GEOS module.

Availability: 2.3.0 - requires GEOS >= 3.6.0

## Examples

    SELECT ST_AsText(ST_MinimumClearanceLine('POLYGON ((0 0, 1 0, 1 1, 0.5 3.2e-4, 0 0))'));
    -------------------------------
    LINESTRING(0.5 0.00032,0.5 0)

## See Also

ST_MinimumClearance

## Name

ST_Perimeter — Returns the length of the boundary of a polygonal geometry or geography.

## Synopsis

`float ST_Perimeter(` geometry g1`)`;

`float ST_Perimeter(` geography geog, boolean use_spheroid = true`)`;

## Description

Returns the 2D perimeter of the geometry/geography if it is a ST_Surface, ST_MultiSurface (Polygon, MultiPolygon). 0 is returned for non-areal geometries. For linear geometries use ST_Length. For geometry types, units for perimeter measures are specified by the spatial reference system of the geometry.

For geography types, the calculations are performed using the inverse geodesic problem, where perimeter units are in meters. If PostGIS is compiled with PROJ version 4.8.0 or later, the spheroid is specified by the SRID, otherwise it is exclusive to WGS84. If `use_spheroid = false`, then calculations will approximate a sphere instead of a spheroid.

Currently this is an alias for ST_Perimeter2D, but this may change to support higher dimensions.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.5.1

This method implements the SQL/MM specification. SQL-MM 3: 8.1.3, 9.5.4

Availability 2.0.0: Support for geography was introduced

## Examples: Geometry

Return perimeter in feet for Polygon and MultiPolygon. Note this is in feet because EPSG:2249 is Massachusetts State Plane Feet

    SELECT ST_Perimeter(ST_GeomFromText('POLYGON((743238 2967416,743238 2967450,743265 2967450,
    743265.625 2967416,743238 2967416))', 2249));
    st_perimeter
    ---------
     122.630744000095
    (1 row)

    SELECT ST_Perimeter(ST_GeomFromText('MULTIPOLYGON(((763104.471273676 2949418.44119003,
    763104.477769673 2949418.42538203,
    763104.189609677 2949418.22343004,763104.471273676 2949418.44119003)),
    ((763104.471273676 2949418.44119003,763095.804579742 2949436.33850239,
    763086.132105649 2949451.46730207,763078.452329651 2949462.11549407,
    763075.354136904 2949466.17407812,763064.362142565 2949477.64291974,
    763059.953961626 2949481.28983009,762994.637609571 2949532.04103014,
    762990.568508415 2949535.06640477,762986.710889563 2949539.61421415,
    763117.237897679 2949709.50493431,763235.236617789 2949617.95619822,
    763287.718121842 2949562.20592617,763111.553321674 2949423.91664605,
    763104.471273676 2949418.44119003)))', 2249));
    st_perimeter
    ---------
     845.227713366825
    (1 row)

## Examples: Geography

Return perimeter in meters and feet for Polygon and MultiPolygon. Note this is geography (WGS 84 long lat)

    SELECT  ST_Perimeter(geog) As per_meters, ST_Perimeter(geog)/0.3048 As per_ft
    FROM ST_GeogFromText('POLYGON((-71.1776848522251 42.3902896512902,-71.1776843766326 42.3903829478009,
    -71.1775844305465 42.3903826677917,-71.1775825927231 42.3902893647987,-71.1776848522251 42.3902896512902))') As geog;

       per_meters    |      per_ft
    -----------------+------------------
    37.3790462565251 | 122.634666195949

    -- MultiPolygon example --
    SELECT  ST_Perimeter(geog) As per_meters, ST_Perimeter(geog,false) As per_sphere_meters,  ST_Perimeter(geog)/0.3048 As per_ft
    FROM ST_GeogFromText('MULTIPOLYGON(((-71.1044543107478 42.340674480411,-71.1044542869917 42.3406744369506,
    -71.1044553562977 42.340673886454,-71.1044543107478 42.340674480411)),
    ((-71.1044543107478 42.340674480411,-71.1044860600303 42.3407237015564,-71.1045215770124 42.3407653385914,
    -71.1045498002983 42.3407946553165,-71.1045611902745 42.3408058316308,-71.1046016507427 42.340837442371,
    -71.104617893173 42.3408475056957,-71.1048586153981 42.3409875993595,-71.1048736143677 42.3409959528211,
    -71.1048878050242 42.3410084812078,-71.1044020965803 42.3414730072048,
    -71.1039672113619 42.3412202916693,-71.1037740497748 42.3410666421308,
    -71.1044280218456 42.3406894151355,-71.1044543107478 42.340674480411)))') As geog;

        per_meters    | per_sphere_meters |      per_ft
    ------------------+-------------------+------------------
     257.634283683311 |  257.412311446337 | 845.256836231335

## See Also

ST_GeogFromText, ST_GeomFromText, ST_Length

## Name

ST_Perimeter2D — Returns the 2D perimeter of a polygonal geometry. Alias for `ST_Perimeter`.

## Synopsis

`float ST_Perimeter2D(` geometry geomA`)`;

## Description

Returns the 2-dimensional perimeter of a polygonal geometry.

This is currently an alias for ST_Perimeter. In future versions ST_Perimeter may return the highest dimension perimeter for a geometry. This is still under consideration

## See Also

ST_Perimeter

## Name

ST_3DPerimeter — Returns the 3D perimeter of a polygonal geometry.

## Synopsis

`float ST_3DPerimeter(` geometry geomA`)`;

## Description

Returns the 3-dimensional perimeter of the geometry, if it is a polygon or multi-polygon. If the geometry is 2-dimensional, then the 2-dimensional perimeter is returned.

This function supports 3d and will not drop the z-index.

This method implements the SQL/MM specification. SQL-MM ISO/IEC 13249-3: 8.1, 10.5

Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D

## Examples

Perimeter of a slightly elevated polygon in the air in Massachusetts state plane feet

    SELECT ST_3DPerimeter(geom), ST_Perimeter2d(geom), ST_Perimeter(geom) FROM
    			(SELECT ST_GeomFromEWKT('SRID=2249;POLYGON((743238 2967416 2,743238 2967450 1,
    743265.625 2967416 1,743238 2967416 2))') As geom) As foo;

      ST_3DPerimeter  |  st_perimeter2d  |   st_perimeter
    ------------------+------------------+------------------
     105.465793597674 | 105.432997272188 | 105.432997272188

## See Also

ST_GeomFromEWKT, ST_Perimeter, ST_Perimeter2D

## Name

ST_ShortestLine — Returns the 2D shortest line between two geometries

## Synopsis

`geometry ST_ShortestLine(` geometry geom1, geometry geom2`)`;

`geography ST_ShortestLine(` geography geom1, geography geom2, boolean use_spheroid = true`)`;

## Description

Returns the 2-dimensional shortest line between two geometries. The line returned starts in `geom1` and ends in `geom2`. If `geom1` and `geom2` intersect the result is a line with start and end at an intersection point. The length of the line is the same as ST_Distance returns for g1 and g2.

Enhanced: 3.4.0 - support for geography.

Availability: 1.5.0

## Examples

Shortest line between Point and LineString

    SELECT ST_AsText(  ST_ShortestLine(
            'POINT (160 40)',
            'LINESTRING (10 30, 50 50, 30 110, 70 90, 180 140, 130 190)')
    	) As sline;
    ---------------------------------------------------------
     LINESTRING(160 40,125.75342465753425 115.34246575342466)

Shortest line between Polygons

    SELECT ST_AsText( ST_ShortestLine(
             'POLYGON ((190 150, 20 10, 160 70, 190 150))',
             ST_Buffer('POINT(80 160)', 30)
                  ) ) AS llinewkt;
    -----------------
    LINESTRING(131.59149149528952 101.89887534906197,101.21320343559644 138.78679656440357)

## See Also

ST_ClosestPoint, ST_Distance, ST_LongestLine, ST_MaxDistance

## Name

ST_3DShortestLine — Returns the 3D shortest line between two geometries

## Synopsis

`geometry ST_3DShortestLine(` geometry g1, geometry g2`)`;

## Description

Returns the 3-dimensional shortest line between two geometries. The function will only return the first shortest line if more than one, that the function finds. If g1 and g2 intersects in just one point the function will return a line with both start and end in that intersection-point. If g1 and g2 are intersecting with more than one point the function will return a line with start and end in the same point but it can be any of the intersecting points. The line returned will always start in g1 and end in g2. The 3D length of the line this function returns will always be the same as ST_3DDistance returns for g1 and g2.

Availability: 2.0.0

Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

## Examples

linestring and point -- both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
    		ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
    	FROM (SELECT 'POINT(100 100 30)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 1000)'::geometry As line
    		) As foo;

     shl3d_line_pt						                 |               shl2d_line_pt
    ----------------------------------------------------------------------------+------------------------------------------------------
     LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30)  | LINESTRING(73.0769230769231 115.384615384615,100 100)
linestring and multipoint -- both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(line,pt)) AS shl3d_line_pt,
    		ST_AsEWKT(ST_ShortestLine(line,pt)) As shl2d_line_pt
    	FROM (SELECT 'MULTIPOINT(100 100 30, 50 74 1000)'::geometry As pt,
    			'LINESTRING (20 80 20, 98 190 1, 110 180 3, 50 75 900)'::geometry As line
    		) As foo;

                           shl3d_line_pt                                       | shl2d_line_pt
    ---------------------------------------------------------------------------+------------------------
     LINESTRING(54.6993798867619 128.935022917228 11.5475869506606,100 100 30) | LINESTRING(50 75,50 74)
MultiLineString and polygon both 3d and 2d shortest line
    SELECT ST_AsEWKT(ST_3DShortestLine(poly, mline)) As shl3d,
        ST_AsEWKT(ST_ShortestLine(poly, mline)) As shl2d
            FROM (SELECT  ST_GeomFromEWKT('POLYGON((175 150 5, 20 40 5, 35 45 5, 50 60 5, 100 100 5, 175 150 5))') As poly,
                    ST_GeomFromEWKT('MULTILINESTRING((175 155 2, 20 40 20, 50 60 -2, 125 100 1, 175 155 1),
                    (1 10 2, 5 20 1))') As mline ) As foo;
                       shl3d                                                                           |     shl2d
    ---------------------------------------------------------------------------------------------------+------------------------
     LINESTRING(39.993580415989 54.1889925532825 5,40.4078575708294 53.6052383805529 5.03423778139177) | LINESTRING(20 40,20 40)

## See Also

ST_3DClosestPoint, ST_3DDistance, ST_LongestLine, ST_ShortestLine, ST_3DMaxDistance

## 7.13. Overlay Functions

Abstract

These functions compute results arising from the overlay of two geometries. These are also known as point-set theoretic boolean operations. Some related functions are also provided.

## Name

ST_ClipByBox2D — Computes the portion of a geometry falling within a rectangle.

## Synopsis

`geometry ST_ClipByBox2D(` geometry geom, box2d box`)`;

## Description

Clips a geometry by a 2D box in a fast and tolerant but possibly invalid way. Topologically invalid input geometries do not result in exceptions being thrown. The output geometry is not guaranteed to be valid (in particular, self-intersections for a polygon may be introduced).

Performed by the GEOS module.

Availability: 2.2.0

## Examples

    -- Rely on implicit cast from geometry to box2d for the second parameter
    SELECT ST_ClipByBox2D(geom, ST_MakeEnvelope(0,0,10,10)) FROM mytab;

## See Also

ST_Intersection, ST_MakeBox2D, ST_MakeEnvelope

## Name

ST_Difference — Computes a geometry representing the part of geometry A that does not intersect geometry B.

## Synopsis

`geometry ST_Difference(` geometry geomA, geometry geomB, float8 gridSize = -1`)`;

## Description

Returns a geometry representing the part of geometry A that does not intersect geometry B. This is equivalent to `A - ST_Intersection(A,B)`. If A is completely contained in B then an empty atomic geometry of appropriate type is returned.

This is the only overlay function where input order matters. ST_Difference(A, B) always returns a portion of A.

If the optional `gridSize` argument is provided, the inputs are snapped to a grid of the given size, and the result vertices are computed on that same grid. (Requires GEOS-3.9.0 or higher)

Performed by the GEOS module

Enhanced: 3.1.0 accept a gridSize parameter.

Requires GEOS >= 3.9.0 to use the gridSize parameter.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.20

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

## Examples

The input linestrings | The difference of the two linestrings

The difference of 2D linestrings.

    SELECT ST_AsText(
        ST_Difference(
                'LINESTRING(50 100, 50 200)'::geometry,
                'LINESTRING(50 50, 50 150)'::geometry
            )
        );

    st_astext
    ---------
    LINESTRING(50 150,50 200)

The difference of 3D points.

    SELECT ST_AsEWKT( ST_Difference(
                       'MULTIPOINT(-118.58 38.38 5,-118.60 38.329 6,-118.614 38.281 7)' :: geometry,
                       'POINT(-118.614 38.281 5)' :: geometry
                      ) );

    st_asewkt
    ---------
    MULTIPOINT(-118.6 38.329 6,-118.58 38.38 5)

## See Also

ST_SymDifference, ST_Intersection, ST_Union

## Name

ST_Intersection — Computes a geometry representing the shared portion of geometries A and B.

## Synopsis

`geometry ST_Intersection(` geometry geomA , geometry geomB , float8 gridSize = -1 `)`;

`geography ST_Intersection(` geography geogA , geography geogB `)`;

## Description

Returns a geometry representing the point-set intersection of two geometries. In other words, that portion of geometry A and geometry B that is shared between the two geometries.

If the geometries have no points in common (i.e. are disjoint) then an empty atomic geometry of appropriate type is returned.

If the optional `gridSize` argument is provided, the inputs are snapped to a grid of the given size, and the result vertices are computed on that same grid. (Requires GEOS-3.9.0 or higher)

ST_Intersection in conjunction with ST_Intersects is useful for clipping geometries such as in bounding box, buffer, or region queries where you only require the portion of a geometry that is inside a country or region of interest.

For geography this is a thin wrapper around the geometry implementation. It first determines the best SRID that fits the bounding box of the 2 geography objects (if geography objects are within one half zone UTM but not same UTM will pick one of those) (favoring UTM or Lambert Azimuthal Equal Area (LAEA) north/south pole, and falling back on mercator in worst case scenario) and then intersection in that best fit planar spatial ref and retransforms back to WGS84 geography.

This function will drop the M coordinate values if present.

If working with 3D geometries, you may want to use SFGCAL based ST_3DIntersection which does a proper 3D intersection for 3D geometries. Although this function works with Z-coordinate, it does an averaging of Z-Coordinate.

Performed by the GEOS module

Enhanced: 3.1.0 accept a gridSize parameter

Requires GEOS >= 3.9.0 to use the gridSize parameter

Changed: 3.0.0 does not depend on SFCGAL.

Availability: 1.5 support for geography data type was introduced.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.18

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

## Examples

    SELECT ST_AsText(ST_Intersection('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry));
     st_astext
    ---------------
    GEOMETRYCOLLECTION EMPTY

    SELECT ST_AsText(ST_Intersection('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry));
     st_astext
    ---------------
    POINT(0 0)

Clip all lines (trails) by country. Here we assume country geom are POLYGON or MULTIPOLYGONS. NOTE: we are only keeping intersections that result in a LINESTRING or MULTILINESTRING because we don't care about trails that just share a point. The dump is needed to expand a geometry collection into individual single MULT* parts. The below is fairly generic and will work for polys, etc. by just changing the where clause.

    select clipped.gid, clipped.f_name, clipped_geom
    from (
             select trails.gid, trails.f_name,
                 (ST_Dump(ST_Intersection(country.geom, trails.geom))).geom clipped_geom
             from country
                  inner join trails on ST_Intersects(country.geom, trails.geom)
         ) as clipped
    where ST_Dimension(clipped.clipped_geom) = 1;

For polys e.g. polygon landmarks, you can also use the sometimes faster hack that buffering anything by 0.0 except a polygon results in an empty geometry collection. (So a geometry collection containing polys, lines and points buffered by 0.0 would only leave the polygons and dissolve the collection shell.)

    select poly.gid,
        ST_Multi(
            ST_Buffer(
                ST_Intersection(country.geom, poly.geom),
                0.0
            )
        ) clipped_geom
    from country
         inner join poly on ST_Intersects(country.geom, poly.geom)
    where not ST_IsEmpty(ST_Buffer(ST_Intersection(country.geom, poly.geom), 0.0));

## Examples: 2.5Dish

Note this is not a true intersection, compare to the same example using ST_3DIntersection.

    select ST_AsText(ST_Intersection(linestring, polygon)) As wkt
    from  ST_GeomFromText('LINESTRING Z (2 2 6,1.5 1.5 7,1 1 8,0.5 0.5 8,0 0 10)') AS linestring
     CROSS JOIN ST_GeomFromText('POLYGON((0 0 8, 0 1 8, 1 1 8, 1 0 8, 0 0 8))') AS polygon;

                   st_astext
    ---------------------------------------
     LINESTRING Z (1 1 8,0.5 0.5 8,0 0 10)

## See Also

ST_3DIntersection, ST_Difference, ST_Union, ST_Dimension, ST_Dump, ST_Force2D, ST_SymDifference, ST_Intersects, ST_Multi

## Name

ST_MemUnion — Aggregate function which unions geometries in a memory-efficent but slower way

## Synopsis

`geometry ST_MemUnion(` geometry set geomfield`)`;

## Description

An aggregate function that unions the input geometries, merging them to produce a result geometry with no overlaps. The output may be a single geometry, a MultiGeometry, or a Geometry Collection.

Produces the same result as ST_Union, but uses less memory and more processor time. This aggregate function works by unioning the geometries incrementally, as opposed to the ST_Union aggregate which first accumulates an array and then unions the contents using a fast algorithm.

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

## Examples

    SELECT id,
           ST_MemUnion(geom) as singlegeom
    FROM sometable f
    GROUP BY id;

## See Also

ST_Union

## Name

ST_Node — Nodes a collection of lines.

## Synopsis

`geometry ST_Node(` geometry geom`)`;

## Description

Returns a (Multi)LineString representing the fully noded version of a collection of linestrings. The noding preserves all of the input nodes, and introduces the least possible number of new nodes. The resulting linework is dissolved (duplicate lines are removed).

This is a good way to create fully-noded linework suitable for use as input to ST_Polygonize.

ST_UnaryUnion can also be used to node and dissolve linework. It provides an option to specify a gridSize, which can provide simpler and more robust output. See also ST_Union for an aggregate variant.

This function supports 3d and will not drop the z-index.

Performed by the GEOS module.

Availability: 2.0.0

Changed: 2.4.0 this function uses GEOSNode internally instead of GEOSUnaryUnion. This may cause the resulting linestrings to have a different order and direction compared to PostGIS < 2.4.

## Examples

Noding a 3D LineString which self-intersects

    SELECT ST_AsText(
            ST_Node('LINESTRINGZ(0 0 0, 10 10 10, 0 10 5, 10 0 3)'::geometry)
        ) As  output;
    output
    -----------
    MULTILINESTRING Z ((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10 0 3))

Noding two LineStrings which share common linework. Note that the result linework is dissolved.

    SELECT ST_AsText(
            ST_Node('MULTILINESTRING ((2 5, 2 1, 7 1), (6 1, 4 1, 2 3, 2 5))'::geometry)
        ) As  output;
    output
    -----------
    MULTILINESTRING((2 5,2 3),(2 3,2 1,4 1),(4 1,2 3),(4 1,6 1),(6 1,7 1))

## See Also

ST_UnaryUnion, ST_Union

## Name

ST_Split — Returns a collection of geometries created by splitting a geometry by another geometry.

## Synopsis

`geometry ST_Split(` geometry input, geometry blade`)`;

## Description

The function supports splitting a LineString by a (Multi)Point, (Multi)LineString or (Multi)Polygon boundary, or a (Multi)Polygon by a LineString. When a (Multi)Polygon is used as as the blade, its linear components (the boundary) are used for splitting the input. The result geometry is always a collection.

This function is in a sense the opposite of ST_Union. Applying ST_Union to the returned collection should theoretically yield the original geometry (although due to numerical rounding this may not be exactly the case).

If the the input and blade do not intersect due to numerical precision issues, the input may not be split as expected. To avoid this situation it may be necessary to snap the input to the blade first, using ST_Snap with a small tolerance.

Availability: 2.0.0 requires GEOS

Enhanced: 2.2.0 support for splitting a line by a multiline, a multipoint or (multi)polygon boundary was introduced.

Enhanced: 2.5.0 support for splitting a polygon by a multiline was introduced.

## Examples

Split a Polygon by a Line.

Before Split | After split

    SELECT ST_AsText( ST_Split(
                    ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50), -- circle
                    ST_MakeLine(ST_Point(10, 10),ST_Point(190, 190)) -- line
        ));

    -- result --
     GEOMETRYCOLLECTION(
                POLYGON((150 90,149.039264020162 80.2454838991936,146.193976625564 70.8658283817455,..),
                POLYGON(..))
    )

Split a MultiLineString by a Point, where the point lies exactly on both LineStrings elements.

Before Split | After split

    SELECT ST_AsText(ST_Split(
        'MULTILINESTRING((10 10, 190 190), (15 15, 30 30, 100 90))',
        ST_Point(30,30))) As split;

    split
    ------
    GEOMETRYCOLLECTION(
        LINESTRING(10 10,30 30),
        LINESTRING(30 30,190 190),
        LINESTRING(15 15,30 30),
        LINESTRING(30 30,100 90)
    )

Split a LineString by a Point, where the point does not lie exactly on the line. Shows using ST_Snap to snap the line to the point to allow it to be split.

    WITH data AS (SELECT
      'LINESTRING(0 0, 100 100)'::geometry AS line,
      'POINT(51 50)':: geometry AS point
    )
    SELECT ST_AsText( ST_Split( ST_Snap(line, point, 1), point)) AS snapped_split,
           ST_AsText( ST_Split(line, point)) AS not_snapped_not_split
           FROM data;

                                snapped_split                            |            not_snapped_not_split
    ---------------------------------------------------------------------+---------------------------------------------
     GEOMETRYCOLLECTION(LINESTRING(0 0,51 50),LINESTRING(51 50,100 100)) | GEOMETRYCOLLECTION(LINESTRING(0 0,100 100))

## See Also

ST_Snap, ST_Union

## Name

ST_Subdivide — Computes a rectilinear subdivision of a geometry.

## Synopsis

`setof geometry ST_Subdivide(` geometry geom, integer max_vertices=256, float8 gridSize = -1`)`;

## Description

Returns a set of geometries that are the result of dividing `geom` into parts using rectilinear lines, with each part containing no more than `max_vertices`.

`max_vertices` must be 5 or more, as 5 points are needed to represent a closed box. `gridSize` can be specified to have clipping work in fixed-precision space (requires GEOS-3.9.0+).

Point-in-polygon and other spatial operations are normally faster for indexed subdivided datasets. Since the bounding boxes for the parts usually cover a smaller area than the original geometry bbox, index queries produce fewer "hit" cases. The "hit" cases are faster because the spatial operations executed by the index recheck process fewer points.

This is a set-returning function (SRF) that return a set of rows containing single geometry values. It can be used in a SELECT list or a FROM clause to produce a result set with one record for each result geometry.

Performed by the GEOS module.

Availability: 2.2.0

Enhanced: 2.5.0 reuses existing points on polygon split, vertex count is lowered from 8 to 5.

Enhanced: 3.1.0 accept a gridSize parameter.

Requires GEOS >= 3.9.0 to use the gridSize parameter

## Examples

Example: Subdivide a polygon into parts with no more than 10 vertices, and assign each part a unique id.

Subdivided to maximum 10 vertices

    SELECT row_number() OVER() As rn, ST_AsText(geom) As wkt
        FROM (SELECT ST_SubDivide(
            'POLYGON((132 10,119 23,85 35,68 29,66 28,49 42,32 56,22 64,32 110,40 119,36 150,
            57 158,75 171,92 182,114 184,132 186,146 178,176 184,179 162,184 141,190 122,
            190 100,185 79,186 56,186 52,178 34,168 18,147 13,132 10))'::geometry,10))  AS f(geom);

     rn │                                                      wkt
    ────┼────────────────────────────────────────────────────────────────────────────────────────────────────────────────
      1 │ POLYGON((119 23,85 35,68 29,66 28,32 56,22 64,29.8260869565217 100,119 100,119 23))
      2 │ POLYGON((132 10,119 23,119 56,186 56,186 52,178 34,168 18,147 13,132 10))
      3 │ POLYGON((119 56,119 100,190 100,185 79,186 56,119 56))
      4 │ POLYGON((29.8260869565217 100,32 110,40 119,36 150,57 158,75 171,92 182,114 184,114 100,29.8260869565217 100))
      5 │ POLYGON((114 184,132 186,146 178,176 184,179 162,184 141,190 122,190 100,114 100,114 184))

Example: Densify a long geography line using ST_Segmentize(geography, distance), and use ST_Subdivide to split the resulting line into sublines of 8 vertices.

The densified and split lines.

    SELECT ST_AsText( ST_Subdivide(
                ST_Segmentize('LINESTRING(0 0, 85 85)'::geography,
                              1200000)::geometry,    8));

    LINESTRING(0 0,0.487578359029357 5.57659056746196,0.984542144675897 11.1527721155093,1.50101059639722 16.7281035483571,1.94532113630331 21.25)
    LINESTRING(1.94532113630331 21.25,2.04869538062779 22.3020741387339,2.64204641967673 27.8740533545155,3.29994062412787 33.443216802941,4.04836719489742 39.0084282520239,4.59890468420694 42.5)
    LINESTRING(4.59890468420694 42.5,4.92498503922732 44.5680389206321,5.98737409390639 50.1195229244701,7.3290919767674 55.6587646879025,8.79638749938413 60.1969505994924)
    LINESTRING(8.79638749938413 60.1969505994924,9.11375579533779 61.1785363177625,11.6558166691368 66.6648504160202,15.642041247655 72.0867690601745,22.8716627200212 77.3609628116894,24.6991785131552 77.8939011989848)
    LINESTRING(24.6991785131552 77.8939011989848,39.4046096622744 82.1822848017636,44.7994523421035 82.5156766227011)
    LINESTRING(44.7994523421035 82.5156766227011,85 85)

Example: Subdivide the complex geometries of a table in-place. The original geometry records are deleted from the source table, and new records for each subdivided result geometry are inserted.

    WITH complex_areas_to_subdivide AS (
        DELETE from polygons_table
        WHERE ST_NPoints(geom) > 255
        RETURNING id, column1, column2, column3, geom
    )
    INSERT INTO polygons_table (fid, column1, column2, column3, geom)
        SELECT fid, column1, column2, column3,
               ST_Subdivide(geom, 255) as geom
        FROM complex_areas_to_subdivide;

Example: Create a new table containing subdivided geometries, retaining the key of the original geometry so that the new table can be joined to the source table. Since ST_Subdivide is a set-returning (table) function that returns a set of single-value rows, this syntax automatically produces a table with one row for each result part.

    CREATE TABLE subdivided_geoms AS
        SELECT pkey, ST_Subdivide(geom) AS geom
        FROM original_geoms;

## See Also

ST_ClipByBox2D, ST_Segmentize, ST_Split, ST_NPoints

## Name

ST_SymDifference — Computes a geometry representing the portions of geometries A and B that do not intersect.

## Synopsis

`geometry ST_SymDifference(` geometry geomA, geometry geomB, float8 gridSize = -1`)`;

## Description

Returns a geometry representing the portions of geonetries A and B that do not intersect. This is equivalent to `ST_Union(A,B) - ST_Intersection(A,B)`. It is called a symmetric difference because `ST_SymDifference(A,B) = ST_SymDifference(B,A)`.

If the optional `gridSize` argument is provided, the inputs are snapped to a grid of the given size, and the result vertices are computed on that same grid. (Requires GEOS-3.9.0 or higher)

Performed by the GEOS module

Enhanced: 3.1.0 accept a gridSize parameter.

Requires GEOS >= 3.9.0 to use the gridSize parameter

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM 3: 5.1.21

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

## Examples

The original linestrings shown together | The symmetric difference of the two linestrings

    --Safe for 2d - symmetric difference of 2 linestrings
    SELECT ST_AsText(
        ST_SymDifference(
            ST_GeomFromText('LINESTRING(50 100, 50 200)'),
            ST_GeomFromText('LINESTRING(50 50, 50 150)')
        )
    );

    st_astext
    ---------
    MULTILINESTRING((50 150,50 200),(50 50,50 100))

    --When used in 3d doesn't quite do the right thing
    SELECT ST_AsEWKT(ST_SymDifference(ST_GeomFromEWKT('LINESTRING(1 2 1, 1 4 2)'),
        ST_GeomFromEWKT('LINESTRING(1 1 3, 1 3 4)')))

    st_astext
    ------------
    MULTILINESTRING((1 3 2.75,1 4 2),(1 1 3,1 2 2.25))

## See Also

ST_Difference, ST_Intersection, ST_Union

## Name

ST_UnaryUnion — Computes the union of the components of a single geometry.

## Synopsis

`geometry ST_UnaryUnion(` geometry geom, float8 gridSize = -1`)`;

## Description

A single-input variant of ST_Union. The input may be a single geometry, a MultiGeometry, or a GeometryCollection. The union is applied to the individual elements of the input.

This function can be used to fix MultiPolygons which are invalid due to overlapping components. However, the input components must each be valid. An invalid input component such as a bow-tie polygon may cause an error. For this reason it may be better to use ST_MakeValid.

Another use of this function is to node and dissolve a collection of linestrings which cross or overlap to make them simple. (ST_Node also does this, but it does not provide the `gridSize` option.)

It is possible to combine ST_UnaryUnion with ST_Collect to fine-tune how many geometries are be unioned at once. This allows trading off between memory usage and compute time, striking a balance between ST_Union and ST_MemUnion.

If the optional `gridSize` argument is provided, the inputs are snapped to a grid of the given size, and the result vertices are computed on that same grid. (Requires GEOS-3.9.0 or higher)

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

Enhanced: 3.1.0 accept a gridSize parameter.

Requires GEOS >= 3.9.0 to use the gridSize parameter

Availability: 2.0.0

## See Also

ST_Union, ST_MemUnion, ST_MakeValid, ST_Collect, ST_Node

## Name

ST_Union — Computes a geometry representing the point-set union of the input geometries.

## Synopsis

`geometry ST_Union(` geometry g1, geometry g2`)`;

`geometry ST_Union(` geometry g1, geometry g2, float8 gridSize`)`;

`geometry ST_Union(` geometry[] g1_array`)`;

`geometry ST_Union(` geometry set g1field`)`;

`geometry ST_Union(` geometry set g1field, float8 gridSize`)`;

## Description

Unions the input geometries, merging geometry to produce a result geometry with no overlaps. The output may be an atomic geometry, a MultiGeometry, or a Geometry Collection. Comes in several variants:

Two-input variant: returns a geometry that is the union of two input geometries. If either input is NULL, then NULL is returned.

Array variant: returns a geometry that is the union of an array of geometries.

Aggregate variant: returns a geometry that is the union of a rowset of geometries. The ST_Union() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do and like most aggregates, it also ignores NULL geometries.

See ST_UnaryUnion for a non-aggregate, single-input variant.

The ST_Union array and set variants use the fast Cascaded Union algorithm described in http://blog.cleverelephant.ca/2009/01/must-faster-unions-in-postgis-14.html

A `gridSize` can be specified to work in fixed-precision space. The inputs are snapped to a grid of the given size, and the result vertices are computed on that same grid. (Requires GEOS-3.9.0 or higher)

ST_Collect may sometimes be used in place of ST_Union, if the result is not required to be non-overlapping. ST_Collect is usually faster than ST_Union because it performs no processing on the collected geometries.

Performed by the GEOS module.

ST_Union creates MultiLineString and does not sew LineStrings into a single LineString. Use ST_LineMerge to sew LineStrings.

NOTE: this function was formerly called GeomUnion(), which was renamed from "Union" because UNION is an SQL reserved word.

Enhanced: 3.1.0 accept a gridSize parameter.

Requires GEOS >= 3.9.0 to use the gridSize parameter

Changed: 3.0.0 does not depend on SFCGAL.

Availability: 1.4.0 - ST_Union was enhanced. ST_Union(geomarray) was introduced and also faster aggregate collection in PostgreSQL.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

Aggregate version is not explicitly defined in OGC SPEC.

This method implements the SQL/MM specification. SQL-MM 3: 5.1.19 the z-index (elevation) when polygons are involved.

This function supports 3d and will not drop the z-index. However, the result is computed using XY only. The result Z values are copied, averaged or interpolated.

## Examples

Aggregate example

    SELECT id,
           ST_Union(geom) as singlegeom
    FROM sometable f
    GROUP BY id;

Non-Aggregate example

    select ST_AsText(ST_Union('POINT(1 2)' :: geometry, 'POINT(-2 3)' :: geometry))

    st_astext
    ----------
    MULTIPOINT(-2 3,1 2)

    select ST_AsText(ST_Union('POINT(1 2)' :: geometry, 'POINT(1 2)' :: geometry))

    st_astext
    ----------
    POINT(1 2)

3D example - sort of supports 3D (and with mixed dimensions!)

    select ST_AsEWKT(ST_Union(geom))
    from (
             select 'POLYGON((-7 4.2,-7.1 4.2,-7.1 4.3, -7 4.2))'::geometry geom
             union all
             select 'POINT(5 5 5)'::geometry geom
             union all
             select 'POINT(-2 3 1)'::geometry geom
             union all
             select 'LINESTRING(5 5 5, 10 10 10)'::geometry geom
         ) as foo;

    st_asewkt
    ---------
    GEOMETRYCOLLECTION(POINT(-2 3 1),LINESTRING(5 5 5,10 10 10),POLYGON((-7 4.2 5,-7.1 4.2 5,-7.1 4.3 5,-7 4.2 5)));

3d example not mixing dimensions

    select ST_AsEWKT(ST_Union(geom))
    from (
             select 'POLYGON((-7 4.2 2,-7.1 4.2 3,-7.1 4.3 2, -7 4.2 2))'::geometry geom
             union all
             select 'POINT(5 5 5)'::geometry geom
             union all
             select 'POINT(-2 3 1)'::geometry geom
             union all
             select 'LINESTRING(5 5 5, 10 10 10)'::geometry geom
         ) as foo;

    st_asewkt
    ---------
    GEOMETRYCOLLECTION(POINT(-2 3 1),LINESTRING(5 5 5,10 10 10),POLYGON((-7 4.2 2,-7.1 4.2 3,-7.1 4.3 2,-7 4.2 2)))

    --Examples using new Array construct
    SELECT ST_Union(ARRAY(SELECT geom FROM sometable));

    SELECT ST_AsText(ST_Union(ARRAY[ST_GeomFromText('LINESTRING(1 2, 3 4)'),
                ST_GeomFromText('LINESTRING(3 4, 4 5)')])) As wktunion;

    --wktunion---
    MULTILINESTRING((3 4,4 5),(1 2,3 4))

## See Also

ST_Collect, ST_UnaryUnion, ST_MemUnion, ST_Intersection, ST_Difference, ST_SymDifference

## 7.14. Geometry Processing

Abstract

These functions compute geometric constructions, or alter geometry size or shape.

## Name

ST_Buffer — Computes a geometry covering all points within a given distance from a geometry.

## Synopsis

`geometry ST_Buffer(` geometry g1, float radius_of_buffer, text buffer_style_parameters = ''`)`;

`geometry ST_Buffer(` geometry g1, float radius_of_buffer, integer num_seg_quarter_circle`)`;

`geography ST_Buffer(` geography g1, float radius_of_buffer, text buffer_style_parameters`)`;

`geography ST_Buffer(` geography g1, float radius_of_buffer, integer num_seg_quarter_circle`)`;

## Description

Computes a POLYGON or MULTIPOLYGON that represents all points whose distance from a geometry/geography is less than or equal to a given distance. A negative distance shrinks the geometry rather than expanding it. A negative distance may shrink a polygon completely, in which case POLYGON EMPTY is returned. For points and lines negative distances always return empty results.

For geometry, the distance is specified in the units of the Spatial Reference System of the geometry. For geography, the distance is specified in meters.

The optional third parameter controls the buffer accuracy and style. The accuracy of circular arcs in the buffer is specified as the number of line segments used to approximate a quarter circle (default is 8). The buffer style can be specified by providing a list of blank-separated key=value pairs as follows:

- 'quad_segs=#' : number of line segments used to approximate a quarter circle (default is 8).

- 'endcap=round|flat|square' : endcap style (defaults to "round"). 'butt' is accepted as a synonym for 'flat'.

- 'join=round|mitre|bevel' : join style (defaults to "round"). 'miter' is accepted as a synonym for 'mitre'.

- 'mitre_limit=#.#' : mitre ratio limit (only affects mitered join style). 'miter_limit' is accepted as a synonym for 'mitre_limit'.

- 'side=both|left|right' : 'left' or 'right' performs a single-sided buffer on the geometry, with the buffered side relative to the direction of the line. This is only applicable to LINESTRING geometry and does not affect POINT or POLYGON geometries. By default end caps are square.

For geography this is a thin wrapper around the geometry implementation. It determines a planar spatial reference system that best fits the bounding box of the geography object (trying UTM, Lambert Azimuthal Equal Area (LAEA) North/South pole, and finally Mercator ). The buffer is computed in the planar space, and then transformed back to WGS84. This may not produce the desired behavior if the input object is much larger than a UTM zone or crosses the dateline

Buffer output is always a valid polygonal geometry. Buffer can handle invalid inputs, so buffering by distance 0 is sometimes used as a way of repairing invalid polygons. ST_MakeValid can also be used for this purpose.

Buffering is sometimes used to perform a within-distance search. For this use case it is more efficient to use ST_DWithin.

This function ignores the Z dimension. It always gives a 2D result even when used on a 3D geometry.

Enhanced: 2.5.0 - ST_Buffer geometry support was enhanced to allow for side buffering specification `side=both|left|right`.

Availability: 1.5 - ST_Buffer was enhanced to support different endcaps and join types. These are useful for example to convert road linestrings into polygon roads with flat or square edges instead of rounded edges. Thin wrapper for geography was added.

Performed by the GEOS module.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1.30

## Examples

quad_segs=8 (default)
    SELECT ST_Buffer(
     ST_GeomFromText('POINT(100 90)'),
     50, 'quad_segs=8');
| quad_segs=2 (lame)
    SELECT ST_Buffer(
     ST_GeomFromText('POINT(100 90)'),
     50, 'quad_segs=2');
endcap=round join=round (default)
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=round join=round');
| endcap=square
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=square join=round');
| endcap=flat
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'endcap=flat join=round');
join=bevel
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=bevel');
| join=mitre mitre_limit=5.0 (default mitre limit)
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=mitre mitre_limit=5.0');
| join=mitre mitre_limit=1
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'join=mitre mitre_limit=1.0');
side=left
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'side=left');
| side=right
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'side=right');
| side=left join=mitre
    SELECT ST_Buffer(
     ST_GeomFromText(
      'LINESTRING(50 50,150 150,150 50)'
     ), 10, 'side=left join=mitre');
right-hand-winding, polygon boundary side=left
    SELECT ST_Buffer(
    ST_ForceRHR(
    ST_Boundary(
     ST_GeomFromText(
    'POLYGON ((50 50, 50 150, 150 150, 150 50, 50 50))'))),
     ), 20, 'side=left');
| right-hand-winding, polygon boundary side=right
    SELECT ST_Buffer(
    ST_ForceRHR(
    ST_Boundary(
     ST_GeomFromText(
    'POLYGON ((50 50, 50 150, 150 150, 150 50, 50 50))'))
    ), 20,'side=right')

    --A buffered point approximates a circle
    -- A buffered point forcing approximation of (see diagram)
    -- 2 points per quarter circle is poly with 8 sides (see diagram)
    SELECT ST_NPoints(ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50)) As promisingcircle_pcount,
    ST_NPoints(ST_Buffer(ST_GeomFromText('POINT(100 90)'), 50, 2)) As lamecircle_pcount;

    promisingcircle_pcount | lamecircle_pcount
    ------------------------+-------------------
                 33 |                9

    --A lighter but lamer circle
    -- only 2 points per quarter circle is an octagon
    --Below is a 100 meter octagon
    -- Note coordinates are in NAD 83 long lat which we transform
    to Mass state plane meter and then buffer to get measurements in meters;
    SELECT ST_AsText(ST_Buffer(
    ST_Transform(
    ST_SetSRID(ST_Point(-71.063526, 42.35785),4269), 26986)
    ,100,2)) As octagon;
    ----------------------
    POLYGON((236057.59057465 900908.759918696,236028.301252769 900838.049240578,235
    957.59057465 900808.759918696,235886.879896532 900838.049240578,235857.59057465
    900908.759918696,235886.879896532 900979.470596815,235957.59057465 901008.759918
    696,236028.301252769 900979.470596815,236057.59057465 900908.759918696))

## See Also

ST_Collect, ST_DWithin, ST_SetSRID, ST_Transform, ST_Union, ST_MakeValid

## Name

ST_BuildArea — Creates a polygonal geometry formed by the linework of a geometry.

## Synopsis

`geometry ST_BuildArea(` geometry geom`)`;

## Description

Creates an areal geometry formed by the constituent linework of the input geometry. The input can be a LineString, MultiLineString, Polygon, MultiPolygon or a GeometryCollection. The result is a Polygon or MultiPolygon, depending on input. If the input linework does not form polygons, NULL is returned.

Unlike ST_MakePolygon, this function accepts rings formed by multiple lines, and can form any number of polygons.

This function converts inner rings into holes. To turn inner rings into polygons as well, use ST_Polygonize.

Input linework must be correctly noded for this function to work properly. ST_Node can be used to node lines. If the input linework crosses, this function will produce invalid polygons. ST_MakeValid can be used to ensure the output is valid.

Availability: 1.1.0

## Examples

Input lines | Area result

    WITH data(geom) AS (VALUES
       ('LINESTRING (180 40, 30 20, 20 90)'::geometry)
      ,('LINESTRING (180 40, 160 160)'::geometry)
      ,('LINESTRING (160 160, 80 190, 80 120, 20 90)'::geometry)
      ,('LINESTRING (80 60, 120 130, 150 80)'::geometry)
      ,('LINESTRING (80 60, 150 80)'::geometry)
    )
    SELECT ST_AsText( ST_BuildArea( ST_Collect( geom )))
        FROM data;

    ------------------------------------------------------------------------------------------
    POLYGON((180 40,30 20,20 90,80 120,80 190,160 160,180 40),(150 80,120 130,80 60,150 80))

Create a donut from two circular polygons

    SELECT ST_BuildArea(ST_Collect(inring,outring))
    FROM (SELECT
        ST_Buffer('POINT(100 90)', 25) As inring,
        ST_Buffer('POINT(100 90)', 50) As outring) As t;

## See Also

ST_Collect, ST_MakePolygon, ST_MakeValid, ST_Node, ST_Polygonize, ST_BdPolyFromText, ST_BdMPolyFromText (wrappers to this function with standard OGC interface)

## Name

ST_Centroid — Returns the geometric center of a geometry.

## Synopsis

`geometry ST_Centroid(` geometry g1`)`;

`geography ST_Centroid(` geography g1, boolean use_spheroid = true`)`;

## Description

Computes a point which is the geometric center of mass of a geometry. For [`MULTI`]`POINT`s, the centroid is the arithmetic mean of the input coordinates. For [`MULTI`]`LINESTRING`s, the centroid is computed using the weighted length of each line segment. For [`MULTI`]`POLYGON`s, the centroid is computed in terms of area. If an empty geometry is supplied, an empty `GEOMETRYCOLLECTION` is returned. If `NULL` is supplied, `NULL` is returned. If `CIRCULARSTRING` or `COMPOUNDCURVE` are supplied, they are converted to linestring with CurveToLine first, then same than for `LINESTRING`

For mixed-dimension input, the result is equal to the centroid of the component Geometries of highest dimension (since the lower-dimension geometries contribute zero "weight" to the centroid).

Note that for polygonal geometries the centroid does not necessarily lie in the interior of the polygon. For example, see the diagram below of the centroid of a C-shaped polygon. To construct a point guaranteed to lie in the interior of a polygon use ST_PointOnSurface.

New in 2.3.0 : supports `CIRCULARSTRING` and `COMPOUNDCURVE` (using CurveToLine)

Availability: 2.4.0 support for geography was introduced.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 8.1.4, 9.5.5

## Examples

In the following illustrations the red dot is the centroid of the source geometry.

Centroid of a `MULTIPOINT` | Centroid of a `LINESTRING`
Centroid of a `POLYGON` | Centroid of a `GEOMETRYCOLLECTION`

    SELECT ST_AsText(ST_Centroid('MULTIPOINT ( -1 0, -1 2, -1 3, -1 4, -1 7, 0 1, 0 3, 1 1, 2 0, 6 0, 7 8, 9 8, 10 6 )'));
                    st_astext
    ------------------------------------------
     POINT(2.30769230769231 3.30769230769231)
    (1 row)

    SELECT ST_AsText(ST_centroid(g))
    FROM  ST_GeomFromText('CIRCULARSTRING(0 2, -1 1,0 0, 0.5 0, 1 0, 2 1, 1 2, 0.5 2, 0 2)')  AS g ;
    ------------------------------------------
    POINT(0.5 1)

    SELECT ST_AsText(ST_centroid(g))
    FROM  ST_GeomFromText('COMPOUNDCURVE(CIRCULARSTRING(0 2, -1 1,0 0),(0 0, 0.5 0, 1 0),CIRCULARSTRING( 1 0, 2 1, 1 2),(1 2, 0.5 2, 0 2))' ) AS g;
    ------------------------------------------
    POINT(0.5 1)

## See Also

ST_PointOnSurface, ST_GeometricMedian

## Name

ST_ChaikinSmoothing — Returns a smoothed version of a geometry, using the Chaikin algorithm

## Synopsis

`geometry ST_ChaikinSmoothing(` geometry geom, integer nIterations = 1, boolean preserveEndPoints = false`)`;

## Description

Smoothes a linear or polygonal geometry using Chaikin's algorithm. The degree of smoothing is controlled by the `nIterations` parameter. On each iteration, each interior vertex is replaced by two vertices located at 1/4 of the length of the line segments before and after the vertex. A reasonable degree of smoothing is provided by 3 iterations; the maximum is limited to 5.

If `preserveEndPoints` is true, the endpoints of Polygon rings are not smoothed. The endpoints of LineStrings are always preserved.

The number of vertices doubles with each iteration, so the result geometry may have many more points than the input. To reduce the number of points use a simplification function on the result (see ST_Simplify, ST_SimplifyPreserveTopology and ST_SimplifyVW).

The result has interpolated values for the Z and M dimensions when present.

This function supports 3d and will not drop the z-index.

Availability: 2.5.0

## Examples

Smoothing a triangle:

    SELECT ST_AsText(ST_ChaikinSmoothing(geom)) smoothed
    FROM (SELECT  'POLYGON((0 0, 8 8, 0 16, 0 0))'::geometry geom) AS foo;

                     smoothed
    ───────────────────────────────────────────
     POLYGON((2 2,6 6,6 10,2 14,0 12,0 4,2 2))

Smoothing a Polygon using 1, 2 and 3 iterations:

nIterations = 1 | nIterations = 2 | nIterations = 3

    SELECT ST_ChaikinSmoothing(
                'POLYGON ((20 20, 60 90, 10 150, 100 190, 190 160, 130 120, 190 50, 140 70, 120 10, 90 60, 20 20))',
                generate_series(1, 3) );

Smoothing a LineString using 1, 2 and 3 iterations:

nIterations = 1 | nIterations = 2 | nIterations = 3

    SELECT ST_ChaikinSmoothing(
                'LINESTRING (10 140, 80 130, 100 190, 190 150, 140 20, 120 120, 50 30, 30 100)',
                generate_series(1, 3) );

## See Also

ST_Simplify, ST_SimplifyPreserveTopology, ST_SimplifyVW

## Name

ST_ConcaveHull — Computes a possibly concave geometry that contains all input geometry vertices

## Synopsis

`geometry ST_ConcaveHull(` geometry param_geom, float param_pctconvex, boolean param_allow_holes = false`)`;

## Description

A concave hull is a (usually) concave geometry which contains the input, and whose vertices are a subset of the input vertices. In the general case the concave hull is a Polygon. The concave hull of two or more collinear points is a two-point LineString. The concave hull of one or more identical points is a Point. The polygon will not contain holes unless the optional `param_allow_holes` argument is specified as true.

One can think of a concave hull as "shrink-wrapping" a set of points. This is different to the convex hull, which is more like wrapping a rubber band around the points. A concave hull generally has a smaller area and represents a more natural boundary for the input points.

The `param_pctconvex` controls the concaveness of the computed hull. A value of 1 produces the convex hull. Values between 1 and 0 produce hulls of increasing concaveness. A value of 0 produces a hull with maximum concaveness (but still a single polygon). Choosing a suitable value depends on the nature of the input data, but often values between 0.3 and 0.1 produce reasonable results.

Technically, the `param_pctconvex` determines a length as a fraction of the difference between the longest and shortest edges in the Delaunay Triangulation of the input points. Edges longer than this length are "eroded" from the triangulation. The triangles remaining form the concave hull.

For point and linear inputs, the hull will enclose all the points of the inputs. For polygonal inputs, the hull will enclose all the points of the input and also all the areas covered by the input. If you want a point-wise hull of a polygonal input, convert it to points first using ST_Points.

This is not an aggregate function. To compute the concave hull of a set of geometries use ST_Collect (e.g. `ST_ConcaveHull( ST_Collect( geom ), 0.80)`.

Availability: 2.0.0

Enhanced: 3.3.0, GEOS native implementation enabled for GEOS 3.11+

## Examples

Concave Hull of a MultiPoint

    SELECT ST_AsText( ST_ConcaveHull(
            'MULTIPOINT ((10 72), (53 76), (56 66), (63 58), (71 51), (81 48), (91 46), (101 45), (111 46), (121 47), (131 50), (140 55), (145 64), (144 74), (135 80), (125 83), (115 85), (105 87), (95 89), (85 91), (75 93), (65 95), (55 98), (45 102), (37 107), (29 114), (22 122), (19 132), (18 142), (21 151), (27 160), (35 167), (44 172), (54 175), (64 178), (74 180), (84 181), (94 181), (104 181), (114 181), (124 181), (134 179), (144 177), (153 173), (162 168), (171 162), (177 154), (182 145), (184 135), (139 132), (136 142), (128 149), (119 153), (109 155), (99 155), (89 155), (79 153), (69 150), (61 144), (63 134), (72 128), (82 125), (92 123), (102 121), (112 119), (122 118), (132 116), (142 113), (151 110), (161 106), (170 102), (178 96), (185 88), (189 78), (190 68), (189 58), (185 49), (179 41), (171 34), (162 29), (153 25), (143 23), (133 21), (123 19), (113 19), (102 19), (92 19), (82 19), (72 21), (62 22), (52 25), (43 29), (33 34), (25 41), (19 49), (14 58), (21 73), (31 74), (42 74), (173 134), (161 134), (150 133), (97 104), (52 117), (157 156), (94 171), (112 106), (169 73), (58 165), (149 40), (70 33), (147 157), (48 153), (140 96), (47 129), (173 55), (144 86), (159 67), (150 146), (38 136), (111 170), (124 94), (26 59), (60 41), (71 162), (41 64), (88 110), (122 34), (151 97), (157 56), (39 146), (88 33), (159 45), (47 56), (138 40), (129 165), (33 48), (106 31), (169 147), (37 122), (71 109), (163 89), (37 156), (82 170), (180 72), (29 142), (46 41), (59 155), (124 106), (157 80), (175 82), (56 50), (62 116), (113 95), (144 167))',
             0.1 ) );
    ---st_astext--
    POLYGON ((18 142, 21 151, 27 160, 35 167, 44 172, 54 175, 64 178, 74 180, 84 181, 94 181, 104 181, 114 181, 124 181, 134 179, 144 177, 153 173, 162 168, 171 162, 177 154, 182 145, 184 135, 173 134, 161 134, 150 133, 139 132, 136 142, 128 149, 119 153, 109 155, 99 155, 89 155, 79 153, 69 150, 61 144, 63 134, 72 128, 82 125, 92 123, 102 121, 112 119, 122 118, 132 116, 142 113, 151 110, 161 106, 170 102, 178 96, 185 88, 189 78, 190 68, 189 58, 185 49, 179 41, 171 34, 162 29, 153 25, 143 23, 133 21, 123 19, 113 19, 102 19, 92 19, 82 19, 72 21, 62 22, 52 25, 43 29, 33 34, 25 41, 19 49, 14 58, 10 72, 21 73, 31 74, 42 74, 53 76, 56 66, 63 58, 71 51, 81 48, 91 46, 101 45, 111 46, 121 47, 131 50, 140 55, 145 64, 144 74, 135 80, 125 83, 115 85, 105 87, 95 89, 85 91, 75 93, 65 95, 55 98, 45 102, 37 107, 29 114, 22 122, 19 132, 18 142))

Concave Hull of a MultiPoint, allowing holes

    SELECT ST_AsText( ST_ConcaveHull(
            'MULTIPOINT ((132 64), (114 64), (99 64), (81 64), (63 64), (57 49), (52 36), (46 20), (37 20), (26 20), (32 36), (39 55), (43 69), (50 84), (57 100), (63 118), (68 133), (74 149), (81 164), (88 180), (101 180), (112 180), (119 164), (126 149), (132 131), (139 113), (143 100), (150 84), (157 69), (163 51), (168 36), (174 20), (163 20), (150 20), (143 36), (139 49), (132 64), (99 151), (92 138), (88 124), (81 109), (74 93), (70 82), (83 82), (99 82), (112 82), (126 82), (121 96), (114 109), (110 122), (103 138), (99 151), (34 27), (43 31), (48 44), (46 58), (52 73), (63 73), (61 84), (72 71), (90 69), (101 76), (123 71), (141 62), (166 27), (150 33), (159 36), (146 44), (154 53), (152 62), (146 73), (134 76), (143 82), (141 91), (130 98), (126 104), (132 113), (128 127), (117 122), (112 133), (119 144), (108 147), (119 153), (110 171), (103 164), (92 171), (86 160), (88 142), (79 140), (72 124), (83 131), (79 118), (68 113), (63 102), (68 93), (35 45))',
             0.15, true ) );
    ---st_astext--
    POLYGON ((43 69, 50 84, 57 100, 63 118, 68 133, 74 149, 81 164, 88 180, 101 180, 112 180, 119 164, 126 149, 132 131, 139 113, 143 100, 150 84, 157 69, 163 51, 168 36, 174 20, 163 20, 150 20, 143 36, 139 49, 132 64, 114 64, 99 64, 81 64, 63 64, 57 49, 52 36, 46 20, 37 20, 26 20, 32 36, 35 45, 39 55, 43 69), (88 124, 81 109, 74 93, 83 82, 99 82, 112 82, 121 96, 114 109, 110 122, 103 138, 92 138, 88 124))

`polygon_hull` | `points_hull`

Comparing a concave hull of a Polygon to the concave hull of the constituent points. The hull respects the boundary of the polygon, whereas the points-based hull does not.

    WITH data(geom) AS (VALUES
       ('POLYGON ((10 90, 39 85, 61 79, 50 90, 80 80, 95 55, 25 60, 90 45, 70 16, 63 38, 60 10, 50 30, 43 27, 30 10, 20 20, 10 90))'::geometry)
    )
    SELECT  ST_ConcaveHull( geom,            0.1) AS polygon_hull,
            ST_ConcaveHull( ST_Points(geom), 0.1) AS points_hull
        FROM data;

Using with ST_Collect to compute the concave hull of a geometry set.

    -- Compute estimate of infected area based on point observations
    SELECT disease_type,
        ST_ConcaveHull( ST_Collect(obs_pnt), 0.3 ) AS geom
      FROM disease_obs
      GROUP BY disease_type;

## See Also

ST_ConvexHull, ST_Collect, ST_AlphaShape, ST_OptimalAlphaShape

## Name

ST_ConvexHull — Computes the convex hull of a geometry.

## Synopsis

`geometry ST_ConvexHull(` geometry geomA`)`;

## Description

Computes the convex hull of a geometry. The convex hull is the smallest convex geometry that encloses all geometries in the input.

One can think of the convex hull as the geometry obtained by wrapping an rubber band around a set of geometries. This is different from a concave hull which is analogous to "shrink-wrapping" the geometries. A convex hull is often used to determine an affected area based on a set of point observations.

In the general case the convex hull is a Polygon. The convex hull of two or more collinear points is a two-point LineString. The convex hull of one or more identical points is a Point.

This is not an aggregate function. To compute the convex hull of a set of geometries, use ST_Collect to aggregate them into a geometry collection (e.g. `ST_ConvexHull(ST_Collect(geom))`.

Performed by the GEOS module

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s2.1.1.3

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1.16

This function supports 3d and will not drop the z-index.

## Examples

Convex Hull of a MultiLinestring and a MultiPoint

    SELECT ST_AsText(ST_ConvexHull(
        ST_Collect(
            ST_GeomFromText('MULTILINESTRING((100 190,10 8),(150 10, 20 30))'),
                ST_GeomFromText('MULTIPOINT(50 5, 150 30, 50 10, 10 10)')
                )) );
    ---st_astext--
    POLYGON((50 5,10 8,10 10,100 190,150 30,150 10,50 5))

Using with ST_Collect to compute the convex hulls of geometry sets.

    --Get estimate of infected area based on point observations
    SELECT d.disease_type,
        ST_ConvexHull(ST_Collect(d.geom)) As geom
        FROM disease_obs As d
        GROUP BY d.disease_type;

## See Also

ST_Collect, ST_ConcaveHull, ST_MinimumBoundingCircle

## Name

ST_DelaunayTriangles — Returns the Delaunay triangulation of the vertices of a geometry.

## Synopsis

`geometry ST_DelaunayTriangles(` geometry g1, float tolerance = 0.0, int4 flags = 0`)`;

## Description

Computes the Delaunay triangulation of the vertices of the input geometry. The optional `tolerance` can be used to snap nearby input vertices together, which improves robustness in some situations. The result geometry is bounded by the convex hull of the input vertices. The result geometry representation is determined by the `flags` code:

- `0` - a GEOMETRYCOLLECTION of triangular POLYGONs (default)

- `1` - a MULTILINESTRING of the edges of the triangulation

- `2` - A TIN of the triangulation

Performed by the GEOS module.

Availability: 2.1.0

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Original polygons
    our original geometry
        ST_Union(ST_GeomFromText('POLYGON((175 150, 20 40,
                50 60, 125 100, 175 150))'),
            ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
            )
ST_DelaunayTriangles of 2 polygons: delaunay triangle polygons each triangle themed in different color
    geometries overlaid multilinestring triangles

    SELECT
        ST_DelaunayTriangles(
            ST_Union(ST_GeomFromText('POLYGON((175 150, 20 40,
                50 60, 125 100, 175 150))'),
            ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
            ))
         As  dtriag;
-- delaunay triangles as multilinestring
    SELECT
        ST_DelaunayTriangles(
            ST_Union(ST_GeomFromText('POLYGON((175 150, 20 40,
                50 60, 125 100, 175 150))'),
            ST_Buffer(ST_GeomFromText('POINT(110 170)'), 20)
            ),0.001,1)
         As  dtriag;
-- delaunay triangles of 45 points as 55 triangle polygons
    this produces a table of 42 points that form an L shape

    SELECT (ST_DumpPoints(ST_GeomFromText(
    'MULTIPOINT(14 14,34 14,54 14,74 14,94 14,114 14,134 14,
    150 14,154 14,154 6,134 6,114 6,94 6,74 6,54 6,34 6,
    14 6,10 6,8 6,7 7,6 8,6 10,6 30,6 50,6 70,6 90,6 110,6 130,
    6 150,6 170,6 190,6 194,14 194,14 174,14 154,14 134,14 114,
    14 94,14 74,14 54,14 34,14 14)'))).geom
        INTO TABLE l_shape;

    output as individual polygon triangles

    SELECT ST_AsText((ST_Dump(geom)).geom) As wkt
    FROM ( SELECT ST_DelaunayTriangles(ST_Collect(geom)) As geom
    FROM l_shape) As foo;

    wkt

    POLYGON((6 194,6 190,14 194,6 194))
    POLYGON((14 194,6 190,14 174,14 194))
    POLYGON((14 194,14 174,154 14,14 194))
    POLYGON((154 14,14 174,14 154,154 14))
    POLYGON((154 14,14 154,150 14,154 14))
    POLYGON((154 14,150 14,154 6,154 14))

Example using vertices with Z values.

    3D multipoint

    SELECT ST_AsText(ST_DelaunayTriangles(ST_GeomFromText(
             'MULTIPOINT Z(14 14 10, 150 14 100,34 6 25, 20 10 150)'))) As wkt;

    wkt

    GEOMETRYCOLLECTION Z (POLYGON Z ((14 14 10,20 10 150,34 6 25,14 14 10))
     ,POLYGON Z ((14 14 10,34 6 25,150 14 100,14 14 10)))

## See Also

ST_VoronoiPolygons, ST_TriangulatePolygon, ST_ConstrainedDelaunayTriangles, ST_VoronoiLines, ST_ConvexHull

## Name

ST_FilterByM — Removes vertices based on their M value

## Synopsis

`geometry ST_FilterByM(` geometry geom, double precision min, double precision max = null, boolean returnM = false`)`;

## Description

Filters out vertex points based on their M-value. Returns a geometry with only vertex points that have a M-value larger or equal to the min value and smaller or equal to the max value. If max-value argument is left out only min value is considered. If fourth argument is left out the m-value will not be in the resulting geometry. If resulting geometry have too few vertex points left for its geometry type an empty geometry will be returned. In a geometry collection geometries without enough points will just be left out silently.

This function is mainly intended to be used in conjunction with ST_SetEffectiveArea. ST_EffectiveArea sets the effective area of a vertex in its m-value. With ST_FilterByM it then is possible to get a simplified version of the geometry without any calculations, just by filtering

There is a difference in what ST_SimplifyVW returns when not enough points meet the criteria compared to ST_FilterByM. ST_SimplifyVW returns the geometry with enough points while ST_FilterByM returns an empty geometry

Note that the returned geometry might be invalid

This function returns all dimensions, including the Z and M values

Availability: 2.5.0

## Examples

A linestring is filtered

    SELECT ST_AsText(ST_FilterByM(geom,30)) simplified
    FROM (SELECT  ST_SetEffectiveArea('LINESTRING(5 2, 3 8, 6 20, 7 25, 10 10)'::geometry) geom) As foo;

    result

             simplified
    ----------------------------
     LINESTRING(5 2,7 25,10 10)

## See Also

ST_SetEffectiveArea, ST_SimplifyVW

## Name

ST_GeneratePoints — Generates a multipoint of random points contained in a Polygon or MultiPolygon.

## Synopsis

`geometry ST_GeneratePoints(` geometry g, integer npoints, integer seed = 0`)`;

## Description

ST_GeneratePoints generates a multipoint consisting of a given number of pseudo-random points which lie within the input area. The optional `seed` is used to regenerate a deterministic sequence of points, and must be greater than zero.

Availability: 2.3.0

Enhanced: 3.0.0, added seed parameter

## Examples

Generated a multipoint consisting of 12 Points overlaid on top of original polygon using a random seed value 1996

    SELECT ST_GeneratePoints(geom, 12, 1996)
    FROM (
        SELECT ST_Buffer(
            ST_GeomFromText(
            'LINESTRING(50 50,150 150,150 50)'),
            10, 'endcap=round join=round') AS geom
    ) AS s;

Given a table of polygons s, return 12 individual points per polygon. Results will be different each time you run.

    SELECT s.id, dp.path[1] AS pt_id, dp.geom
    FROM s, ST_DumpPoints(ST_GeneratePoints(s.geom,12)) AS dp;

## See Also

ST_DumpPoints

## Name

ST_GeometricMedian — Returns the geometric median of a MultiPoint.

## Synopsis

`geometry ST_GeometricMedian (` geometry geom, float8 tolerance = NULL, int max_iter = 10000, boolean fail_if_not_converged = false`)`;

## Description

Computes the approximate geometric median of a MultiPoint geometry using the Weiszfeld algorithm. The geometric median is the point minimizing the sum of distances to the input points. It provides a centrality measure that is less sensitive to outlier points than the centroid (center of mass).

The algorithm iterates until the distance change between successive iterations is less than the supplied `tolerance` parameter. If this condition has not been met after `max_iterations` iterations, the function produces an error and exits, unless `fail_if_not_converged` is set to `false` (the default).

If a `tolerance` argument is not provided, the tolerance value is calculated based on the extent of the input geometry.

If present, the input point M values are interpreted as their relative weights.

Availability: 2.3.0

Enhanced: 2.5.0 Added support for M as weight of points.

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

Comparison of the geometric median (red) and centroid (turquoise) of a MultiPoint.

    WITH test AS (
    SELECT 'MULTIPOINT((10 10), (10 40), (40 10), (190 190))'::geometry geom)
    SELECT
      ST_AsText(ST_Centroid(geom)) centroid,
      ST_AsText(ST_GeometricMedian(geom)) median
    FROM test;

          centroid      |                 median
    --------------------+----------------------------------------
       POINT(62.5 62.5) | POINT(25.01778421249728 25.01778421249728)
    (1 row)

## See Also

ST_Centroid

## Name

ST_LineMerge — Return the lines formed by sewing together a MultiLineString.

## Synopsis

`geometry ST_LineMerge(` geometry amultilinestring`)`;

`geometry ST_LineMerge(` geometry amultilinestring, boolean directed`)`;

## Description

Returns a LineString or MultiLineString formed by joining together the line elements of a MultiLineString. Lines are joined at their endpoints at 2-way intersections. Lines are not joined across intersections of 3-way or greater degree.

If directed is TRUE, then ST_LineMerge will not change point order within LineStrings, so lines with opposite directions will not be merged

Only use with MultiLineString/LineStrings. Other geometry types return an empty GeometryCollection

Performed by the GEOS module.

Enhanced: 3.3.0 accept a directed parameter.

Requires GEOS >= 3.11.0 to use the directed parameter.

Availability: 1.1.0

This function strips the M dimension.

## Examples

Merging lines with different orientation.

    SELECT ST_AsText(ST_LineMerge(
    'MULTILINESTRING((10 160, 60 120), (120 140, 60 120), (120 140, 180 120))'
    		));
    --------------------------------------------
     LINESTRING(10 160,60 120,120 140,180 120)

Lines are not merged across intersections with degree > 2.

    SELECT ST_AsText(ST_LineMerge(
    'MULTILINESTRING((10 160, 60 120), (120 140, 60 120), (120 140, 180 120), (100 180, 120 140))'
    		));
    --------------------------------------------
     MULTILINESTRING((10 160,60 120,120 140),(100 180,120 140),(120 140,180 120))

If merging is not possible due to non-touching lines, the original MultiLineString is returned.

    SELECT ST_AsText(ST_LineMerge(
    'MULTILINESTRING((-29 -27,-30 -29.7,-36 -31,-45 -33),(-45.2 -33.2,-46 -32))'
    ));
    ----------------
    MULTILINESTRING((-45.2 -33.2,-46 -32),(-29 -27,-30 -29.7,-36 -31,-45 -33))

Lines with opposite directions are not merged if directed = TRUE.

    SELECT ST_AsText(ST_LineMerge(
    'MULTILINESTRING((60 30, 10 70), (120 50, 60 30), (120 50, 180 30))',
    TRUE));
    -------------------------------------------------------
     MULTILINESTRING((120 50,60 30,10 70),(120 50,180 30))

Example showing Z-dimension handling.

    SELECT ST_AsText(ST_LineMerge(
          'MULTILINESTRING((-29 -27 11,-30 -29.7 10,-36 -31 5,-45 -33 6), (-29 -27 12,-30 -29.7 5), (-45 -33 1,-46 -32 11))'
            ));
    --------------------------------------------------------------------------------------------------
    LINESTRING Z (-30 -29.7 5,-29 -27 11,-30 -29.7 10,-36 -31 5,-45 -33 1,-46 -32 11)

## See Also

ST_Segmentize, ST_LineSubstring

## Name

ST_MaximumInscribedCircle — Computes the largest circle contained within a geometry.

## Synopsis

`(geometry, geometry, double precision) ST_MaximumInscribedCircle(` geometry geom`)`;

## Description

Finds the largest circle that is contained within a (multi)polygon, or which does not overlap any lines and points. Returns a record with fields:

- `center` - center point of the circle

- `nearest` - a point on the geometry nearest to the center

- `radius` - radius of the circle

For polygonal inputs, the circle is inscribed within the boundary rings, using the internal rings as boundaries. For linear and point inputs, the circle is inscribed within the convex hull of the input, using the input lines and points as further boundaries.

Availability: 3.1.0.

Requires GEOS >= 3.9.0.

## Examples

Maximum inscribed circle of a polygon. Center, nearest point, and radius are returned.

    SELECT radius, ST_AsText(center) AS center, ST_AsText(nearest) AS nearest
        FROM ST_MaximumInscribedCircle(
            'POLYGON ((40 180, 110 160, 180 180, 180 120, 140 90, 160 40, 80 10, 70 40, 20 50, 40 180),
            (60 140, 50 90, 90 140, 60 140))');

         radius      |           center           |    nearest
    -----------------+----------------------------+---------------
     45.165845650018 | POINT(96.953125 76.328125) | POINT(140 90)

Maximum inscribed circle of a multi-linestring. Center, nearest point, and radius are returned.

## See Also

ST_MinimumBoundingRadius, ST_LargestEmptyCircle

## Name

ST_LargestEmptyCircle — Computes the largest circle not overlapping a geometry.

## Synopsis

`(geometry, geometry, double precision) ST_LargestEmptyCircle(` geometry geom, double precision tolerance=0.0, geometry boundary=POINT EMPTY`)`;

## Description

Finds the largest circle which does not overlap a set of point and line obstacles. (Polygonal geometries may be included as obstacles, but only their boundary lines are used.) The center of the circle is constrained to lie inside a polygonal boundary, which by default is the convex hull of the input geometry. The circle center is the point in the interior of the boundary which has the farthest distance from the obstacles. The circle itself is provided by the center point and a nearest point lying on an obstacle determining the circle radius.

The circle center is determined to a given accuracy specified by a distance tolerance, using an iterative algorithm. If the accuracy distance is not specified a reasonable default is used.

Returns a record with fields:

- `center` - center point of the circle

- `nearest` - a point on the geometry nearest to the center

- `radius` - radius of the circle

To find the largest empty circle in the interior of a polygon, see ST_MaximumInscribedCircle.

Availability: 3.4.0.

Requires GEOS >= 3.9.0.

## Examples

    SELECT radius,
          center,
          nearest
      FROM ST_LargestEmptyCircle(
            'MULTILINESTRING (
              (10 100, 60 180, 130 150, 190 160),
              (20 50, 70 70, 90 20, 110 40),
              (160 30, 100 100, 180 100))');

Largest Empty Circle within a set of lines.

    SELECT radius,
           center,
           nearest
      FROM ST_LargestEmptyCircle(
             ST_Collect(
               'MULTIPOINT ((70 50), (60 130), (130 150), (80 90))'::geometry,
               'POLYGON ((90 190, 10 100, 60 10, 190 40, 120 100, 190 180, 90 190))'::geometry),
               0,
             'POLYGON ((90 190, 10 100, 60 10, 190 40, 120 100, 190 180, 90 190))'::geometry
           );

Largest Empty Circle within a set of points, constrained to lie in a polygon. The constraint polygon boundary must be included as an obstacle, as well as specified as the constraint for the circle center.

## See Also

ST_MinimumBoundingRadius

## Name

ST_MinimumBoundingCircle — Returns the smallest circle polygon that contains a geometry.

## Synopsis

`geometry ST_MinimumBoundingCircle(` geometry geomA, integer num_segs_per_qt_circ=48`)`;

## Description

Returns the smallest circle polygon that contains a geometry.

The bounding circle is approximated by a polygon with a default of 48 segments per quarter circle. Because the polygon is an approximation of the minimum bounding circle, some points in the input geometry may not be contained within the polygon. The approximation can be improved by increasing the number of segments. For applications where an approximation is not suitable ST_MinimumBoundingRadius may be used.

Use with ST_Collect to get the minimum bounding circle of a set of geometries.

To compute two points lying on the minimum circle (the "maximum diameter") use ST_LongestLine.

The ratio of the area of a polygon divided by the area of its Minimum Bounding Circle is referred to as the Reock compactness score.

Performed by the GEOS module.

Availability: 1.4.0

## Examples

    SELECT d.disease_type,
        ST_MinimumBoundingCircle(ST_Collect(d.geom)) As geom
        FROM disease_obs As d
        GROUP BY d.disease_type;

Minimum bounding circle of a point and linestring. Using 8 segs to approximate a quarter circle

    SELECT ST_AsText(ST_MinimumBoundingCircle(
            ST_Collect(
                ST_GeomFromText('LINESTRING(55 75,125 150)'),
                    ST_Point(20, 80)), 8
                    )) As wktmbc;
    wktmbc
    -----------
    POLYGON((135.59714732062 115,134.384753327498 102.690357210921,130.79416296937 90.8537670908995,124.963360620072 79.9451031602111,117.116420743937 70.3835792560632,107.554896839789 62.5366393799277,96.6462329091006 56.70583703063,84.8096427890789 53.115246672502,72.5000000000001 51.9028526793802,60.1903572109213 53.1152466725019,48.3537670908996 56.7058370306299,37.4451031602112 62.5366393799276,27.8835792560632 70.383579256063,20.0366393799278 79.9451031602109,14.20583703063 90.8537670908993,10.615246672502 102.690357210921,9.40285267938019 115,10.6152466725019 127.309642789079,14.2058370306299 139.1462329091,20.0366393799275 150.054896839789,27.883579256063 159.616420743937,
    37.4451031602108 167.463360620072,48.3537670908992 173.29416296937,60.190357210921 176.884753327498,
    72.4999999999998 178.09714732062,84.8096427890786 176.884753327498,96.6462329091003 173.29416296937,107.554896839789 167.463360620072,
    117.116420743937 159.616420743937,124.963360620072 150.054896839789,130.79416296937 139.146232909101,134.384753327498 127.309642789079,135.59714732062 115))

## See Also

ST_Collect, ST_MinimumBoundingRadius, ST_LargestEmptyCircle, ST_LongestLine

## Name

ST_MinimumBoundingRadius — Returns the center point and radius of the smallest circle that contains a geometry.

## Synopsis

`(geometry, double precision) ST_MinimumBoundingRadius(` geometry geom`)`;

## Description

Computes the center point and radius of the smallest circle that contains a geometry. Returns a record with fields:

- `center` - center point of the circle

- `radius` - radius of the circle

Use with ST_Collect to get the minimum bounding circle of a set of geometries.

To compute two points lying on the minimum circle (the "maximum diameter") use ST_LongestLine.

Availability - 2.3.0

## Examples

    SELECT ST_AsText(center), radius FROM ST_MinimumBoundingRadius('POLYGON((26426 65078,26531 65242,26075 65136,26096 65427,26426 65078))');

                    st_astext                 |      radius
    ------------------------------------------+------------------
     POINT(26284.8418027133 65267.1145090825) | 247.436045591407

## See Also

ST_Collect, ST_MinimumBoundingCircle, ST_LongestLine

## Name

ST_OrientedEnvelope — Returns a minimum-area rectangle containing a geometry.

## Synopsis

`geometry ST_OrientedEnvelope(` geometry geom `)`;

## Description

Returns the minimum-area rotated rectangle enclosing a geometry. Note that more than one such rectangle may exist. May return a Point or LineString in the case of degenerate inputs.

Availability: 2.5.0.

Requires GEOS >= 3.6.0.

## Examples

                    SELECT ST_AsText(ST_OrientedEnvelope('MULTIPOINT ((0 0), (-1 -1), (3 2))'));

                    st_astext
                    ------------------------------------------------
                    POLYGON((3 2,2.88 2.16,-1.12 -0.84,-1 -1,3 2))

Oriented envelope of a point and linestring.

    SELECT ST_AsText(ST_OrientedEnvelope(
            ST_Collect(
                ST_GeomFromText('LINESTRING(55 75,125 150)'),
                    ST_Point(20, 80))
                    )) As wktenv;
    wktenv
    -----------
    POLYGON((19.9999999999997 79.9999999999999,33.0769230769229 60.3846153846152,138.076923076924 130.384615384616,125.000000000001 150.000000000001,19.9999999999997 79.9999999999999))

## See Also

ST_Envelope ST_MinimumBoundingCircle

## Name

ST_OffsetCurve — Returns an offset line at a given distance and side from an input line.

## Synopsis

`geometry ST_OffsetCurve(` geometry line, float signed_distance, text style_parameters=''`)`;

## Description

Return an offset line at a given distance and side from an input line. All points of the returned geometries are not further than the given distance from the input geometry. Useful for computing parallel lines about a center line.

For positive distance the offset is on the left side of the input line and retains the same direction. For a negative distance it is on the right side and in the opposite direction.

Units of distance are measured in units of the spatial reference system.

Note that output may be a MULTILINESTRING or EMPTY for some jigsaw-shaped input geometries.

The optional third parameter allows specifying a list of blank-separated key=value pairs to tweak operations as follows:

- 'quad_segs=#' : number of segments used to approximate a quarter circle (defaults to 8).

- 'join=round|mitre|bevel' : join style (defaults to "round"). 'miter' is also accepted as a synonym for 'mitre'.

- 'mitre_limit=#.#' : mitre ratio limit (only affects mitred join style). 'miter_limit' is also accepted as a synonym for 'mitre_limit'.

Performed by the GEOS module.

Behavior changed in GEOS 3.11 so offset curves now have the same direction as the input line, for both positive and negative offsets.

Availability: 2.0

Enhanced: 2.5 - added support for GEOMETRYCOLLECTION and MULTILINESTRING

This function ignores the Z dimension. It always gives a 2D result even when used on a 3D geometry.

## Examples

Compute an open buffer around roads

    SELECT ST_Union(
     ST_OffsetCurve(f.geom,  f.width/2, 'quad_segs=4 join=round'),
     ST_OffsetCurve(f.geom, -f.width/2, 'quad_segs=4 join=round')
    ) as track
    FROM someroadstable;

15, 'quad_segs=4 join=round' original line and its offset 15 units.
    SELECT ST_AsText(ST_OffsetCurve(ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)'),
        15, 'quad_segs=4 join=round'));

    output

    LINESTRING(164 1,18 1,12.2597485145237 2.1418070123307,
        7.39339828220179 5.39339828220179,
        5.39339828220179 7.39339828220179,
        2.14180701233067 12.2597485145237,1 18,1 195)
| -15, 'quad_segs=4 join=round' original line and its offset -15 units
    SELECT ST_AsText(ST_OffsetCurve(geom,
        -15, 'quad_segs=4 join=round')) As notsocurvy
        FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)') As geom;

    notsocurvy

    LINESTRING(31 195,31 31,164 31)
double-offset to get more curvy, note the first reverses direction, so -30 + 15 = -15
    SELECT ST_AsText(ST_OffsetCurve(ST_OffsetCurve(geom,
        -30, 'quad_segs=4 join=round'), -15, 'quad_segs=4 join=round')) As morecurvy
        FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)') As geom;

    morecurvy

    LINESTRING(164 31,46 31,40.2597485145236 32.1418070123307,
    35.3933982822018 35.3933982822018,
    32.1418070123307 40.2597485145237,31 46,31 195)
| double-offset to get more curvy,combined with regular offset 15 to get parallel lines. Overlaid with original.
    SELECT ST_AsText(ST_Collect(
        ST_OffsetCurve(geom, 15, 'quad_segs=4 join=round'),
        ST_OffsetCurve(ST_OffsetCurve(geom,
        -30, 'quad_segs=4 join=round'), -15, 'quad_segs=4 join=round')
        )
    ) As parallel_curves
        FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)') As geom;

    parallel curves

    MULTILINESTRING((164 1,18 1,12.2597485145237 2.1418070123307,
    7.39339828220179 5.39339828220179,5.39339828220179 7.39339828220179,
    2.14180701233067 12.2597485145237,1 18,1 195),
    (164 31,46 31,40.2597485145236 32.1418070123307,35.3933982822018 35.3933982822018,
    32.1418070123307 40.2597485145237,31 46,31 195))
15, 'quad_segs=4 join=bevel' shown with original line
    SELECT ST_AsText(ST_OffsetCurve(ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)'),
            15, 'quad_segs=4 join=bevel'));

    output

    LINESTRING(164 1,18 1,7.39339828220179 5.39339828220179,
        5.39339828220179 7.39339828220179,1 18,1 195)
| 15,-15 collected, join=mitre mitre_limit=2.1
    SELECT ST_AsText(ST_Collect(
        ST_OffsetCurve(geom, 15, 'quad_segs=4 join=mitre mitre_limit=2.2'),
        ST_OffsetCurve(geom, -15, 'quad_segs=4 join=mitre mitre_limit=2.2')
        ) )
        FROM ST_GeomFromText(
    'LINESTRING(164 16,144 16,124 16,104 16,84 16,64 16,
        44 16,24 16,20 16,18 16,17 17,
        16 18,16 20,16 40,16 60,16 80,16 100,
        16 120,16 140,16 160,16 180,16 195)') As geom;

    output

    MULTILINESTRING((164 1,11.7867965644036 1,1 11.7867965644036,1 195),
        (31 195,31 31,164 31))

## See Also

ST_Buffer

## Name

ST_PointOnSurface — Computes a point guaranteed to lie in a polygon, or on a geometry.

## Synopsis

`geometry ST_PointOnSurface(` geometry g1`)`;

## Description

Returns a `POINT` which is guaranteed to lie in the interior of a surface (`POLYGON`, `MULTIPOLYGON`, and `CURVEPOLYGON`). In PostGIS this function also works on line and point geometries.

This method implements the OGC Simple Features Implementation Specification for SQL 1.1. s3.2.14.2 // s3.2.18.2

This method implements the SQL/MM specification. SQL-MM 3: 8.1.5, 9.5.6. The specifications define ST_PointOnSurface for surface geometries only. PostGIS extends the function to support all common geometry types. Other databases (Oracle, DB2, ArcSDE) seem to support this function only for surfaces. SQL Server 2008 supports all common geometry types.

This function supports 3d and will not drop the z-index.

## Examples

Point on surface of a `MULTIPOINT` | Point on surface of a `LINESTRING`
Point on surface of a `POLYGON` | Point on surface of a `GEOMETRYCOLLECTION`

    SELECT ST_AsText(ST_PointOnSurface('POINT(0 5)'::geometry));
    ------------
     POINT(0 5)

    SELECT ST_AsText(ST_PointOnSurface('LINESTRING(0 5, 0 10)'::geometry));
    ------------
     POINT(0 5)

    SELECT ST_AsText(ST_PointOnSurface('POLYGON((0 0, 0 5, 5 5, 5 0, 0 0))'::geometry));
    ----------------
     POINT(2.5 2.5)

    SELECT ST_AsEWKT(ST_PointOnSurface(ST_GeomFromEWKT('LINESTRING(0 5 1, 0 0 1, 0 10 2)')));
    ----------------
     POINT(0 0 1)

Example: The result of ST_PointOnSurface is guaranteed to lie within polygons, whereas the point computed by ST_Centroid may be outside.

Red: point on surface; Green: centroid

    SELECT ST_AsText(ST_PointOnSurface(geom)) AS pt_on_surf,
           ST_AsText(ST_Centroid(geom)) AS centroid
        FROM (SELECT 'POLYGON ((130 120, 120 190, 30 140, 50 20, 190 20,
                          170 100, 90 60, 90 130, 130 120))'::geometry AS geom) AS t;

       pt_on_surf    |                  centroid
    -----------------+---------------------------------------------
     POINT(62.5 110) | POINT(100.18264840182648 85.11415525114155)

## See Also

ST_Centroid, ST_MaximumInscribedCircle

## Name

ST_Polygonize — Computes a collection of polygons formed from the linework of a set of geometries.

## Synopsis

`geometry ST_Polygonize(` geometry set geomfield`)`;

`geometry ST_Polygonize(` geometry[] geom_array`)`;

## Description

Creates a GeometryCollection containing the polygons formed by the linework of a set of geometries. If the input linework does not form any polygons, an empty GeometryCollection is returned.

This function creates polygons covering all delimited areas. If the result is intended to form a valid polygonal geometry, use ST_BuildArea to prevent holes being filled.

The input linework must be correctly noded for this function to work properly. To ensure input is noded use ST_Node on the input geometry before polygonizing.

GeometryCollections can be difficult to handle with external tools. Use ST_Dump to convert the polygonized result into separate polygons.

Performed by the GEOS module.

Availability: 1.0.0RC1

## Examples

Input lines | Polygonized result

    WITH data(geom) AS (VALUES
       ('LINESTRING (180 40, 30 20, 20 90)'::geometry)
      ,('LINESTRING (180 40, 160 160)'::geometry)
      ,('LINESTRING (80 60, 120 130, 150 80)'::geometry)
      ,('LINESTRING (80 60, 150 80)'::geometry)
      ,('LINESTRING (20 90, 70 70, 80 130)'::geometry)
      ,('LINESTRING (80 130, 160 160)'::geometry)
      ,('LINESTRING (20 90, 20 160, 70 190)'::geometry)
      ,('LINESTRING (70 190, 80 130)'::geometry)
      ,('LINESTRING (70 190, 160 160)'::geometry)
    )
    SELECT ST_AsText( ST_Polygonize( geom ))
        FROM data;

    ------------------------------------------------------------------------------------------
    GEOMETRYCOLLECTION (POLYGON ((180 40, 30 20, 20 90, 70 70, 80 130, 160 160, 180 40), (150 80, 120 130, 80 60, 150 80)),
                        POLYGON ((20 90, 20 160, 70 190, 80 130, 70 70, 20 90)),
                        POLYGON ((160 160, 80 130, 70 190, 160 160)),
                        POLYGON ((80 60, 120 130, 150 80, 80 60)))

Polygonizing a table of linestrings:

    SELECT ST_AsEWKT(ST_Polygonize(geom_4269)) As geomtextrep
    FROM (SELECT geom_4269 FROM ma.suffolk_edges) As foo;

    -------------------------------------
     SRID=4269;GEOMETRYCOLLECTION(POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,-71.040878 42.285678)),
     POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358,-71.171794 42.354971,-71.170511 42.354855,
     -71.17112 42.354238,-71.17166 42.353675)))

    --Use ST_Dump to dump out the polygonize geoms into individual polygons
    SELECT ST_AsEWKT((ST_Dump(t.polycoll)).geom) AS geomtextrep
    FROM (SELECT ST_Polygonize(geom_4269) AS polycoll
        FROM (SELECT geom_4269 FROM ma.suffolk_edges)
            As foo) AS t;

    ------------------------
     SRID=4269;POLYGON((-71.040878 42.285678,-71.040943 42.2856,-71.04096 42.285752,
    -71.040878 42.285678))
     SRID=4269;POLYGON((-71.17166 42.353675,-71.172026 42.354044,-71.17239 42.354358
    ,-71.171794 42.354971,-71.170511 42.354855,-71.17112 42.354238,-71.17166 42.353675))

## See Also

ST_BuildArea, ST_Dump, ST_Node

## Name

ST_ReducePrecision — Returns a valid geometry with points rounded to a grid tolerance.

## Synopsis

`geometry ST_ReducePrecision(` geometry g, float8 gridsize`)`;

## Description

Returns a valid geometry with all points rounded to the provided grid tolerance, and features below the tolerance removed.

Unlike ST_SnapToGrid the returned geometry will be valid, with no ring self-intersections or collapsed components.

Precision reduction can be used to:

- match coordinate precision to the data accuracy

- reduce the number of coordinates needed to represent a geometry

- ensure valid geometry output to formats which use lower precision (e.g. text formats such as WKT, GeoJSON or KML when the number of output decimal places is limited).

- export valid geometry to systems which use lower or limited precision (e.g. SDE, Oracle tolerance value)

Availability: 3.1.0.

Requires GEOS >= 3.9.0.

## Examples

    SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 0.1));
        st_astext
    -----------------
     POINT(1.4 19.3)

    SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 1.0));
      st_astext
    -------------
     POINT(1 19)

    SELECT ST_AsText(ST_ReducePrecision('POINT(1.412 19.323)', 10));
      st_astext
    -------------
     POINT(0 20)

Precision reduction can reduce number of vertices

    SELECT ST_AsText(ST_ReducePrecision('LINESTRING (10 10, 19.6 30.1, 20 30, 20.3 30, 40 40)', 1));
      st_astext
    -------------
     LINESTRING (10 10, 20 30, 40 40)

Precision reduction splits polygons if needed to ensure validity

    SELECT ST_AsText(ST_ReducePrecision('POLYGON ((10 10, 60 60.1, 70 30, 40 40, 50 10, 10 10))', 10));
      st_astext
    -------------
     MULTIPOLYGON (((60 60, 70 30, 40 40, 60 60)), ((40 40, 50 10, 10 10, 40 40)))

## See Also

ST_SnapToGrid, ST_Simplify, ST_SimplifyVW

## Name

ST_SharedPaths — Returns a collection containing paths shared by the two input linestrings/multilinestrings.

## Synopsis

`geometry ST_SharedPaths(` geometry lineal1, geometry lineal2`)`;

## Description

Returns a collection containing paths shared by the two input geometries. Those going in the same direction are in the first element of the collection, those going in the opposite direction are in the second element. The paths themselves are given in the direction of the first geometry.

Performed by the GEOS module.

Availability: 2.0.0

## Examples: Finding shared paths

A multilinestring and a linestring
The shared path of multilinestring and linestring overlaid with original geometries.
     SELECT ST_AsText(
      ST_SharedPaths(
        ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
           (51 150,101 150,76 175,51 150))'),
        ST_GeomFromText('LINESTRING(151 100,126 156.25,126 125,90 161, 76 175)')
        )
      ) As wkt

                                    wkt
    -------------------------------------------------------------
    GEOMETRYCOLLECTION(MULTILINESTRING((126 156.25,126 125),
     (101 150,90 161),(90 161,76 175)),MULTILINESTRING EMPTY)
    same example but linestring orientation flipped

    SELECT ST_AsText(
      ST_SharedPaths(
       ST_GeomFromText('LINESTRING(76 175,90 161,126 125,126 156.25,151 100)'),
       ST_GeomFromText('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),
           (51 150,101 150,76 175,51 150))')
        )
      ) As wkt

                                    wkt
    -------------------------------------------------------------
    GEOMETRYCOLLECTION(MULTILINESTRING EMPTY,
    MULTILINESTRING((76 175,90 161),(90 161,101 150),(126 125,126 156.25)))

## See Also

ST_Dump, ST_GeometryN, ST_NumGeometries

## Name

ST_Simplify — Returns a simplified representation of a geometry, using the Douglas-Peucker algorithm.

## Synopsis

`geometry ST_Simplify(` geometry geom, float tolerance`)`;

`geometry ST_Simplify(` geometry geom, float tolerance, boolean preserveCollapsed`)`;

## Description

Computes a simplified representation of a geometry using the Douglas-Peucker algorithm. The simplification `tolerance` is a distance value, in the units of the input SRS. Simplification removes vertices which are within the tolerance distance of the simplified linework. The result may not be valid even if the input is.

The function can be called with any kind of geometry (including GeometryCollections), but only line and polygon elements are simplified. Endpoints of linear geometry are preserved.

The `preserveCollapsed` flag retains small geometries that would otherwise be removed at the given tolerance. For example, if a 1m long line is simplified with a 10m tolerance, when `preserveCollapsed` is true the line will not disappear. This flag is useful for rendering purposes, to prevent very small features disappearing from a map.

The returned geometry may lose its simplicity (see ST_IsSimple), topology may not be preserved, and polygonal results may be invalid (see ST_IsValid). Use ST_SimplifyPreserveTopology to preserve topology and ensure validity.

This function does not preserve boundaries shared between polygons. Use ST_CoverageSimplify if this is required.

Availability: 1.2.2

## Examples

A circle simplified too much becomes a triangle, medium an octagon,

    SELECT ST_Npoints(geom) AS np_before,
           ST_NPoints(ST_Simplify(geom, 0.1)) AS np01_notbadcircle,
           ST_NPoints(ST_Simplify(geom, 0.5)) AS np05_notquitecircle,
           ST_NPoints(ST_Simplify(geom, 1)) AS np1_octagon,
           ST_NPoints(ST_Simplify(geom, 10)) AS np10_triangle,
           (ST_Simplify(geom, 100) is null) AS  np100_geometrygoesaway
      FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) As geom) AS t;

     np_before | np01_notbadcircle | np05_notquitecircle | np1_octagon | np10_triangle | np100_geometrygoesaway
    -----------+-------------------+---------------------+-------------+---------------+------------------------
            49 |                33 |                  17 |           9 |             4 | t

Simplifying a set of lines. Lines may intersect after simplification.

    SELECT ST_Simplify(
      'MULTILINESTRING ((20 180, 20 150, 50 150, 50 100, 110 150, 150 140, 170 120), (20 10, 80 30, 90 120), (90 120, 130 130), (130 130, 130 70, 160 40, 180 60, 180 90, 140 80), (50 40, 70 40, 80 70, 70 60, 60 60, 50 50, 50 40))',
        40);

Simplifying a MultiPolygon. Polygonal results may be invalid.

    SELECT ST_Simplify(
      'MULTIPOLYGON (((90 110, 80 180, 50 160, 10 170, 10 140, 20 110, 90 110)), ((40 80, 100 100, 120 160, 170 180, 190 70, 140 10, 110 40, 60 40, 40 80), (180 70, 170 110, 142.5 128.5, 128.5 77.5, 90 60, 180 70)))',
        40);

## See Also

ST_IsSimple, ST_SimplifyPreserveTopology, ST_SimplifyVW, ST_CoverageSimplify, Topology ST_Simplify

## Name

ST_SimplifyPreserveTopology — Returns a simplified and valid representation of a geometry, using the Douglas-Peucker algorithm.

## Synopsis

`geometry ST_SimplifyPreserveTopology(` geometry geom, float tolerance`)`;

## Description

Computes a simplified representation of a geometry using a variant of the Douglas-Peucker algorithm which limits simplification to ensure the result has the same topology as the input. The simplification `tolerance` is a distance value, in the units of the input SRS. Simplification removes vertices which are within the tolerance distance of the simplified linework, as long as topology is preserved. The result will be valid and simple if the input is.

The function can be called with any kind of geometry (including GeometryCollections), but only line and polygon elements are simplified. For polygonal inputs, the result will have the same number of rings (shells and holes), and the rings will not cross. Ring endpoints may be simplified. For linear inputs, the result will have the same number of lines, and lines will not intersect if they did not do so in the original geometry. Endpoints of linear geometry are preserved.

This function does not preserve boundaries shared between polygons. Use ST_CoverageSimplify if this is required.

Performed by the GEOS module.

Availability: 1.3.3

## Examples

For the same example as ST_Simplify, ST_SimplifyPreserveTopology prevents oversimplification. The circle can at most become a square.

    SELECT  ST_Npoints(geom) AS np_before,
            ST_NPoints(ST_SimplifyPreserveTopology(geom, 0.1)) AS np01_notbadcircle,
            ST_NPoints(ST_SimplifyPreserveTopology(geom, 0.5)) AS np05_notquitecircle,
            ST_NPoints(ST_SimplifyPreserveTopology(geom, 1))   AS np1_octagon,
            ST_NPoints(ST_SimplifyPreserveTopology(geom, 10))  AS np10_square,
            ST_NPoints(ST_SimplifyPreserveTopology(geom, 100)) AS np100_stillsquare
    FROM (SELECT ST_Buffer('POINT(1 3)', 10,12) AS geom) AS t;

     np_before | np01_notbadcircle | np05_notquitecircle | np1_octagon | np10_square | np100_stillsquare
    -----------+-------------------+---------------------+-------------+-------------+-------------------
            49 |                33 |                  17 |           9 |           5 |                 5

Simplifying a set of lines, preserving topology of non-intersecting lines.

    SELECT ST_SimplifyPreserveTopology(
      'MULTILINESTRING ((20 180, 20 150, 50 150, 50 100, 110 150, 150 140, 170 120), (20 10, 80 30, 90 120), (90 120, 130 130), (130 130, 130 70, 160 40, 180 60, 180 90, 140 80), (50 40, 70 40, 80 70, 70 60, 60 60, 50 50, 50 40))',
        40);

Simplifying a MultiPolygon, preserving topology of shells and holes.

    SELECT ST_SimplifyPreserveTopology(
      'MULTIPOLYGON (((90 110, 80 180, 50 160, 10 170, 10 140, 20 110, 90 110)), ((40 80, 100 100, 120 160, 170 180, 190 70, 140 10, 110 40, 60 40, 40 80), (180 70, 170 110, 142.5 128.5, 128.5 77.5, 90 60, 180 70)))',
        40);

## See Also

ST_Simplify, ST_SimplifyVW, ST_CoverageSimplify

## Name

ST_SimplifyPolygonHull — Computes a simplifed topology-preserving outer or inner hull of a polygonal geometry.

## Synopsis

`geometry ST_SimplifyPolygonHull(` geometry param_geom, float vertex_fraction, boolean is_outer = true`)`;

## Description

Computes a simplified topology-preserving outer or inner hull of a polygonal geometry. An outer hull completely covers the input geometry. An inner hull is completely covered by the input geometry. The result is a polygonal geometry formed by a subset of the input vertices. MultiPolygons and holes are handled and produce a result with the same structure as the input.

The reduction in vertex count is controlled by the `vertex_fraction` parameter, which is a number in the range 0 to 1. Lower values produce simpler results, with smaller vertex count and less concaveness. For both outer and inner hulls a vertex fraction of 1.0 produces the original geometry. For outer hulls a value of 0.0 produces the convex hull (for a single polygon); for inner hulls it produces a triangle.

The simplification process operates by progressively removing concave corners that contain the least amount of area, until the vertex count target is reached. It prevents edges from crossing, so the result is always a valid polygonal geometry.

To get better results with geometries that contain relatively long line segments, it might be necessary to "segmentize" the input, as shown below.

Performed by the GEOS module.

Availability: 3.3.0.

Requires GEOS >= 3.11.0.

## Examples

Outer hull of a Polygon

    SELECT ST_SimplifyPolygonHull(
      'POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))',
        0.3);

Inner hull of a Polygon

    SELECT ST_SimplifyPolygonHull(
      'POLYGON ((131 158, 136 163, 161 165, 173 156, 179 148, 169 140, 186 144, 190 137, 185 131, 174 128, 174 124, 166 119, 158 121, 158 115, 165 107, 161 97, 166 88, 166 79, 158 57, 145 57, 112 53, 111 47, 93 43, 90 48, 88 40, 80 39, 68 32, 51 33, 40 31, 39 34, 49 38, 34 38, 25 34, 28 39, 36 40, 44 46, 24 41, 17 41, 14 46, 19 50, 33 54, 21 55, 13 52, 11 57, 22 60, 34 59, 41 68, 75 72, 62 77, 56 70, 46 72, 31 69, 46 76, 52 82, 47 84, 56 90, 66 90, 64 94, 56 91, 33 97, 36 100, 23 100, 22 107, 29 106, 31 112, 46 116, 36 118, 28 131, 53 132, 59 127, 62 131, 76 130, 80 135, 89 137, 87 143, 73 145, 80 150, 88 150, 85 157, 99 162, 116 158, 115 165, 123 165, 122 170, 134 164, 131 158))',
        0.3, false);

Outer hull simplification of a MultiPolygon, with segmentization

    SELECT ST_SimplifyPolygonHull(
      ST_Segmentize(ST_Letters('xt'), 2.0),
        0.1);

## See Also

ST_ConvexHull, ST_SimplifyVW, ST_ConcaveHull, ST_Segmentize

## Name

ST_SimplifyVW — Returns a simplified representation of a geometry, using the Visvalingam-Whyatt algorithm

## Synopsis

`geometry ST_SimplifyVW(` geometry geom, float tolerance`)`;

## Description

Returns a simplified representation of a geometry using the Visvalingam-Whyatt algorithm. The simplification `tolerance` is an area value, in the units of the input SRS. Simplification removes vertices which form "corners" with area less than the tolerance. The result may not be valid even if the input is.

The function can be called with any kind of geometry (including GeometryCollections), but only line and polygon elements are simplified. Endpoints of linear geometry are preserved.

The returned geometry may lose its simplicity (see ST_IsSimple), topology may not be preserved, and polygonal results may be invalid (see ST_IsValid). Use ST_SimplifyPreserveTopology to preserve topology and ensure validity. ST_CoverageSimplify also preserves topology and validity.

This function does not preserve boundaries shared between polygons. Use ST_CoverageSimplify if this is required.

This function handles 3D and the third dimension will affect the result.

Availability: 2.2.0

## Examples

A LineString is simplified with a minimum-area tolerance of 30.

    SELECT ST_AsText(ST_SimplifyVW(geom,30)) simplified
      FROM (SELECT 'LINESTRING(5 2, 3 8, 6 20, 7 25, 10 10)'::geometry AS geom) AS t;

     simplified
    ------------------------------
    LINESTRING(5 2,7 25,10 10)

Simplifying a line.

    SELECT ST_SimplifyVW(
      'LINESTRING (10 10, 50 40, 30 70, 50 60, 70 80, 50 110, 100 100, 90 140, 100 180, 150 170, 170 140, 190 90, 180 40, 110 40, 150 20)',
        1600);

Simplifying a polygon.

    SELECT ST_SimplifyVW(
      'MULTIPOLYGON (((90 110, 80 180, 50 160, 10 170, 10 140, 20 110, 90 110)), ((40 80, 100 100, 120 160, 170 180, 190 70, 140 10, 110 40, 60 40, 40 80), (180 70, 170 110, 142.5 128.5, 128.5 77.5, 90 60, 180 70)))',
        40);

## See Also

ST_SetEffectiveArea, ST_Simplify, ST_SimplifyPreserveTopology, ST_CoverageSimplify, Topology ST_Simplify

## Name

ST_SetEffectiveArea — Sets the effective area for each vertex, using the Visvalingam-Whyatt algorithm.

## Synopsis

`geometry ST_SetEffectiveArea(` geometry geom, float threshold = 0, integer set_area = 1`)`;

## Description

Sets the effective area for each vertex, using the Visvalingam-Whyatt algorithm. The effective area is stored as the M-value of the vertex. If the optional "threshold" parameter is used, a simplified geometry will be returned, containing only vertices with an effective area greater than or equal to the threshold value.

This function can be used for server-side simplification when a threshold is specified. Another option is to use a threshold value of zero. In this case, the full geometry will be returned with effective areas as M-values, which can be used by the client to simplify very quickly.

Will actually do something only with (multi)lines and (multi)polygons but you can safely call it with any kind of geometry. Since simplification occurs on a object-by-object basis you can also feed a GeometryCollection to this function.

Note that returned geometry might lose its simplicity (see ST_IsSimple)

Note topology may not be preserved and may result in invalid geometries. Use (see ST_SimplifyPreserveTopology) to preserve topology.

The output geometry will lose all previous information in the M-values

This function handles 3D and the third dimension will affect the effective area

Availability: 2.2.0

## Examples

Calculating the effective area of a LineString. Because we use a threshold value of zero, all vertices in the input geometry are returned.

    select ST_AsText(ST_SetEffectiveArea(geom)) all_pts, ST_AsText(ST_SetEffectiveArea(geom,30) ) thrshld_30
    FROM (SELECT  'LINESTRING(5 2, 3 8, 6 20, 7 25, 10 10)'::geometry geom) As foo;
    -result
     all_pts | thrshld_30
    -----------+-------------------+
    LINESTRING M (5 2 3.40282346638529e+38,3 8 29,6 20 1.5,7 25 49.5,10 10 3.40282346638529e+38) | LINESTRING M (5 2 3.40282346638529e+38,7 25 49.5,10 10 3.40282346638529e+38)

## See Also

ST_SimplifyVW

## Name

ST_TriangulatePolygon — Computes the constrained Delaunay triangulation of polygons

## Synopsis

`geometry ST_TriangulatePolygon(` geometry geom`)`;

## Description

Computes the constrained Delaunay triangulation of polygons. Holes and Multipolygons are supported.

The "constrained Delaunay triangulation" of a polygon is a set of triangles formed from the vertices of the polygon, and covering it exactly, with the maximum total interior angle over all possible triangulations. It provides the "best quality" triangulation of the polygon.

Availability: 3.3.0.

Requires GEOS >= 3.11.0.

## Example

Triangulation of a square.

    SELECT ST_AsText(
        ST_TriangulatePolygon('POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))'));

                                     st_astext
    ---------------------------------------------------------------------------
     GEOMETRYCOLLECTION(POLYGON((0 0,0 1,1 1,0 0)),POLYGON((1 1,1 0,0 0,1 1)))

## Example

Triangulation of the letter P.

    SELECT ST_AsText(ST_TriangulatePolygon(
        'POLYGON ((26 17, 31 19, 34 21, 37 24, 38 29, 39 43, 39 161, 38 172, 36 176, 34 179, 30 181, 25 183, 10 185, 10 190, 100 190, 121 189, 139 187, 154 182, 167 177, 177 169, 184 161, 189 152, 190 141, 188 128, 186 123, 184 117, 180 113, 176 108, 170 104, 164 101, 151 96, 136 92, 119 89, 100 89, 86 89, 73 89, 73 39, 74 32, 75 27, 77 23, 79 20, 83 18, 89 17, 106 15, 106 10, 10 10, 10 15, 26 17), (152 147, 151 152, 149 157, 146 162, 142 166, 137 169, 132 172, 126 175, 118 177, 109 179, 99 180, 89 180, 80 179, 76 178, 74 176, 73 171, 73 100, 85 99, 91 99, 102 99, 112 100, 121 102, 128 104, 134 107, 139 110, 143 114, 147 118, 149 123, 151 128, 153 141, 152 147))'
        ));

Polygon Triangulation

## Same example as ST_Tesselate

    SELECT ST_TriangulatePolygon(
                    'POLYGON (( 10 190, 10 70, 80 70, 80 130, 50 160, 120 160, 120 190, 10 190 ))'::geometry
                    );

ST_AsText output

    GEOMETRYCOLLECTION(POLYGON((50 160,120 190,120 160,50 160))
        ,POLYGON((10 70,80 130,80 70,10 70))
        ,POLYGON((50 160,10 70,10 190,50 160))
        ,POLYGON((120 190,50 160,10 190,120 190))
        ,POLYGON((80 130,10 70,50 160,80 130)))

Original polygon | Triangulated Polygon

## See Also

ST_ConstrainedDelaunayTriangles, ST_DelaunayTriangles, ST_Tesselate

## Name

ST_VoronoiLines — Returns the boundaries of the Voronoi diagram of the vertices of a geometry.

## Synopsis

`geometry ST_VoronoiLines(` geometry geom , float8 tolerance = 0.0 , geometry extend_to = NULL `)`;

## Description

Computes a two-dimensional Voronoi diagram from the vertices of the supplied geometry and returns the boundaries between cells in the diagram as a MultiLineString. Returns null if input geometry is null. Returns an empty geometry collection if the input geometry contains only one vertex. Returns an empty geometry collection if the `extend_to` envelope has zero area.

Optional parameters:

- `tolerance`: The distance within which vertices will be considered equivalent. Robustness of the algorithm can be improved by supplying a nonzero tolerance distance. (default = 0.0)

- `extend_to`: If present, the diagram is extended to cover the envelope of the supplied geometry, unless smaller than the default envelope (default = NULL, default envelope is the bounding box of the input expanded by about 50%).

Performed by the GEOS module.

Availability: 2.3.0

## Examples

Voronoi diagram lines, with tolerance of 30 units

    SELECT ST_VoronoiLines(
                'MULTIPOINT (50 30, 60 30, 100 100,10 150, 110 120)'::geometry,
                30) AS geom;

    ST_AsText output
    MULTILINESTRING((135.555555555556 270,36.8181818181818 92.2727272727273),(36.8181818181818 92.2727272727273,-110 43.3333333333333),(230 -45.7142857142858,36.8181818181818 92.2727272727273))

## See Also

ST_DelaunayTriangles, ST_VoronoiPolygons

## Name

ST_VoronoiPolygons — Returns the cells of the Voronoi diagram of the vertices of a geometry.

## Synopsis

`geometry ST_VoronoiPolygons(` geometry geom , float8 tolerance = 0.0 , geometry extend_to = NULL `)`;

## Description

Computes a two-dimensional Voronoi diagram from the vertices of the supplied geometry. The result is a GEOMETRYCOLLECTION of POLYGONs that covers an envelope larger than the extent of the input vertices. Returns null if input geometry is null. Returns an empty geometry collection if the input geometry contains only one vertex. Returns an empty geometry collection if the `extend_to` envelope has zero area.

Optional parameters:

- `tolerance`: The distance within which vertices will be considered equivalent. Robustness of the algorithm can be improved by supplying a nonzero tolerance distance. (default = 0.0)

- `extend_to`: If present, the diagram is extended to cover the envelope of the supplied geometry, unless smaller than the default envelope (default = NULL, default envelope is the bounding box of the input expanded by about 50%).

Performed by the GEOS module.

Availability: 2.3.0

## Examples

Points overlaid on top of Voronoi diagram

    SELECT ST_VoronoiPolygons(
                    'MULTIPOINT (50 30, 60 30, 100 100,10 150, 110 120)'::geometry
                ) AS geom;

    ST_AsText output
    GEOMETRYCOLLECTION(POLYGON((-110 43.3333333333333,-110 270,100.5 270,59.3478260869565 132.826086956522,36.8181818181818 92.2727272727273,-110 43.3333333333333)),
    POLYGON((55 -90,-110 -90,-110 43.3333333333333,36.8181818181818 92.2727272727273,55 79.2857142857143,55 -90)),
    POLYGON((230 47.5,230 -20.7142857142857,55 79.2857142857143,36.8181818181818 92.2727272727273,59.3478260869565 132.826086956522,230 47.5)),POLYGON((230 -20.7142857142857,230 -90,55 -90,55 79.2857142857143,230 -20.7142857142857)),
    POLYGON((100.5 270,230 270,230 47.5,59.3478260869565 132.826086956522,100.5 270)))

Voronoi diagram, with tolerance of 30 units

    SELECT ST_VoronoiPolygons(
                'MULTIPOINT (50 30, 60 30, 100 100,10 150, 110 120)'::geometry,
                30) AS geom;

    ST_AsText output
    GEOMETRYCOLLECTION(POLYGON((-110 43.3333333333333,-110 270,100.5 270,59.3478260869565 132.826086956522,36.8181818181818 92.2727272727273,-110 43.3333333333333)),
    POLYGON((230 47.5,230 -45.7142857142858,36.8181818181818 92.2727272727273,59.3478260869565 132.826086956522,230 47.5)),POLYGON((230 -45.7142857142858,230 -90,-110 -90,-110 43.3333333333333,36.8181818181818 92.2727272727273,230 -45.7142857142858)),
    POLYGON((100.5 270,230 270,230 47.5,59.3478260869565 132.826086956522,100.5 270)))

## See Also

ST_DelaunayTriangles, ST_VoronoiLines

## 7.15. Coverages

Abstract

These functions operate on sets of polygonal geometry that form "implicit coverages". To form a valid coverage polygons must not overlap, and the vertices of adjacent edges must match exactly. Coverages are fast to process, and can be operated on with window functions, which retain the coverage topology inside the window partition while altering the edges.

## Name

ST_CoverageInvalidEdges — Window function that finds locations where polygons fail to form a valid coverage.

## Synopsis

`geometry ST_CoverageInvalidEdges(` geometry winset geom, float8 tolerance = 0`)`;

## Description

A window function which checks if the polygons in the window partition form a valid polygonal coverage. It returns linear indicators showing the location of invalid edges (if any) in each polygon.

A set of valid polygons is a valid coverage if the following conditions hold:

- Non-overlapping - polygons do not overlap (their interiors do not intersect)

- Edge-Matched - vertices along shared edges are identical

As a window function a value is returned for every input polygon. For polygons which violate one or more of the validity conditions the return value is a MULTILINESTRING containing the problematic edges. Coverage-valid polygons return the value NULL. Non-polygonal or empty geometries also produce NULL values.

The conditions allow a valid coverage to contain holes (gaps between polygons), as long as the surrounding polygons are edge-matched. However, very narrow gaps are often undesirable. If the `tolerance` parameter is specified with a non-zero distance, edges forming narrower gaps will also be returned as invalid.

The polygons being checked for coverage validity must also be valid geometries. This can be checked with ST_IsValid.

Availability: 3.4.0

Requires GEOS >= 3.12.0

## Examples

Invalid edges caused by overlap and non-matching vertices

    WITH coverage(id, geom) AS (VALUES
      (1, 'POLYGON ((10 190, 30 160, 40 110, 100 70, 120 10, 10 10, 10 190))'::geometry),
      (2, 'POLYGON ((100 190, 10 190, 30 160, 40 110, 50 80, 74 110.5, 100 130, 140 120, 140 160, 100 190))'::geometry),
      (3, 'POLYGON ((140 190, 190 190, 190 80, 140 80, 140 190))'::geometry),
      (4, 'POLYGON ((180 40, 120 10, 100 70, 140 80, 190 80, 180 40))'::geometry)
    )
    SELECT id, ST_AsText(ST_CoverageInvalidEdges(geom) OVER ())
      FROM coverage;

     id |               st_astext
    ----+---------------------------------------
      1 | LINESTRING (40 110, 100 70)
      2 | MULTILINESTRING ((100 130, 140 120, 140 160, 100 190), (40 110, 50 80, 74 110.5))
      3 | LINESTRING (140 80, 140 190)
      4 | null

    -- Test entire table for coverage validity
    SELECT true = ALL (
        SELECT ST_CoverageInvalidEdges(geom) OVER () IS NULL
        FROM coverage
        );

## See Also

ST_IsValid, ST_CoverageUnion, ST_CoverageSimplify

## Name

ST_CoverageSimplify — Window function that simplifies the edges of a polygonal coverage.

## Synopsis

`geometry ST_CoverageSimplify(` geometry winset geom, float8 tolerance, boolean simplifyBoundary = true`)`;

## Description

A window function which simplifies the edges of polygons in a polygonal coverage. The simplification preserves the coverage topology. This means the simplified output polygons are consistent along shared edges, and still form a valid coverage.

The simplification uses a variant of the Visvalingam–Whyatt algorithm. The `tolerance` parameter has units of distance, and is roughly equal to the square root of triangular areas to be simplified.

To simplify only the "internal" edges of the coverage (those that are shared by two polygons) set the `simplifyBoundary` parameter to false.

If the input is not a valid coverage there may be unexpected artifacts in the output (such as boundary intersections, or separated boundaries which appeared to be shared). Use ST_CoverageInvalidEdges to determine if a coverage is valid.

Availability: 3.4.0

Requires GEOS >= 3.12.0

## Examples

Input coverage | Simplified coverage

    WITH coverage(id, geom) AS (VALUES
      (1, 'POLYGON ((160 150, 110 130, 90 100, 90 70, 60 60, 50 10, 30 30, 40 50, 25 40, 10 60, 30 100, 30 120, 20 170, 60 180, 90 190, 130 180, 130 160, 160 150), (40 160, 50 140, 66 125, 60 100, 80 140, 90 170, 60 160, 40 160))'::geometry),
      (2, 'POLYGON ((40 160, 60 160, 90 170, 80 140, 60 100, 66 125, 50 140, 40 160))'::geometry),
      (3, 'POLYGON ((110 130, 160 50, 140 50, 120 33, 90 30, 50 10, 60 60, 90 70, 90 100, 110 130))'::geometry),
      (4, 'POLYGON ((160 150, 150 120, 160 90, 160 50, 110 130, 160 150))'::geometry)
    )
    SELECT id, ST_AsText(ST_CoverageSimplify(geom, 30) OVER ())
      FROM coverage;

     id |               st_astext
    ----+---------------------------------------
      1 | POLYGON ((160 150, 110 130, 50 10, 10 60, 20 170, 90 190, 160 150), (40 160, 66 125, 90 170, 40 160))
      2 | POLYGON ((40 160, 66 125, 90 170, 40 160))
      3 | POLYGON ((110 130, 160 50, 50 10, 110 130))
      4 | POLYGON ((160 150, 160 50, 110 130, 160 150))

## See Also

ST_CoverageInvalidEdges

## Name

ST_CoverageUnion — Computes the union of a set of polygons forming a coverage by removing shared edges.

## Synopsis

`geometry ST_CoverageUnion(` geometry set geom`)`;

## Description

An aggregate function which unions a set of polygons forming a polygonal coverage. The result is a polygonal geometry covering the same area as the coverage. This function produces the same result as ST_Union, but uses the coverage structure to compute the union much faster.

If the input is not a valid coverage there may be unexpected artifacts in the output (such as unmerged or overlapping polygons). Use ST_CoverageInvalidEdges to determine if a coverage is valid.

Availability: 3.4.0 - requires GEOS >= 3.8.0

## Examples

Input coverage | Union result

    WITH coverage(id, geom) AS (VALUES
      (1, 'POLYGON ((10 10, 10 150, 80 190, 110 150, 90 110, 40 110, 50 60, 10 10))'::geometry),
      (2, 'POLYGON ((120 10, 10 10, 50 60, 100 70, 120 10))'::geometry),
      (3, 'POLYGON ((140 80, 120 10, 100 70, 40 110, 90 110, 110 150, 140 80))'::geometry),
      (4, 'POLYGON ((140 190, 120 170, 140 130, 160 150, 140 190))'::geometry),
      (5, 'POLYGON ((180 160, 170 140, 140 130, 160 150, 140 190, 180 160))'::geometry)
    )
    SELECT ST_AsText(ST_CoverageUnion(geom))
      FROM coverage;

    --------------------------------------
    MULTIPOLYGON (((10 150, 80 190, 110 150, 140 80, 120 10, 10 10, 10 150), (50 60, 100 70, 40 110, 50 60)), ((120 170, 140 190, 180 160, 170 140, 140 130, 120 170)))

## See Also

ST_CoverageInvalidEdges, ST_Union

## 7.16. Affine Transformations

Abstract

These functions change the position and shape of geometries using affine transformations.

## Name

ST_Affine — Apply a 3D affine transformation to a geometry.

## Synopsis

`geometry ST_Affine(` geometry geomA, float a, float b, float c, float d, float e, float f, float g, float h, float i, float xoff, float yoff, float zoff`)`;

`geometry ST_Affine(` geometry geomA, float a, float b, float d, float e, float xoff, float yoff`)`;

## Description

Applies a 3D affine transformation to the geometry to do things like translate, rotate, scale in one step.

Version 1: The call

    ST_Affine(geom, a, b, c, d, e, f, g, h, i, xoff, yoff, zoff)

represents the transformation matrix

    / a  b  c  xoff \
    | d  e  f  yoff |
    | g  h  i  zoff |
    \ 0  0  0     1 /

and the vertices are transformed as follows:

    x' = a*x + b*y + c*z + xoff
    y' = d*x + e*y + f*z + yoff
    z' = g*x + h*y + i*z + zoff

All of the translate / scale functions below are expressed via such an affine transformation.

Version 2: Applies a 2d affine transformation to the geometry. The call

    ST_Affine(geom, a, b, d, e, xoff, yoff)

represents the transformation matrix

    /  a  b  0  xoff  \       /  a  b  xoff  \
    |  d  e  0  yoff  | rsp.  |  d  e  yoff  |
    |  0  0  1     0  |       \  0  0     1  /
    \  0  0  0     1  /

and the vertices are transformed as follows:

    x' = a*x + b*y + xoff
    y' = d*x + e*y + yoff
    z' = z

This method is a subcase of the 3D method above.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from Affine to ST_Affine in 1.2.2

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    --Rotate a 3d line 180 degrees about the z axis.  Note this is long-hand for doing ST_Rotate();
     SELECT ST_AsEWKT(ST_Affine(geom,  cos(pi()), -sin(pi()), 0,  sin(pi()), cos(pi()), 0,  0, 0, 1,  0, 0, 0)) As using_affine,
    	 ST_AsEWKT(ST_Rotate(geom, pi())) As using_rotate
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As geom) As foo;
            using_affine         |        using_rotate
    -----------------------------+-----------------------------
     LINESTRING(-1 -2 3,-1 -4 3) | LINESTRING(-1 -2 3,-1 -4 3)
    (1 row)

    --Rotate a 3d line 180 degrees in both the x and z axis
    SELECT ST_AsEWKT(ST_Affine(geom, cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), -sin(pi()), 0, sin(pi()), cos(pi()), 0, 0, 0))
    	FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 1 4 3)') As geom) As foo;
               st_asewkt
    -------------------------------
     LINESTRING(-1 -2 -3,-1 -4 -3)
    (1 row)

## See Also

ST_Rotate, ST_Scale, ST_Translate, ST_TransScale

## Name

ST_Rotate — Rotates a geometry about an origin point.

## Synopsis

`geometry ST_Rotate(` geometry geomA, float rotRadians`)`;

`geometry ST_Rotate(` geometry geomA, float rotRadians, float x0, float y0`)`;

`geometry ST_Rotate(` geometry geomA, float rotRadians, geometry pointOrigin`)`;

## Description

Rotates geometry rotRadians counter-clockwise about the origin point. The rotation origin can be specified either as a POINT geometry, or as x and y coordinates. If the origin is not specified, the geometry is rotated about POINT(0 0).

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added.

Availability: 1.1.2. Name changed from Rotate to ST_Rotate in 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate 180 degrees
    SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()));
                   st_asewkt
    ---------------------------------------
     LINESTRING(-50 -160,-50 -50,-100 -50)
    (1 row)

    --Rotate 30 degrees counter-clockwise at x=50, y=160
    SELECT ST_AsEWKT(ST_Rotate('LINESTRING (50 160, 50 50, 100 50)', pi()/6, 50, 160));
                                     st_asewkt
    ---------------------------------------------------------------------------
     LINESTRING(50 160,105 64.7372055837117,148.301270189222 89.7372055837117)
    (1 row)

    --Rotate 60 degrees clockwise from centroid
    SELECT ST_AsEWKT(ST_Rotate(geom, -pi()/3, ST_Centroid(geom)))
    FROM (SELECT 'LINESTRING (50 160, 50 50, 100 50)'::geometry AS geom) AS foo;
                               st_asewkt
    --------------------------------------------------------------
     LINESTRING(116.4225 130.6721,21.1597 75.6721,46.1597 32.3708)
    (1 row)

## See Also

ST_Affine, ST_RotateX, ST_RotateY, ST_RotateZ

## Name

ST_RotateX — Rotates a geometry about the X axis.

## Synopsis

`geometry ST_RotateX(` geometry geomA, float rotRadians`)`;

## Description

Rotates a geometry geomA - rotRadians about the X axis.

`ST_RotateX(geomA, rotRadians)` is short-hand for `ST_Affine(geomA, 1, 0, 0, 0, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0)`.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateX to ST_RotateX in 1.2.2

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along x-axis
    SELECT ST_AsEWKT(ST_RotateX(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(1 -3 2,1 -1 1)

## See Also

ST_Affine, ST_RotateY, ST_RotateZ

## Name

ST_RotateY — Rotates a geometry about the Y axis.

## Synopsis

`geometry ST_RotateY(` geometry geomA, float rotRadians`)`;

## Description

Rotates a geometry geomA - rotRadians about the y axis.

`ST_RotateY(geomA, rotRadians)` is short-hand for `ST_Affine(geomA, cos(rotRadians), 0, sin(rotRadians), 0, 1, 0, -sin(rotRadians), 0, cos(rotRadians), 0, 0, 0)`.

Availability: 1.1.2. Name changed from RotateY to ST_RotateY in 1.2.2

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along y-axis
     SELECT ST_AsEWKT(ST_RotateY(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(3 2 -1,1 1 -1)

## See Also

ST_Affine, ST_RotateX, ST_RotateZ

## Name

ST_RotateZ — Rotates a geometry about the Z axis.

## Synopsis

`geometry ST_RotateZ(` geometry geomA, float rotRadians`)`;

## Description

Rotates a geometry geomA - rotRadians about the Z axis.

This is a synonym for ST_Rotate

`ST_RotateZ(geomA, rotRadians)` is short-hand for `SELECT ST_Affine(geomA, cos(rotRadians), -sin(rotRadians), 0, sin(rotRadians), cos(rotRadians), 0, 0, 0, 1, 0, 0, 0)`.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Availability: 1.1.2. Name changed from RotateZ to ST_RotateZ in 1.2.2

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    --Rotate a line 90 degrees along z-axis
    SELECT ST_AsEWKT(ST_RotateZ(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), pi()/2));
    		 st_asewkt
    ---------------------------
     LINESTRING(-2 1 3,-1 1 1)

     --Rotate a curved circle around z-axis
    SELECT ST_AsEWKT(ST_RotateZ(geom, pi()/2))
    FROM (SELECT ST_LineToCurve(ST_Buffer(ST_GeomFromText('POINT(234 567)'), 3)) As geom) As foo;

    													   st_asewkt
    ----------------------------------------------------------------------------------------------------------------------------
     CURVEPOLYGON(CIRCULARSTRING(-567 237,-564.87867965644 236.12132034356,-564 234,-569.12132034356 231.87867965644,-567 237))

## See Also

ST_Affine, ST_RotateX, ST_RotateY

## Name

ST_Scale — Scales a geometry by given factors.

## Synopsis

`geometry ST_Scale(` geometry geomA, float XFactor, float YFactor, float ZFactor`)`;

`geometry ST_Scale(` geometry geomA, float XFactor, float YFactor`)`;

`geometry ST_Scale(` geometry geom, geometry factor`)`;

`geometry ST_Scale(` geometry geom, geometry factor, geometry origin`)`;

## Description

Scales the geometry to a new size by multiplying the ordinates with the corresponding factor parameters.

The version taking a geometry as the `factor` parameter allows passing a 2d, 3dm, 3dz or 4d point to set scaling factor for all supported dimensions. Missing dimensions in the `factor` point are equivalent to no scaling the corresponding dimension.

The three-geometry variant allows a "false origin" for the scaling to be passed in. This allows "scaling in place", for example using the centroid of the geometry as the false origin. Without a false origin, scaling takes place relative to the actual origin, so all coordinates are just multiplied by the scale factor.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.2.0 support for scaling all dimension (`factor` parameter) was introduced.

Enhanced: 2.5.0 support for scaling relative to a local origin (`origin` parameter) was introduced.

This function supports Polyhedral surfaces.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports M coordinates.

## Examples

    --Version 1: scale X, Y, Z
    SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75, 0.8));
    			  st_asewkt
    --------------------------------------
     LINESTRING(0.5 1.5 2.4,0.5 0.75 0.8)

    --Version 2: Scale X Y
     SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 0.75));
    			st_asewkt
    ----------------------------------
     LINESTRING(0.5 1.5 3,0.5 0.75 1)

    --Version 3: Scale X Y Z M
     SELECT ST_AsEWKT(ST_Scale(ST_GeomFromEWKT('LINESTRING(1 2 3 4, 1 1 1 1)'),
       ST_MakePoint(0.5, 0.75, 2, -1)));
    			       st_asewkt
    ----------------------------------------
     LINESTRING(0.5 1.5 6 -4,0.5 0.75 2 -1)

    --Version 4: Scale X Y using false origin
    SELECT ST_AsText(ST_Scale('LINESTRING(1 1, 2 2)', 'POINT(2 2)', 'POINT(1 1)'::geometry));
          st_astext
    ---------------------
     LINESTRING(1 1,3 3)

## See Also

ST_Affine, ST_TransScale

## Name

ST_Translate — Translates a geometry by given offsets.

## Synopsis

`geometry ST_Translate(` geometry g1, float deltax, float deltay`)`;

`geometry ST_Translate(` geometry g1, float deltax, float deltay, float deltaz`)`;

## Description

Returns a new geometry whose coordinates are translated delta x,delta y,delta z units. Units are based on the units defined in spatial reference (SRID) for this geometry.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.2.2

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

Move a point 1 degree longitude

    	SELECT ST_AsText(ST_Translate(ST_GeomFromText('POINT(-71.01 42.37)',4326),1,0)) As wgs_transgeomtxt;

    	wgs_transgeomtxt
    	---------------------
    	POINT(-70.01 42.37)

Move a linestring 1 degree longitude and 1/2 degree latitude

    SELECT ST_AsText(ST_Translate(ST_GeomFromText('LINESTRING(-71.01 42.37,-71.11 42.38)',4326),1,0.5)) As wgs_transgeomtxt;
    		   wgs_transgeomtxt
    	---------------------------------------
    	LINESTRING(-70.01 42.87,-70.11 42.88)

Move a 3d point

    SELECT ST_AsEWKT(ST_Translate(CAST('POINT(0 0 0)' As geometry), 5, 12,3));
    	st_asewkt
    	---------
    	POINT(5 12 3)

Move a curve and a point

    SELECT ST_AsText(ST_Translate(ST_Collect('CURVEPOLYGON(CIRCULARSTRING(4 3,3.12 0.878,1 0,-1.121 5.1213,6 7, 8 9,4 3))','POINT(1 3)'),1,2));
    														 st_astext
    ------------------------------------------------------------------------------------------------------------
     GEOMETRYCOLLECTION(CURVEPOLYGON(CIRCULARSTRING(5 5,4.12 2.878,2 2,-0.121 7.1213,7 9,9 11,5 5)),POINT(2 5))

## See Also

ST_Affine, ST_AsText, ST_GeomFromText

## Name

ST_TransScale — Translates and scales a geometry by given offsets and factors.

## Synopsis

`geometry ST_TransScale(` geometry geomA, float deltaX, float deltaY, float XFactor, float YFactor`)`;

## Description

Translates the geometry using the deltaX and deltaY args, then scales it using the XFactor, YFactor args, working in 2D only.

`ST_TransScale(geomA, deltaX, deltaY, XFactor, YFactor)` is short-hand for `ST_Affine(geomA, XFactor, 0, 0, 0, YFactor, 0, 0, 0, 1, deltaX*XFactor, deltaY*YFactor, 0)`.

Prior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+

Availability: 1.1.0.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_AsEWKT(ST_TransScale(ST_GeomFromEWKT('LINESTRING(1 2 3, 1 1 1)'), 0.5, 1, 1, 2));
    		  st_asewkt
    -----------------------------
     LINESTRING(1.5 6 3,1.5 4 1)

    --Buffer a point to get an approximation of a circle, convert to curve and then translate 1,2 and scale it 3,4
      SELECT ST_AsText(ST_Transscale(ST_LineToCurve(ST_Buffer('POINT(234 567)', 3)),1,2,3,4));
    														  st_astext
    ------------------------------------------------------------------------------------------------------------------------------
     CURVEPOLYGON(CIRCULARSTRING(714 2276,711.363961030679 2267.51471862576,705 2264,698.636038969321 2284.48528137424,714 2276))

## See Also

ST_Affine, ST_Translate

## 7.17. Clustering Functions

Abstract

These functions implement clustering algorithms for sets of geometries.

## Name

ST_ClusterDBSCAN — Window function that returns a cluster id for each input geometry using the DBSCAN algorithm.

## Synopsis

`integer ST_ClusterDBSCAN(` geometry winset geom, float8 eps, integer minpoints`)`;

## Description

A window function that returns a cluster number for each input geometry, using the 2D Density-based spatial clustering of applications with noise (DBSCAN) algorithm. Unlike ST_ClusterKMeans, it does not require the number of clusters to be specified, but instead uses the desired distance (`eps`) and density (`minpoints`) parameters to determine each cluster.

An input geometry is added to a cluster if it is either:

- A "core" geometry, that is within `eps` distance of at least `minpoints` input geometries (including itself); or

- A "border" geometry, that is within `eps` distance of a core geometry.

Note that border geometries may be within `eps` distance of core geometries in more than one cluster. Either assignment would be correct, so the border geometry will be arbitrarily asssigned to one of the available clusters. In this situation it is possible for a correct cluster to be generated with fewer than `minpoints` geometries. To ensure deterministic assignment of border geometries (so that repeated calls to ST_ClusterDBSCAN will produce identical results) use an `ORDER BY` clause in the window definition. Ambiguous cluster assignments may differ from other DBSCAN implementations.

Geometries that do not meet the criteria to join any cluster are assigned a cluster number of NULL.

Availability: 2.3.0

This method supports Circular Strings and Curves.

## Examples

Clustering polygon within 50 meters of each other, and requiring at least 2 polygons per cluster.

Clusters within 50 meters with at least 2 items per cluster. Singletons have NULL for cid
    SELECT name, ST_ClusterDBSCAN(geom, eps => 50, minpoints => 2) over () AS cid
    FROM boston_polys
    WHERE name > '' AND building > ''
    	AND ST_DWithin(geom,
            ST_Transform(
                ST_GeomFromText('POINT(-71.04054 42.35141)', 4326), 26986),
               500);
                    name                 | bucket
    -------------------------------------+--------
     Manulife Tower                      |      0
     Park Lane Seaport I                 |      0
     Park Lane Seaport II                |      0
     Renaissance Boston Waterfront Hotel |      0
     Seaport Boston Hotel                |      0
     Seaport Hotel & World Trade Center  |      0
     Waterside Place                     |      0
     World Trade Center East             |      0
     100 Northern Avenue                 |      1
     100 Pier 4                          |      1
     The Institute of Contemporary Art   |      1
     101 Seaport                         |      2
     District Hall                       |      2
     One Marina Park Drive               |      2
     Twenty Two Liberty                  |      2
     Vertex                              |      2
     Vertex                              |      2
     Watermark Seaport                   |      2
     Blue Hills Bank Pavilion            |   NULL
     World Trade Center West             |   NULL
    (20 rows)

A example showing combining parcels with the same cluster number into geometry collections.

    SELECT cid, ST_Collect(geom) AS cluster_geom, array_agg(parcel_id) AS ids_in_cluster FROM (
        SELECT parcel_id, ST_ClusterDBSCAN(geom, eps => 0.5, minpoints => 5) over () AS cid, geom
        FROM parcels) sq
    GROUP BY cid;

## See Also

ST_DWithin, ST_ClusterKMeans, ST_ClusterIntersecting, ST_ClusterIntersectingWin, ST_ClusterWithin, ST_ClusterWithinWin

## Name

ST_ClusterIntersecting — Aggregate function that clusters input geometries into connected sets.

## Synopsis

`geometry[] ST_ClusterIntersecting(` geometry set g`)`;

## Description

An aggregate function that returns an array of GeometryCollections partitioning the input geometries into connected clusters that are disjoint. Each geometry in a cluster intersects at least one other geometry in the cluster, and does not intersect any geometry in other clusters.

Availability: 2.2.0

## Examples

    WITH testdata AS
      (SELECT unnest(ARRAY['LINESTRING (0 0, 1 1)'::geometry,
               'LINESTRING (5 5, 4 4)'::geometry,
               'LINESTRING (6 6, 7 7)'::geometry,
               'LINESTRING (0 0, -1 -1)'::geometry,
               'POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))'::geometry]) AS geom)

    SELECT ST_AsText(unnest(ST_ClusterIntersecting(geom))) FROM testdata;

    --result

    st_astext
    ---------
    GEOMETRYCOLLECTION(LINESTRING(0 0,1 1),LINESTRING(5 5,4 4),LINESTRING(0 0,-1 -1),POLYGON((0 0,4 0,4 4,0 4,0 0)))
    GEOMETRYCOLLECTION(LINESTRING(6 6,7 7))

## See Also

ST_ClusterIntersectingWin, ST_ClusterWithin, ST_ClusterWithinWin

## Name

ST_ClusterIntersectingWin — Window function that returns a cluster id for each input geometry, clustering input geometries into connected sets.

## Synopsis

`integer ST_ClusterIntersectingWin(` geometry winset geom`)`;

## Description

A window function that builds connected clusters of geometries that intersect. It is possible to traverse all geometries in a cluster without leaving the cluster. The return value is the cluster number that the geometry argument participates in, or null for null inputs.

Availability: 3.4.0

## Examples

    WITH testdata AS (
      SELECT id, geom::geometry FROM (
      VALUES  (1, 'LINESTRING (0 0, 1 1)'),
              (2, 'LINESTRING (5 5, 4 4)'),
              (3, 'LINESTRING (6 6, 7 7)'),
              (4, 'LINESTRING (0 0, -1 -1)'),
              (5, 'POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))')) AS t(id, geom)
    )
    SELECT id,
      ST_AsText(geom),
      ST_ClusterIntersectingWin(geom) OVER () AS cluster
    FROM testdata;

     id |           st_astext            | cluster
    ----+--------------------------------+---------
      1 | LINESTRING(0 0,1 1)            |       0
      2 | LINESTRING(5 5,4 4)            |       0
      3 | LINESTRING(6 6,7 7)            |       1
      4 | LINESTRING(0 0,-1 -1)          |       0
      5 | POLYGON((0 0,4 0,4 4,0 4,0 0)) |       0

## See Also

ST_ClusterIntersecting, ST_ClusterWithin, ST_ClusterWithinWin

## Name

ST_ClusterKMeans — Window function that returns a cluster id for each input geometry using the K-means algorithm.

## Synopsis

`integer ST_ClusterKMeans(` geometry winset geom, integer number_of_clusters, float max_radius`)`;

## Description

Returns K-means cluster number for each input geometry. The distance used for clustering is the distance between the centroids for 2D geometries, and distance between bounding box centers for 3D geometries. For POINT inputs, M coordinate will be treated as weight of input and has to be larger than 0.

`max_radius`, if set, will cause ST_ClusterKMeans to generate more clusters than `k` ensuring that no cluster in output has radius larger than `max_radius`. This is useful in reachability analysis.

Enhanced: 3.2.0 Support for `max_radius`

Enhanced: 3.1.0 Support for 3D geometries and weights

Availability: 2.3.0

## Examples

Generate dummy set of parcels for examples:

    CREATE TABLE parcels AS
    SELECT lpad((row_number() over())::text,3,'0') As parcel_id, geom,
    ('{residential, commercial}'::text[])[1 + mod(row_number()OVER(),2)] As type
    FROM
        ST_Subdivide(ST_Buffer('SRID=3857;LINESTRING(40 100, 98 100, 100 150, 60 90)'::geometry,
        40, 'endcap=square'),12) As geom;

Parcels color-coded by cluster number (cid)

    SELECT ST_ClusterKMeans(geom, 3) OVER() AS cid, parcel_id, geom
        FROM parcels;

     cid | parcel_id |   geom
    -----+-----------+---------------
       0 | 001       | 0103000000...
       0 | 002       | 0103000000...
       1 | 003       | 0103000000...
       0 | 004       | 0103000000...
       1 | 005       | 0103000000...
       2 | 006       | 0103000000...
       2 | 007       | 0103000000...

Partitioning parcel clusters by type:

    SELECT ST_ClusterKMeans(geom, 3) over (PARTITION BY type) AS cid, parcel_id, type
        FROM parcels;

     cid | parcel_id |    type
    -----+-----------+-------------
       1 | 005       | commercial
       1 | 003       | commercial
       2 | 007       | commercial
       0 | 001       | commercial
       1 | 004       | residential
       0 | 002       | residential
       2 | 006       | residential

Example: Clustering a preaggregated planetary-scale data population dataset using 3D clusering and weighting. Identify at least 20 regions based on Kontur Population Data that do not span more than 3000 km from their center:

    create table kontur_population_3000km_clusters as
    select
        geom,
        ST_ClusterKMeans(
            ST_Force4D(
                ST_Transform(ST_Force3D(geom), 4978), -- cluster in 3D XYZ CRS
                mvalue => population -- set clustering to be weighed by population
            ),
            20,                      -- aim to generate at least 20 clusters
            max_radius => 3000000    -- but generate more to make each under 3000 km radius
        ) over () as cid
    from
        kontur_population;

World population clustered to above specs produces 46 clusters. Clusters are centered at well-populated regions (New York, Moscow). Greenland is one cluster. There are island clusters that span across the antimeridian. Cluster edges follow Earth's curvature.

## See Also

ST_ClusterDBSCAN, ST_ClusterIntersectingWin, ST_ClusterWithinWin, ST_ClusterIntersecting, ST_ClusterWithin, ST_Subdivide, ST_Force3D, ST_Force4D,

## Name

ST_ClusterWithin — Aggregate function that clusters geometries by separation distance.

## Synopsis

`geometry[] ST_ClusterWithin(` geometry set g, float8 distance`)`;

## Description

An aggregate function that returns an array of GeometryCollections, where each collection is a cluster containing some input geometries. Clustering partitions the input geometries into sets in which each geometry is within the specified `distance` of at least one other geometry in the same cluster. Distances are Cartesian distances in the units of the SRID.

ST_ClusterWithin is equivalent to running ST_ClusterDBSCAN with `minpoints => 0`.

Availability: 2.2.0

This method supports Circular Strings and Curves.

## Examples

    WITH testdata AS
      (SELECT unnest(ARRAY['LINESTRING (0 0, 1 1)'::geometry,
    		       'LINESTRING (5 5, 4 4)'::geometry,
    		       'LINESTRING (6 6, 7 7)'::geometry,
    		       'LINESTRING (0 0, -1 -1)'::geometry,
    		       'POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))'::geometry]) AS geom)

    SELECT ST_AsText(unnest(ST_ClusterWithin(geom, 1.4))) FROM testdata;

    --result

    st_astext
    ---------
    GEOMETRYCOLLECTION(LINESTRING(0 0,1 1),LINESTRING(5 5,4 4),LINESTRING(0 0,-1 -1),POLYGON((0 0,4 0,4 4,0 4,0 0)))
    GEOMETRYCOLLECTION(LINESTRING(6 6,7 7))

## See Also

ST_ClusterWithinWin, ST_ClusterDBSCAN, ST_ClusterIntersecting, ST_ClusterIntersectingWin

## Name

ST_ClusterWithinWin — Window function that returns a cluster id for each input geometry, clustering using separation distance.

## Synopsis

`integer ST_ClusterWithinWin(` geometry winset geom, float8 distance`)`;

## Description

A window function that returns a cluster number for each input geometry. Clustering partitions the geometries into sets in which each geometry is within the specified `distance` of at least one other geometry in the same cluster. Distances are Cartesian distances in the units of the SRID.

ST_ClusterWithinWin is equivalent to running ST_ClusterDBSCAN with `minpoints => 0`.

Availability: 3.4.0

This method supports Circular Strings and Curves.

## Examples

    WITH testdata AS (
      SELECT id, geom::geometry FROM (
      VALUES  (1, 'LINESTRING (0 0, 1 1)'),
              (2, 'LINESTRING (5 5, 4 4)'),
              (3, 'LINESTRING (6 6, 7 7)'),
              (4, 'LINESTRING (0 0, -1 -1)'),
              (5, 'POLYGON ((0 0, 4 0, 4 4, 0 4, 0 0))')) AS t(id, geom)
    )
    SELECT id,
      ST_AsText(geom),
      ST_ClusterWithinWin(geom, 1.4) OVER () AS cluster
    FROM testdata;

     id |           st_astext            | cluster
    ----+--------------------------------+---------
      1 | LINESTRING(0 0,1 1)            |       0
      2 | LINESTRING(5 5,4 4)            |       0
      3 | LINESTRING(6 6,7 7)            |       1
      4 | LINESTRING(0 0,-1 -1)          |       0
      5 | POLYGON((0 0,4 0,4 4,0 4,0 0)) |       0

## See Also

ST_ClusterWithin, ST_ClusterDBSCAN, ST_ClusterIntersecting, ST_ClusterIntersectingWin,

## 7.18. Bounding Box Functions

Abstract

These functions produce or operate on bounding boxes. They can also provide and accept geometry values, by using automatic or explicit casts.

See also Section 13.7, “PostGIS Box Functions”.

## Name

Box2D — Returns a BOX2D representing the 2D extent of a geometry.

## Synopsis

`box2d Box2D(` geometry geom`)`;

## Description

Returns a box2d representing the 2D extent of the geometry.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT Box2D(ST_GeomFromText('LINESTRING(1 2, 3 4, 5 6)'));

    box2d
    ---------
    BOX(1 2,5 6)

    SELECT Box2D(ST_GeomFromText('CIRCULARSTRING(220268 150415,220227 150505,220227 150406)'));

    box2d
    --------
    BOX(220186.984375 150406,220288.25 150506.140625)

## See Also

Box3D, ST_GeomFromText

## Name

Box3D — Returns a BOX3D representing the 3D extent of a geometry.

## Synopsis

`box3d Box3D(` geometry geom`)`;

## Description

Returns a box3d representing the 3D extent of the geometry.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This function supports 3d and will not drop the z-index.

## Examples

    SELECT Box3D(ST_GeomFromEWKT('LINESTRING(1 2 3, 3 4 5, 5 6 5)'));

    Box3d
    ---------
    BOX3D(1 2 3,5 6 5)

    SELECT Box3D(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 1,220227 150406 1)'));

    Box3d
    --------
    BOX3D(220227 150406 1,220268 150415 1)

## See Also

Box2D, ST_GeomFromEWKT

## Name

ST_EstimatedExtent — Returns the estimated extent of a spatial table.

## Synopsis

`box2d ST_EstimatedExtent(` text schema_name, text table_name, text geocolumn_name, boolean parent_only`)`;

`box2d ST_EstimatedExtent(` text schema_name, text table_name, text geocolumn_name`)`;

`box2d ST_EstimatedExtent(` text table_name, text geocolumn_name`)`;

## Description

Returns the estimated extent of a spatial table as a box2d. The current schema is used if not specified. The estimated extent is taken from the geometry column's statistics. This is usually much faster than computing the exact extent of the table using ST_Extent or ST_3DExtent.

The default behavior is to also use statistics collected from child tables (tables with INHERITS) if available. If `parent_only` is set to TRUE, only statistics for the given table are used and child tables are ignored.

For PostgreSQL >= 8.0.0 statistics are gathered by VACUUM ANALYZE and the result extent will be about 95% of the actual one. For PostgreSQL < 8.0.0 statistics are gathered by running `update_geometry_stats()` and the result extent is exact.

In the absence of statistics (empty table or no ANALYZE called) this function returns NULL. Prior to version 1.5.4 an exception was thrown instead.

Escaping names for tables and/or namespaces that include special characters and quotes may require special handling. A user notes: "For schemas and tables, use identifier escaping rules to produce a double-quoted string, and afterwards remove the first and last double-quote character. For geometry column pass as is."

Availability: 1.0.0

Changed: 2.1.0. Up to 2.0.x this was called ST_Estimated_Extent.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_EstimatedExtent('ny', 'edges', 'geom');
    --result--
    BOX(-8877653 4912316,-8010225.5 5589284)

    SELECT ST_EstimatedExtent('feature_poly', 'geom');
    --result--
    BOX(-124.659652709961 24.6830825805664,-67.7798080444336 49.0012092590332)

## See Also

ST_Extent, ST_3DExtent

## Name

ST_Expand — Returns a bounding box expanded from another bounding box or a geometry.

## Synopsis

`geometry ST_Expand(` geometry geom, float units_to_expand`)`;

`geometry ST_Expand(` geometry geom, float dx, float dy, float dz=0, float dm=0`)`;

`box2d ST_Expand(` box2d box, float units_to_expand`)`;

`box2d ST_Expand(` box2d box, float dx, float dy`)`;

`box3d ST_Expand(` box3d box, float units_to_expand`)`;

`box3d ST_Expand(` box3d box, float dx, float dy, float dz=0`)`;

## Description

Returns a bounding box expanded from the bounding box of the input, either by specifying a single distance with which the box should be expanded on both axes, or by specifying an expansion distance for each axis. Uses double-precision. Can be used for distance queries, or to add a bounding box filter to a query to take advantage of a spatial index.

In addition to the version of ST_Expand accepting and returning a geometry, variants are provided that accept and return box2d and box3d data types.

Distances are in the units of the spatial reference system of the input.

ST_Expand is similar to ST_Buffer, except while buffering expands a geometry in all directions, ST_Expand expands the bounding box along each axis.

Pre version 1.3, ST_Expand was used in conjunction with ST_Distance to do indexable distance queries. For example, `geom && ST_Expand('POINT(10 20)', 10) AND ST_Distance(geom, 'POINT(10 20)') < 10`. This has been replaced by the simpler and more efficient ST_DWithin function.

Availability: 1.5.0 behavior changed to output double precision instead of float4 coordinates.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Enhanced: 2.3.0 support was added to expand a box by different amounts in different dimensions.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Examples below use US National Atlas Equal Area (SRID=2163) which is a meter projection

    --10 meter expanded box around bbox of a linestring
    SELECT CAST(ST_Expand(ST_GeomFromText('LINESTRING(2312980 110676,2312923 110701,2312892 110714)', 2163),10) As box2d);
    					 st_expand
    ------------------------------------
     BOX(2312882 110666,2312990 110724)

    --10 meter expanded 3D box of a 3D box
    SELECT ST_Expand(CAST('BOX3D(778783 2951741 1,794875 2970042.61545891 10)' As box3d),10)
    							  st_expand
    -----------------------------------------------------
     BOX3D(778773 2951731 -9,794885 2970052.61545891 20)

     --10 meter geometry astext rep of a expand box around a point geometry
     SELECT ST_AsEWKT(ST_Expand(ST_GeomFromEWKT('SRID=2163;POINT(2312980 110676)'),10));
    											st_asewkt
    -------------------------------------------------------------------------------------------------
     SRID=2163;POLYGON((2312970 110666,2312970 110686,2312990 110686,2312990 110666,2312970 110666))

## See Also

ST_Buffer, ST_DWithin, ST_SRID

## Name

ST_Extent — Aggregate function that returns the bounding box of geometries.

## Synopsis

`box2d ST_Extent(` geometry set geomfield`)`;

## Description

An aggregate function that returns a box2d bounding box that bounds a set of geometries.

The bounding box coordinates are in the spatial reference system of the input geometries.

ST_Extent is similar in concept to Oracle Spatial/Locator's SDO_AGGR_MBR.

ST_Extent returns boxes with only X and Y ordinates even with 3D geometries. To return XYZ ordinates use ST_3DExtent.

The returned `box3d` value does not include a SRID. Use ST_SetSRID to convert it into a geometry with SRID metadata. The SRID is the same as the input geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Examples below use Massachusetts State Plane ft (SRID=2249)

    SELECT ST_Extent(geom) as bextent FROM sometable;
    					 st_bextent
    ------------------------------------
    BOX(739651.875 2908247.25,794875.8125 2970042.75)

    --Return extent of each category of geometries
    SELECT ST_Extent(geom) as bextent
    FROM sometable
    GROUP BY category ORDER BY category;

    					  bextent                       |         name
    ----------------------------------------------------+----------------
     BOX(778783.5625 2951741.25,794875.8125 2970042.75) | A
     BOX(751315.8125 2919164.75,765202.6875 2935417.25) | B
     BOX(739651.875 2917394.75,756688.375 2935866)      | C

     --Force back into a geometry
     -- and render the extended text representation of that geometry
    SELECT ST_SetSRID(ST_Extent(geom),2249) as bextent FROM sometable;

    				bextent
    --------------------------------------------------------------------------------
     SRID=2249;POLYGON((739651.875 2908247.25,739651.875 2970042.75,794875.8125 2970042.75,
     794875.8125 2908247.25,739651.875 2908247.25))

## See Also

ST_EstimatedExtent, ST_3DExtent, ST_SetSRID

## Name

ST_3DExtent — Aggregate function that returns the 3D bounding box of geometries.

## Synopsis

`box3d ST_3DExtent(` geometry set geomfield`)`;

## Description

An aggregate function that returns a box3d (includes Z ordinate) bounding box that bounds a set of geometries.

The bounding box coordinates are in the spatial reference system of the input geometries.

The returned `box3d` value does not include a SRID. Use ST_SetSRID to convert it into a geometry with SRID metadata. The SRID is the same as the input geometries.

Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced.

Changed: 2.0.0 In prior versions this used to be called ST_Extent3D

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_3DExtent(foo.geom) As b3extent
    FROM (SELECT ST_MakePoint(x,y,z) As geom
    	FROM generate_series(1,3) As x
    		CROSS JOIN generate_series(1,2) As y
    		CROSS JOIN generate_series(0,2) As Z) As foo;
    	  b3extent
    --------------------
     BOX3D(1 1 0,3 2 2)

    --Get the extent of various elevated circular strings
    SELECT ST_3DExtent(foo.geom) As b3extent
    FROM (SELECT ST_Translate(ST_Force_3DZ(ST_LineToCurve(ST_Buffer(ST_Point(x,y),1))),0,0,z) As geom
    	FROM generate_series(1,3) As x
    		CROSS JOIN generate_series(1,2) As y
    		CROSS JOIN generate_series(0,2) As Z) As foo;

    	b3extent
    --------------------
     BOX3D(1 0 0,4 2 2)

## See Also

ST_Extent, ST_Force3DZ, ST_SetSRID

## Name

ST_MakeBox2D — Creates a BOX2D defined by two 2D point geometries.

## Synopsis

`box2d ST_MakeBox2D(` geometry pointLowLeft, geometry pointUpRight`)`;

## Description

Creates a box2d defined by two Point geometries. This is useful for doing range queries.

## Examples

    --Return all features that fall reside or partly reside in a US national atlas coordinate bounding box
    --It is assumed here that the geometries are stored with SRID = 2163 (US National atlas equal area)
    SELECT feature_id, feature_name, geom
    FROM features
    WHERE geom && ST_SetSRID(ST_MakeBox2D(ST_Point(-989502.1875, 528439.5625),
    	ST_Point(-987121.375 ,529933.1875)),2163)

## See Also

ST_Point, ST_SetSRID, ST_SRID

## Name

ST_3DMakeBox — Creates a BOX3D defined by two 3D point geometries.

## Synopsis

`box3d ST_3DMakeBox(` geometry point3DLowLeftBottom, geometry point3DUpRightTop`)`;

## Description

Creates a box3d defined by two 3D Point geometries.

This function supports 3D and will not drop the z-index.

Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D

## Examples

    SELECT ST_3DMakeBox(ST_MakePoint(-989502.1875, 528439.5625, 10),
    	ST_MakePoint(-987121.375 ,529933.1875, 10)) As abb3d

    --bb3d--
    --------
    BOX3D(-989502.1875 528439.5625 10,-987121.375 529933.1875 10)

## See Also

ST_MakePoint, ST_SetSRID, ST_SRID

## Name

ST_XMax — Returns the X maxima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_XMax(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the X maxima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However, it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_XMax('BOX3D(1 2 3, 4 5 6)');
    st_xmax
    -------
    4

    SELECT ST_XMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_xmax
    -------
    5

    SELECT ST_XMax(CAST('BOX(-3 2, 3 4)' As box2d));
    st_xmax
    -------
    3
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_XMax('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_XMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_xmax
    --------
    220288.248780547

## See Also

ST_XMin, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_XMin — Returns the X minima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_XMin(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the X minima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_XMin('BOX3D(1 2 3, 4 5 6)');
    st_xmin
    -------
    1

    SELECT ST_XMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_xmin
    -------
    1

    SELECT ST_XMin(CAST('BOX(-3 2, 3 4)' As box2d));
    st_xmin
    -------
    -3
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_XMin('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_XMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_xmin
    --------
    220186.995121892

## See Also

ST_XMax, ST_YMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_YMax — Returns the Y maxima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_YMax(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the Y maxima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_YMax('BOX3D(1 2 3, 4 5 6)');
    st_ymax
    -------
    5

    SELECT ST_YMax(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_ymax
    -------
    6

    SELECT ST_YMax(CAST('BOX(-3 2, 3 4)' As box2d));
    st_ymax
    -------
    4
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_YMax('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_YMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_ymax
    --------
    150506.126829327

## See Also

ST_XMin, ST_XMax, ST_YMin, ST_ZMax, ST_ZMin

## Name

ST_YMin — Returns the Y minima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_YMin(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the Y minima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_YMin('BOX3D(1 2 3, 4 5 6)');
    st_ymin
    -------
    2

    SELECT ST_YMin(ST_GeomFromText('LINESTRING(1 3 4, 5 6 7)'));
    st_ymin
    -------
    3

    SELECT ST_YMin(CAST('BOX(-3 2, 3 4)' As box2d));
    st_ymin
    -------
    2
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_YMin('LINESTRING(1 3, 5 6)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_YMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_ymin
    --------
    150406

## See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_ZMax, ST_ZMin

## Name

ST_ZMax — Returns the Z maxima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_ZMax(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the Z maxima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_ZMax('BOX3D(1 2 3, 4 5 6)');
    st_zmax
    -------
    6

    SELECT ST_ZMax(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
    st_zmax
    -------
    7

    SELECT ST_ZMax('BOX3D(-3 2 1, 3 4 1)' );
    st_zmax
    -------
    1
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_ZMax('LINESTRING(1 3 4, 5 6 7)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_ZMax(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_zmax
    --------
    3

## See Also

ST_GeomFromEWKT, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

## Name

ST_ZMin — Returns the Z minima of a 2D or 3D bounding box or a geometry.

## Synopsis

`float ST_ZMin(` box3d aGeomorBox2DorBox3D`)`;

## Description

Returns the Z minima of a 2D or 3D bounding box or a geometry.

Although this function is only defined for box3d, it also works for box2d and geometry values due to automatic casting. However it will not accept a geometry or box2d text representation, since those do not auto-cast.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves.

## Examples

    SELECT ST_ZMin('BOX3D(1 2 3, 4 5 6)');
    st_zmin
    -------
    3

    SELECT ST_ZMin(ST_GeomFromEWKT('LINESTRING(1 3 4, 5 6 7)'));
    st_zmin
    -------
    4

    SELECT ST_ZMin('BOX3D(-3 2 1, 3 4 1)' );
    st_zmin
    -------
    1
    --Observe THIS DOES NOT WORK because it will try to auto-cast the string representation to a BOX3D
    SELECT ST_ZMin('LINESTRING(1 3 4, 5 6 7)');

    --ERROR:  BOX3D parser - doesn't start with BOX3D(

    SELECT ST_ZMin(ST_GeomFromEWKT('CIRCULARSTRING(220268 150415 1,220227 150505 2,220227 150406 3)'));
    st_zmin
    --------
    1

## See Also

ST_GeomFromEWKT, ST_GeomFromText, ST_XMin, ST_XMax, ST_YMax, ST_YMin, ST_ZMax

## 7.19. Linear Referencing

## Name

ST_LineInterpolatePoint — Returns a point interpolated along a line at a fractional location.

## Synopsis

`geometry ST_LineInterpolatePoint(` geometry a_linestring, float8 a_fraction`)`;

`geography ST_LineInterpolatePoint(` geography a_linestring, float8 a_fraction, boolean use_spheroid = true`)`;

## Description

Returns a point interpolated along a line at a fractional location. First argument must be a LINESTRING. Second argument is a float between 0 and 1 representing the fraction of line length where the point is to be located. The Z and M values are interpolated if present.

See ST_LineLocatePoint for computing the line location nearest to a Point.

This function computes points in 2D and then interpolates values for Z and M, while ST_3DLineInterpolatePoint computes points in 3D and only interpolates the M value.

Since release 1.1.1 this function also interpolates M and Z values (when present), while prior releases set them to 0.0.

Availability: 0.8.2, Z and M supported added in 1.1.1

Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Interpolate_Point.

This function supports 3d and will not drop the z-index.

## Examples

A LineString with the interpolated point at 20% position (0.20)

    -- The point 20% along a line

    SELECT ST_AsEWKT(  ST_LineInterpolatePoint(
            'LINESTRING(25 50, 100 125, 150 190)',
            0.2 ));
    ----------------
     POINT(51.5974135047432 76.5974135047432)

The mid-point of a 3D line:

    SELECT ST_AsEWKT(  ST_LineInterpolatePoint('
            LINESTRING(1 2 3, 4 5 6, 6 7 8)',
            0.5 ));
    --------------------
     POINT(3.5 4.5 5.5)

The closest point on a line to a point:

    SELECT ST_AsText( ST_LineInterpolatePoint( line.geom,
                          ST_LineLocatePoint( line.geom, 'POINT(4 3)')))
    FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As geom) AS line;
    ------------
     POINT(3 4)

## See Also

ST_LineInterpolatePoints, ST_3DLineInterpolatePoint, ST_LineLocatePoint

## Name

ST_3DLineInterpolatePoint — Returns a point interpolated along a 3D line at a fractional location.

## Synopsis

`geometry ST_3DLineInterpolatePoint(` geometry a_linestring, float8 a_fraction`)`;

## Description

Returns a point interpolated along a 3D line at a fractional location. First argument must be a LINESTRING. Second argument is a float between 0 and 1 representing the point location as a fraction of line length. The M value is interpolated if present.

ST_LineInterpolatePoint computes points in 2D and then interpolates the values for Z and M, while this function computes points in 3D and only interpolates the M value.

Availability: 3.0.0

This function supports 3d and will not drop the z-index.

## Examples

Return point 20% along 3D line

    SELECT ST_AsText(
        ST_3DLineInterpolatePoint('LINESTRING(25 50 70, 100 125 90, 150 190 200)',
            0.20));

       st_asetext
    ----------------
     POINT Z (59.0675892910822 84.0675892910822 79.0846904776219)

## See Also

ST_LineInterpolatePoint, ST_LineInterpolatePoints, ST_LineLocatePoint

## Name

ST_LineInterpolatePoints — Returns points interpolated along a line at a fractional interval.

## Synopsis

`geometry ST_LineInterpolatePoints(` geometry a_linestring, float8 a_fraction, boolean repeat`)`;

`geography ST_LineInterpolatePoints(` geography a_linestring, float8 a_fraction, boolean use_spheroid = true, boolean repeat = true`)`;

## Description

Returns one or more points interpolated along a line at a fractional interval. The first argument must be a LINESTRING. The second argument is a float8 between 0 and 1 representing the spacing between the points as a fraction of line length. If the third argument is false, at most one point will be constructed (which is equivalent to ST_LineInterpolatePoint.)

If the result has zero or one points, it is returned as a POINT. If it has two or more points, it is returned as a MULTIPOINT.

Availability: 2.5.0

This function supports 3d and will not drop the z-index.

This function supports M coordinates.

## Examples

A LineString with points interpolated every 20%

    --Return points each 20% along a 2D line
    SELECT ST_AsText(ST_LineInterpolatePoints('LINESTRING(25 50, 100 125, 150 190)', 0.20))
    ----------------
     MULTIPOINT((51.5974135047432 76.5974135047432),(78.1948270094864 103.194827009486),(104.132163186446 130.37181214238),(127.066081593223 160.18590607119),(150 190))

## See Also

ST_LineInterpolatePoint, ST_LineLocatePoint

## Name

ST_LineLocatePoint — Returns the fractional location of the closest point on a line to a point.

## Synopsis

`float8 ST_LineLocatePoint(` geometry a_linestring, geometry a_point`)`;

`float8 ST_LineLocatePoint(` geography a_linestring, geography a_point, boolean use_spheroid = true`)`;

## Description

Returns a float between 0 and 1 representing the location of the closest point on a LineString to the given Point, as a fraction of 2d line length.

You can use the returned location to extract a Point (ST_LineInterpolatePoint) or a substring (ST_LineSubstring).

This is useful for approximating numbers of addresses

Availability: 1.1.0

Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Locate_Point.

## Examples

    --Rough approximation of finding the street number of a point along the street
    --Note the whole foo thing is just to generate dummy data that looks
    --like house centroids and street
    --We use ST_DWithin to exclude
    --houses too far away from the street to be considered on the street
    SELECT ST_AsText(house_loc) As as_text_house_loc,
    	startstreet_num +
    		CAST( (endstreet_num - startstreet_num)
    			* ST_LineLocatePoint(street_line, house_loc) As integer) As street_num
    FROM
    (SELECT ST_GeomFromText('LINESTRING(1 2, 3 4)') As street_line,
    	ST_Point(x*1.01,y*1.03) As house_loc, 10 As startstreet_num,
    		20 As endstreet_num
    FROM generate_series(1,3) x CROSS JOIN generate_series(2,4) As y)
    As foo
    WHERE ST_DWithin(street_line, house_loc, 0.2);

     as_text_house_loc | street_num
    -------------------+------------
     POINT(1.01 2.06)  |         10
     POINT(2.02 3.09)  |         15
     POINT(3.03 4.12)  |         20

     --find closest point on a line to a point or other geometry
     SELECT ST_AsText(ST_LineInterpolatePoint(foo.the_line, ST_LineLocatePoint(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
    FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
       st_astext
    ----------------
     POINT(3 4)

## See Also

ST_DWithin, ST_Length2D, ST_LineInterpolatePoint, ST_LineSubstring

## Name

ST_LineSubstring — Returns the part of a line between two fractional locations.

## Synopsis

`geometry ST_LineSubstring(` geometry a_linestring, float8 startfraction, float8 endfraction`)`;

`geography ST_LineSubstring(` geography a_linestring, float8 startfraction, float8 endfraction`)`;

## Description

Computes the line which is the section of the input line starting and ending at the given fractional locations. The first argument must be a LINESTRING. The second and third arguments are values in the range [0, 1] representing the start and end locations as fractions of line length. The Z and M values are interpolated for added endpoints if present.

If `startfraction` and `endfraction` have the same value this is equivalent to ST_LineInterpolatePoint.

This only works with LINESTRINGs. To use on contiguous MULTILINESTRINGs first join them with ST_LineMerge.

Since release 1.1.1 this function interpolates M and Z values. Prior releases set Z and M to unspecified values.

Enhanced: 3.4.0 - Support for geography was introduced.

Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Substring.

Availability: 1.1.0, Z and M supported added in 1.1.1

This function supports 3d and will not drop the z-index.

## Examples

A LineString seen with 1/3 midrange overlaid (0.333, 0.666)

    SELECT ST_AsText(ST_LineSubstring( 'LINESTRING (20 180, 50 20, 90 80, 120 40, 180 150)', 0.333, 0.666));
    ------------------------------------------------------------------------------------------------
    LINESTRING (45.17311810399485 45.74337011202746, 50 20, 90 80, 112.97593050157862 49.36542599789519)

If start and end locations are the same, the result is a POINT.

    SELECT ST_AsText(ST_LineSubstring( 'LINESTRING(25 50, 100 125, 150 190)', 0.333, 0.333));
    ------------------------------------------
     POINT(69.2846934853974 94.2846934853974)

A query to cut a LineString into sections of length 100 or shorter. It uses `generate_series()` with a CROSS JOIN LATERAL to produce the equivalent of a FOR loop.

    WITH data(id, geom) AS (VALUES
            ( 'A', 'LINESTRING( 0 0, 200 0)'::geometry ),
            ( 'B', 'LINESTRING( 0 100, 350 100)'::geometry ),
            ( 'C', 'LINESTRING( 0 200, 50 200)'::geometry )
        )
    SELECT id, i,
           ST_AsText( ST_LineSubstring( geom, startfrac, LEAST( endfrac, 1 )) ) AS geom
    FROM (
        SELECT id, geom, ST_Length(geom) len, 100 sublen FROM data
        ) AS d
    CROSS JOIN LATERAL (
        SELECT i, (sublen * i) / len AS startfrac,
                  (sublen * (i+1)) / len AS endfrac
        FROM generate_series(0, floor( len / sublen )::integer ) AS t(i)
        -- skip last i if line length is exact multiple of sublen
        WHERE (sublen * i) / len <> 1.0
        ) AS d2;

     id | i |            geom
    ----+---+-----------------------------
     A  | 0 | LINESTRING(0 0,100 0)
     A  | 1 | LINESTRING(100 0,200 0)
     B  | 0 | LINESTRING(0 100,100 100)
     B  | 1 | LINESTRING(100 100,200 100)
     B  | 2 | LINESTRING(200 100,300 100)
     B  | 3 | LINESTRING(300 100,350 100)
     C  | 0 | LINESTRING(0 200,50 200)

Geography implementation measures along a spheroid, geometry along a line

    SELECT ST_AsText(ST_LineSubstring( 'LINESTRING(-118.2436 34.0522, -71.0570 42.3611)'::geography, 0.333, 0.666),6) AS geog_sub
     , ST_AsText(ST_LineSubstring('LINESTRING(-118.2436 34.0522, -71.0570 42.3611)'::geometry, 0.333, 0.666),6) AS geom_sub;
    ---------------------------------------------------------------
    geog_sub | LINESTRING(-104.167064 38.854691,-87.674646 41.849854)
    geom_sub | LINESTRING(-102.530462 36.819064,-86.817324 39.585927)

## See Also

ST_Length, ST_LineExtend, ST_LineInterpolatePoint, ST_LineMerge

## Name

ST_LocateAlong — Returns the point(s) on a geometry that match a measure value.

## Synopsis

`geometry ST_LocateAlong(` geometry geom_with_measure, float8 measure, float8 offset = 0`)`;

## Description

Returns the location(s) along a measured geometry that have the given measure values. The result is a Point or MultiPoint. Polygonal inputs are not supported.

If `offset` is provided, the result is offset to the left or right of the input line by the specified distance. A positive offset will be to the left, and a negative one to the right.

Use this function only for linear geometries with an M component

The semantic is specified by the ISO/IEC 13249-3 SQL/MM Spatial standard.

Availability: 1.1.0 by old name ST_Locate_Along_Measure.

Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure.

This function supports M coordinates.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1.13

## Examples

    SELECT ST_AsText(
      ST_LocateAlong(
        'MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),(1 2 3, 5 4 5))'::geometry,
        3 ));

    ----------------------------------
     MULTIPOINT M ((1 2 3),(9 4 3),(1 2 3))

## See Also

ST_LocateBetween, ST_LocateBetweenElevations, ST_InterpolatePoint

## Name

ST_LocateBetween — Returns the portions of a geometry that match a measure range.

## Synopsis

`geometry ST_LocateBetween(` geometry geom, float8 measure_start, float8 measure_end, float8 offset = 0`)`;

## Description

Return a geometry (collection) with the portions of the input measured geometry that match the specified measure range (inclusively).

If the `offset` is provided, the result is offset to the left or right of the input line by the specified distance. A positive offset will be to the left, and a negative one to the right.

Clipping a non-convex POLYGON may produce invalid geometry.

The semantic is specified by the ISO/IEC 13249-3 SQL/MM Spatial standard.

Availability: 1.1.0 by old name ST_Locate_Between_Measures.

Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures.

Enhanced: 3.0.0 - added support for POLYGON, TIN, TRIANGLE.

This function supports M coordinates.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

## Examples

    SELECT ST_AsText(
      ST_LocateBetween(
           'MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3),(1 2 3, 5 4 5))':: geometry,
           1.5, 3 ));
    ------------------------------------------------------------------------
     GEOMETRYCOLLECTION M (LINESTRING M (1 2 3,3 4 2,9 4 3),POINT M (1 2 3))

A LineString with the section between measures 2 and 8, offset to the left

    SELECT ST_AsText( ST_LocateBetween(
      ST_AddMeasure('LINESTRING (20 180, 50 20, 100 120, 180 20)', 0, 10),
      2, 8,
      20
    ));
    ------------------------------------------------------------------------
    MULTILINESTRING((54.49835019899045 104.53426957938231,58.70056060327303 82.12248075654186,69.16695286779743 103.05526528559065,82.11145618000168 128.94427190999915,84.24893681714357 132.32493442618113,87.01636951231555 135.21267035596549,90.30307285299679 137.49198684843182,93.97759758337769 139.07172433557758,97.89298381958797 139.8887023914453,101.89263860095893 139.9102465862721,105.81659870902816 139.13549527600819,109.50792827749828 137.5954340631298,112.81899532549731 135.351656550512,115.6173761888606 132.49390095108848,145.31017306064817 95.37790486135405))

## See Also

ST_LocateAlong, ST_LocateBetweenElevations

## Name

ST_LocateBetweenElevations — Returns the portions of a geometry that lie in an elevation (Z) range.

## Synopsis

`geometry ST_LocateBetweenElevations(` geometry geom, float8 elevation_start, float8 elevation_end`)`;

## Description

Returns a geometry (collection) with the portions of a geometry that lie in an elevation (Z) range.

Clipping a non-convex POLYGON may produce invalid geometry.

Availability: 1.4.0

Enhanced: 3.0.0 - added support for POLYGON, TIN, TRIANGLE.

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(
      ST_LocateBetweenElevations(
        'LINESTRING(1 2 3, 4 5 6)'::geometry,
        2, 4 ));

                 st_astext
    -----------------------------------
     MULTILINESTRING Z ((1 2 3,2 3 4))

    SELECT ST_AsText(
        ST_LocateBetweenElevations(
          'LINESTRING(1 2 6, 4 5 -1, 7 8 9)',
          6, 9)) As ewelev;

                                    ewelev
    -----------------------------------------------------------------------
     GEOMETRYCOLLECTION Z (POINT Z (1 2 6),LINESTRING Z (6.1 7.1 6,7 8 9))

## See Also

ST_Dump, ST_LocateBetween

## Name

ST_InterpolatePoint — Returns the interpolated measure of a geometry closest to a point.

## Synopsis

`float8 ST_InterpolatePoint(` geometry linear_geom_with_measure, geometry point`)`;

## Description

Returns an interpolated measure value of a linear measured geometry at the location closest to the given point.

Use this function only for linear geometries with an M component

Availability: 2.0.0

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_InterpolatePoint('LINESTRING M (0 0 0, 10 0 20)', 'POINT(5 5)');
     ---------------------
             10

## See Also

ST_AddMeasure, ST_LocateAlong, ST_LocateBetween

## Name

ST_AddMeasure — Interpolates measures along a linear geometry.

## Synopsis

`geometry ST_AddMeasure(` geometry geom_mline, float8 measure_start, float8 measure_end`)`;

## Description

Return a derived geometry with measure values linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.

Availability: 1.5.0

This function supports 3d and will not drop the z-index.

## Examples

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRING(1 0, 2 0, 4 0)'),1,4)) As ewelev;
               ewelev
    --------------------------------
     LINESTRINGM(1 0 1,2 0 2,4 0 4)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRING(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
                     ewelev
    ----------------------------------------
     LINESTRING(1 0 4 10,2 0 4 20,4 0 4 40)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('LINESTRINGM(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
                     ewelev
    ----------------------------------------
     LINESTRINGM(1 0 10,2 0 20,4 0 40)

    SELECT ST_AsText(ST_AddMeasure(
    ST_GeomFromEWKT('MULTILINESTRINGM((1 0 4, 2 0 4, 4 0 4),(1 0 4, 2 0 4, 4 0 4))'),10,70)) As ewelev;
                                 ewelev
    -----------------------------------------------------------------
     MULTILINESTRINGM((1 0 10,2 0 20,4 0 40),(1 0 40,2 0 50,4 0 70))

## 7.20. Trajectory Functions

Abstract

These functions support working with trajectories. A trajectory is a linear geometry with increasing measures (M value) on each coordinate. Spatio-temporal data can be modeled by using relative times (such as the epoch) as the measure values.

## Name

ST_IsValidTrajectory — Tests if the geometry is a valid trajectory.

## Synopsis

`boolean ST_IsValidTrajectory(` geometry line`)`;

## Description

Tests if a geometry encodes a valid trajectory. A valid trajectory is represented as a `LINESTRING` with measures (M values). The measure values must increase from each vertex to the next.

Valid trajectories are expected as input to spatio-temporal functions like ST_ClosestPointOfApproach

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

## Examples

    -- A valid trajectory
    SELECT ST_IsValidTrajectory(ST_MakeLine(
      ST_MakePointM(0,0,1),
      ST_MakePointM(0,1,2))
    );
     t

    -- An invalid trajectory
    SELECT ST_IsValidTrajectory(ST_MakeLine(ST_MakePointM(0,0,1), ST_MakePointM(0,1,0)));
    NOTICE:  Measure of vertex 1 (0) not bigger than measure of vertex 0 (1)
     st_isvalidtrajectory
    ----------------------
     f

## See Also

ST_ClosestPointOfApproach

## Name

ST_ClosestPointOfApproach — Returns a measure at the closest point of approach of two trajectories.

## Synopsis

`float8 ST_ClosestPointOfApproach(` geometry track1, geometry track2`)`;

## Description

Returns the smallest measure at which points interpolated along the given trajectories are the least distance apart.

Inputs must be valid trajectories as checked by ST_IsValidTrajectory. Null is returned if the trajectories do not overlap in their M ranges.

To obtain the actual points at the computed measure use ST_LocateAlong .

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

## Examples

    -- Return the time in which two objects moving between 10:00 and 11:00
    -- are closest to each other and their distance at that point
    WITH inp AS ( SELECT
      ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) a,
      ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) b
    ), cpa AS (
      SELECT ST_ClosestPointOfApproach(a,b) m FROM inp
    ), points AS (
      SELECT ST_GeometryN(ST_LocateAlong(a,m),1) pa,
             ST_GeometryN(ST_LocateAlong(b,m),1) pb
      FROM inp, cpa
    )
    SELECT to_timestamp(m) t,
           ST_Distance(pa,pb) distance,
           ST_AsText(pa, 2) AS pa, ST_AsText(pb, 2) AS pb
    FROM points, cpa;

                   t               |      distance      |                  pa                  |                   pb
    -------------------------------+--------------------+--------------------------------------+----------------------------------------
     2015-05-26 10:45:31.034483-07 | 1.9603683315139542 | POINT ZM (7.59 0 3.79 1432662331.03) | POINT ZM (9.1 1.24 3.93 1432662331.03)

## See Also

ST_IsValidTrajectory, ST_DistanceCPA, ST_LocateAlong, ST_AddMeasure

## Name

ST_DistanceCPA — Returns the distance between the closest point of approach of two trajectories.

## Synopsis

`float8 ST_DistanceCPA(` geometry track1, geometry track2`)`;

## Description

Returns the distance (in 2D) between two trajectories at their closest point of approach.

Inputs must be valid trajectories as checked by ST_IsValidTrajectory. Null is returned if the trajectories do not overlap in their M ranges.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

## Examples

    -- Return the minimum distance of two objects moving between 10:00 and 11:00
    WITH inp AS ( SELECT
      ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) a,
      ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) b
    )
    SELECT ST_DistanceCPA(a,b) distance FROM inp;

         distance
    ------------------
     1.96036833151395

## See Also

ST_IsValidTrajectory, ST_ClosestPointOfApproach, ST_AddMeasure, |=|

## Name

ST_CPAWithin — Tests if the closest point of approach of two trajectories is within the specified distance.

## Synopsis

`boolean ST_CPAWithin(` geometry track1, geometry track2, float8 dist`)`;

## Description

Tests whether two moving objects have ever been closer than the specified distance.

Inputs must be valid trajectories as checked by ST_IsValidTrajectory. False is returned if the trajectories do not overlap in their M ranges.

Availability: 2.2.0

This function supports 3d and will not drop the z-index.

## Examples

    WITH inp AS ( SELECT
      ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) a,
      ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
        extract(epoch from '2015-05-26 10:00'::timestamptz),
        extract(epoch from '2015-05-26 11:00'::timestamptz)
      ) b
    )
    SELECT ST_CPAWithin(a,b,2), ST_DistanceCPA(a,b) distance FROM inp;

     st_cpawithin |     distance
    --------------+------------------
     t            | 1.96521473776207

## See Also

ST_IsValidTrajectory, ST_ClosestPointOfApproach, ST_DistanceCPA, |=|

## 7.21. Version Functions

Abstract

These functions report and upgrade PostGIS versions.

## Name

PostGIS_Extensions_Upgrade — Packages and upgrades PostGIS extensions (e.g. postgis_raster, postgis_topology, postgis_sfcgal) to given or latest version.

## Synopsis

`text PostGIS_Extensions_Upgrade(` text target_version=null`)`;

## Description

Packages and upgrades PostGIS extensions to given or latest version. Only extensions you have installed in the database will be packaged and upgraded if needed. Reports full PostGIS version and build configuration infos after. This is short-hand for doing multiple CREATE EXTENSION .. FROM unpackaged and ALTER EXTENSION .. UPDATE for each PostGIS extension. Currently only tries to upgrade extensions postgis, postgis_raster, postgis_sfcgal, postgis_topology, and postgis_tiger_geocoder.

Availability: 2.5.0

Changed: 3.4.0 to add target_version argument. Changed: 3.3.0 support for upgrades from any PostGIS version. Does not work on all systems. Changed: 3.0.0 to repackage loose extensions and support postgis_raster.

## Examples

    SELECT PostGIS_Extensions_Upgrade();

    NOTICE:  Packaging extension postgis
    NOTICE:  Packaging extension postgis_raster
    NOTICE:  Packaging extension postgis_sfcgal
    NOTICE:  Extension postgis_topology is not available or not packagable for some reason
    NOTICE:  Extension postgis_tiger_geocoder is not available or not packagable for some reason

                        postgis_extensions_upgrade
    -------------------------------------------------------------------
     Upgrade completed, run SELECT postgis_full_version(); for details
    (1 row)

## See Also

Section 3.4, “Upgrading spatial databases”, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_Full_Version — Reports full PostGIS version and build configuration infos.

## Synopsis

`text PostGIS_Full_Version(` `)`;

## Description

Reports full PostGIS version and build configuration infos. Also informs about synchronization between libraries and scripts suggesting upgrades as needed.

Enhanced: 3.4.0 now includes extra PROJ configurations NETWORK_ENABLED, URL_ENDPOINT and DATABASE_PATH of proj.db location

## Examples

    SELECT PostGIS_Full_Version();
    							   postgis_full_version
    ----------------------------------------------------------------------------------
    POSTGIS="3.4.0dev 3.3.0rc2-993-g61bdf43a7" [EXTENSION] PGSQL="160" GEOS="3.12.0dev-CAPI-1.18.0" SFCGAL="1.3.8" PROJ="7.2.1 NETWORK_ENABLED=OFF URL_ENDPOINT=https://cdn.proj.org USER_WRITABLE_DIRECTORY=/tmp/proj DATABASE_PATH=/usr/share/proj/proj.db" GDAL="GDAL 3.2.2, released 2021/03/05" LIBXML="2.9.10" LIBJSON="0.15" LIBPROTOBUF="1.3.3" WAGYU="0.5.0 (Internal)" TOPOLOGY RASTER
    (1 row)

## See Also

Section 3.4, “Upgrading spatial databases”, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Wagyu_Version, PostGIS_Version

## Name

PostGIS_GEOS_Version — Returns the version number of the GEOS library.

## Synopsis

`text PostGIS_GEOS_Version(` `)`;

## Description

Returns the version number of the GEOS library, or `NULL` if GEOS support is not enabled.

## Examples

    SELECT PostGIS_GEOS_Version();
     postgis_geos_version
    ----------------------
    3.12.0dev-CAPI-1.18.0
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_GEOS_Compiled_Version — Returns the version number of the GEOS library against which PostGIS was built.

## Synopsis

`text PostGIS_GEOS_Compiled_Version(` `)`;

## Description

Returns the version number of the GEOS library, or against which PostGIS was built.

Availability: 3.4.0

## Examples

    SELECT PostGIS_GEOS_Compiled_Version();
     postgis_geos_compiled_version
    -------------------------------
     3.12.0
    (1 row)

## See Also

PostGIS_GEOS_Version, PostGIS_Full_Version

## Name

PostGIS_Liblwgeom_Version — Returns the version number of the liblwgeom library. This should match the version of PostGIS.

## Synopsis

`text PostGIS_Liblwgeom_Version(` `)`;

## Description

Returns the version number of the liblwgeom library/

## Examples

    SELECT PostGIS_Liblwgeom_Version();
    postgis_liblwgeom_version
    --------------------------
    3.4.0dev 3.3.0rc2-993-g61bdf43a7
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_LibXML_Version — Returns the version number of the libxml2 library.

## Synopsis

`text PostGIS_LibXML_Version(` `)`;

## Description

Returns the version number of the LibXML2 library.

Availability: 1.5

## Examples

    SELECT PostGIS_LibXML_Version();
     postgis_libxml_version
    ----------------------
     2.9.10
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_PROJ_Version, PostGIS_GEOS_Version, PostGIS_Version

## Name

PostGIS_LibJSON_Version — Returns the version number of the libjson-c library.

## Synopsis

`text PostGIS_LibJSON_Version(` `)`;

## Description

Returns the version number of the LibJSON-C library.

## Examples

    SELECT PostGIS_LibJSON_Version();
     postgis_libjson_version
    -------------------------
     0.17

## See Also

PostGIS_Full_Version, PostGIS_Lib_Version, PostGIS_PROJ_Version, PostGIS_GEOS_Version, PostGIS_Version

## Name

PostGIS_Lib_Build_Date — Returns build date of the PostGIS library.

## Synopsis

`text PostGIS_Lib_Build_Date(` `)`;

## Description

Returns build date of the PostGIS library.

## Examples

    SELECT PostGIS_Lib_Build_Date();
     postgis_lib_build_date
    ------------------------
     2023-06-22 03:56:11
    (1 row)

## Name

PostGIS_Lib_Version — Returns the version number of the PostGIS library.

## Synopsis

`text PostGIS_Lib_Version(` `)`;

## Description

Returns the version number of the PostGIS library.

## Examples

    SELECT PostGIS_Lib_Version();
     postgis_lib_version
    ---------------------
     3.4.0dev
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version, PostGIS_Version

## Name

PostGIS_PROJ_Version — Returns the version number of the PROJ4 library.

## Synopsis

`text PostGIS_PROJ_Version(` `)`;

## Description

Returns the version number of the PROJ library and some configuration options of proj.

Enhanced: 3.4.0 now includes NETWORK_ENABLED, URL_ENDPOINT and DATABASE_PATH of proj.db location

## Examples

    SELECT PostGIS_PROJ_Version();
      postgis_proj_version
    -------------------------
    7.2.1 NETWORK_ENABLED=OFF URL_ENDPOINT=https://cdn.proj.org USER_WRITABLE_DIRECTORY=/tmp/proj DATABASE_PATH=/usr/share/proj/proj.db
    (1 row)

## See Also

PostGIS_PROJ_Compiled_Version, PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

## Name

PostGIS_PROJ_Compiled_Version — Returns the version number of the PROJ library against which PostGIS was built.

## Synopsis

`text PostGIS_PROJ_Compiled_Version(` `)`;

## Description

Returns the version number of the PROJ library, or against which PostGIS was built.

Availability: 3.5.0

## Examples

    SELECT PostGIS_PROJ_Compiled_Version();
     postgis_proj_compiled_version
    -------------------------------
     9.1.1
    (1 row)

## See Also

PostGIS_PROJ_Version, PostGIS_Full_Version

## Name

PostGIS_Wagyu_Version — Returns the version number of the internal Wagyu library.

## Synopsis

`text PostGIS_Wagyu_Version(` `)`;

## Description

Returns the version number of the internal Wagyu library, or `NULL` if Wagyu support is not enabled.

## Examples

    SELECT PostGIS_Wagyu_Version();
     postgis_wagyu_version
    -----------------------
     0.5.0 (Internal)
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_PROJ_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

## Name

PostGIS_Scripts_Build_Date — Returns build date of the PostGIS scripts.

## Synopsis

`text PostGIS_Scripts_Build_Date(` `)`;

## Description

Returns build date of the PostGIS scripts.

Availability: 1.0.0RC1

## Examples

    SELECT PostGIS_Scripts_Build_Date();
      postgis_scripts_build_date
    -------------------------
     2023-06-22 03:56:11
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_Version

## Name

PostGIS_Scripts_Installed — Returns version of the PostGIS scripts installed in this database.

## Synopsis

`text PostGIS_Scripts_Installed(` `)`;

## Description

Returns version of the PostGIS scripts installed in this database.

If the output of this function doesn't match the output of PostGIS_Scripts_Released you probably missed to properly upgrade an existing database. See the Upgrading section for more info.

Availability: 0.9.0

## Examples

    SELECT PostGIS_Scripts_Installed();
      postgis_scripts_installed
    -------------------------
     3.4.0dev 3.3.0rc2-993-g61bdf43a7
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Scripts_Released, PostGIS_Version

## Name

PostGIS_Scripts_Released — Returns the version number of the postgis.sql script released with the installed PostGIS lib.

## Synopsis

`text PostGIS_Scripts_Released(` `)`;

## Description

Returns the version number of the postgis.sql script released with the installed PostGIS lib.

Starting with version 1.1.0 this function returns the same value of PostGIS_Lib_Version. Kept for backward compatibility.

Availability: 0.9.0

## Examples

    SELECT PostGIS_Scripts_Released();
      postgis_scripts_released
    -------------------------
     3.4.0dev 3.3.0rc2-993-g61bdf43a7
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_Scripts_Installed, PostGIS_Lib_Version

## Name

PostGIS_Version — Returns PostGIS version number and compile-time options.

## Synopsis

`text PostGIS_Version(` `)`;

## Description

Returns PostGIS version number and compile-time options.

## Examples

    SELECT PostGIS_Version();
    			postgis_version
    ---------------------------------------
     3.4 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
    (1 row)

## See Also

PostGIS_Full_Version, PostGIS_GEOS_Version, PostGIS_Lib_Version, PostGIS_LibXML_Version, PostGIS_PROJ_Version

## 7.22. Grand Unified Custom Variables (GUCs)

Abstract

This section lists custom PostGIS Grand Unified Custom Variables (GUC). These can be set globally, by database, by session or by transaction. Best set at global or database level.

For more examples of usage refer to SQL SET and SQL ALTER SYSTEM

## Name

postgis.backend — The backend to service a function where GEOS and SFCGAL overlap. Options: geos or sfcgal. Defaults to geos.

## Description

This GUC is only relevant if you compiled PostGIS with sfcgal support. By default `geos` backend is used for functions where both GEOS and SFCGAL have the same named function. This variable allows you to override and make sfcgal the backend to service the request.

Availability: 2.1.0

## Examples

Sets backend just for life of connection

    set postgis.backend = sfcgal;

Sets backend for new connections to database

    ALTER DATABASE mygisdb SET postgis.backend = sfcgal;

## See Also

Chapter 8, SFCGAL Functions Reference

## Name

postgis.gdal_datapath — A configuration option to assign the value of GDAL's GDAL_DATA option. If not set, the environmentally set GDAL_DATA variable is used.

## Description

A PostgreSQL GUC variable for setting the value of GDAL's GDAL_DATA option. The `postgis.gdal_datapath` value should be the complete physical path to GDAL's data files.

This configuration option is of most use for Windows platforms where GDAL's data files path is not hard-coded. This option should also be set when GDAL's data files are not located in GDAL's expected path.

This option can be set in PostgreSQL's configuration file postgresql.conf. It can also be set by connection or transaction.

Availability: 2.2.0

Additional information about GDAL_DATA is available at GDAL's Configuration Options.

## Examples

Set and reset `postgis.gdal_datapath`

    SET postgis.gdal_datapath TO '/usr/local/share/gdal.hidden';
    SET postgis.gdal_datapath TO default;

Setting on windows for a particular database

    ALTER DATABASE gisdb
    SET postgis.gdal_datapath = 'C:/Program Files/PostgreSQL/9.3/gdal-data';

## See Also

PostGIS_GDAL_Version, ST_Transform

## Name

postgis.gdal_enabled_drivers — A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP.

## Description

A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP. This option can be set in PostgreSQL's configuration file: postgresql.conf. It can also be set by connection or transaction.

The initial value of `postgis.gdal_enabled_drivers` may also be set by passing the environment variable `POSTGIS_GDAL_ENABLED_DRIVERS` with the list of enabled drivers to the process starting PostgreSQL.

Enabled GDAL specified drivers can be specified by the driver's short-name or code. Driver short-names or codes can be found at GDAL Raster Formats. Multiple drivers can be specified by putting a space between each driver.

There are three special codes available for `postgis.gdal_enabled_drivers`. The codes are case-sensitive. `DISABLE_ALL` disables all GDAL drivers. If present, `DISABLE_ALL` overrides all other values in `postgis.gdal_enabled_drivers`. `ENABLE_ALL` enables all GDAL drivers. `VSICURL` enables GDAL's `/vsicurl/` virtual file system. When `postgis.gdal_enabled_drivers` is set to DISABLE_ALL, attempts to use out-db rasters, ST_FromGDALRaster(), ST_AsGDALRaster(), ST_AsTIFF(), ST_AsJPEG() and ST_AsPNG() will result in error messages.

In the standard PostGIS installation, `postgis.gdal_enabled_drivers` is set to DISABLE_ALL.

Additional information about GDAL_SKIP is available at GDAL's Configuration Options.

Availability: 2.2.0

## Examples

To set and reset `postgis.gdal_enabled_drivers` for current session

    SET postgis.gdal_enabled_drivers = 'ENABLE_ALL';
    SET postgis.gdal_enabled_drivers = default;

Set for all new connections to a specific database to specific drivers

    ALTER DATABASE mygisdb SET postgis.gdal_enabled_drivers TO 'GTiff PNG JPEG';

Setting for whole database cluster to enable all drivers. Requires super user access. Also note that database, session, and user settings override this.

     --writes to postgres.auto.conf
    ALTER SYSTEM SET postgis.gdal_enabled_drivers TO 'ENABLE_ALL';
     --Reloads postgres conf
    SELECT pg_reload_conf();

## See Also

ST_FromGDALRaster, ST_AsGDALRaster, ST_AsTIFF, ST_AsPNG, ST_AsJPEG, postgis.enable_outdb_rasters

## Name

postgis.enable_outdb_rasters — A boolean configuration option to enable access to out-db raster bands.

## Description

A boolean configuration option to enable access to out-db raster bands. This option can be set in PostgreSQL's configuration file: postgresql.conf. It can also be set by connection or transaction.

The initial value of `postgis.enable_outdb_rasters` may also be set by passing the environment variable `POSTGIS_ENABLE_OUTDB_RASTERS` with a non-zero value to the process starting PostgreSQL.

Even if `postgis.enable_outdb_rasters` is True, the GUC `postgis.gdal_enabled_drivers` determines the accessible raster formats.

In the standard PostGIS installation, `postgis.enable_outdb_rasters` is set to False.

Availability: 2.2.0

## Examples

Set and reset `postgis.enable_outdb_rasters` for current session

    SET postgis.enable_outdb_rasters TO True;
    SET postgis.enable_outdb_rasters = default;
    SET postgis.enable_outdb_rasters = True;
    SET postgis.enable_outdb_rasters = False;

Set for all new connections to a specific database

    ALTER DATABASE gisdb SET postgis.enable_outdb_rasters = true;

Setting for whole database cluster. Requires super user access. Also note that database, session, and user settings override this.

     --writes to postgres.auto.conf
    ALTER SYSTEM SET postgis.enable_outdb_rasters = true;
     --Reloads postgres conf
    SELECT pg_reload_conf();

## See Also

postgis.gdal_enabled_drivers postgis.gdal_vsi_options

## Name

postgis.gdal_vsi_options — A string configuration to set options used when working with an out-db raster.

## Description

A string configuration to set options used when working with an out-db raster. Configuration options control things like how much space GDAL allocates to local data cache, whether to read overviews, and what access keys to use for remote out-db data sources.

Availability: 3.2.0

## Examples

Set `postgis.gdal_vsi_options` for current session:

    SET postgis.gdal_vsi_options = 'AWS_ACCESS_KEY_ID=xxxxxxxxxxxxxxx AWS_SECRET_ACCESS_KEY=yyyyyyyyyyyyyyyyyyyyyyyyyy';

Set `postgis.gdal_vsi_options` just for the current transaction using the `LOCAL` keyword:

    SET LOCAL postgis.gdal_vsi_options = 'AWS_ACCESS_KEY_ID=xxxxxxxxxxxxxxx AWS_SECRET_ACCESS_KEY=yyyyyyyyyyyyyyyyyyyyyyyyyy';

## See Also

postgis.enable_outdb_rasters postgis.gdal_enabled_drivers

## 7.23. Troubleshooting Functions

Abstract

These functions are utilities for troubleshooting and repairing geometry data. They are only needed if the geometry data is corrupted in some way, which should never happen under normal circumstances.

## Name

PostGIS_AddBBox — Add bounding box to the geometry.

## Synopsis

`geometry PostGIS_AddBBox(` geometry geomA`)`;

## Description

Add bounding box to the geometry. This would make bounding box based queries faster, but will increase the size of the geometry.

Bounding boxes are automatically added to geometries so in general this is not needed unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and re-add.

This method supports Circular Strings and Curves.

## Examples

    UPDATE sometable
     SET geom =  PostGIS_AddBBox(geom)
     WHERE PostGIS_HasBBox(geom) = false;

## See Also

PostGIS_DropBBox, PostGIS_HasBBox

## Name

PostGIS_DropBBox — Drop the bounding box cache from the geometry.

## Synopsis

`geometry PostGIS_DropBBox(` geometry geomA`)`;

## Description

Drop the bounding box cache from the geometry. This reduces geometry size, but makes bounding-box based queries slower. It is also used to drop a corrupt bounding box. A tale-tell sign of a corrupt cached bounding box is when your ST_Intersects and other relation queries leave out geometries that rightfully should return true.

Bounding boxes are automatically added to geometries and improve speed of queries so in general this is not needed unless the generated bounding box somehow becomes corrupted or you have an old install that is lacking bounding boxes. Then you need to drop the old and re-add. This kind of corruption has been observed in 8.3-8.3.6 series whereby cached bboxes were not always recalculated when a geometry changed and upgrading to a newer version without a dump reload will not correct already corrupted boxes. So one can manually correct using below and re-add the bbox or do a dump reload.

This method supports Circular Strings and Curves.

## Examples

    --This example drops bounding boxes where the cached box is not correct
    			--The force to ST_AsBinary before applying Box2D forces a recalculation of the box, and Box2D applied to the table geometry always
    			-- returns the cached bounding box.
    			UPDATE sometable
     SET geom =  PostGIS_DropBBox(geom)
     WHERE Not (Box2D(ST_AsBinary(geom)) = Box2D(geom));

    	UPDATE sometable
     SET geom =  PostGIS_AddBBox(geom)
     WHERE Not PostGIS_HasBBOX(geom);

## See Also

PostGIS_AddBBox, PostGIS_HasBBox, Box2D

## Name

PostGIS_HasBBox — Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.

## Synopsis

`boolean PostGIS_HasBBox(` geometry geomA`)`;

## Description

Returns TRUE if the bbox of this geometry is cached, FALSE otherwise. Use PostGIS_AddBBox and PostGIS_DropBBox to control caching.

This method supports Circular Strings and Curves.

## Examples

    SELECT geom
    FROM sometable WHERE PostGIS_HasBBox(geom) = false;

## See Also

PostGIS_AddBBox, PostGIS_DropBBox

# Chapter 8. SFCGAL Functions Reference

SFCGAL is a C++ wrapper library around CGAL that provides advanced 2D and 3D spatial functions. For robustness, geometry coordinates have an exact rational number representation.

Installation instructions for the library can be found on the SFCGAL home page (http://www.sfcgal.org). To enable the functions use `create extension postgis_sfcgal`.

## 8.1. SFCGAL Management Functions

Abstract

This section lists functions for determining version of SFCGAL and library dependencies you are running.

## Name

postgis_sfcgal_version — Returns the version of SFCGAL in use

## Synopsis

`text postgis_sfcgal_version(` `void)`;

## Description

Returns the version of SFCGAL in use

Availability: 2.1.0

This method needs SFCGAL backend.

## See Also

postgis_sfcgal_full_version

## Name

postgis_sfcgal_full_version — Returns the full version of SFCGAL in use including CGAL and Boost versions

## Synopsis

`text postgis_sfcgal_full_version(` `void)`;

## Description

Returns the full version of SFCGAL in use including CGAL and Boost versions

Availability: 3.3.0

This method needs SFCGAL backend.

## See Also

postgis_sfcgal_version

## 8.2. SFCGAL Accessors and Setters

Abstract

These functions access or set properties of geometries. Geometries primarily supported by these functions are TINS and Polyhedral Surfaces.

## Name

CG_ForceLHR — Force LHR orientation

## Synopsis

`geometry CG_ForceLHR(` geometry geom`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_IsPlanar — Check if a surface is or not planar

## Synopsis

`boolean CG_IsPlanar(` geometry geom`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_IsSolid — Test if the geometry is a solid. No validity check is performed.

## Synopsis

`boolean CG_IsSolid(` geometry geom1`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_MakeSolid — Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.

## Synopsis

`geometry CG_MakeSolid(` geometry geom1`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_Orientation — Determine surface orientation

## Synopsis

`integer CG_Orientation(` geometry geom`)`;

## Description

The function only applies to polygons. It returns -1 if the polygon is counterclockwise oriented and 1 if the polygon is clockwise oriented.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

## Name

CG_Area — Calculates the area of a geometry

## Synopsis

`double precision CG_Area(` geometry geom `)`;

## Description

Calculates the area of a geometry.

Performed by the SFCGAL module

NOTE: this function returns a double precision value representing the area.

Availability: 3.5.0

This method needs SFCGAL backend.

## Geometry Examples

    SELECT CG_Area('Polygon ((0 0, 0 5, 5 5, 5 0, 0 0), (1 1, 2 1, 2 2, 1 2, 1 1), (3 3, 4 3, 4 4, 3 4, 3 3))');
                    cg_area
                    --------
                    25
                    (1 row)

## See Also

ST_3DArea, ST_Area

## Name

CG_3DArea — Computes area of 3D surface geometries. Will return 0 for solids.

## Synopsis

`floatCG_3DArea(` geometry geom1`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 8.1, 10.5

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Note: By default a PolyhedralSurface built from WKT is a surface geometry, not solid. It therefore has surface area. Once converted to a solid, no area.

    SELECT CG_3DArea(geom) As cube_surface_area,
                CG_3DArea(CG_MakeSolid(geom)) As solid_surface_area
                FROM (SELECT 'POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
                ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
                ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'::geometry) As f(geom);

                cube_surface_area | solid_surface_area
                -------------------+--------------------
                6 |                  0

## See Also

CG_Area, CG_MakeSolid, CG_IsSolid, CG_Area

## Name

CG_Volume — Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.

## Synopsis

`float CG_Volume(` geometry geom1`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 9.1 (same as CG_3DVolume)

## Example

When closed surfaces are created with WKT, they are treated as areal rather than solid. To make them solid, you need to use CG_MakeSolid. Areal geometries have no volume. Here is an example to demonstrate.

    SELECT CG_Volume(geom) As cube_surface_vol,
        CG_Volume(CG_MakeSolid(geom)) As solid_surface_vol
        FROM (SELECT 'POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
        ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
        ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
        ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
        ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
        ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'::geometry) As f(geom);

        cube_surface_vol | solid_surface_vol
        ------------------+-------------------
        0 |                 1

## See Also

CG_3DArea, CG_MakeSolid, CG_IsSolid

## Name

ST_ForceLHR — Force LHR orientation

## Synopsis

`geometry ST_ForceLHR(` geometry geom`)`;

## Description

ST_ForceLHR is deprecated as of 3.5.0. Use CG_ForceLHR instead.

Availability: 2.1.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

ST_IsPlanar — Check if a surface is or not planar

## Synopsis

`boolean ST_IsPlanar(` geometry geom`)`;

## Description

ST_IsPlanar is deprecated as of 3.5.0. Use CG_IsPlanar instead.

Availability: 2.2.0: This was documented in 2.1.0 but got accidentally left out in 2.1 release.

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

ST_IsSolid — Test if the geometry is a solid. No validity check is performed.

## Synopsis

`boolean ST_IsSolid(` geometry geom1`)`;

## Description

ST_IsSolid is deprecated as of 3.5.0. Use CG_IsSolid instead.

Availability: 2.2.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

ST_MakeSolid — Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.

## Synopsis

`geometry ST_MakeSolid(` geometry geom1`)`;

## Description

ST_MakeSolid is deprecated as of 3.5.0. Use CG_MakeSolid instead.

Availability: 2.2.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

ST_Orientation — Determine surface orientation

## Synopsis

`integer ST_Orientation(` geometry geom`)`;

## Description

ST_Orientation is deprecated as of 3.5.0. Use CG_Orientation instead.

The function only applies to polygons. It returns -1 if the polygon is counterclockwise oriented and 1 if the polygon is clockwise oriented.

Availability: 2.1.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

## Name

ST_3DArea — Computes area of 3D surface geometries. Will return 0 for solids.

## Synopsis

`floatST_3DArea(` geometry geom1`)`;

## Description

ST_3DArea is deprecated as of 3.5.0. Use CG_3DArea instead.

Availability: 2.1.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 8.1, 10.5

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

Note: By default a PolyhedralSurface built from WKT is a surface geometry, not solid. It therefore has surface area. Once converted to a solid, no area.

    SELECT ST_3DArea(geom) As cube_surface_area,
                ST_3DArea(ST_MakeSolid(geom)) As solid_surface_area
                FROM (SELECT 'POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
                ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
                ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'::geometry) As f(geom);

                cube_surface_area | solid_surface_area
                -------------------+--------------------
                6 |                  0

## See Also

ST_Area, ST_MakeSolid, ST_IsSolid, ST_Area

## Name

ST_Volume — Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.

## Synopsis

`float ST_Volume(` geometry geom1`)`;

## Description

ST_Volume is deprecated as of 3.5.0. Use CG_Volume instead.

Availability: 2.2.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 9.1 (same as ST_3DVolume)

## Example

When closed surfaces are created with WKT, they are treated as areal rather than solid. To make them solid, you need to use ST_MakeSolid. Areal geometries have no volume. Here is an example to demonstrate.

    SELECT ST_Volume(geom) As cube_surface_vol,
        ST_Volume(ST_MakeSolid(geom)) As solid_surface_vol
        FROM (SELECT 'POLYHEDRALSURFACE( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
        ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)),
        ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
        ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
        ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)),
        ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'::geometry) As f(geom);

        cube_surface_vol | solid_surface_vol
        ------------------+-------------------
        0 |                 1

## See Also

ST_3DArea, ST_MakeSolid, ST_IsSolid

## 8.3. SFCGAL Processing and Relationship Functions

## Name

CG_Intersection — Computes the intersection of two geometries

## Synopsis

`geometry CG_Intersection(` geometry geomA , geometry geomB `)`;

## Description

Computes the intersection of two geometries.

Performed by the SFCGAL module

NOTE: this function returns a geometry representing the intersection.

Availability: 3.5.0

This method needs SFCGAL backend.

## Geometry Examples

    SELECT ST_AsText(CG_Intersection('LINESTRING(0 0, 5 5)', 'LINESTRING(5 0, 0 5)'));
                    cg_intersection
                    -----------------
                    POINT(2.5 2.5)
                    (1 row)

## See Also

ST_3DIntersection, ST_Intersection

## Name

CG_Intersects — Tests if two geometries intersect (they have at least one point in common)

## Synopsis

`boolean CG_Intersects(` geometry geomA , geometry geomB `)`;

## Description

Returns `true` if two geometries intersect. Geometries intersect if they have any point in common.

Performed by the SFCGAL module

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT CG_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
        cg_intersects
        ---------------
        f
        (1 row)
        SELECT CG_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
        cg_intersects
        ---------------
        t
        (1 row)

## See Also

CG_3DIntersects, ST_3DIntersects, ST_Intersects, ST_Disjoint

## Name

CG_3DIntersects — Tests if two 3D geometries intersect

## Synopsis

`boolean CG_3DIntersects(` geometry geomA , geometry geomB `)`;

## Description

Tests if two 3D geometries intersect. 3D geometries intersect if they have any point in common in the three-dimensional space.

Performed by the SFCGAL module

NOTE: this is the "allowable" version that returns a boolean, not an integer.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT CG_3DIntersects('POINT(1.2 0.1 0)','POLYHEDRALSURFACE(((0 0 0,0.5 0.5 0,1 0 0,1 1 0,0 1 0,0 0 0)),((1 0 0,2 0 0,2 1 0,1 1 0,1 0 0),(1.2 0.2 0,1.2 0.8 0,1.8 0.8 0,1.8 0.2 0,1.2 0.2 0)))');
            cg_3dintersects
            ---------------
            t
            (1 row)

## See Also

CG_Intersects, ST_3DIntersects, ST_Intersects, ST_Disjoint

## Name

CG_Difference — Computes the geometric difference between two geometries

## Synopsis

`geometry CG_Difference(` geometry geomA , geometry geomB `)`;

## Description

Computes the geometric difference between two geometries. The resulting geometry is a set of points that are present in geomA but not in geomB.

Performed by the SFCGAL module

NOTE: this function returns a geometry.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT ST_AsText(CG_Difference('POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))'::geometry, 'LINESTRING(0 0, 2 2)'::geometry));
        cg_difference
        ---------------
        POLYGON((0 0,1 0,1 1,0 1,0 0))
        (1 row)

## See Also

ST_3DDifference, ST_Difference

## Name

ST_3DDifference — Perform 3D difference

## Synopsis

`geometry ST_3DDifference(` geometry geom1, geometry geom2`)`;

## Description

ST_3DDifference is deprecated as of 3.5.0. Use CG_3DDifference instead.

Returns that part of geom1 that is not part of geom2.

Availability: 2.2.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_3DDifference — Perform 3D difference

## Synopsis

`geometry CG_3DDifference(` geometry geom1, geometry geom2`)`;

## Description

Returns that part of geom1 that is not part of geom2.

Availability: 3.5.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

3D images were generated using PostGIS ST_AsX3D and rendering in HTML using X3Dom HTML Javascript rendering library.

    SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                    50, 'quad_segs=2'),0,0,30) AS geom1,
                                    CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                    50, 'quad_segs=1'),0,0,30) AS geom2;
Original 3D geometries overlaid. geom2 is the part that will be removed. |
    SELECT CG_3DDifference(geom1,geom2)
                                FROM ( SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                50, 'quad_segs=2'),0,0,30) AS geom1,
                                CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                50, 'quad_segs=1'),0,0,30) AS geom2 ) As t;
What's left after removing geom2

## See Also

CG_Extrude, ST_AsX3D, CG_3DIntersection CG_3DUnion

## Name

CG_Distance — Computes the minimum distance between two geometries

## Synopsis

`double precision CG_Distance(` geometry geomA , geometry geomB `)`;

## Description

Computes the minimum distance between two geometries.

Performed by the SFCGAL module

NOTE: this function returns a double precision value representing the distance.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT CG_Distance('LINESTRING(0.0 0.0,-1.0 -1.0)', 'LINESTRING(3.0 4.0,4.0 5.0)');
            cg_distance
            -------------
            2.0
            (1 row)

## See Also

CG_3DDistance, CG_Distance

## Name

CG_3DDistance — Computes the minimum 3D distance between two geometries

## Synopsis

`double precision CG_3DDistance(` geometry geomA , geometry geomB `)`;

## Description

Computes the minimum 3D distance between two geometries.

Performed by the SFCGAL module

NOTE: this function returns a double precision value representing the 3D distance.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Geometry Examples

    SELECT CG_3DDistance('LINESTRING(-1.0 0.0 2.0,1.0 0.0 3.0)', 'TRIANGLE((-4.0 0.0 1.0,4.0 0.0 1.0,0.0 4.0 1.0,-4.0 0.0 1.0))');
            cg_3ddistance
            ----------------
            1
            (1 row)

## See Also

CG_Distance, ST_3DDistance

## Name

ST_3DConvexHull — Computes the 3D convex hull of a geometry.

## Synopsis

`geometry ST_3DConvexHull(` geometry geom1`)`;

## Description

ST_3DConvexHull is deprecated as of 3.5.0. Use CG_3DConvexHull instead.

Availability: 3.3.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_3DConvexHull — Computes the 3D convex hull of a geometry.

## Synopsis

`geometry CG_3DConvexHull(` geometry geom1`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_AsText(CG_3DConvexHull('LINESTRING Z(0 0 5, 1 5 3, 5 7 6, 9 5 3 , 5 7 5, 6 3 5)'::geometry));

    POLYHEDRALSURFACE Z (((1 5 3,9 5 3,0 0 5,1 5 3)),((1 5 3,0 0 5,5 7 6,1 5 3)),((5 7 6,5 7 5,1 5 3,5 7 6)),((0 0 5,6 3 5,5 7 6,0 0 5)),((6 3 5,9 5 3,5 7 6,6 3 5)),((0 0 5,9 5 3,6 3 5,0 0 5)),((9 5 3,5 7 5,5 7 6,9 5 3)),((1 5 3,5 7 5,9 5 3,1 5 3)))

    WITH f AS (SELECT i, CG_Extrude(geom, 0,0, i ) AS geom
            FROM ST_Subdivide(ST_Letters('CH'),5) WITH ORDINALITY AS sd(geom,i)
            )
            SELECT CG_3DConvexHull(ST_Collect(f.geom) )
            FROM f;

Original geometry overlaid with 3D convex hull

## See Also

ST_Letters, ST_AsX3D

## Name

ST_3DIntersection — Perform 3D intersection

## Synopsis

`geometry ST_3DIntersection(` geometry geom1, geometry geom2`)`;

## Description

ST_3DIntersection is deprecated as of 3.5.0. Use CG_3DIntersection instead.

Return a geometry that is the shared portion between geom1 and geom2.

Availability: 2.1.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_3DIntersection — Perform 3D intersection

## Synopsis

`geometry CG_3DIntersection(` geometry geom1, geometry geom2`)`;

## Description

Return a geometry that is the shared portion between geom1 and geom2.

Availability: 3.5.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

3D images were generated using PostGIS ST_AsX3D and rendering in HTML using X3Dom HTML Javascript rendering library.

    SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                        50, 'quad_segs=2'),0,0,30) AS geom1,
                                        CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                        50, 'quad_segs=1'),0,0,30) AS geom2;
Original 3D geometries overlaid. geom2 is shown semi-transparent |
    SELECT CG_3DIntersection(geom1,geom2)
                                    FROM ( SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                    50, 'quad_segs=2'),0,0,30) AS geom1,
                                    CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                    50, 'quad_segs=1'),0,0,30) AS geom2 ) As t;
Intersection of geom1 and geom2

3D linestrings and polygons

    	SELECT ST_AsText(CG_3DIntersection(linestring, polygon)) As wkt
        FROM  ST_GeomFromText('LINESTRING Z (2 2 6,1.5 1.5 7,1 1 8,0.5 0.5 8,0 0 10)') AS linestring
        CROSS JOIN ST_GeomFromText('POLYGON((0 0 8, 0 1 8, 1 1 8, 1 0 8, 0 0 8))') AS polygon;

        wkt
        --------------------------------
        LINESTRING Z (1 1 8,0.5 0.5 8)

Cube (closed Polyhedral Surface) and Polygon Z

    SELECT ST_AsText(CG_3DIntersection(
    ST_GeomFromText('POLYHEDRALSURFACE Z( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'),
    'POLYGON Z ((0 0 0, 0 0 0.5, 0 0.5 0.5, 0 0.5 0, 0 0 0))'::geometry))

    TIN Z (((0 0 0,0 0 0.5,0 0.5 0.5,0 0 0)),((0 0.5 0,0 0 0,0 0.5 0.5,0 0.5 0)))

Intersection of 2 solids that result in volumetric intersection is also a solid (ST_Dimension returns 3)

    SELECT ST_AsText(CG_3DIntersection( CG_Extrude(ST_Buffer('POINT(10 20)'::geometry,10,1),0,0,30),
                CG_Extrude(ST_Buffer('POINT(10 20)'::geometry,10,1),2,0,10) ));

    POLYHEDRALSURFACE Z (((13.3333333333333 13.3333333333333 10,20 20 0,20 20 10,13.3333333333333 13.3333333333333 10)),
            ((20 20 10,16.6666666666667 23.3333333333333 10,13.3333333333333 13.3333333333333 10,20 20 10)),
            ((20 20 0,16.6666666666667 23.3333333333333 10,20 20 10,20 20 0)),
            ((13.3333333333333 13.3333333333333 10,10 10 0,20 20 0,13.3333333333333 13.3333333333333 10)),
            ((16.6666666666667 23.3333333333333 10,12 28 10,13.3333333333333 13.3333333333333 10,16.6666666666667 23.3333333333333 10)),
            ((20 20 0,9.99999999999995 30 0,16.6666666666667 23.3333333333333 10,20 20 0)),
            ((10 10 0,9.99999999999995 30 0,20 20 0,10 10 0)),((13.3333333333333 13.3333333333333 10,12 12 10,10 10 0,13.3333333333333 13.3333333333333 10)),
            ((12 28 10,12 12 10,13.3333333333333 13.3333333333333 10,12 28 10)),
            ((16.6666666666667 23.3333333333333 10,9.99999999999995 30 0,12 28 10,16.6666666666667 23.3333333333333 10)),
            ((10 10 0,0 20 0,9.99999999999995 30 0,10 10 0)),
            ((12 12 10,11 11 10,10 10 0,12 12 10)),((12 28 10,11 11 10,12 12 10,12 28 10)),
            ((9.99999999999995 30 0,11 29 10,12 28 10,9.99999999999995 30 0)),((0 20 0,2 20 10,9.99999999999995 30 0,0 20 0)),
            ((10 10 0,2 20 10,0 20 0,10 10 0)),((11 11 10,2 20 10,10 10 0,11 11 10)),((12 28 10,11 29 10,11 11 10,12 28 10)),
            ((9.99999999999995 30 0,2 20 10,11 29 10,9.99999999999995 30 0)),((11 11 10,11 29 10,2 20 10,11 11 10)))

## Name

CG_Union — Computes the union of two geometries

## Synopsis

`geometry CG_Union(` geometry geomA , geometry geomB `)`;

## Description

Computes the union of two geometries.

Performed by the SFCGAL module

NOTE: this function returns a geometry representing the union.

Availability: 3.5.0

This method needs SFCGAL backend.

## Geometry Examples

    SELECT CG_Union('POINT(.5 0)', 'LINESTRING(-1 0,1 0)');
                    cg_union
                    -----------
                    LINESTRING(-1 0,0.5 0,1 0)
                    (1 row)

## See Also

ST_3DUnion, ST_Union

## Name

ST_3DUnion — Perform 3D union.

## Synopsis

`geometry ST_3DUnion(` geometry geom1, geometry geom2`)`;

`geometry ST_3DUnion(` geometry set g1field`)`;

## Description

ST_3DUnion is deprecated as of 3.5.0. Use CG_3DUnion instead.

Availability: 2.2.0

Availability: 3.3.0 aggregate variant was added

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Aggregate variant: returns a geometry that is the 3D union of a rowset of geometries. The ST_3DUnion() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do and like most aggregates, it also ignores NULL geometries.

## Name

CG_3DUnion — Perform 3D union using postgis_sfcgal.

## Synopsis

`geometry CG_3DUnion(` geometry geom1, geometry geom2`)`;

`geometry CG_3DUnion(` geometry set g1field`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This method implements the SQL/MM specification. SQL-MM IEC 13249-3: 5.1

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

Aggregate variant: returns a geometry that is the 3D union of a rowset of geometries. The CG_3DUnion() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do and like most aggregates, it also ignores NULL geometries.

## Examples

3D images were generated using PostGIS ST_AsX3D and rendering in HTML using X3Dom HTML Javascript rendering library.

    SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                        50, 'quad_segs=2'),0,0,30) AS geom1,
                                        CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                        50, 'quad_segs=1'),0,0,30) AS geom2;
Original 3D geometries overlaid. geom2 is the one with transparency. |
    SELECT CG_3DUnion(geom1,geom2)
                                    FROM ( SELECT CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                    50, 'quad_segs=2'),0,0,30) AS geom1,
                                    CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(80 80)'),
                                    50, 'quad_segs=1'),0,0,30) AS geom2 ) As t;
Union of geom1 and geom2

## See Also

CG_Extrude, ST_AsX3D, CG_3DIntersection CG_3DDifference

## Name

ST_AlphaShape — Computes an Alpha-shape enclosing a geometry

## Synopsis

`geometry ST_AlphaShape(` geometry geom, float alpha, boolean allow_holes = false`)`;

## Description

ST_AlphaShape is deprecated as of 3.5.0. Use CG_AlphaShape instead.

Computes the Alpha-Shape of the points in a geometry. An alpha-shape is a (usually) concave polygonal geometry which contains all the vertices of the input, and whose vertices are a subset of the input vertices. An alpha-shape provides a closer fit to the shape of the input than the shape produced by the convex hull.

## Name

CG_AlphaShape — Computes an Alpha-shape enclosing a geometry

## Synopsis

`geometry CG_AlphaShape(` geometry geom, float alpha, boolean allow_holes = false`)`;

## Description

Computes the Alpha-Shape of the points in a geometry. An alpha-shape is a (usually) concave polygonal geometry which contains all the vertices of the input, and whose vertices are a subset of the input vertices. An alpha-shape provides a closer fit to the shape of the input than the shape produced by the convex hull.

The "closeness of fit" is controlled by the `alpha` parameter, which can have values from 0 to infinity. Smaller alpha values produce more concave results. Alpha values greater than some data-dependent value produce the convex hull of the input.

Following the CGAL implementation, the alpha value is the square of the radius of the disc used in the Alpha-Shape algorithm to "erode" the Delaunay Triangulation of the input points. See CGAL Alpha-Shapes for more information. This is different from the original definition of alpha-shapes, which defines alpha as the radius of the eroding disc.

The computed shape does not contain holes unless the optional `allow_holes` argument is specified as true.

This function effectively computes a concave hull of a geometry in a similar way to ST_ConcaveHull, but uses CGAL and a different algorithm.

Availability: 3.5.0 - requires SFCGAL >= 1.4.1.

This method needs SFCGAL backend.

## Examples

Alpha-shape of a MultiPoint (same example As CG_OptimalAlphaShape)

    SELECT ST_AsText(CG_AlphaShape('MULTIPOINT((63 84),(76 88),(68 73),(53 18),(91 50),(81 70),
                (88 29),(24 82),(32 51),(37 23),(27 54),(84 19),(75 87),(44 42),(77 67),(90 30),(36 61),(32 65),
                (81 47),(88 58),(68 73),(49 95),(81 60),(87 50),
                (78 16),(79 21),(30 22),(78 43),(26 85),(48 34),(35 35),(36 40),(31 79),(83 29),(27 84),(52 98),(72 95),(85 71),
                (75 84),(75 77),(81 29),(77 73),(41 42),(83 72),(23 36),(89 53),(27 57),(57 97),(27 77),(39 88),(60 81),
                (80 72),(54 32),(55 26),(62 22),(70 20),(76 27),(84 35),(87 42),(82 54),(83 64),(69 86),(60 90),(50 86),(43 80),(36 73),
                (36 68),(40 75),(24 67),(23 60),(26 44),(28 33),(40 32),(43 19),(65 16),(73 16),(38 46),(31 59),(34 86),(45 90),(64 97))'::geometry,80.2));

    POLYGON((89 53,91 50,87 42,90 30,88 29,84 19,78 16,73 16,65 16,53 18,43 19,
            37 23,30 22,28 33,23 36,26 44,27 54,23 60,24 67,27 77,
            24 82,26 85,34 86,39 88,45 90,49 95,52 98,57 97,
            64 97,72 95,76 88,75 84,83 72,85 71,88 58,89 53))

Alpha-shape of a MultiPoint, allowing holes (same example as CG_OptimalAlphaShape)

    SELECT ST_AsText(CG_AlphaShape('MULTIPOINT((63 84),(76 88),(68 73),(53 18),(91 50),(81 70),(88 29),(24 82),(32 51),(37 23),(27 54),(84 19),(75 87),(44 42),(77 67),(90 30),(36 61),(32 65),(81 47),(88 58),(68 73),(49 95),(81 60),(87 50),
        (78 16),(79 21),(30 22),(78 43),(26 85),(48 34),(35 35),(36 40),(31 79),(83 29),(27 84),(52 98),(72 95),(85 71),
        (75 84),(75 77),(81 29),(77 73),(41 42),(83 72),(23 36),(89 53),(27 57),(57 97),(27 77),(39 88),(60 81),
        (80 72),(54 32),(55 26),(62 22),(70 20),(76 27),(84 35),(87 42),(82 54),(83 64),(69 86),(60 90),(50 86),(43 80),(36 73),
        (36 68),(40 75),(24 67),(23 60),(26 44),(28 33),(40 32),(43 19),(65 16),(73 16),(38 46),(31 59),(34 86),(45 90),(64 97))'::geometry, 100.1,true))

    POLYGON((89 53,91 50,87 42,90 30,84 19,78 16,73 16,65 16,53 18,43 19,30 22,28 33,23 36,
    26 44,27 54,23 60,24 67,27 77,24 82,26 85,34 86,39 88,45 90,49 95,52 98,57 97,64 97,72 95,
    76 88,75 84,83 72,85 71,88 58,89 53),(36 61,36 68,40 75,43 80,60 81,68 73,77 67,
    81 60,82 54,81 47,78 43,76 27,62 22,54 32,44 42,38 46,36 61))

Alpha-shape of a MultiPoint, allowing holes (same example as ST_ConcaveHull)

    SELECT ST_AsText(CG_AlphaShape(
                    'MULTIPOINT ((132 64), (114 64), (99 64), (81 64), (63 64), (57 49), (52 36), (46 20), (37 20), (26 20), (32 36), (39 55), (43 69), (50 84), (57 100), (63 118), (68 133), (74 149), (81 164), (88 180), (101 180), (112 180), (119 164), (126 149), (132 131), (139 113), (143 100), (150 84), (157 69), (163 51), (168 36), (174 20), (163 20), (150 20), (143 36), (139 49), (132 64), (99 151), (92 138), (88 124), (81 109), (74 93), (70 82), (83 82), (99 82), (112 82), (126 82), (121 96), (114 109), (110 122), (103 138), (99 151), (34 27), (43 31), (48 44), (46 58), (52 73), (63 73), (61 84), (72 71), (90 69), (101 76), (123 71), (141 62), (166 27), (150 33), (159 36), (146 44), (154 53), (152 62), (146 73), (134 76), (143 82), (141 91), (130 98), (126 104), (132 113), (128 127), (117 122), (112 133), (119 144), (108 147), (119 153), (110 171), (103 164), (92 171), (86 160), (88 142), (79 140), (72 124), (83 131), (79 118), (68 113), (63 102), (68 93), (35 45))'::geometry,102.2, true));

    POLYGON((26 20,32 36,35 45,39 55,43 69,50 84,57 100,63 118,68 133,74 149,81 164,88 180,
                101 180,112 180,119 164,126 149,132 131,139 113,143 100,150 84,157 69,163 51,168 36,
                174 20,163 20,150 20,143 36,139 49,132 64,114 64,99 64,90 69,81 64,63 64,57 49,52 36,46 20,37 20,26 20),
                (74 93,81 109,88 124,92 138,103 138,110 122,114 109,121 96,112 82,99 82,83 82,74 93))

## See Also

ST_ConcaveHull, CG_OptimalAlphaShape

## Name

CG_ApproxConvexPartition — Computes approximal convex partition of the polygon geometry

## Synopsis

`geometry CG_ApproxConvexPartition(` geometry geom`)`;

## Description

Computes approximal convex partition of the polygon geometry (using a triangulation).

A partition of a polygon P is a set of polygons such that the interiors of the polygons do not intersect and the union of the polygons is equal to the interior of the original polygon P. CG_ApproxConvexPartition and CG_GreeneApproxConvexPartition functions produce approximately optimal convex partitions. Both these functions produce convex decompositions by first decomposing the polygon into simpler polygons; CG_ApproxConvexPartition uses a triangulation and CG_GreeneApproxConvexPartition a monotone partition. These two functions both guarantee that they will produce no more than four times the optimal number of convex pieces but they differ in their runtime complexities. Though the triangulation-based approximation algorithm often results in fewer convex pieces, this is not always the case.

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

## Examples

Approximal Convex Partition (same example As CG_YMonotonePartition, CG_GreeneApproxConvexPartition and CG_OptimalConvexPartition)

    SELECT ST_AsText(CG_ApproxConvexPartition('POLYGON((156 150,83 181,89 131,148 120,107 61,32 159,0 45,41 86,45 1,177 2,67 24,109 31,170 60,180 110,156 150))'::geometry));

    GEOMETRYCOLLECTION(POLYGON((156 150,83 181,89 131,148 120,156 150)),POLYGON((32 159,0 45,41 86,32 159)),POLYGON((107 61,32 159,41 86,107 61)),POLYGON((45 1,177 2,67 24,45 1)),POLYGON((41 86,45 1,67 24,41 86)),POLYGON((107 61,41 86,67 24,109 31,107 61)),POLYGON((148 120,107 61,109 31,170 60,148 120)),POLYGON((156 150,148 120,170 60,180 110,156 150)))

## See Also

CG_YMonotonePartition, CG_GreeneApproxConvexPartition, CG_OptimalConvexPartition

## Name

ST_ApproximateMedialAxis — Compute the approximate medial axis of an areal geometry.

## Synopsis

`geometry ST_ApproximateMedialAxis(` geometry geom`)`;

## Description

ST_ApproximateMedialAxis is deprecated as of 3.5.0. Use CG_ApproximateMedialAxis instead.

Return an approximate medial axis for the areal input based on its straight skeleton. Uses an SFCGAL specific API when built against a capable version (1.2.0+). Otherwise the function is just a wrapper around CG_StraightSkeleton (slower case).

Availability: 2.2.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_ApproximateMedialAxis — Compute the approximate medial axis of an areal geometry.

## Synopsis

`geometry CG_ApproximateMedialAxis(` geometry geom`)`;

## Description

Return an approximate medial axis for the areal input based on its straight skeleton. Uses an SFCGAL specific API when built against a capable version (1.2.0+). Otherwise the function is just a wrapper around CG_StraightSkeleton (slower case).

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT CG_ApproximateMedialAxis(ST_GeomFromText('POLYGON (( 190 190, 10 190, 10 10, 190 10, 190 20, 160 30, 60 30, 60 130, 190 140, 190 190 ))'));

A polygon and its approximate medial axis

## See Also

CG_StraightSkeleton

## Name

ST_ConstrainedDelaunayTriangles — Return a constrained Delaunay triangulation around the given input geometry.

## Synopsis

`geometry ST_ConstrainedDelaunayTriangles(` geometry g1`)`;

## Description

ST_ConstrainedDelaunayTriangles is deprecated as of 3.5.0. Use CG_ConstrainedDelaunayTriangles instead.

Return a Constrained Delaunay triangulation around the vertices of the input geometry. Output is a TIN.

This method needs SFCGAL backend.

Availability: 3.0.0

This function supports 3d and will not drop the z-index.

## Name

CG_ConstrainedDelaunayTriangles — Return a constrained Delaunay triangulation around the given input geometry.

## Synopsis

`geometry CG_ConstrainedDelaunayTriangles(` geometry g1`)`;

## Description

Return a Constrained Delaunay triangulation around the vertices of the input geometry. Output is a TIN.

This method needs SFCGAL backend.

Availability: 3.0.0

This function supports 3d and will not drop the z-index.

## Examples

CG_ConstrainedDelaunayTriangles of 2 polygons
                                            select CG_ConstrainedDelaunayTriangles(
                                            ST_Union(
                                            'POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'::geometry,
                                            ST_Buffer('POINT(110 170)'::geometry, 20)
                                            )
                                            );
| ST_DelaunayTriangles of 2 polygons. Triangle edges cross polygon boundaries.
                                            select ST_DelaunayTriangles(
                                            ST_Union(
                                            'POLYGON((175 150, 20 40, 50 60, 125 100, 175 150))'::geometry,
                                            ST_Buffer('POINT(110 170)'::geometry, 20)
                                            )
                                            );

## See Also

ST_DelaunayTriangles, ST_TriangulatePolygon, CG_Tesselate, ST_ConcaveHull, ST_Dump

## Name

ST_Extrude — Extrude a surface to a related volume

## Synopsis

`geometry ST_Extrude(` geometry geom, float x, float y, float z`)`;

## Description

ST_Extrude is deprecated as of 3.5.0. Use CG_Extrude instead.

Availability: 2.1.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_Extrude — Extrude a surface to a related volume

## Synopsis

`geometry CG_Extrude(` geometry geom, float x, float y, float z`)`;

## Description

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

3D images were generated using PostGIS ST_AsX3D and rendering in HTML using X3Dom HTML Javascript rendering library.

    SELECT ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                        50, 'quad_segs=2'),0,0,30);
Original octagon formed from buffering point |
    CG_Extrude(ST_Buffer(ST_GeomFromText('POINT(100 90)'),
                                    50, 'quad_segs=2'),0,0,30);
Hexagon extruded 30 units along Z produces a PolyhedralSurfaceZ
    SELECT ST_GeomFromText('LINESTRING(50 50, 100 90, 95 150)')
Original linestring |
    SELECT CG_Extrude(
                                ST_GeomFromText('LINESTRING(50 50, 100 90, 95 150)'),0,0,10));
LineString Extruded along Z produces a PolyhedralSurfaceZ

## See Also

ST_AsX3D, CG_ExtrudeStraightSkeleton

## Name

CG_ExtrudeStraightSkeleton — Straight Skeleton Extrusion

## Synopsis

`geometry CG_ExtrudeStraightSkeleton(` geometry geom, float roof_height, float body_height = 0`)`;

## Description

Computes an extrusion with a maximal height of the polygon geometry.

Perhaps the first (historically) use-case of straight skeletons: given a polygonal roof, the straight skeleton directly gives the layout of each tent. If each skeleton edge is lifted from the plane a height equal to its offset distance, the resulting roof is "correct" in that water will always fall down to the contour edges (the roof's border), regardless of where it falls on the roof. The function computes this extrusion aka "roof" on a polygon. If the argument body_height > 0, so the polygon is extruded like with CG_Extrude(polygon, 0, 0, body_height). The result is an union of these polyhedralsurfaces.

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

## Examples

    SELECT ST_AsText(CG_ExtrudeStraightSkeleton('POLYGON (( 0 0, 5 0, 5 5, 4 5, 4 4, 0 4, 0 0 ), (1 1, 1 2,2 2, 2 1, 1 1))', 3.0, 2.0));

    POLYHEDRALSURFACE Z (((0 0 0,0 4 0,4 4 0,4 5 0,5 5 0,5 0 0,0 0 0),(1 1 0,2 1 0,2 2 0,1 2 0,1 1 0)),((0 0 0,0 0 2,0 4 2,0 4 0,0 0 0)),((0 4 0,0 4 2,4 4 2,4 4 0,0 4 0)),((4 4 0,4 4 2,4 5 2,4 5 0,4 4 0)),((4 5 0,4 5 2,5 5 2,5 5 0,4 5 0)),((5 5 0,5 5 2,5 0 2,5 0 0,5 5 0)),((5 0 0,5 0 2,0 0 2,0 0 0,5 0 0)),((1 1 0,1 1 2,2 1 2,2 1 0,1 1 0)),((2 1 0,2 1 2,2 2 2,2 2 0,2 1 0)),((2 2 0,2 2 2,1 2 2,1 2 0,2 2 0)),((1 2 0,1 2 2,1 1 2,1 1 0,1 2 0)),((4 5 2,5 5 2,4 4 2,4 5 2)),((2 1 2,5 0 2,0 0 2,2 1 2)),((5 5 2,5 0 2,4 4 2,5 5 2)),((2 1 2,0 0 2,1 1 2,2 1 2)),((1 2 2,1 1 2,0 0 2,1 2 2)),((0 4 2,2 2 2,1 2 2,0 4 2)),((0 4 2,1 2 2,0 0 2,0 4 2)),((4 4 2,5 0 2,2 2 2,4 4 2)),((4 4 2,2 2 2,0 4 2,4 4 2)),((2 2 2,5 0 2,2 1 2,2 2 2)),((0.5 2.5 2.5,0 0 2,0.5 0.5 2.5,0.5 2.5 2.5)),((1 3 3,0 4 2,0.5 2.5 2.5,1 3 3)),((0.5 2.5 2.5,0 4 2,0 0 2,0.5 2.5 2.5)),((2.5 0.5 2.5,5 0 2,3.5 1.5 3.5,2.5 0.5 2.5)),((0 0 2,5 0 2,2.5 0.5 2.5,0 0 2)),((0.5 0.5 2.5,0 0 2,2.5 0.5 2.5,0.5 0.5 2.5)),((4.5 3.5 2.5,5 5 2,4.5 4.5 2.5,4.5 3.5 2.5)),((3.5 2.5 3.5,3.5 1.5 3.5,4.5 3.5 2.5,3.5 2.5 3.5)),((4.5 3.5 2.5,5 0 2,5 5 2,4.5 3.5 2.5)),((3.5 1.5 3.5,5 0 2,4.5 3.5 2.5,3.5 1.5 3.5)),((5 5 2,4 5 2,4.5 4.5 2.5,5 5 2)),((4.5 4.5 2.5,4 4 2,4.5 3.5 2.5,4.5 4.5 2.5)),((4.5 4.5 2.5,4 5 2,4 4 2,4.5 4.5 2.5)),((3 3 3,0 4 2,1 3 3,3 3 3)),((3.5 2.5 3.5,4.5 3.5 2.5,3 3 3,3.5 2.5 3.5)),((3 3 3,4 4 2,0 4 2,3 3 3)),((4.5 3.5 2.5,4 4 2,3 3 3,4.5 3.5 2.5)),((2 1 2,1 1 2,0.5 0.5 2.5,2 1 2)),((2.5 0.5 2.5,2 1 2,0.5 0.5 2.5,2.5 0.5 2.5)),((1 1 2,1 2 2,0.5 2.5 2.5,1 1 2)),((0.5 0.5 2.5,1 1 2,0.5 2.5 2.5,0.5 0.5 2.5)),((1 3 3,2 2 2,3 3 3,1 3 3)),((0.5 2.5 2.5,1 2 2,1 3 3,0.5 2.5 2.5)),((1 3 3,1 2 2,2 2 2,1 3 3)),((2 2 2,2 1 2,2.5 0.5 2.5,2 2 2)),((3.5 2.5 3.5,3 3 3,3.5 1.5 3.5,3.5 2.5 3.5)),((3.5 1.5 3.5,2 2 2,2.5 0.5 2.5,3.5 1.5 3.5)),((3 3 3,2 2 2,3.5 1.5 3.5,3 3 3)))

## See Also

ST_Extrude, CG_StraightSkeleton

## Name

CG_GreeneApproxConvexPartition — Computes approximal convex partition of the polygon geometry

## Synopsis

`geometry CG_GreeneApproxConvexPartition(` geometry geom`)`;

## Description

Computes approximal monotone convex partition of the polygon geometry.

A partition of a polygon P is a set of polygons such that the interiors of the polygons do not intersect and the union of the polygons is equal to the interior of the original polygon P. CG_ApproxConvexPartition and CG_GreeneApproxConvexPartition functions produce approximately optimal convex partitions. Both these functions produce convex decompositions by first decomposing the polygon into simpler polygons; CG_ApproxConvexPartition uses a triangulation and CG_GreeneApproxConvexPartition a monotone partition. These two functions both guarantee that they will produce no more than four times the optimal number of convex pieces but they differ in their runtime complexities. Though the triangulation-based approximation algorithm often results in fewer convex pieces, this is not always the case.

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

## Examples

Greene Approximal Convex Partition (same example As CG_YMonotonePartition, CG_ApproxConvexPartition and CG_OptimalConvexPartition)

    SELECT ST_AsText(CG_GreeneApproxConvexPartition('POLYGON((156 150,83 181,89 131,148 120,107 61,32 159,0 45,41 86,45 1,177 2,67 24,109 31,170 60,180 110,156 150))'::geometry));

    GEOMETRYCOLLECTION(POLYGON((32 159,0 45,41 86,32 159)),POLYGON((45 1,177 2,67 24,45 1)),POLYGON((67 24,109 31,170 60,107 61,67 24)),POLYGON((41 86,45 1,67 24,41 86)),POLYGON((107 61,32 159,41 86,67 24,107 61)),POLYGON((148 120,107 61,170 60,148 120)),POLYGON((148 120,170 60,180 110,156 150,148 120)),POLYGON((156 150,83 181,89 131,148 120,156 150)))

## See Also

CG_YMonotonePartition, CG_ApproxConvexPartition, CG_OptimalConvexPartition

## Name

ST_MinkowskiSum — Performs Minkowski sum

## Synopsis

`geometry ST_MinkowskiSum(` geometry geom1, geometry geom2`)`;

## Description

ST_MinkowskiSum is deprecated as of 3.5.0. Use CG_MinkowskiSum instead.

This function performs a 2D minkowski sum of a point, line or polygon with a polygon.

A minkowski sum of two geometries A and B is the set of all points that are the sum of any point in A and B. Minkowski sums are often used in motion planning and computer-aided design. More details on Wikipedia Minkowski addition.

The first parameter can be any 2D geometry (point, linestring, polygon). If a 3D geometry is passed, it will be converted to 2D by forcing Z to 0, leading to possible cases of invalidity. The second parameter must be a 2D polygon.

Implementation utilizes CGAL 2D Minkowskisum.

Availability: 2.1.0

This method needs SFCGAL backend.

## Name

CG_MinkowskiSum — Performs Minkowski sum

## Synopsis

`geometry CG_MinkowskiSum(` geometry geom1, geometry geom2`)`;

## Description

This function performs a 2D minkowski sum of a point, line or polygon with a polygon.

A minkowski sum of two geometries A and B is the set of all points that are the sum of any point in A and B. Minkowski sums are often used in motion planning and computer-aided design. More details on Wikipedia Minkowski addition.

The first parameter can be any 2D geometry (point, linestring, polygon). If a 3D geometry is passed, it will be converted to 2D by forcing Z to 0, leading to possible cases of invalidity. The second parameter must be a 2D polygon.

Implementation utilizes CGAL 2D Minkowskisum.

Availability: 3.5.0

This method needs SFCGAL backend.

## Examples

Minkowski Sum of Linestring and circle polygon where Linestring cuts thru the circle

Before Summing | After summing

                SELECT CG_MinkowskiSum(line, circle))
                FROM (SELECT
                ST_MakeLine(ST_Point(10, 10),ST_Point(100, 100)) As line,
                ST_Buffer(ST_GeomFromText('POINT(50 50)'), 30) As circle) As foo;

                -- wkt --
                MULTIPOLYGON(((30 59.9999999999999,30.5764415879031 54.1472903395161,32.2836140246614 48.5194970290472,35.0559116309237 43.3328930094119,38.7867965644036 38.7867965644035,43.332893009412 35.0559116309236,48.5194970290474 32.2836140246614,54.1472903395162 30.5764415879031,60.0000000000001 30,65.8527096604839 30.5764415879031,71.4805029709527 32.2836140246614,76.6671069905881 35.0559116309237,81.2132034355964 38.7867965644036,171.213203435596 128.786796564404,174.944088369076 133.332893009412,177.716385975339 138.519497029047,179.423558412097 144.147290339516,180 150,179.423558412097 155.852709660484,177.716385975339 161.480502970953,174.944088369076 166.667106990588,171.213203435596 171.213203435596,166.667106990588 174.944088369076,
                161.480502970953 177.716385975339,155.852709660484 179.423558412097,150 180,144.147290339516 179.423558412097,138.519497029047 177.716385975339,133.332893009412 174.944088369076,128.786796564403 171.213203435596,38.7867965644035 81.2132034355963,35.0559116309236 76.667106990588,32.2836140246614 71.4805029709526,30.5764415879031 65.8527096604838,30 59.9999999999999)))

Minkowski Sum of a polygon and multipoint

Before Summing | After summing: polygon is duplicated and translated to position of points

    SELECT CG_MinkowskiSum(mp, poly)
            FROM (SELECT 'MULTIPOINT(25 50,70 25)'::geometry As mp,
            'POLYGON((130 150, 20 40, 50 60, 125 100, 130 150))'::geometry As poly
            ) As foo

            -- wkt --
            MULTIPOLYGON(
            ((70 115,100 135,175 175,225 225,70 115)),
            ((120 65,150 85,225 125,275 175,120 65))
            )

## Name

ST_OptimalAlphaShape — Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.

## Synopsis

`geometry ST_OptimalAlphaShape(` geometry geom, boolean allow_holes = false, integer nb_components = 1`)`;

## Description

ST_OptimalAlphaShape is deprecated as of 3.5.0. Use CG_OptimalAlphaShape instead.

Computes the "optimal" alpha-shape of the points in a geometry. The alpha-shape is computed using a value of α chosen so that:

1. the number of polygon elements is equal to or smaller than `nb_components` (which defaults to 1)

2. all input points are contained in the shape

The result will not contain holes unless the optional `allow_holes` argument is specified as true.

Availability: 3.3.0 - requires SFCGAL >= 1.4.1.

This method needs SFCGAL backend.

## Name

CG_OptimalAlphaShape — Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.

## Synopsis

`geometry CG_OptimalAlphaShape(` geometry geom, boolean allow_holes = false, integer nb_components = 1`)`;

## Description

Computes the "optimal" alpha-shape of the points in a geometry. The alpha-shape is computed using a value of α chosen so that:

1. the number of polygon elements is equal to or smaller than `nb_components` (which defaults to 1)

2. all input points are contained in the shape

The result will not contain holes unless the optional `allow_holes` argument is specified as true.

Availability: 3.5.0 - requires SFCGAL >= 1.4.1.

This method needs SFCGAL backend.

## Examples

Optimal alpha-shape of a MultiPoint (same example as CG_AlphaShape)

    SELECT ST_AsText(CG_OptimalAlphaShape('MULTIPOINT((63 84),(76 88),(68 73),(53 18),(91 50),(81 70),
                    (88 29),(24 82),(32 51),(37 23),(27 54),(84 19),(75 87),(44 42),(77 67),(90 30),(36 61),(32 65),
                    (81 47),(88 58),(68 73),(49 95),(81 60),(87 50),
                    (78 16),(79 21),(30 22),(78 43),(26 85),(48 34),(35 35),(36 40),(31 79),(83 29),(27 84),(52 98),(72 95),(85 71),
                    (75 84),(75 77),(81 29),(77 73),(41 42),(83 72),(23 36),(89 53),(27 57),(57 97),(27 77),(39 88),(60 81),
                    (80 72),(54 32),(55 26),(62 22),(70 20),(76 27),(84 35),(87 42),(82 54),(83 64),(69 86),(60 90),(50 86),(43 80),(36 73),
                    (36 68),(40 75),(24 67),(23 60),(26 44),(28 33),(40 32),(43 19),(65 16),(73 16),(38 46),(31 59),(34 86),(45 90),(64 97))'::geometry));

    POLYGON((89 53,91 50,87 42,90 30,88 29,84 19,78 16,73 16,65 16,53 18,43 19,37 23,30 22,28 33,23 36,
                26 44,27 54,23 60,24 67,27 77,24 82,26 85,34 86,39 88,45 90,49 95,52 98,57 97,64 97,72 95,76 88,75 84,75 77,83 72,85 71,83 64,88 58,89 53))

Optimal alpha-shape of a MultiPoint, allowing holes (same example as CG_AlphaShape)

    SELECT ST_AsText(CG_OptimalAlphaShape('MULTIPOINT((63 84),(76 88),(68 73),(53 18),(91 50),(81 70),(88 29),(24 82),(32 51),(37 23),(27 54),(84 19),(75 87),(44 42),(77 67),(90 30),(36 61),(32 65),(81 47),(88 58),(68 73),(49 95),(81 60),(87 50),
            (78 16),(79 21),(30 22),(78 43),(26 85),(48 34),(35 35),(36 40),(31 79),(83 29),(27 84),(52 98),(72 95),(85 71),
            (75 84),(75 77),(81 29),(77 73),(41 42),(83 72),(23 36),(89 53),(27 57),(57 97),(27 77),(39 88),(60 81),
            (80 72),(54 32),(55 26),(62 22),(70 20),(76 27),(84 35),(87 42),(82 54),(83 64),(69 86),(60 90),(50 86),(43 80),(36 73),
            (36 68),(40 75),(24 67),(23 60),(26 44),(28 33),(40 32),(43 19),(65 16),(73 16),(38 46),(31 59),(34 86),(45 90),(64 97))'::geometry, allow_holes => true));

    POLYGON((89 53,91 50,87 42,90 30,88 29,84 19,78 16,73 16,65 16,53 18,43 19,37 23,30 22,28 33,23 36,26 44,27 54,23 60,24 67,27 77,24 82,26 85,34 86,39 88,45 90,49 95,52 98,57 97,64 97,72 95,76 88,75 84,75 77,83 72,85 71,83 64,88 58,89 53),(36 61,36 68,40 75,43 80,50 86,60 81,68 73,77 67,81 60,82 54,81 47,78 43,81 29,76 27,70 20,62 22,55 26,54 32,48 34,44 42,38 46,36 61))

## See Also

ST_ConcaveHull, CG_AlphaShape

## Name

CG_OptimalConvexPartition — Computes an optimal convex partition of the polygon geometry

## Synopsis

`geometry CG_OptimalConvexPartition(` geometry geom`)`;

## Description

Computes an optimal convex partition of the polygon geometry.

A partition of a polygon P is a set of polygons such that the interiors of the polygons do not intersect and the union of the polygons is equal to the interior of the original polygon P. CG_OptimalConvexPartition produces a partition that is optimal in the number of pieces.

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

## Examples

Optimal Convex Partition (same example As CG_YMonotonePartition, CG_ApproxConvexPartition and CG_GreeneApproxConvexPartition)

    SELECT ST_AsText(CG_OptimalConvexPartition('POLYGON((156 150,83 181,89 131,148 120,107 61,32 159,0 45,41 86,45 1,177 2,67 24,109 31,170 60,180 110,156 150))'::geometry));

    GEOMETRYCOLLECTION(POLYGON((156 150,83 181,89 131,148 120,156 150)),POLYGON((32 159,0 45,41 86,32 159)),POLYGON((45 1,177 2,67 24,45 1)),POLYGON((41 86,45 1,67 24,41 86)),POLYGON((107 61,32 159,41 86,67 24,109 31,107 61)),POLYGON((148 120,107 61,109 31,170 60,180 110,148 120)),POLYGON((156 150,148 120,180 110,156 150)))

## See Also

CG_YMonotonePartition, CG_ApproxConvexPartition, CG_GreeneApproxConvexPartition

## Name

CG_StraightSkeleton — Compute a straight skeleton from a geometry

## Synopsis

`geometry CG_StraightSkeleton(` geometry geom, boolean use_distance_as_m = false`)`;

## Description

Availability: 3.5.0

Requires SFCGAL >= 1.3.8 for option use_distance_as_m

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT CG_StraightSkeleton(ST_GeomFromText('POLYGON (( 190 190, 10 190, 10 10, 190 10, 190 20, 160 30, 60 30, 60 130, 190 140, 190 190 ))'));

    ST_AsText(CG_StraightSkeleton('POLYGON((0 0,1 0,1 1,0 1,0 0))', true);

    MULTILINESTRING M ((0 0 0,0.5 0.5 0.5),(1 0 0,0.5 0.5 0.5),(1 1 0,0.5 0.5 0.5),(0 1 0,0.5 0.5 0.5))

Original polygon | Straight Skeleton of polygon

## See Also

CG_ExtrudeStraightSkeleton

## Name

ST_StraightSkeleton — Compute a straight skeleton from a geometry

## Synopsis

`geometry ST_StraightSkeleton(` geometry geom`)`;

## Description

ST_StraightSkeleton is deprecated as of 3.5.0. Use CG_StraightSkeleton instead.

Availability: 2.1.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_StraightSkeleton(ST_GeomFromText('POLYGON (( 190 190, 10 190, 10 10, 190 10, 190 20, 160 30, 60 30, 60 130, 190 140, 190 190 ))'));

Original polygon | Straight Skeleton of polygon

## See Also

CG_ExtrudeStraightSkeleton

## Name

ST_Tesselate — Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS

## Synopsis

`geometry ST_Tesselate(` geometry geom`)`;

## Description

ST_Tesselate is deprecated as of 3.5.0. Use CG_Tesselate instead.

Takes as input a surface such a MULTI(POLYGON) or POLYHEDRALSURFACE and returns a TIN representation via the process of tessellation using triangles.

ST_TriangulatePolygon does similar to this function except that it returns a geometry collection of polygons instead of a TIN and also only works with 2D geometries.

Availability: 2.1.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Name

CG_Tesselate — Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS

## Synopsis

`geometry CG_Tesselate(` geometry geom`)`;

## Description

Takes as input a surface such a MULTI(POLYGON) or POLYHEDRALSURFACE and returns a TIN representation via the process of tessellation using triangles.

ST_TriangulatePolygon does similar to this function except that it returns a geometry collection of polygons instead of a TIN and also only works with 2D geometries.

Availability: 3.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT ST_GeomFromText('POLYHEDRALSURFACE Z( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                                        ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                                        ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                                        ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )');
Original Cube |
    SELECT CG_Tesselate(ST_GeomFromText('POLYHEDRALSURFACE Z( ((0 0 0, 0 0 1, 0 1 1, 0 1 0, 0 0 0)),
                                    ((0 0 0, 0 1 0, 1 1 0, 1 0 0, 0 0 0)), ((0 0 0, 1 0 0, 1 0 1, 0 0 1, 0 0 0)),
                                    ((1 1 0, 1 1 1, 1 0 1, 1 0 0, 1 1 0)),
                                    ((0 1 0, 0 1 1, 1 1 1, 1 1 0, 0 1 0)), ((0 0 1, 1 0 1, 1 1 1, 0 1 1, 0 0 1)) )'));
ST_AsText output:
    TIN Z (((0 0 0,0 0 1,0 1 1,0 0 0)),((0 1 0,0 0 0,0 1 1,0 1 0)),
                            ((0 0 0,0 1 0,1 1 0,0 0 0)),
                            ((1 0 0,0 0 0,1 1 0,1 0 0)),((0 0 1,1 0 0,1 0 1,0 0 1)),
                            ((0 0 1,0 0 0,1 0 0,0 0 1)),
                            ((1 1 0,1 1 1,1 0 1,1 1 0)),((1 0 0,1 1 0,1 0 1,1 0 0)),
                            ((0 1 0,0 1 1,1 1 1,0 1 0)),((1 1 0,0 1 0,1 1 1,1 1 0)),
                            ((0 1 1,1 0 1,1 1 1,0 1 1)),((0 1 1,0 0 1,1 0 1,0 1 1)))
Tessellated Cube with triangles colored
    SELECT 'POLYGON (( 10 190, 10 70, 80 70, 80 130, 50 160, 120 160, 120 190, 10 190 ))'::geometry;
Original polygon |
    SELECT
                            CG_Tesselate('POLYGON (( 10 190, 10 70, 80 70, 80 130, 50 160, 120 160, 120 190, 10 190 ))'::geometry);
ST_AsText output
    TIN(((80 130,50 160,80 70,80 130)),((50 160,10 190,10 70,50 160)),
                    ((80 70,50 160,10 70,80 70)),((120 160,120 190,50 160,120 160)),
                    ((120 190,10 190,50 160,120 190)))
Tessellated Polygon

## See Also

CG_ConstrainedDelaunayTriangles, ST_DelaunayTriangles, ST_TriangulatePolygon

## Name

CG_Triangulate — Triangulates a polygonal geometry

## Synopsis

`geometry CG_Triangulate(` geometry geom `)`;

## Description

Triangulates a polygonal geometry.

Performed by the SFCGAL module

NOTE: this function returns a geometry representing the triangulated result.

Availability: 3.5.0

This method needs SFCGAL backend.

## Geometry Examples

    SELECT CG_Triangulate('POLYGON((0.0 0.0,1.0 0.0,1.0 1.0,0.0 1.0,0.0 0.0),(0.2 0.2,0.2 0.8,0.8 0.8,0.8 0.2,0.2 0.2))');
                    cg_triangulate
                    ----------------
                    TIN(((0.8 0.2,0.2 0.2,1 0,0.8 0.2)),((0.2 0.2,0 0,1 0,0.2 0.2)),((1 1,0.8 0.8,0.8 0.2,1 1)),((0 1,0 0,0.2 0.2,0 1)),((0 1,0.2 0.8,1 1,0 1)),((0 1,0.2 0.2,0.2 0.8,0 1)),((0.2 0.8,0.8 0.8,1 1,0.2 0.8)),((0.2 0.8,0.2 0.2,0.8 0.2,0.2 0.8)),((1 1,0.8 0.2,1 0,1 1)),((0.8 0.8,0.2 0.8,0.8 0.2,0.8 0.8)))

                    (1 row)

## See Also

CG_ConstrainedDelaunayTriangles, ST_DelaunayTriangles, ST_TriangulatePolygon

## Name

CG_Visibility — Compute a visibility polygon from a point or a segment in a polygon geometry

## Synopsis

`geometry CG_Visibility(` geometry polygon, geometry point`)`;

`geometry CG_Visibility(` geometry polygon, geometry pointA, geometry pointB`)`;

## Description

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

This function supports 3d and will not drop the z-index.

This function supports Polyhedral surfaces.

This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).

## Examples

    SELECT CG_Visibility('POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150))'::geometry, 'POINT(91 87)'::geometry);

    SELECT CG_Visibility('POLYGON((23.5 23.5,23.5 173.5,173.5 173.5,173.5 23.5,23.5 23.5),(108 98,108 36,156 37,155 99,108 98),(107 157.5,107 106.5,135 107.5,133 127.5,143.5 127.5,143.5 108.5,153.5 109.5,151.5 166,107 157.5),(41 95.5,41 35,100.5 36,98.5 68,78.5 68,77.5 96.5,41 95.5),(39 150,40 104,97.5 106.5,95.5 152,39 150))'::geometry,'POINT(78.5 68)'::geometry, 'POINT(98.5 68)'::geometry);

Original polygon | Visibility from the point | Visibility from the segment

## Name

CG_YMonotonePartition — Computes y-monotone partition of the polygon geometry

## Synopsis

`geometry CG_YMonotonePartition(` geometry geom`)`;

## Description

Computes y-monotone partition of the polygon geometry.

A partition of a polygon P is a set of polygons such that the interiors of the polygons do not intersect and the union of the polygons is equal to the interior of the original polygon P. A y-monotone polygon is a polygon whose vertices v1,…,vn can be divided into two chains v1,…,vk and vk,…,vn,v1, such that any horizontal line intersects either chain at most once. This algorithm does not guarantee a bound on the number of polygons produced with respect to the optimal number.

Availability: 3.5.0 - requires SFCGAL >= 1.5.0.

Requires SFCGAL >= 1.5.0

This method needs SFCGAL backend.

## Examples

Original polygon | Y-Monotone Partition (same example As CG_ApproxConvexPartition, CG_GreeneApproxConvexPartition and CG_OptimalConvexPartition)

    SELECT ST_AsText(CG_YMonotonePartition('POLYGON((156 150,83 181,89 131,148 120,107 61,32 159,0 45,41 86,45 1,177 2,67 24,109 31,170 60,180 110,156 150))'::geometry));

    GEOMETRYCOLLECTION(POLYGON((32 159,0 45,41 86,32 159)),POLYGON((107 61,32 159,41 86,45 1,177 2,67 24,109 31,170 60,107 61)),POLYGON((156 150,83 181,89 131,148 120,107 61,170 60,180 110,156 150)))

## See Also

CG_ApproxConvexPartition, CG_GreeneApproxConvexPartition, CG_OptimalConvexPartition

# Chapter 9. Topology

The PostGIS Topology types and functions are used to manage topological objects such as faces, edges and nodes.

Sandro Santilli's presentation at PostGIS Day Paris 2011 conference gives a good synopsis of PostGIS Topology and where it is headed Topology with PostGIS 2.0 slide deck.

Vincent Picavet provides a good synopsis and overview of what is Topology, how is it used, and various FOSS4G tools that support it in PostGIS Topology PGConf EU 2012.

An example of a topologically based GIS database is the US Census Topologically Integrated Geographic Encoding and Referencing System (TIGER) database. If you want to experiment with PostGIS topology and need some data, check out Topology_Load_Tiger.

The PostGIS topology module has existed in prior versions of PostGIS but was never part of the Official PostGIS documentation. In PostGIS 2.0.0 major cleanup is going on to remove use of all deprecated functions in it, fix known usability issues, better document the features and functions, add new functions, and enhance to closer conform to SQL-MM standards.

Details of this project can be found at PostGIS Topology Wiki

All functions and tables associated with this module are installed in a schema called `topology`.

Functions that are defined in SQL/MM standard are prefixed with ST_ and functions specific to PostGIS are not prefixed.

Topology support is build by default starting with PostGIS 2.0, and can be disabled specifying --without-topology configure option at build time as described in Chapter 2, PostGIS Installation

## 9.1. Topology Types

Abstract

This section lists the PostgreSQL data types installed by PostGIS Topology. Note we describe the casting behavior of these which is very important especially when designing your own functions.

## Name

getfaceedges_returntype — A composite type that consists of a sequence number and an edge number.

## Description

A composite type that consists of a sequence number and an edge number. This is the return type for `ST_GetFaceEdges` and `GetNodeEdges` functions.

1. `sequence` is an integer: Refers to a topology defined in the topology.topology table which defines the topology schema and srid.

2. `edge` is an integer: The identifier of an edge.

## Name

TopoGeometry — A composite type representing a topologically defined geometry.

## Description

A composite type that refers to a topology geometry in a specific topology layer, having a specific type and a specific id. The elements of a TopoGeometry are the properties: topology_id, layer_id, id integer, type integer.

1. `topology_id` is an integer: Refers to a topology defined in the topology.topology table which defines the topology schema and srid.

2. `layer_id` is an integer: The layer_id in the layers table that the TopoGeometry belongs to. The combination of topology_id, layer_id provides a unique reference in the topology.layers table.

3. `id` is an integer: The id is the autogenerated sequence number that uniquely defines the topogeometry in the respective topology layer.

4. `type` integer between 1 - 4 that defines the geometry type: 1:[multi]point, 2:[multi]line, 3:[multi]poly, 4:collection

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
geometry | automatic

## See Also

CreateTopoGeom

## Name

validatetopology_returntype — A composite type that consists of an error message and id1 and id2 to denote location of error. This is the return type for `ValidateTopology`.

## Description

A composite type that consists of an error message and two integers. The ValidateTopology function returns a set of these to denote validation errors and the id1 and id2 to denote the ids of the topology objects involved in the error.

1. `error` is varchar: Denotes type of error.

   Current error descriptors are: coincident nodes, edge crosses node, edge not simple, edge end node geometry mismatch, edge start node geometry mismatch, face overlaps face,face within face,

2. `id1` is an integer: Denotes identifier of edge / face / nodes in error.

3. `id2` is an integer: For errors that involve 2 objects denotes the secondary edge / or node

## See Also

ValidateTopology

## 9.2. Topology Domains

Abstract

This section lists the PostgreSQL domains installed by PostGIS Topology. Domains can be used like object types as return objects of functions or table columns. The distinction between a domain and a type is that a domain is an existing type with a check constraint bound to it.

## Name

TopoElement — An array of 2 integers generally used to identify a TopoGeometry component.

## Description

An array of 2 integers used to represent one component of a simple or hierarchical TopoGeometry.

In the case of a simple TopoGeometry the first element of the array represents the identifier of a topological primitive and the second element represents its type (1:node, 2:edge, 3:face). In the case of a hierarchical TopoGeometry the first element of the array represents the identifier of a child TopoGeometry and the second element represents its layer identifier.

For any given hierarchical TopoGeometry all child TopoGeometry elements will come from the same child layer, as specified in the topology.layer record for the layer of the TopoGeometry being defined.

## Examples

    SELECT te[1] AS id, te[2] AS type FROM
    ( SELECT ARRAY[1,2]::topology.topoelement AS te ) f;
     id | type
    ----+------
      1 |    2

    SELECT ARRAY[1,2]::topology.topoelement;
      te
    -------
     {1,2}

    --Example of what happens when you try to case a 3 element array to topoelement
    -- NOTE: topoement has to be a 2 element array so fails dimension check
    SELECT ARRAY[1,2,3]::topology.topoelement;
    ERROR:  value for domain topology.topoelement violates check constraint "dimensions"

## See Also

GetTopoGeomElements, TopoElementArray, TopoGeometry, TopoGeom_addElement, TopoGeom_remElement

## Name

TopoElementArray — An array of TopoElement objects.

## Description

An array of 1 or more TopoElement objects, generally used to pass around components of TopoGeometry objects.

## Examples

    SELECT '{{1,2},{4,3}}'::topology.topoelementarray As tea;
      tea
    -------
    {{1,2},{4,3}}

    -- more verbose equivalent --
    SELECT ARRAY[ARRAY[1,2], ARRAY[4,3]]::topology.topoelementarray As tea;

      tea
    -------
    {{1,2},{4,3}}

    --using the array agg function packaged with topology --
    SELECT topology.TopoElementArray_Agg(ARRAY[e,t]) As tea
      FROM generate_series(1,4) As e CROSS JOIN generate_series(1,3) As t;
      tea
    --------------------------------------------------------------------------
    {{1,1},{1,2},{1,3},{2,1},{2,2},{2,3},{3,1},{3,2},{3,3},{4,1},{4,2},{4,3}}

    SELECT '{{1,2,4},{3,4,5}}'::topology.topoelementarray As tea;
    ERROR:  value for domain topology.topoelementarray violates check constraint "dimensions"

## See Also

TopoElement, GetTopoGeomElementArray, TopoElementArray_Agg

## 9.3. Topology and TopoGeometry Management

Abstract

This section lists the Topology functions for building new Topology schemas, validating topologies, and managing TopoGeometry Columns

## Name

AddTopoGeometryColumn — Adds a topogeometry column to an existing table, registers this new column as a layer in topology.layer and returns the new layer_id.

## Synopsis

`integer AddTopoGeometryColumn(` varchar topology_name, varchar schema_name, varchar table_name, varchar column_name, varchar feature_type`)`;

`integer AddTopoGeometryColumn(` varchar topology_name, varchar schema_name, varchar table_name, varchar column_name, varchar feature_type, integer child_layer`)`;

## Description

Each TopoGeometry object belongs to a specific Layer of a specific Topology. Before creating a TopoGeometry object you need to create its TopologyLayer. A Topology Layer is an association of a feature-table with the topology. It also contain type and hierarchy information. We create a layer using the AddTopoGeometryColumn() function:

This function will both add the requested column to the table and add a record to the topology.layer table with all the given info.

If you don't specify [child_layer] (or set it to NULL) this layer would contain Basic TopoGeometries (composed by primitive topology elements). Otherwise this layer will contain hierarchical TopoGeometries (composed by TopoGeometries from the child_layer).

Once the layer is created (its id is returned by the AddTopoGeometryColumn function) you're ready to construct TopoGeometry objects in it

Valid `feature_type`s are: POINT, MULTIPOINT, LINE, MULTILINE, POLYGON, MULTIPOLYGON, COLLECTION

Availability: 1.1

## Examples

    -- Note for this example we created our new table in the ma_topo schema
    -- though we could have created it in a different schema -- in which case topology_name and schema_name would be different
    CREATE SCHEMA ma;
    CREATE TABLE ma.parcels(gid serial, parcel_id varchar(20) PRIMARY KEY, address text);
    SELECT topology.AddTopoGeometryColumn('ma_topo', 'ma', 'parcels', 'topo', 'POLYGON');

    CREATE SCHEMA ri;
    CREATE TABLE ri.roads(gid serial PRIMARY KEY, road_name text);
    SELECT topology.AddTopoGeometryColumn('ri_topo', 'ri', 'roads', 'topo', 'LINE');

## See Also

DropTopoGeometryColumn, toTopoGeom, CreateTopology, CreateTopoGeom

## Name

RenameTopoGeometryColumn — Renames a topogeometry column

## Synopsis

`topology.layer RenameTopoGeometryColumn(` regclass layer_table, name feature_column, name new_name`)`;

## Description

This function changes the name of an existing TopoGeometry column ensuring metadata information about it is updated accordingly.

Availability: 3.4.0

## Examples

    SELECT topology.RenameTopoGeometryColumn('public.parcels', 'topogeom', 'tgeom');

## See Also

AddTopoGeometryColumn, RenameTopology

## Name

DropTopology — Use with caution: Drops a topology schema and deletes its reference from topology.topology table and references to tables in that schema from the geometry_columns table.

## Synopsis

`integer DropTopology(` varchar topology_schema_name`)`;

## Description

Drops a topology schema and deletes its reference from topology.topology table and references to tables in that schema from the geometry_columns table. This function should be USED WITH CAUTION, as it could destroy data you care about. If the schema does not exist, it just removes reference entries the named schema.

Availability: 1.1

## Examples

Cascade drops the ma_topo schema and removes all references to it in topology.topology and geometry_columns.

    SELECT topology.DropTopology('ma_topo');

## See Also

DropTopoGeometryColumn

## Name

RenameTopology — Renames a topology

## Synopsis

`varchar RenameTopology(` varchar old_name, varchar new_name`)`;

## Description

Renames a topology schema, updating its metadata record in the `topology.topology` table.

Availability: 3.4.0

## Examples

Rename a topology from `topo_stage` to `topo_prod`.

    SELECT topology.RenameTopology('topo_stage', 'topo_prod');

## See Also

CopyTopology, RenameTopoGeometryColumn

## Name

DropTopoGeometryColumn — Drops the topogeometry column from the table named `table_name` in schema `schema_name` and unregisters the columns from topology.layer table.

## Synopsis

`text DropTopoGeometryColumn(` varchar schema_name, varchar table_name, varchar column_name`)`;

## Description

Drops the topogeometry column from the table named `table_name` in schema `schema_name` and unregisters the columns from topology.layer table. Returns summary of drop status. NOTE: it first sets all values to NULL before dropping to bypass referential integrity checks.

Availability: 1.1

## Examples

    SELECT topology.DropTopoGeometryColumn('ma_topo', 'parcel_topo', 'topo');

## See Also

AddTopoGeometryColumn

## Name

Populate_Topology_Layer — Adds missing entries to topology.layer table by reading metadata from topo tables.

## Synopsis

`setof record Populate_Topology_Layer(` `)`;

## Description

Adds missing entries to the `topology.layer` table by inspecting topology constraints on tables. This function is useful for fixing up entries in topology catalog after restores of schemas with topo data.

It returns the list of entries created. Returned columns are `schema_name`, `table_name`, `feature_column`.

Availability: 2.3.0

## Examples

    SELECT CreateTopology('strk_topo');
    CREATE SCHEMA strk;
    CREATE TABLE strk.parcels(gid serial, parcel_id varchar(20) PRIMARY KEY, address text);
    SELECT topology.AddTopoGeometryColumn('strk_topo', 'strk', 'parcels', 'topo', 'POLYGON');
    -- this will return no records because this feature is already registered
    SELECT *
      FROM topology.Populate_Topology_Layer();

    -- let's rebuild
    TRUNCATE TABLE topology.layer;

    SELECT *
      FROM topology.Populate_Topology_Layer();

    SELECT topology_id,layer_id, schema_name As sn, table_name As tn, feature_column As fc
    FROM topology.layer;

     schema_name | table_name | feature_column
    -------------+------------+----------------
     strk        | parcels    | topo
    (1 row)

     topology_id | layer_id |  sn  |   tn    |  fc
    -------------+----------+------+---------+------
               2 |        2 | strk | parcels | topo
    (1 row)

## See Also

AddTopoGeometryColumn

## Name

TopologySummary — Takes a topology name and provides summary totals of types of objects in topology.

## Synopsis

`text TopologySummary(` varchar topology_schema_name`)`;

## Description

Takes a topology name and provides summary totals of types of objects in topology.

Availability: 2.0.0

## Examples

    SELECT topology.topologysummary('city_data');
                        topologysummary
    --------------------------------------------------------
     Topology city_data (329), SRID 4326, precision: 0
     22 nodes, 24 edges, 10 faces, 29 topogeoms in 5 layers
     Layer 1, type Polygonal (3), 9 topogeoms
      Deploy: features.land_parcels.feature
     Layer 2, type Puntal (1), 8 topogeoms
      Deploy: features.traffic_signs.feature
     Layer 3, type Lineal (2), 8 topogeoms
      Deploy: features.city_streets.feature
     Layer 4, type Polygonal (3), 3 topogeoms
      Hierarchy level 1, child layer 1
      Deploy: features.big_parcels.feature
     Layer 5, type Puntal (1), 1 topogeoms
      Hierarchy level 1, child layer 2
      Deploy: features.big_signs.feature

## See Also

Topology_Load_Tiger

## Name

ValidateTopology — Returns a set of validatetopology_returntype objects detailing issues with topology.

## Synopsis

`setof validatetopology_returntype ValidateTopology(` varchar toponame, geometry bbox`)`;

## Description

Returns a set of validatetopology_returntype objects detailing issues with topology, optionally limiting the check to the area specified by the `bbox` parameter.

List of possible errors, what they mean and what the returned ids represent are displayed below:

Error | id1 | id2 | Meaning
--- | --- | --- | ---
coincident nodes | Identifier of first node. | Identifier of second node. | Two nodes have the same geometry.
edge crosses node | Identifier of the edge. | Identifier of the node. | An edge has a node in its interior. See ST_Relate.
invalid edge | Identifier of the edge. |  | An edge geometry is invalid. See ST_IsValid.
edge not simple | Identifier of the edge. |  | An edge geometry has self-intersections. See ST_IsSimple.
edge crosses edge | Identifier of first edge. | Identifier of second edge. | Two edges have an interior intersection. See ST_Relate.
edge start node geometry mismatch | Identifier of the edge. | Identifier of the indicated start node. | The geometry of the node indicated as the starting node for an edge does not match the first point of the edge geometry. See ST_StartPoint.
edge end node geometry mismatch | Identifier of the edge. | Identifier of the indicated end node. | The geometry of the node indicated as the ending node for an edge does not match the last point of the edge geometry. See ST_EndPoint.
face without edges | Identifier of the orphaned face. |  | No edge reports an existing face on either of its sides (left_face, right_face).
face has no rings | Identifier of the partially-defined face. |  | Edges reporting a face on their sides do not form a ring.
face has wrong mbr | Identifier of the face with wrong mbr cache. |  | Minimum bounding rectangle of a face does not match minimum bounding box of the collection of edges reporting the face on their sides.
hole not in advertised face | Signed identifier of an edge, identifying the ring. See GetRingEdges. |  | A ring of edges reporting a face on its exterior is contained in different face.
not-isolated node has not- containing_face | Identifier of the ill-defined node. |  | A node which is reported as being on the boundary of one or more edges is indicating a containing face.
isolated node has containing_face | Identifier of the ill-defined node. |  | A node which is not reported as being on the boundary of any edges is lacking the indication of a containing face.
isolated node has wrong containing_face | Identifier of the misrepresented node. |  | A node which is not reported as being on the boundary of any edges indicates a containing face which is not the actual face containing it. See GetFaceContainingPoint.
invalid next_right_edge | Identifier of the misrepresented edge. | Signed id of the edge which should be indicated as the next right edge. | The edge indicated as the next edge encountered walking on the right side of an edge is wrong.
invalid next_left_edge | Identifier of the misrepresented edge. | Signed id of the edge which should be indicated as the next left edge. | The edge indicated as the next edge encountered walking on the left side of an edge is wrong.
mixed face labeling in ring | Signed identifier of an edge, identifying the ring. See GetRingEdges. |  | Edges in a ring indicate conflicting faces on the walking side. This is also known as a "Side Location Conflict".
non-closed ring | Signed identifier of an edge, identifying the ring. See GetRingEdges. |  | A ring of edges formed by following next_left_edge/next_right_edge attributes starts and ends on different nodes.
face has multiple shells | Identifier of the contended face. | Signed identifier of an edge, identifying the ring. See GetRingEdges. | More than a one ring of edges indicate the same face on its interior.

Availability: 1.0.0

Enhanced: 2.0.0 more efficient edge crossing detection and fixes for false positives that were existent in prior versions.

Changed: 2.2.0 values for id1 and id2 were swapped for 'edge crosses node' to be consistent with error description.

Changed: 3.2.0 added optional bbox parameter, perform face labeling and edge linking checks.

## Examples

    SELECT * FROM  topology.ValidateTopology('ma_topo');
          error        | id1 | id2
    -------------------+-----+-----
    face without edges |   1 |

## See Also

validatetopology_returntype, Topology_Load_Tiger

## Name

ValidateTopologyRelation — Returns info about invalid topology relation records

## Synopsis

`setof record ValidateTopologyRelation(` varchar toponame`)`;

## Description

Returns a set records giving information about invalidities in the relation table of the topology.

Availability: 3.2.0

## See Also

ValidateTopology

## Name

FindTopology — Returns a topology record by different means.

## Synopsis

`topology FindTopology(` TopoGeometry topogeom`)`;

`topology FindTopology(` regclass layerTable, name layerColumn`)`;

`topology FindTopology(` name layerSchema, name layerTable, name layerColumn`)`;

`topology FindTopology(` text topoName`)`;

`topology FindTopology(` int id`)`;

## Description

Takes a topology identifier or the identifier of a topology-related object and returns a topology.topology record.

Availability: 3.2.0

## Examples

    SELECT name(findTopology('features.land_parcels', 'feature'));
       name
    -----------
     city_data
    (1 row)

## See Also

FindLayer

## Name

FindLayer — Returns a topology.layer record by different means.

## Synopsis

`topology.layer FindLayer(` TopoGeometry tg`)`;

`topology.layer FindLayer(` regclass layer_table, name feature_column`)`;

`topology.layer FindLayer(` name schema_name, name table_name, name feature_column`)`;

`topology.layer FindLayer(` integer topology_id, integer layer_id`)`;

## Description

Takes a layer identifier or the identifier of a topology-related object and returns a topology.layer record.

Availability: 3.2.0

## Examples

    SELECT layer_id(findLayer('features.land_parcels', 'feature'));
     layer_id
    ----------
            1
    (1 row)

## See Also

FindTopology

## 9.4. Topology Statistics Management

Abstract

This section discusses management of database statistics during topology building.

Adding elements to a topology triggers many database queries for finding existing edges that will be split, adding nodes and updating edges that will node with the new linework. For this reason it is useful that statistics about the data in the topology tables are up-to-date.

PostGIS Topology population and editing functions do not automatically update the statistics because a updating stats after each and every change in a topology would be overkill, so it is the caller's duty to take care of that.

That the statistics updated by autovacuum will NOT be visible to transactions which started before autovacuum process completed, so long-running transactions will need to run ANALYZE themselves, to use updated statistics.

## 9.5. Topology Constructors

Abstract

This section covers the topology functions for creating new topologies.

## Name

CreateTopology — Creates a new topology schema and registers it in the topology.topology table.

## Synopsis

`integer CreateTopology(` varchar topology_schema_name`)`;

`integer CreateTopology(` varchar topology_schema_name, integer srid`)`;

`integer CreateTopology(` varchar topology_schema_name, integer srid, double precision prec`)`;

`integer CreateTopology(` varchar topology_schema_name, integer srid, double precision prec, boolean hasz`)`;

## Description

Creates a new topology schema with name `topology_name` and registers it in the `topology.topology` table. Topologies must be uniquely named. The topology tables (`edge_data`, `face`, `node`,and `relation` are created in the schema. It returns the id of the topology.

The `srid` is the spatial reference system SRID for the topology.

The tolerance `prec` is measured in the units of the spatial reference system. The tolerance defaults to 0.

`hasz` defaults to false if not specified.

This is similar to the SQL/MM ST_InitTopoGeo but has more functionality.

Availability: 1.1

Enhanced: 2.0 added the signature accepting hasZ

## Examples

Create a topology schema called `ma_topo` that stores edges and nodes in Massachusetts State Plane-meters (SRID = 26986). The tolerance represents 0.5 meters since the spatial reference system is meter-based.

    SELECT topology.CreateTopology('ma_topo', 26986, 0.5);

Create a topology for Rhode Island called `ri_topo` in spatial reference system State Plane-feet (SRID = 3438)

    SELECT topology.CreateTopology('ri_topo', 3438) AS topoid;
    topoid
    ------
    2

## See Also

Section 4.5, “Spatial Reference Systems”, ST_InitTopoGeo, Topology_Load_Tiger

## Name

CopyTopology — Makes a copy of a topology (nodes, edges, faces, layers and TopoGeometries) into a new schema

## Synopsis

`integer CopyTopology(` varchar existing_topology_name, varchar new_name`)`;

## Description

Creates a new topology with name `new_name`, with SRID and precision copied from `existing_topology_name` The nodes, edges and faces in `existing_topology_name` are copied into the new topology, as well as Layers and their associated TopoGeometries.

The new rows in the `topology.layer` table contain synthetic values for schema_name, table_name and feature_column. This is because the TopoGeometry objects exist only as a definition and are not yet available in a user-defined table.

Availability: 2.0.0

## Examples

Make a backup of a topology called `ma_topo`.

    SELECT topology.CopyTopology('ma_topo', 'ma_topo_backup');

## See Also

Section 4.5, “Spatial Reference Systems”, CreateTopology, RenameTopology

## Name

ST_InitTopoGeo — Creates a new topology schema and registers it in the topology.topology table.

## Synopsis

`text ST_InitTopoGeo(` varchar topology_schema_name`)`;

## Description

This is the SQL-MM equivalent of CreateTopology. It lacks options for spatial reference system and tolerance. it returns a text description of the topology creation, instead of the topology id.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.17

## Examples

    SELECT topology.ST_InitTopoGeo('topo_schema_to_create') AS topocreation;
                          astopocreation
    ------------------------------------------------------------
     Topology-Geometry 'topo_schema_to_create' (id:7) created.

## See Also

CreateTopology

## Name

ST_CreateTopoGeo — Adds a collection of geometries to a given empty topology and returns a message detailing success.

## Synopsis

`text ST_CreateTopoGeo(` varchar atopology, geometry acollection`)`;

## Description

Adds a collection of geometries to a given empty topology and returns a message detailing success.

Useful for populating an empty topology.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details -- X.3.18

## Examples

    -- Populate topology --
    SELECT topology.ST_CreateTopoGeo('ri_topo',
     ST_GeomFromText('MULTILINESTRING((384744 236928,384750 236923,384769 236911,384799 236895,384811 236890,384833 236884,
      384844 236882,384866 236881,384879 236883,384954 236898,385087 236932,385117 236938,
      385167 236938,385203 236941,385224 236946,385233 236950,385241 236956,385254 236971,
      385260 236979,385268 236999,385273 237018,385273 237037,385271 237047,385267 237057,
      385225 237125,385210 237144,385192 237161,385167 237192,385162 237202,385159 237214,
      385159 237227,385162 237241,385166 237256,385196 237324,385209 237345,385234 237375,
      385237 237383,385238 237399,385236 237407,385227 237419,385213 237430,385193 237439,
      385174 237451,385170 237455,385169 237460,385171 237475,385181 237503,385190 237521,
      385200 237533,385206 237538,385213 237541,385221 237542,385235 237540,385242 237541,
      385249 237544,385260 237555,385270 237570,385289 237584,385292 237589,385291 237596,385284 237630))',3438)
      );

          st_createtopogeo
    ----------------------------
     Topology ri_topo populated

    -- create tables and topo geometries --
    CREATE TABLE ri.roads(gid serial PRIMARY KEY, road_name text);

    SELECT topology.AddTopoGeometryColumn('ri_topo', 'ri', 'roads', 'topo', 'LINE');

## See Also

TopoGeo_LoadGeometry, AddTopoGeometryColumn, CreateTopology, DropTopology

## Name

TopoGeo_AddPoint — Adds a point to an existing topology using a tolerance and possibly splitting an existing edge.

## Synopsis

`integer TopoGeo_AddPoint(` varchar atopology, geometry apoint, float8 tolerance`)`;

## Description

Adds a point to an existing topology and returns its identifier. The given point will snap to existing nodes or edges within given tolerance. An existing edge may be split by the snapped point.

Availability: 2.0.0

## See Also

TopoGeo_AddLineString, TopoGeo_AddPolygon, TopoGeo_LoadGeometry, AddNode, CreateTopology

## Name

TopoGeo_AddLineString — Adds a linestring to an existing topology using a tolerance and possibly splitting existing edges/faces.

## Synopsis

`SETOF integer TopoGeo_AddLineString(` varchar atopology, geometry aline, float8 tolerance`)`;

## Description

Adds a linestring to an existing topology and returns a set of signed edge identifiers forming it up (negative identifies mean the edge goes in the opposite direction of the input linestring). The given line will snap to existing nodes or edges within given tolerance. Existing edges and faces may be split by the line. New nodes and faces may be added.

Updating statistics about topologies being loaded via this function is up to caller, see maintaining statistics during topology editing and population.

Availability: 2.0.0

Enhanced: 3.2.0 added support for returning signed identifier.

## See Also

TopoGeo_AddPoint, TopoGeo_AddPolygon, TopoGeo_LoadGeometry, AddEdge, CreateTopology

## Name

TopoGeo_AddPolygon — Adds a polygon to an existing topology using a tolerance and possibly splitting existing edges/faces. Returns face identifiers.

## Synopsis

`SETOF integer TopoGeo_AddPolygon(` varchar atopology, geometry apoly, float8 tolerance`)`;

## Description

Adds a polygon to an existing topology and returns a set of face identifiers forming it up. The boundary of the given polygon will snap to existing nodes or edges within given tolerance. Existing edges and faces may be split by the boundary of the new polygon.

Updating statistics about topologies being loaded via this function is up to caller, see maintaining statistics during topology editing and population.

Availability: 2.0.0

## See Also

TopoGeo_AddPoint, TopoGeo_AddLineString, TopoGeo_LoadGeometry, AddFace, CreateTopology

## Name

TopoGeo_LoadGeometry — Load a geometry into an existing topology, snapping and splitting as needed.

## Synopsis

`void TopoGeo_LoadGeometry(` varchar atopology, geometry ageom, float8 tolerance`)`;

## Description

Loads a geometry into an existing topology. The given geometry will snap to existing nodes or edges within given tolerance. Existing edges and faces may be split as a consequence of the load.

Updating statistics about topologies being loaded via this function is up to caller, see maintaining statistics during topology editing and population.

Availability: 3.5.0

## See Also

TopoGeo_AddPoint, TopoGeo_AddLineString, TopoGeo_AddPolygon, CreateTopology

## 9.6. Topology Editors

Abstract

This section covers topology functions for adding, moving, deleting, and splitting edges, faces, and nodes. All of these functions are defined by ISO SQL/MM.

## Name

ST_AddIsoNode — Adds an isolated node to a face in a topology and returns the nodeid of the new node. If face is null, the node is still created.

## Synopsis

`integer ST_AddIsoNode(` varchar atopology, integer aface, geometry apoint`)`;

## Description

Adds an isolated node with point location `apoint` to an existing face with faceid `aface` to a topology `atopology` and returns the nodeid of the new node.

If the spatial reference system (srid) of the point geometry is not the same as the topology, the `apoint` is not a point geometry, the point is null, or the point intersects an existing edge (even at the boundaries) then an exception is thrown. If the point already exists as a node, an exception is thrown.

If `aface` is not null and the `apoint` is not within the face, then an exception is thrown.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X+1.3.1

## Examples

## See Also

AddNode, CreateTopology, DropTopology, ST_Intersects

## Name

ST_AddIsoEdge — Adds an isolated edge defined by geometry `alinestring` to a topology connecting two existing isolated nodes `anode` and `anothernode` and returns the edge id of the new edge.

## Synopsis

`integer ST_AddIsoEdge(` varchar atopology, integer anode, integer anothernode, geometry alinestring`)`;

## Description

Adds an isolated edge defined by geometry `alinestring` to a topology connecting two existing isolated nodes `anode` and `anothernode` and returns the edge id of the new edge.

If the spatial reference system (srid) of the `alinestring` geometry is not the same as the topology, any of the input arguments are null, or the nodes are contained in more than one face, or the nodes are start or end nodes of an existing edge, then an exception is thrown.

If the `alinestring` is not within the face of the face the `anode` and `anothernode` belong to, then an exception is thrown.

If the `anode` and `anothernode` are not the start and end points of the `alinestring` then an exception is thrown.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.4

## Examples

## See Also

ST_AddIsoNode, ST_IsSimple, ST_Within

## Name

ST_AddEdgeNewFaces — Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces.

## Synopsis

`integer ST_AddEdgeNewFaces(` varchar atopology, integer anode, integer anothernode, geometry acurve`)`;

## Description

Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces. Returns the id of the newly added edge.

Updates all existing joined edges and relationships accordingly.

If any arguments are null, the given nodes are unknown (must already exist in the `node` table of the topology schema) , the `acurve` is not a `LINESTRING`, the `anode` and `anothernode` are not the start and endpoints of `acurve` then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.12

## Examples

## See Also

ST_RemEdgeNewFace

ST_AddEdgeModFace

## Name

ST_AddEdgeModFace — Add a new edge and, if in doing so it splits a face, modify the original face and add a new face.

## Synopsis

`integer ST_AddEdgeModFace(` varchar atopology, integer anode, integer anothernode, geometry acurve`)`;

## Description

Add a new edge and, if doing so splits a face, modify the original face and add a new one.

If possible, the new face will be created on left side of the new edge. This will not be possible if the face on the left side will need to be the Universe face (unbounded).

Returns the id of the newly added edge.

Updates all existing joined edges and relationships accordingly.

If any arguments are null, the given nodes are unknown (must already exist in the `node` table of the topology schema) , the `acurve` is not a `LINESTRING`, the `anode` and `anothernode` are not the start and endpoints of `acurve` then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.13

## Examples

## See Also

ST_RemEdgeModFace

ST_AddEdgeNewFaces

## Name

ST_RemEdgeNewFace — Removes an edge and, if the removed edge separated two faces, delete the original faces and replace them with a new face.

## Synopsis

`integer ST_RemEdgeNewFace(` varchar atopology, integer anedge`)`;

## Description

Removes an edge and, if the removed edge separated two faces, delete the original faces and replace them with a new face.

Returns the id of a newly created face or NULL, if no new face is created. No new face is created when the removed edge is dangling or isolated or confined with the universe face (possibly making the universe flood into the face on the other side).

Updates all existing joined edges and relationships accordingly.

Refuses to remove an edge participating in the definition of an existing TopoGeometry. Refuses to heal two faces if any TopoGeometry is defined by only one of them (and not the other).

If any arguments are null, the given edge is unknown (must already exist in the `edge` table of the topology schema), the topology name is invalid then an error is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.14

## Examples

## See Also

ST_RemEdgeModFace

ST_AddEdgeNewFaces

## Name

ST_RemEdgeModFace — Removes an edge, and if the edge separates two faces deletes one face and modifies the other face to cover the space of both.

## Synopsis

`integer ST_RemEdgeModFace(` varchar atopology, integer anedge`)`;

## Description

Removes an edge, and if the removed edge separates two faces deletes one face and modifies the other face to cover the space of both. Preferentially keeps the face on the right, to be consistent with ST_AddEdgeModFace. Returns the id of the face which is preserved.

Updates all existing joined edges and relationships accordingly.

Refuses to remove an edge participating in the definition of an existing TopoGeometry. Refuses to heal two faces if any TopoGeometry is defined by only one of them (and not the other).

If any arguments are null, the given edge is unknown (must already exist in the `edge` table of the topology schema), the topology name is invalid then an error is thrown.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.15

## Examples

## See Also

ST_AddEdgeModFace

ST_RemEdgeNewFace

## Name

ST_ChangeEdgeGeom — Changes the shape of an edge without affecting the topology structure.

## Synopsis

`text ST_ChangeEdgeGeom(` varchar atopology, integer anedge, geometry acurve`)`;

## Description

Changes the shape of an edge without affecting the topology structure.

If any arguments are null, the given edge does not exist in the `edge` table of the topology schema, the `acurve` is not a `LINESTRING`, or the modification would change the underlying topology then an error is thrown.

If the spatial reference system (srid) of the `acurve` geometry is not the same as the topology an exception is thrown.

If the new `acurve` is not simple, then an error is thrown.

If moving the edge from old to new position would hit an obstacle then an error is thrown.

Availability: 1.1.0

Enhanced: 2.0.0 adds topological consistency enforcement

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details X.3.6

## Examples

    SELECT topology.ST_ChangeEdgeGeom('ma_topo', 1,
    		ST_GeomFromText('LINESTRING(227591.9 893900.4,227622.6 893844.3,227641.6 893816.6, 227704.5 893778.5)', 26986) );
     ----
     Edge 1 changed

## See Also

ST_AddEdgeModFace

ST_RemEdgeModFace

ST_ModEdgeSplit

## Name

ST_ModEdgeSplit — Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge.

## Synopsis

`integer ST_ModEdgeSplit(` varchar atopology, integer anedge, geometry apoint`)`;

## Description

Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge. Updates all existing joined edges and relationships accordingly. Returns the identifier of the newly added node.

Availability: 1.1

Changed: 2.0 - In prior versions, this was misnamed ST_ModEdgesSplit

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## Examples

    -- Add an edge --
     SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227592 893910, 227600 893910)', 26986) ) As edgeid;

    -- edgeid-
    3

    -- Split the edge  --
    SELECT topology.ST_ModEdgeSplit('ma_topo',  3, ST_SetSRID(ST_Point(227594,893910),26986)  ) As node_id;
            node_id
    -------------------------
    7

## See Also

ST_NewEdgesSplit, ST_ModEdgeHeal, ST_NewEdgeHeal, AddEdge

## Name

ST_ModEdgeHeal — Heals two edges by deleting the node connecting them, modifying the first edge and deleting the second edge. Returns the id of the deleted node.

## Synopsis

`int ST_ModEdgeHeal(` varchar atopology, integer anedge, integer anotheredge`)`;

## Description

Heals two edges by deleting the node connecting them, modifying the first edge and deleting the second edge. Returns the id of the deleted node. Updates all existing joined edges and relationships accordingly.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## See Also

ST_ModEdgeSplit ST_NewEdgesSplit

## Name

ST_NewEdgeHeal — Heals two edges by deleting the node connecting them, deleting both edges, and replacing them with an edge whose direction is the same as the first edge provided.

## Synopsis

`int ST_NewEdgeHeal(` varchar atopology, integer anedge, integer anotheredge`)`;

## Description

Heals two edges by deleting the node connecting them, deleting both edges, and replacing them with an edge whose direction is the same as the first edge provided. Returns the id of the new edge replacing the healed ones. Updates all existing joined edges and relationships accordingly.

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X.3.9

## See Also

ST_ModEdgeHeal ST_ModEdgeSplit ST_NewEdgesSplit

## Name

ST_MoveIsoNode — Moves an isolated node in a topology from one point to another. If new `apoint` geometry exists as a node an error is thrown. Returns description of move.

## Synopsis

`text ST_MoveIsoNode(` varchar atopology, integer anode, geometry apoint`)`;

## Description

Moves an isolated node in a topology from one point to another. If new `apoint` geometry exists as a node an error is thrown.

If any arguments are null, the `apoint` is not a point, the existing node is not isolated (is a start or end point of an existing edge), new node location intersects an existing edge (even at the end points) or the new location is in a different face (since 3.2.0) then an exception is thrown.

If the spatial reference system (srid) of the point geometry is not the same as the topology an exception is thrown.

Availability: 2.0.0

Enhanced: 3.2.0 ensures the nod cannot be moved in a different face

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.2

## Examples

    -- Add an isolated node with no face  --
    SELECT topology.ST_AddIsoNode('ma_topo',  NULL, ST_GeomFromText('POINT(227579 893916)', 26986) ) As nodeid;
     nodeid
    --------
          7
    -- Move the new node --
    SELECT topology.ST_MoveIsoNode('ma_topo', 7,  ST_GeomFromText('POINT(227579.5 893916.5)', 26986) ) As descrip;
                          descrip
    ----------------------------------------------------
    Isolated Node 7 moved to location 227579.5,893916.5

## See Also

ST_AddIsoNode

## Name

ST_NewEdgesSplit — Split an edge by creating a new node along an existing edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges.

## Synopsis

`integer ST_NewEdgesSplit(` varchar atopology, integer anedge, geometry apoint`)`;

## Description

Split an edge with edge id `anedge` by creating a new node with point location `apoint` along current edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges. Updates all existing joined edges and relationships accordingly.

If the spatial reference system (srid) of the point geometry is not the same as the topology, the `apoint` is not a point geometry, the point is null, the point already exists as a node, the edge does not correspond to an existing edge or the point is not within the edge then an exception is thrown.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM: Topo-Net Routines: X.3.8

## Examples

    -- Add an edge  --
    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227575 893917,227592 893900)', 26986) ) As edgeid;
    -- result-
    edgeid
    ------
    	2
    -- Split the new edge --
    SELECT topology.ST_NewEdgesSplit('ma_topo', 2,  ST_GeomFromText('POINT(227578.5 893913.5)', 26986) ) As newnodeid;
     newnodeid
    ---------
           6

## See Also

ST_ModEdgeSplit ST_ModEdgeHeal ST_NewEdgeHeal AddEdge

## Name

ST_RemoveIsoNode — Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown.

## Synopsis

`text ST_RemoveIsoNode(` varchar atopology, integer anode`)`;

## Description

Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X+1.3.3

## Examples

    -- Remove an isolated node with no face  --
    SELECT topology.ST_RemoveIsoNode('ma_topo',  7 ) As result;
             result
    -------------------------
     Isolated node 7 removed

## See Also

ST_AddIsoNode

## Name

ST_RemoveIsoEdge — Removes an isolated edge and returns description of action. If the edge is not isolated, then an exception is thrown.

## Synopsis

`text ST_RemoveIsoEdge(` varchar atopology, integer anedge`)`;

## Description

Removes an isolated edge and returns description of action. If the edge is not isolated, then an exception is thrown.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM: Topo-Geo and Topo-Net 3: Routine Details: X+1.3.3

## Examples

    -- Remove an isolated node with no face  --
    SELECT topology.ST_RemoveIsoNode('ma_topo',  7 ) As result;
             result
    -------------------------
     Isolated node 7 removed

## See Also

ST_AddIsoNode

## 9.7. Topology Accessors

## Name

GetEdgeByPoint — Finds the edge-id of an edge that intersects a given point.

## Synopsis

`integer GetEdgeByPoint(` varchar atopology, geometry apoint, float8 tol1`)`;

## Description

Retrieves the id of an edge that intersects a Point.

The function returns an integer (id-edge) given a topology, a POINT and a tolerance. If tolerance = 0 then the point has to intersect the edge.

If `apoint` doesn't intersect an edge, returns 0 (zero).

If use tolerance > 0 and there is more than one edge near the point then an exception is thrown.

If tolerance = 0, the function uses ST_Intersects otherwise uses ST_DWithin.

Performed by the GEOS module.

Availability: 2.0.0

## Examples

These examples use edges we created in AddEdge

    SELECT topology.GetEdgeByPoint('ma_topo',geom, 1) As with1mtol, topology.GetEdgeByPoint('ma_topo',geom,0) As withnotol
    FROM ST_GeomFromEWKT('SRID=26986;POINT(227622.6 893843)') As geom;
     with1mtol | withnotol
    -----------+-----------
             2 |         0

    SELECT topology.GetEdgeByPoint('ma_topo',geom, 1) As nearnode
    FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;

    -- get error --
    ERROR:  Two or more edges found

## See Also

AddEdge, GetNodeByPoint, GetFaceByPoint

## Name

GetFaceByPoint — Finds face intersecting a given point.

## Synopsis

`integer GetFaceByPoint(` varchar atopology, geometry apoint, float8 tol1`)`;

## Description

Finds a face referenced by a Point, with given tolerance.

The function will effectively look for a face intersecting a circle having the point as center and the tolerance as radius.

If no face intersects the given query location, 0 is returned (universal face).

If more than one face intersect the query location an exception is thrown.

Availability: 2.0.0

Enhanced: 3.2.0 more efficient implementation and clearer contract, stops working with invalid topologies.

## Examples

    SELECT topology.GetFaceByPoint('ma_topo',geom, 10) As with1mtol, topology.GetFaceByPoint('ma_topo',geom,0) As withnotol
    	FROM ST_GeomFromEWKT('POINT(234604.6 899382.0)') As geom;

    	 with1mtol | withnotol
    	-----------+-----------
    			 1 |         0

    SELECT topology.GetFaceByPoint('ma_topo',geom, 1) As nearnode
    	FROM ST_GeomFromEWKT('POINT(227591.9 893900.4)') As geom;

    -- get error --
    ERROR:  Two or more faces found

## See Also

GetFaceContainingPoint, AddFace, GetNodeByPoint, GetEdgeByPoint

## Name

GetFaceContainingPoint — Finds the face containing a point.

## Synopsis

`integer GetFaceContainingPoint(` text atopology, geometry apoint`)`;

## Description

Returns the id of the face containing a point.

An exception is thrown if the point falls on a face boundary.

The function relies on a valid topology, using edge linking and face labeling.

Availability: 3.2.0

## See Also

ST_GetFaceGeometry

## Name

GetNodeByPoint — Finds the node-id of a node at a point location.

## Synopsis

`integer GetNodeByPoint(` varchar atopology, geometry apoint, float8 tol1`)`;

## Description

Retrieves the id of a node at a point location.

The function returns an integer (id-node) given a topology, a POINT and a tolerance. If tolerance = 0 means exact intersection, otherwise retrieves the node from an interval.

If `apoint` doesn't intersect a node, returns 0 (zero).

If use tolerance > 0 and there is more than one node near the point then an exception is thrown.

If tolerance = 0, the function uses ST_Intersects otherwise uses ST_DWithin.

Performed by the GEOS module.

Availability: 2.0.0

## Examples

These examples use edges we created in AddEdge

    SELECT topology.GetNodeByPoint('ma_topo',geom, 1) As nearnode
     FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;
      nearnode
    ----------
            2

    SELECT topology.GetNodeByPoint('ma_topo',geom, 1000) As too_much_tolerance
     FROM ST_GeomFromEWKT('SRID=26986;POINT(227591.9 893900.4)') As geom;

     ----get error--
     ERROR:  Two or more nodes found

## See Also

AddEdge, GetEdgeByPoint, GetFaceByPoint

## Name

GetTopologyID — Returns the id of a topology in the topology.topology table given the name of the topology.

## Synopsis

`integer GetTopologyID(` varchar toponame`)`;

## Description

Returns the id of a topology in the topology.topology table given the name of the topology.

Availability: 1.1

## Examples

    SELECT topology.GetTopologyID('ma_topo') As topo_id;
     topo_id
    ---------
           1

## See Also

CreateTopology, DropTopology, GetTopologyName, GetTopologySRID

## Name

GetTopologySRID — Returns the SRID of a topology in the topology.topology table given the name of the topology.

## Synopsis

`integer GetTopologyID(` varchar toponame`)`;

## Description

Returns the spatial reference id of a topology in the topology.topology table given the name of the topology.

Availability: 2.0.0

## Examples

    SELECT topology.GetTopologySRID('ma_topo') As SRID;
     SRID
    -------
      4326

## See Also

CreateTopology, DropTopology, GetTopologyName, GetTopologyID

## Name

GetTopologyName — Returns the name of a topology (schema) given the id of the topology.

## Synopsis

`varchar GetTopologyName(` integer topology_id`)`;

## Description

Returns the topology name (schema) of a topology from the topology.topology table given the topology id of the topology.

Availability: 1.1

## Examples

    SELECT topology.GetTopologyName(1) As topo_name;
     topo_name
    -----------
     ma_topo

## See Also

CreateTopology, DropTopology, GetTopologyID, GetTopologySRID

## Name

ST_GetFaceEdges — Returns a set of ordered edges that bound `aface`.

## Synopsis

`getfaceedges_returntype ST_GetFaceEdges(` varchar atopology, integer aface`)`;

## Description

Returns a set of ordered edges that bound `aface`. Each output consists of a sequence and edgeid. Sequence numbers start with value 1.

Enumeration of each ring edges start from the edge with smallest identifier. Order of edges follows a left-hand-rule (bound face is on the left of each directed edge).

Availability: 2.0

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.5

## Examples

    -- Returns the edges bounding face 1
    SELECT (topology.ST_GetFaceEdges('tt', 1)).*;
    -- result --
     sequence | edge
    ----------+------
            1 |   -4
            2 |    5
            3 |    7
            4 |   -6
            5 |    1
            6 |    2
            7 |    3
    (7 rows)

    -- Returns the sequence, edge id
    -- and geometry of the edges that bound face 1
    -- If you just need geom and seq, can use ST_GetFaceGeometry
    SELECT t.seq, t.edge, geom
    FROM topology.ST_GetFaceEdges('tt',1) As t(seq,edge)
    	INNER JOIN tt.edge AS e ON abs(t.edge) = e.edge_id;

## See Also

GetRingEdges, AddFace, ST_GetFaceGeometry

## Name

ST_GetFaceGeometry — Returns the polygon in the given topology with the specified face id.

## Synopsis

`geometry ST_GetFaceGeometry(` varchar atopology, integer aface`)`;

## Description

Returns the polygon in the given topology with the specified face id. Builds the polygon from the edges making up the face.

Availability: 1.1

This method implements the SQL/MM specification. SQL-MM 3 Topo-Geo and Topo-Net 3: Routine Details: X.3.16

## Examples

    -- Returns the wkt of the polygon added with AddFace
    SELECT ST_AsText(topology.ST_GetFaceGeometry('ma_topo', 1)) As facegeomwkt;
    -- result --
                   facegeomwkt

    --------------------------------------------------------------------------------
     POLYGON((234776.9 899563.7,234896.5 899456.7,234914 899436.4,234946.6 899356.9,
    234872.5 899328.7,234891 899285.4,234992.5 899145,234890.6 899069,
    234755.2 899255.4,234612.7 899379.4,234776.9 899563.7))

## See Also

AddFace

## Name

GetRingEdges — Returns the ordered set of signed edge identifiers met by walking on an a given edge side.

## Synopsis

`getfaceedges_returntype GetRingEdges(` varchar atopology, integer aring, integer max_edges=null`)`;

## Description

Returns the ordered set of signed edge identifiers met by walking on an a given edge side. Each output consists of a sequence and a signed edge id. Sequence numbers start with value 1.

If you pass a positive edge id, the walk starts on the left side of the corresponding edge and follows the edge direction. If you pass a negative edge id, the walk starts on the right side of it and goes backward.

If `max_edges` is not null no more than those records are returned by that function. This is meant to be a safety parameter when dealing with possibly invalid topologies.

This function uses edge ring linking metadata.

Availability: 2.0.0

## See Also

ST_GetFaceEdges, GetNodeEdges

## Name

GetNodeEdges — Returns an ordered set of edges incident to the given node.

## Synopsis

`getfaceedges_returntype GetNodeEdges(` varchar atopology, integer anode`)`;

## Description

Returns an ordered set of edges incident to the given node. Each output consists of a sequence and a signed edge id. Sequence numbers start with value 1. A positive edge starts at the given node. A negative edge ends into the given node. Closed edges will appear twice (with both signs). Order is clockwise starting from northbound.

This function computes ordering rather than deriving from metadata and is thus usable to build edge ring linking.

Availability: 2.0

## See Also

getfaceedges_returntype, GetRingEdges, ST_Azimuth

## 9.8. Topology Processing

Abstract

This section covers the functions for processing topologies in non-standard ways.

## Name

Polygonize — Finds and registers all faces defined by topology edges.

## Synopsis

`text Polygonize(` varchar toponame`)`;

## Description

Registers all faces that can be built out a topology edge primitives.

The target topology is assumed to contain no self-intersecting edges.

Already known faces are recognized, so it is safe to call Polygonize multiple times on the same topology.

This function does not use nor set the next_left_edge and next_right_edge fields of the edge table.

Availability: 2.0.0

## See Also

AddFace, ST_Polygonize

## Name

AddNode — Adds a point node to the node table in the specified topology schema and returns the nodeid of new node. If point already exists as node, the existing nodeid is returned.

## Synopsis

`integer AddNode(` varchar toponame, geometry apoint, boolean allowEdgeSplitting=false, boolean computeContainingFace=false`)`;

## Description

Adds a point node to the node table in the specified topology schema. The AddEdge function automatically adds start and end points of an edge when called so not necessary to explicitly add nodes of an edge.

If any edge crossing the node is found either an exception is raised or the edge is split, depending on the `allowEdgeSplitting` parameter value.

If `computeContainingFace` is true a newly added node would get the correct containing face computed.

If the `apoint` geometry already exists as a node, the node is not added but the existing nodeid is returned.

Availability: 2.0.0

## Examples

    SELECT topology.AddNode('ma_topo', ST_GeomFromText('POINT(227641.6 893816.5)', 26986) ) As nodeid;
    -- result --
    nodeid
    --------
     4

## See Also

AddEdge, CreateTopology

## Name

AddEdge — Adds a linestring edge to the edge table and associated start and end points to the point nodes table of the specified topology schema using the specified linestring geometry and returns the edgeid of the new (or existing) edge.

## Synopsis

`integer AddEdge(` varchar toponame, geometry aline`)`;

## Description

Adds an edge to the edge table and associated nodes to the nodes table of the specified `toponame` schema using the specified linestring geometry and returns the edgeid of the new or existing record. The newly added edge has "universe" face on both sides and links to itself.

If the `aline` geometry crosses, overlaps, contains or is contained by an existing linestring edge, then an error is thrown and the edge is not added.

The geometry of `aline` must have the same `srid` as defined for the topology otherwise an invalid spatial reference sys error will be thrown.

Performed by the GEOS module.

AddEdge is deprecated as of 3.5.0. Use TopoGeo_AddLineString instead.

Availability: 2.0.0

## Examples

    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227575.8 893917.2,227591.9 893900.4)', 26986) ) As edgeid;
    -- result-
    edgeid
    --------
     1

    SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227591.9 893900.4,227622.6 893844.2,227641.6 893816.5,
     227704.5 893778.5)', 26986) ) As edgeid;
    -- result --
    edgeid
    --------
     2

     SELECT topology.AddEdge('ma_topo', ST_GeomFromText('LINESTRING(227591.2 893900, 227591.9 893900.4,
      227704.5 893778.5)', 26986) ) As edgeid;
     -- gives error --
     ERROR:  Edge intersects (not on endpoints) with existing edge 1

## See Also

TopoGeo_AddLineString, CreateTopology, Section 4.5, “Spatial Reference Systems”

## Name

AddFace — Registers a face primitive to a topology and gets its identifier.

## Synopsis

`integer AddFace(` varchar toponame, geometry apolygon, boolean force_new=false`)`;

## Description

Registers a face primitive to a topology and gets its identifier.

For a newly added face, the edges forming its boundaries and the ones contained in the face will be updated to have correct values in the left_face and right_face fields. Isolated nodes contained in the face will also be updated to have a correct containing_face field value.

This function does not use nor set the next_left_edge and next_right_edge fields of the edge table.

The target topology is assumed to be valid (containing no self-intersecting edges). An exception is raised if: The polygon boundary is not fully defined by existing edges or the polygon overlaps an existing face.

If the `apolygon` geometry already exists as a face, then: if `force_new` is false (the default) the face id of the existing face is returned; if `force_new` is true a new id will be assigned to the newly registered face.

When a new registration of an existing face is performed (force_new=true), no action will be taken to resolve dangling references to the existing face in the edge, node an relation tables, nor will the MBR field of the existing face record be updated. It is up to the caller to deal with that.

The `apolygon` geometry must have the same `srid` as defined for the topology otherwise an invalid spatial reference sys error will be thrown.

Availability: 2.0.0

## Examples

    -- first add the edges we use generate_series as an iterator (the below
    -- will only work for polygons with < 10000 points because of our max in gs)
    SELECT topology.AddEdge('ma_topo', ST_MakeLine(ST_PointN(geom,i), ST_PointN(geom, i + 1) )) As edgeid
        FROM (SELECT  ST_NPoints(geom) AS npt, geom
                FROM
                    (SELECT ST_Boundary(ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
                    234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
                    234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) )  As geom
                )  As geoms) As facen CROSS JOIN generate_series(1,10000) As i
             WHERE i < npt;
    -- result --
     edgeid
    --------
          3
          4
          5
          6
          7
          8
          9
         10
         11
         12
    (10 rows)
    -- then add the face -

    SELECT topology.AddFace('ma_topo',
        ST_GeomFromText('POLYGON((234896.5 899456.7,234914 899436.4,234946.6 899356.9,234872.5 899328.7,
        234891 899285.4,234992.5 899145, 234890.6 899069,234755.2 899255.4,
        234612.7 899379.4,234776.9 899563.7,234896.5 899456.7))', 26986) ) As faceid;
    -- result --
    faceid
    --------
     1

## See Also

AddEdge, CreateTopology, Section 4.5, “Spatial Reference Systems”

## Name

ST_Simplify — Returns a "simplified" geometry version of the given TopoGeometry using the Douglas-Peucker algorithm.

## Synopsis

`geometry ST_Simplify(` TopoGeometry tg, float8 tolerance`)`;

## Description

Returns a "simplified" geometry version of the given TopoGeometry using the Douglas-Peucker algorithm on each component edge.

The returned geometry may be non-simple or non-valid. Splitting component edges may help retaining simplicity/validity.

Performed by the GEOS module.

Availability: 2.1.0

## See Also

Geometry ST_Simplify, ST_IsSimple, ST_IsValid, ST_ModEdgeSplit

## Name

RemoveUnusedPrimitives — Removes topology primitives which not needed to define existing TopoGeometry objects.

## Synopsis

`int RemoveUnusedPrimitives(` text topology_name, geometry bbox`)`;

## Description

Finds all primitives (nodes, edges, faces) that are not strictly needed to represent existing TopoGeometry objects and removes them, maintaining topology validity (edge linking, face labeling) and TopoGeometry space occupation.

No new primitive identifiers are created, but rather existing primitives are expanded to include merged faces (upon removing edges) or healed edges (upon removing nodes).

Availability: 3.3.0

## See Also

ST_ModEdgeHeal, ST_RemEdgeModFace

## 9.9. TopoGeometry Constructors

Abstract

This section covers the topology functions for creating new topogeometries.

## Name

CreateTopoGeom — Creates a new topo geometry object from topo element array - tg_type: 1:[multi]point, 2:[multi]line, 3:[multi]poly, 4:collection

## Synopsis

`topogeometry CreateTopoGeom(` varchar toponame, integer tg_type, integer layer_id, topoelementarray tg_objs`)`;

`topogeometry CreateTopoGeom(` varchar toponame, integer tg_type, integer layer_id`)`;

## Description

Creates a topogeometry object for layer denoted by `layer_id` and registers it in the relations table in the `toponame` schema.

`tg_type` is an integer: 1:[multi]point (punctal), 2:[multi]line (lineal), 3:[multi]poly (areal), 4:collection. `layer_id` is the layer id in the topology.layer table.

punctal layers are formed from set of nodes, lineal layers are formed from a set of edges, areal layers are formed from a set of faces, and collections can be formed from a mixture of nodes, edges, and faces.

Omitting the array of components generates an empty TopoGeometry object.

Availability: 1.1

## Examples: Form from existing edges

Create a topogeom in ri_topo schema for layer 2 (our ri_roads), of type (2) LINE, for the first edge (we loaded in `ST_CreateTopoGeo`).

    INSERT INTO ri.ri_roads(road_name, topo) VALUES('Unknown', topology.CreateTopoGeom('ri_topo',2,2,'{{1,2}}'::topology.topoelementarray);

## Examples: Convert an areal geometry to best guess topogeometry

Lets say we have geometries that should be formed from a collection of faces. We have for example blockgroups table and want to know the topo geometry of each block group. If our data was perfectly aligned, we could do this:

    -- create our topo geometry column --
    SELECT topology.AddTopoGeometryColumn(
    	'topo_boston',
    	'boston', 'blockgroups', 'topo', 'POLYGON');

    -- addtopgeometrycolumn --
    1

    -- update our column assuming
    -- everything is perfectly aligned with our edges
    UPDATE boston.blockgroups AS bg
    	SET topo = topology.CreateTopoGeom('topo_boston'
            ,3,1
            , foo.bfaces)
    FROM (SELECT b.gid,  topology.TopoElementArray_Agg(ARRAY[f.face_id,3]) As bfaces
    	FROM boston.blockgroups As b
                INNER JOIN topo_boston.face As f ON b.geom && f.mbr
            WHERE ST_Covers(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
                GROUP BY b.gid) As foo
    WHERE foo.gid = bg.gid;

    --the world is rarely perfect allow for some error
    --count the face if 50% of it falls
    -- within what we think is our blockgroup boundary
    UPDATE boston.blockgroups AS bg
    	SET topo = topology.CreateTopoGeom('topo_boston'
            ,3,1
            , foo.bfaces)
    FROM (SELECT b.gid,  topology.TopoElementArray_Agg(ARRAY[f.face_id,3]) As bfaces
    	FROM boston.blockgroups As b
                INNER JOIN topo_boston.face As f ON b.geom && f.mbr
            WHERE ST_Covers(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
    	OR
     (  ST_Intersects(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id))
                AND ST_Area(ST_Intersection(b.geom, topology.ST_GetFaceGeometry('topo_boston', f.face_id) ) ) >
                    ST_Area(topology.ST_GetFaceGeometry('topo_boston', f.face_id))*0.5
                    )
                GROUP BY b.gid) As foo
    WHERE foo.gid = bg.gid;

    -- and if we wanted to convert our topogeometry back
    -- to a denormalized geometry aligned with our faces and edges
    -- cast the topo to a geometry
    -- The really cool thing is my new geometries
    -- are now aligned with my tiger street centerlines
    UPDATE boston.blockgroups SET new_geom = topo::geometry;

## See Also

AddTopoGeometryColumn, toTopoGeom ST_CreateTopoGeo, ST_GetFaceGeometry, TopoElementArray, TopoElementArray_Agg

## Name

toTopoGeom — Converts a simple Geometry into a topo geometry.

## Synopsis

`topogeometry toTopoGeom(` geometry geom, varchar toponame, integer layer_id, float8 tolerance`)`;

`topogeometry toTopoGeom(` geometry geom, topogeometry topogeom, float8 tolerance`)`;

## Description

Converts a simple Geometry into a TopoGeometry.

Topological primitives required to represent the input geometry will be added to the underlying topology, possibly splitting existing ones, and they will be associated with the output TopoGeometry in the `relation` table.

Existing TopoGeometry objects (with the possible exception of `topogeom`, if given) will retain their shapes.

When `tolerance` is given it will be used to snap the input geometry to existing primitives.

In the first form a new TopoGeometry will be created for the given layer (`layer_id`) of the given topology (`toponame`).

In the second form the primitives resulting from the conversion will be added to the pre-existing TopoGeometry (`topogeom`), possibly adding space to its final shape. To have the new shape completely replace the old one see clearTopoGeom.

Availability: 2.0

Enhanced: 2.1.0 adds the version taking an existing TopoGeometry.

## Examples

This is a full self-contained workflow

     -- do this if you don't have a topology setup already
    -- creates topology not allowing any tolerance
    SELECT topology.CreateTopology('topo_boston_test', 2249);
    -- create a new table
    CREATE TABLE nei_topo(gid serial primary key, nei varchar(30));
    --add a topogeometry column to it
    SELECT topology.AddTopoGeometryColumn('topo_boston_test', 'public', 'nei_topo', 'topo', 'MULTIPOLYGON') As new_layer_id;
    new_layer_id
    -----------
    1

    --use new layer id in populating the new topogeometry column
    -- we add the topogeoms to the new layer with 0 tolerance
    INSERT INTO nei_topo(nei, topo)
    SELECT nei,  topology.toTopoGeom(geom, 'topo_boston_test', 1)
    FROM neighborhoods
    WHERE gid BETWEEN 1 and 15;

    --use to verify what has happened --
    SELECT * FROM
        topology.TopologySummary('topo_boston_test');

    -- summary--
    Topology topo_boston_test (5), SRID 2249, precision 0
    61 nodes, 87 edges, 35 faces, 15 topogeoms in 1 layers
    Layer 1, type Polygonal (3), 15 topogeoms
     Deploy: public.nei_topo.topo

    -- Shrink all TopoGeometry polygons by 10 meters
    UPDATE nei_topo SET topo = ST_Buffer(clearTopoGeom(topo), -10);

    -- Get the no-one-lands left by the above operation
    -- I think GRASS calls this "polygon0 layer"
    SELECT ST_GetFaceGeometry('topo_boston_test', f.face_id)
      FROM topo_boston_test.face f
      WHERE f.face_id > 0 -- don't consider the universe face
      AND NOT EXISTS ( -- check that no TopoGeometry references the face
        SELECT * FROM topo_boston_test.relation
        WHERE layer_id = 1 AND element_id = f.face_id
      );

## See Also

CreateTopology, AddTopoGeometryColumn, CreateTopoGeom, TopologySummary, clearTopoGeom

## Name

TopoElementArray_Agg — Returns a `topoelementarray` for a set of element_id, type arrays (topoelements).

## Synopsis

`topoelementarray TopoElementArray_Agg(` topoelement set tefield`)`;

## Description

Used to create a TopoElementArray from a set of TopoElement.

Availability: 2.0.0

## Examples

    SELECT topology.TopoElementArray_Agg(ARRAY[e,t]) As tea
      FROM generate_series(1,3) As e CROSS JOIN generate_series(1,4) As t;
      tea
    --------------------------------------------------------------------------
    {{1,1},{1,2},{1,3},{1,4},{2,1},{2,2},{2,3},{2,4},{3,1},{3,2},{3,3},{3,4}}

## See Also

TopoElement, TopoElementArray

## Name

TopoElement — Converts a topogeometry to a topoelement.

## Synopsis

`topoelement TopoElement(` topogeometry topo`)`;

## Description

Converts a TopoGeometry to a TopoElement.

Availability: 3.4.0

## Examples

This is a full self-contained workflow

    -- do this if you don't have a topology setup already
    -- Creates topology not allowing any tolerance
    SELECT TopoElement(topo)
    FROM neighborhoods;

    -- using as cast
    SELECT topology.TopoElementArray_Agg(topo::topoelement)
    FROM neighborhoods
    GROUP BY city;

## See Also

TopoElementArray_Agg, TopoGeometry, TopoElement

## 9.10. TopoGeometry Editors

Abstract

This section covers the topology functions for editing existing topogeometries.

## Name

clearTopoGeom — Clears the content of a topo geometry.

## Synopsis

`topogeometry clearTopoGeom(` topogeometry topogeom`)`;

## Description

Clears the content a TopoGeometry turning it into an empty one. Mostly useful in conjunction with toTopoGeom to replace the shape of existing objects and any dependent object in higher hierarchical levels.

Availability: 2.1

## Examples

    -- Shrink all TopoGeometry polygons by 10 meters
    UPDATE nei_topo SET topo = ST_Buffer(clearTopoGeom(topo), -10);

## See Also

toTopoGeom

## Name

TopoGeom_addElement — Adds an element to the definition of a TopoGeometry.

## Synopsis

`topogeometry TopoGeom_addElement(` topogeometry tg, topoelement el`)`;

## Description

Adds a TopoElement to the definition of a TopoGeometry object. Does not error out if the element is already part of the definition.

Availability: 2.3

## Examples

    -- Add edge 5 to TopoGeometry tg
    UPDATE mylayer SET tg = TopoGeom_addElement(tg, '{5,2}');

## See Also

TopoGeom_remElement, CreateTopoGeom

## Name

TopoGeom_remElement — Removes an element from the definition of a TopoGeometry.

## Synopsis

`topogeometry TopoGeom_remElement(` topogeometry tg, topoelement el`)`;

## Description

Removes a TopoElement from the definition of a TopoGeometry object.

Availability: 2.3

## Examples

    -- Remove face 43 from TopoGeometry tg
    UPDATE mylayer SET tg = TopoGeom_remElement(tg, '{43,3}');

## See Also

TopoGeom_addElement, CreateTopoGeom

## Name

TopoGeom_addTopoGeom — Adds element of a TopoGeometry to the definition of another TopoGeometry.

## Synopsis

`topogeometry TopoGeom_addTopoGeom(` topogeometry tgt, topogeometry src`)`;

## Description

Adds the elements of a TopoGeometry to the definition of another TopoGeometry, possibly changing its cached type (type attribute) to a collection, if needed to hold all elements in the source object.

The two TopoGeometry objects need be defined against the *same* topology and, if hierarchically defined, need be composed by elements of the same child layer.

Availability: 3.2

## Examples

    -- Set an "overall" TopoGeometry value to be composed by all
    -- elements of specific TopoGeometry values
    UPDATE mylayer SET tg_overall = TopoGeom_addTopogeom(
        TopoGeom_addTopoGeom(
            clearTopoGeom(tg_overall),
            tg_specific1
        ),
        tg_specific2
    );

## See Also

TopoGeom_addElement, clearTopoGeom, CreateTopoGeom

## Name

toTopoGeom — Adds a geometry shape to an existing topo geometry.

## Description

Refer to toTopoGeom.

## 9.11. TopoGeometry Accessors

## Name

GetTopoGeomElementArray — Returns a `topoelementarray` (an array of topoelements) containing the topological elements and type of the given TopoGeometry (primitive elements).

## Synopsis

`topoelementarray GetTopoGeomElementArray(` varchar toponame, integer layer_id, integer tg_id`)`;

`topoelementarray GetTopoGeomElementArray(` topogeometry tg`)`;

## Description

Returns a TopoElementArray containing the topological elements and type of the given TopoGeometry (primitive elements). This is similar to GetTopoGeomElements except it returns the elements as an array rather than as a dataset.

tg_id is the topogeometry id of the topogeometry object in the topology in the layer denoted by `layer_id` in the topology.layer table.

Availability: 1.1

## Examples

## See Also

GetTopoGeomElements, TopoElementArray

## Name

GetTopoGeomElements — Returns a set of `topoelement` objects containing the topological element_id,element_type of the given TopoGeometry (primitive elements).

## Synopsis

`setof topoelement GetTopoGeomElements(` varchar toponame, integer layer_id, integer tg_id`)`;

`setof topoelement GetTopoGeomElements(` topogeometry tg`)`;

## Description

Returns a set of element_id,element_type (topoelements) corresponding to primitive topology elements TopoElement (1: nodes, 2: edges, 3: faces) that a given topogeometry object in `toponame` schema is composed of.

tg_id is the topogeometry id of the topogeometry object in the topology in the layer denoted by `layer_id` in the topology.layer table.

Availability: 2.0.0

## Examples

## See Also

GetTopoGeomElementArray, TopoElement, TopoGeom_addElement, TopoGeom_remElement

## Name

ST_SRID — Returns the spatial reference identifier for a topogeometry.

## Synopsis

`integer ST_SRID(` topogeometry tg`)`;

## Description

Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table. Section 4.5, “Spatial Reference Systems”

spatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformations from one spatial reference system to another. So verifying you have the right spatial reference system identifier is important if you plan to ever transform your geometries.

Availability: 3.2.0

This method implements the SQL/MM specification. SQL-MM 3: 14.1.5

## Examples

    SELECT ST_SRID(ST_GeomFromText('POINT(-71.1043 42.315)',4326));
    		--result
    		4326

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SetSRID, ST_Transform, ST_SRID

## 9.12. TopoGeometry Outputs

## Name

AsGML — Returns the GML representation of a topogeometry.

## Synopsis

`text AsGML(` topogeometry tg`)`;

`text AsGML(` topogeometry tg, text nsprefix_in`)`;

`text AsGML(` topogeometry tg, regclass visitedTable`)`;

`text AsGML(` topogeometry tg, regclass visitedTable, text nsprefix`)`;

`text AsGML(` topogeometry tg, text nsprefix_in, integer precision, integer options`)`;

`text AsGML(` topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable`)`;

`text AsGML(` topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable, text idprefix`)`;

`text AsGML(` topogeometry tg, text nsprefix_in, integer precision, integer options, regclass visitedTable, text idprefix, int gmlversion`)`;

## Description

Returns the GML representation of a topogeometry in version GML3 format. If no `nsprefix_in` is specified then `gml` is used. Pass in an empty string for nsprefix to get a non-qualified name space. The precision (default: 15) and options (default 1) parameters, if given, are passed untouched to the underlying call to ST_AsGML.

The `visitedTable` parameter, if given, is used for keeping track of the visited Node and Edge elements so to use cross-references (xlink:xref) rather than duplicating definitions. The table is expected to have (at least) two integer fields: 'element_type' and 'element_id'. The calling user must have both read and write privileges on the given table. For best performance, an index should be defined on `element_type` and `element_id`, in that order. Such index would be created automatically by adding a unique constraint to the fields. Example:

    CREATE TABLE visited (
      element_type integer, element_id integer,
      unique(element_type, element_id)
    );

The `idprefix` parameter, if given, will be prepended to Edge and Node tag identifiers.

The `gmlver` parameter, if given, will be passed to the underlying ST_AsGML. Defaults to 3.

Availability: 2.0.0

## Examples

This uses the topo geometry we created in CreateTopoGeom

    SELECT topology.AsGML(topo) As rdgml
      FROM ri.roads
      WHERE road_name = 'Unknown';

    -- rdgml--
    <gml:TopoCurve>
        <gml:directedEdge>
            <gml:Edge gml:id="E1">
                <gml:directedNode orientation="-">
                    <gml:Node gml:id="N1"/>
                </gml:directedNode>
                <gml:directedNode></gml:directedNode>
                <gml:curveProperty>
                    <gml:Curve srsName="urn:ogc:def:crs:EPSG::3438">
                        <gml:segments>
                            <gml:LineStringSegment>
                                <gml:posList srsDimension="2">384744 236928 384750 236923 384769 236911 384799 236895 384811 236890
                                384833 236884 384844 236882 384866 236881 384879 236883 384954 236898 385087 236932 385117 236938
                                385167 236938 385203 236941 385224 236946 385233 236950 385241 236956 385254 236971
                                385260 236979 385268 236999 385273 237018 385273 237037 385271 237047 385267 237057 385225 237125
                                385210 237144 385192 237161 385167 237192 385162 237202 385159 237214 385159 237227 385162 237241
                                385166 237256 385196 237324 385209 237345 385234 237375 385237 237383 385238 237399 385236 237407
                                385227 237419 385213 237430 385193 237439 385174 237451 385170 237455 385169 237460 385171 237475
                                385181 237503 385190 237521 385200 237533 385206 237538 385213 237541 385221 237542 385235 237540 385242 237541
                                385249 237544 385260 237555 385270 237570 385289 237584 385292 237589 385291 237596 385284 237630</gml:posList>
                            </gml:LineStringSegment>
                        </gml:segments>
                    </gml:Curve>
                </gml:curveProperty>
            </gml:Edge>
        </gml:directedEdge>
    </gml:TopoCurve>

Same exercise as previous without namespace

    SELECT topology.AsGML(topo,'') As rdgml
      FROM ri.roads
      WHERE road_name = 'Unknown';

    -- rdgml--
    <TopoCurve>
        <directedEdge>
            <Edge id="E1">
                <directedNode orientation="-">
                    <Node id="N1"/>
                </directedNode>
                <directedNode></directedNode>
                <curveProperty>
                    <Curve srsName="urn:ogc:def:crs:EPSG::3438">
                        <segments>
                            <LineStringSegment>
                                <posList srsDimension="2">384744 236928 384750 236923 384769 236911 384799 236895 384811 236890
                                384833 236884 384844 236882 384866 236881 384879 236883 384954 236898 385087 236932 385117 236938
                                385167 236938 385203 236941 385224 236946 385233 236950 385241 236956 385254 236971
                                385260 236979 385268 236999 385273 237018 385273 237037 385271 237047 385267 237057 385225 237125
                                385210 237144 385192 237161 385167 237192 385162 237202 385159 237214 385159 237227 385162 237241
                                385166 237256 385196 237324 385209 237345 385234 237375 385237 237383 385238 237399 385236 237407
                                385227 237419 385213 237430 385193 237439 385174 237451 385170 237455 385169 237460 385171 237475
                                385181 237503 385190 237521 385200 237533 385206 237538 385213 237541 385221 237542 385235 237540 385242 237541
                                385249 237544 385260 237555 385270 237570 385289 237584 385292 237589 385291 237596 385284 237630</posList>
                             </LineStringSegment>
                        </segments>
                    </Curve>
                </curveProperty>
            </Edge>
        </directedEdge>
    </TopoCurve>

## See Also

CreateTopoGeom, ST_CreateTopoGeo

## Name

AsTopoJSON — Returns the TopoJSON representation of a topogeometry.

## Synopsis

`text AsTopoJSON(` topogeometry tg, regclass edgeMapTable`)`;

## Description

Returns the TopoJSON representation of a topogeometry. If `edgeMapTable` is not null, it will be used as a lookup/storage mapping of edge identifiers to arc indices. This is to be able to allow for a compact "arcs" array in the final document.

The table, if given, is expected to have an "arc_id" field of type "serial" and an "edge_id" of type integer; the code will query the table for "edge_id" so it is recommended to add an index on that field.

Arc indices in the TopoJSON output are 0-based but they are 1-based in the "edgeMapTable" table.

A full TopoJSON document will be need to contain, in addition to the snippets returned by this function, the actual arcs plus some headers. See the TopoJSON specification.

Availability: 2.1.0

Enhanced: 2.2.1 added support for puntal inputs

## See Also

ST_AsGeoJSON

## Examples

    CREATE TEMP TABLE edgemap(arc_id serial, edge_id int unique);

    -- header
    SELECT '{ "type": "Topology", "transform": { "scale": [1,1], "translate": [0,0] }, "objects": {'

    -- objects
    UNION ALL SELECT '"' || feature_name || '": ' || AsTopoJSON(feature, 'edgemap')
    FROM features.big_parcels WHERE feature_name = 'P3P4';

    -- arcs
    WITH edges AS (
      SELECT m.arc_id, e.geom FROM edgemap m, city_data.edge e
      WHERE e.edge_id = m.edge_id
    ), points AS (
      SELECT arc_id, (st_dumppoints(geom)).* FROM edges
    ), compare AS (
      SELECT p2.arc_id,
             CASE WHEN p1.path IS NULL THEN p2.geom
                  ELSE ST_Translate(p2.geom, -ST_X(p1.geom), -ST_Y(p1.geom))
             END AS geom
      FROM points p2 LEFT OUTER JOIN points p1
      ON ( p1.arc_id = p2.arc_id AND p2.path[1] = p1.path[1]+1 )
      ORDER BY arc_id, p2.path
    ), arcsdump AS (
      SELECT arc_id, (regexp_matches( ST_AsGeoJSON(geom), '\[.*\]'))[1] as t
      FROM compare
    ), arcs AS (
      SELECT arc_id, '[' || array_to_string(array_agg(t), ',') || ']' as a FROM arcsdump
      GROUP BY arc_id
      ORDER BY arc_id
    )
    SELECT '}, "arcs": [' UNION ALL
    SELECT array_to_string(array_agg(a), E',\n') from arcs

    -- footer
    UNION ALL SELECT ']}'::text as t;

    -- Result:
    { "type": "Topology", "transform": { "scale": [1,1], "translate": [0,0] }, "objects": {
    "P3P4": { "type": "MultiPolygon", "arcs": [[[-1]],[[6,5,-5,-4,-3,1]]]}
    }, "arcs": [
     [[25,30],[6,0],[0,10],[-14,0],[0,-10],[8,0]],
     [[35,6],[0,8]],
     [[35,6],[12,0]],
     [[47,6],[0,8]],
     [[47,14],[0,8]],
     [[35,22],[12,0]],
     [[35,14],[0,8]]
     ]}

## 9.13. Topology Spatial Relationships

Abstract

This section lists the Topology functions used to check relationships between topogeometries and topology primitives

## Name

Equals — Returns true if two topogeometries are composed of the same topology primitives.

## Synopsis

`boolean Equals(` topogeometry tg1, topogeometry tg2`)`;

## Description

Returns true if two topogeometries are composed of the same topology primitives: faces, edges, nodes.

This function not supported for topogeometries that are geometry collections. It also can not compare topogeometries from different topologies.

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

## See Also

GetTopoGeomElements, ST_Equals

## Name

Intersects — Returns true if any pair of primitives from the two topogeometries intersect.

## Synopsis

`boolean Intersects(` topogeometry tg1, topogeometry tg2`)`;

## Description

Returns true if any pair of primitives from the two topogeometries intersect.

This function not supported for topogeometries that are geometry collections. It also can not compare topogeometries from different topologies. Also not currently supported for hierarchical topogeometries (topogeometries composed of other topogeometries).

Availability: 1.1.0

This function supports 3d and will not drop the z-index.

## Examples

## See Also

ST_Intersects

## 9.14. Importing and exporting Topologies

Once you have created topologies, and maybe associated topological layers, you might want to export them into a file-based format for backup or transfer into another database.

Using the standard dump/restore tools of PostgreSQL is problematic because topologies are composed by a set of tables (4 for primitives, an arbitrary number for layers) and records in metadata tables (topology.topology and topology.layer). Additionally, topology identifiers are not univoque across databases so that parameter of your topology will need to be changes upon restoring it.

In order to simplify export/restore of topologies a pair of executables are provided: `pgtopo_export` and `pgtopo_import`. Example usage:

    pgtopo_export dev_db topo1 | pgtopo_import topo1 | psql staging_db

### 9.14.1. Using the Topology exporter

The `pgtopo_export` script takes the name of a database and a topology and outputs a dump file which can be used to import the topology (and associated layers) into a new database.

By default `pgtopo_export` writes the dump file to the standard output so that it can be piped to `pgtopo_import` or redirected to a file (refusing to write to terminal). You can optionally specify an output filename with the `-f` commandline switch.

By default `pgtopo_export` includes a dump of all layers defined against the given topology. This may be more data than you need, or may be non-working (in case your layer tables have complex dependencies) in which case you can request skipping the layers with the `--skip-layers` switch and deal with those separately.

Invoking `pgtopo_export` with the `--help` (or `-h` for short) switch will always print short usage string.

The dump file format is a compressed tar archive of a `pgtopo_export` directory containing at least a `pgtopo_dump_version` file with format version info. As of version `1` the directory contains tab-delimited CSV files with data of the topology primitive tables (node, edge_data, face, relation), the topology and layer records associated with it and (unless `--skip-layers` is given) a custom-format PostgreSQL dump of tables reported as being layers of the given topology.

### 9.14.2. Using the Topology importer

The `pgtopo_import` script takes a `pgtopo_export` format topology dump and a name to give to the topology to be created and outputs an SQL script reconstructing the topology and associated layers.

The generated SQL file will contain statements that create a topology with the given name, load primitive data in it, restores and registers all topology layers by properly linking all TopoGeometry values to their correct topology.

By default `pgtopo_import` reads the dump from the standard input so that it can be used in conjunction with `pgtopo_export` in a pipeline. You can optionally specify an input filename with the `-f` commandline switch.

By default `pgtopo_import` includes in the output SQL file the code to restore all layers found in the dump.

This may be unwanted or non-working in case your target database already have tables with the same name as the ones in the dump. In that case you can request skipping the layers with the `--skip-layers` switch and deal with those separately (or later).

SQL to only load and link layers to a named topology can be generated using the `--only-layers` switch. This can be useful to load layers AFTER resolving the naming conflicts or to link layers to a different topology (say a spatially-simplified version of the starting topology).

# Chapter 10. Raster Data Management, Queries, and Applications

## 10.1. Loading and Creating Rasters

For most use cases, you will create PostGIS rasters by loading existing raster files using the packaged `raster2pgsql` raster loader.

### 10.1.1. Using raster2pgsql to load rasters

The `raster2pgsql` is a raster loader executable that loads GDAL supported raster formats into SQL suitable for loading into a PostGIS raster table. It is capable of loading folders of raster files as well as creating overviews of rasters.

Since the raster2pgsql is compiled as part of PostGIS most often (unless you compile your own GDAL library), the raster types supported by the executable will be the same as those compiled in the GDAL dependency library. To get a list of raster types your particular `raster2pgsql` supports use the `-G` switch.

When creating overviews of a specific factor from a set of rasters that are aligned, it is possible for the overviews to not align. Visit http://trac.osgeo.org/postgis/ticket/1764 for an example where the overviews do not align.

#### 10.1.1.1. Example Usage

An example session using the loader to create an input file and uploading it chunked in 100x100 tiles might look like this:

    # -s use srid 4326
    # -I create spatial index
    # -C use standard raster constraints
    # -M vacuum analyze after load
    # *.tif load all these files
    # -F include a filename column in the raster table
    # -t tile the output 100x100
    # public.demelevation load into this table
    raster2pgsql -s 4326 -I -C -M -F -t 100x100 *.tif public.demelevation > elev.sql

    # -d connect to this database
    # -f read this file after connecting
    psql -d gisdb -f elev.sql

If you do not specify the schema as part of the target table name, the table will be created in the default schema of the database or user you are connecting with.

A conversion and upload can be done all in one step using UNIX pipes:

    raster2pgsql -s 4326 -I -C -M *.tif -F -t 100x100 public.demelevation | psql -d gisdb

Load rasters Massachusetts state plane meters aerial tiles into a schema called `aerial` and create a full view, 2 and 4 level overview tables, use copy mode for inserting (no intermediary file just straight to db), and -e don't force everything in a transaction (good if you want to see data in tables right away without waiting). Break up the rasters into 128x128 pixel tiles and apply raster constraints. Use copy mode instead of table insert. (-F) Include a field called filename to hold the name of the file the tiles were cut from.

    raster2pgsql -I -C -e -Y -F -s 26986 -t 128x128  -l 2,4 bostonaerials2008/*.jpg aerials.boston | psql -U postgres -d gisdb -h localhost -p 5432

    --get a list of raster types supported:
    raster2pgsql -G

The -G commands outputs a list something like

    Available GDAL raster formats:
      Virtual Raster
      GeoTIFF
      National Imagery Transmission Format
      Raster Product Format TOC format
      ECRG TOC format
      Erdas Imagine Images (.img)
      CEOS SAR Image
      CEOS Image
      ...
      Arc/Info Export E00 GRID
      ZMap Plus Grid
      NOAA NGS Geoid Height Grids

#### 10.1.1.2. raster2pgsql options

`-?`

  Display help screen. Help will also display if you don't pass in any arguments.

`-G`

  Print the supported raster formats.

(c|a|d|p) These are mutually exclusive options:

  `-c`

    Create new table and populate it with raster(s), this is the default mode

  `-a`

    Append raster(s) to an existing table.

  `-d`

    Drop table, create new one and populate it with raster(s)

  `-p`

    Prepare mode, only create the table.

Raster processing: Applying constraints for proper registering in raster catalogs

  `-C`

    Apply raster constraints -- srid, pixelsize etc. to ensure raster is properly registered in `raster_columns` view.

  `-x`

    Disable setting the max extent constraint. Only applied if -C flag is also used.

  `-r`

    Set the constraints (spatially unique and coverage tile) for regular blocking. Only applied if -C flag is also used.

Raster processing: Optional parameters used to manipulate input raster dataset

  `-s <SRID>`

    Assign output raster with specified SRID. If not provided or is zero, raster's metadata will be checked to determine an appropriate SRID.

  `-b BAND`

    Index (1-based) of band to extract from raster. For more than one band index, separate with comma (,). If unspecified, all bands of raster will be extracted.

  `-t TILE_SIZE`

    Cut raster into tiles to be inserted one per table row. `TILE_SIZE` is expressed as WIDTHxHEIGHT or set to the value "auto" to allow the loader to compute an appropriate tile size using the first raster and applied to all rasters.

  `-P`

    Pad right-most and bottom-most tiles to guarantee that all tiles have the same width and height.

  `-R, --register`

    Register the raster as a filesystem (out-db) raster.

    Only the metadata of the raster and path location to the raster is stored in the database (not the pixels).

  `-l OVERVIEW_FACTOR`

    Create overview of the raster. For more than one factor, separate with comma(,). Overview table name follows the pattern o_`overview factor`_`table`, where `overview factor` is a placeholder for numerical overview factor and `table` is replaced with the base table name. Created overview is stored in the database and is not affected by -R. Note that your generated sql file will contain both the main table and overview tables.

  `-N NODATA`

    NODATA value to use on bands without a NODATA value.

Optional parameters used to manipulate database objects

  `-f COLUMN`

    Specify name of destination raster column, default is 'rast'

  `-F`

    Add a column with the name of the file

  `-n COLUMN`

    Specify the name of the filename column. Implies -F.

  `-q`

    Wrap PostgreSQL identifiers in quotes.

  `-I`

    Create a GiST index on the raster column.

  `-M`

    Vacuum analyze the raster table.

  `-k`

    Keeps empty tiles and skips NODATA value checks for each raster band. Note you save time in checking, but could end up with far more junk rows in your database and those junk rows are not marked as empty tiles.

  `-T tablespace`

    Specify the tablespace for the new table. Note that indices (including the primary key) will still use the default tablespace unless the -X flag is also used.

  `-X tablespace`

    Specify the tablespace for the table's new index. This applies to the primary key and the spatial index if the -I flag is used.

  `-Y max_rows_per_copy=50`

    Use copy statements instead of insert statements. Optionally specify `max_rows_per_copy`; default 50 when not specified.

`-e`

  Execute each statement individually, do not use a transaction.

`-E ENDIAN`

  Control endianness of generated binary output of raster; specify 0 for XDR and 1 for NDR (default); only NDR output is supported now

`-V version`

  Specify version of output format. Default is 0. Only 0 is supported at this time.

### 10.1.2. Creating rasters using PostGIS raster functions

On many occasions, you'll want to create rasters and raster tables right in the database. There are a plethora of functions to do that. The general steps to follow.

1. Create a table with a raster column to hold the new raster records which can be accomplished with:

       CREATE TABLE myrasters(rid serial primary key, rast raster);

2. There are many functions to help with that goal. If you are creating rasters not as a derivative of other rasters, you will want to start with: ST_MakeEmptyRaster, followed by ST_AddBand

   You can also create rasters from geometries. To achieve that you'll want to use ST_AsRaster perhaps accompanied with other functions such as ST_Union or ST_MapAlgebraFct or any of the family of other map algebra functions.

   There are even many more options for creating new raster tables from existing tables. For example you can create a raster table in a different projection from an existing one using ST_Transform

3. Once you are done populating your table initially, you'll want to create a spatial index on the raster column with something like:

       CREATE INDEX myrasters_rast_st_convexhull_idx ON myrasters USING gist( ST_ConvexHull(rast) );

   Note the use of ST_ConvexHull since most raster operators are based on the convex hull of the rasters.

   Pre-2.0 versions of PostGIS raster were based on the envelop rather than the convex hull. For the spatial indexes to work properly you'll need to drop those and replace with convex hull based index.

4. Apply raster constraints using AddRasterConstraints

### 10.1.3. Using "out db" cloud rasters

The `raster2pgsql` tool uses GDAL to access raster data, and can take advantage of a key GDAL feature: the ability to read from rasters that are stored remotely in cloud "object stores" (e.g. AWS S3, Google Cloud Storage).

Efficient use of cloud stored rasters requires the use of a "cloud optimized" format. The most well-known and widely used is the "cloud optimized GeoTIFF" format. Using a non-cloud format, like a JPEG, or an un-tiled TIFF will result in very poor performance, as the system will have to download the entire raster each time it needs to access a subset.

First, load your raster into the cloud storage of your choice. Once it is loaded, you will have a URI to access it with, either an "http" URI, or sometimes a URI specific to the service. (e.g., "s3://bucket/object"). To access non-public buckets, you will need to supply GDAL config options to authenticate your connection. Note that this command is reading from the cloud raster and writing to the database.

    AWS_ACCESS_KEY_ID=xxxxxxxxxxxxxxxxxxxx \
    AWS_SECRET_ACCESS_KEY=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx \
    raster2pgsql \
      -s 990000 \
      -t 256x256 \
      -I \
      -R \
      /vsis3/your.bucket.com/your_file.tif \
      your_table \
      | psql your_db

Once the table is loaded, you need to give the database permission to read from remote rasters, by setting two permissions, postgis.enable_outdb_rasters and postgis.gdal_enabled_drivers.

    SET postgis.enable_outdb_rasters = true;
    SET postgis.gdal_enabled_drivers TO 'ENABLE_ALL';

To make the changes sticky, set them directly on your database. You will need to re-connect to experience the new settings.

    ALTER DATABASE your_db SET postgis.enable_outdb_rasters = true;
    ALTER DATABASE your_db SET postgis.gdal_enabled_drivers TO 'ENABLE_ALL';

For non-public rasters, you may have to provide access keys to read from the cloud rasters. The same keys you used to write the `raster2pgsql` call can be set for use inside the database, with the postgis.gdal_vsi_options configuration. Note that multiple options can be set by space-separating the `key=value` pairs.

    SET postgis.gdal_vsi_options = 'AWS_ACCESS_KEY_ID=xxxxxxxxxxxxxxxxxxxx
    AWS_SECRET_ACCESS_KEY=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';

Once you have the data loaded and permissions set you can interact with the raster table like any other raster table, using the same functions. The database will handle all the mechanics of connecting to the cloud data when it needs to read pixel data.

## 10.2. Raster Catalogs

There are two raster catalog views that come packaged with PostGIS. Both views utilize information embedded in the constraints of the raster tables. As a result the catalog views are always consistent with the raster data in the tables since the constraints are enforced.

1. `raster_columns` this view catalogs all the raster table columns in your database.

2. `raster_overviews` this view catalogs all the raster table columns in your database that serve as overviews for a finer grained table. Tables of this type are generated when you use the `-l` switch during load.

### 10.2.1. Raster Columns Catalog

The `raster_columns` is a catalog of all raster table columns in your database that are of type raster. It is a view utilizing the constraints on the tables so the information is always consistent even if you restore one raster table from a backup of another database. The following columns exist in the `raster_columns` catalog.

If you created your tables not with the loader or forgot to specify the `-C` flag during load, you can enforce the constraints after the fact using AddRasterConstraints so that the `raster_columns` catalog registers the common information about your raster tiles.

- `r_table_catalog` The database the table is in. This will always read the current database.

- `r_table_schema` The database schema the raster table belongs to.

- `r_table_name` raster table

- `r_raster_column` the column in the `r_table_name` table that is of type raster. There is nothing in PostGIS preventing you from having multiple raster columns per table so its possible to have a raster table listed multiple times with a different raster column for each.

- `srid` The spatial reference identifier of the raster. Should be an entry in the Section 4.5, “Spatial Reference Systems”.

- `scale_x` The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same `scale_x` and this constraint is applied. Refer to ST_ScaleX for more details.

- `scale_y` The scaling between geometric spatial coordinates and pixel. This is only available if all tiles in the raster column have the same `scale_y` and the `scale_y` constraint is applied. Refer to ST_ScaleY for more details.

- `blocksize_x` The width (number of pixels across) of each raster tile . Refer to ST_Width for more details.

- `blocksize_y` The width (number of pixels down) of each raster tile . Refer to ST_Height for more details.

- `same_alignment` A boolean that is true if all the raster tiles have the same alignment . Refer to ST_SameAlignment for more details.

- `regular_blocking` If the raster column has the spatially unique and coverage tile constraints, the value with be TRUE. Otherwise, it will be FALSE.

- `num_bands` The number of bands in each tile of your raster set. This is the same information as what is provided by ST_NumBands

- `pixel_types` An array defining the pixel type for each band. You will have the same number of elements in this array as you have number of bands. The pixel_types are one of the following defined in ST_BandPixelType.

- `nodata_values` An array of double precision numbers denoting the `nodata_value` for each band. You will have the same number of elements in this array as you have number of bands. These numbers define the pixel value for each band that should be ignored for most operations. This is similar information provided by ST_BandNoDataValue.

- `out_db` An array of boolean flags indicating if the raster bands data is maintained outside the database. You will have the same number of elements in this array as you have number of bands.

- `extent` This is the extent of all the raster rows in your raster set. If you plan to load more data that will change the extent of the set, you'll want to run the DropRasterConstraints function before load and then reapply constraints with AddRasterConstraints after load.

- `spatial_index` A boolean that is true if raster column has a spatial index.

### 10.2.2. Raster Overviews

`raster_overviews` catalogs information about raster table columns used for overviews and additional information about them that is useful to know when utilizing overviews. Overview tables are cataloged in both `raster_columns` and `raster_overviews` because they are rasters in their own right but also serve an additional special purpose of being a lower resolution caricature of a higher resolution table. These are generated along-side the main raster table when you use the `-l` switch in raster loading or can be generated manually using AddOverviewConstraints.

Overview tables contain the same constraints as other raster tables as well as additional informational only constraints specific to overviews.

The information in `raster_overviews` does not duplicate the information in `raster_columns`. If you need the information about an overview table present in `raster_columns` you can join the `raster_overviews` and `raster_columns` together to get the full set of information you need.

Two main reasons for overviews are:

1. Low resolution representation of the core tables commonly used for fast mapping zoom-out.

2. Computations are generally faster to do on them than their higher resolution parents because there are fewer records and each pixel covers more territory. Though the computations are not as accurate as the high-res tables they support, they can be sufficient in many rule-of-thumb computations.

The `raster_overviews` catalog contains the following columns of information.

- `o_table_catalog` The database the overview table is in. This will always read the current database.

- `o_table_schema` The database schema the overview raster table belongs to.

- `o_table_name` raster overview table name

- `o_raster_column` the raster column in the overview table.

- `r_table_catalog` The database the raster table that this overview services is in. This will always read the current database.

- `r_table_schema` The database schema the raster table that this overview services belongs to.

- `r_table_name` raster table that this overview services.

- `r_raster_column` the raster column that this overview column services.

- `overview_factor` - this is the pyramid level of the overview table. The higher the number the lower the resolution of the table. raster2pgsql if given a folder of images, will compute overview of each image file and load separately. Level 1 is assumed and always the original file. Level 2 is will have each tile represent 4 of the original. So for example if you have a folder of 5000x5000 pixel image files that you chose to chunk 125x125, for each image file your base table will have (5000*5000)/(125*125) records = 1600, your (l=2) `o_2` table will have ceiling(1600/Power(2,2)) = 400 rows, your (l=3) `o_3` will have ceiling(1600/Power(2,3) ) = 200 rows. If your pixels aren't divisible by the size of your tiles, you'll get some scrap tiles (tiles not completely filled). Note that each overview tile generated by raster2pgsql has the same number of pixels as its parent, but is of a lower resolution where each pixel of it represents (Power(2,overview_factor) pixels of the original).

## 10.3. Building Custom Applications with PostGIS Raster

The fact that PostGIS raster provides you with SQL functions to render rasters in known image formats gives you a lot of options for rendering them. For example you can use OpenOffice / LibreOffice for rendering as demonstrated in Rendering PostGIS Raster graphics with LibreOffice Base Reports. In addition you can use a wide variety of languages as demonstrated in this section.

### 10.3.1. PHP Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use the PHP PostgreSQL driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

You would call the below using

    http://mywebserver/test_raster.php?srid=2249

to get the raster image in Massachusetts state plane feet.

    <?php
    /** contents of test_raster.php **/
    $conn_str ='dbname=mydb host=localhost port=5432 user=myuser password=mypwd';
    $dbconn = pg_connect($conn_str);
    header('Content-Type: image/png');
    /**If a particular projection was requested use it otherwise use mass state plane meters **/
    if (!empty( $_REQUEST['srid'] ) &amp;&amp; is_numeric( $_REQUEST['srid']) ){
    		$input_srid = intval($_REQUEST['srid']);
    }
    else { $input_srid = 26986; }
    /** The set bytea_output may be needed for PostgreSQL 9.0+, but not for 8.4 **/
    $sql = "set bytea_output='escape';
    SELECT ST_AsPNG(ST_Transform(
    			ST_AddBand(ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
    				,$input_srid) ) As new_rast
     FROM aerials.boston
    	WHERE
    	 ST_Intersects(rast, ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
    $result = pg_query($sql);
    $row = pg_fetch_row($result);
    pg_free_result($result);
    if ($row === false) return;
    echo pg_unescape_bytea($row[0]);
    ?>

### 10.3.2. ASP.NET C# Example Outputting using ST_AsPNG in concert with other raster functions

In this section, we'll demonstrate how to use Npgsql PostgreSQL .NET driver and the ST_AsGDALRaster family of functions to output band 1,2,3 of a raster to a PHP request stream that can then be embedded in an img src html tag.

You will need the npgsql .NET PostgreSQL driver for this exercise which you can get the latest of from http://npgsql.projects.postgresql.org/. Just download the latest and drop into your ASP.NET bin folder and you'll be good to go.

The sample query demonstrates how to combine a whole bunch of raster functions together to grab all tiles that intersect a particular wgs 84 bounding box and then unions with ST_Union the intersecting tiles together returning all bands, transforms to user specified projection using ST_Transform, and then outputs the results as a png using ST_AsPNG.

This is same example as Section 10.3.1, “PHP Example Outputting using ST_AsPNG in concert with other raster functions” except implemented in C#.

You would call the below using

    http://mywebserver/TestRaster.ashx?srid=2249

to get the raster image in Massachusetts state plane feet.

     -- web.config connection string section --
    <connectionStrings>
        <add name="DSN"
            connectionString="server=localhost;database=mydb;Port=5432;User Id=myuser;password=mypwd"/>
    </connectionStrings>

    // Code for TestRaster.ashx
    <%@ WebHandler Language="C#" Class="TestRaster" %>
    using System;
    using System.Data;
    using System.Web;
    using Npgsql;

    public class TestRaster : IHttpHandler
    {
    	public void ProcessRequest(HttpContext context)
    	{

    		context.Response.ContentType = "image/png";
    		context.Response.BinaryWrite(GetResults(context));

    	}

    	public bool IsReusable {
    		get { return false; }
    	}

    	public byte[] GetResults(HttpContext context)
    	{
    		byte[] result = null;
    		NpgsqlCommand command;
    		string sql = null;
    		int input_srid = 26986;
            try {
    		    using (NpgsqlConnection conn = new NpgsqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["DSN"].ConnectionString)) {
    			    conn.Open();

                    if (context.Request["srid"] != null)
                    {
                        input_srid = Convert.ToInt32(context.Request["srid"]);
                    }
                    sql = @"SELECT ST_AsPNG(
                                ST_Transform(
    			                ST_AddBand(
                                    ST_Union(rast,1), ARRAY[ST_Union(rast,2),ST_Union(rast,3)])
    				                    ,:input_srid) ) As new_rast
                            FROM aerials.boston
    	                        WHERE
    	                            ST_Intersects(rast,
                                        ST_Transform(ST_MakeEnvelope(-71.1217, 42.227, -71.1210, 42.218,4326),26986) )";
    			    command = new NpgsqlCommand(sql, conn);
                    command.Parameters.Add(new NpgsqlParameter("input_srid", input_srid));

    			    result = (byte[]) command.ExecuteScalar();
                    conn.Close();
    			}

    		}
            catch (Exception ex)
            {
                result = null;
                context.Response.Write(ex.Message.Trim());
            }
    		return result;
    	}
    }

### 10.3.3. Java console app that outputs raster query as Image file

This is a simple java console app that takes a query that returns one image and outputs to specified file.

You can download the latest PostgreSQL JDBC drivers from http://jdbc.postgresql.org/download.html

You can compile the following code using a command something like:

    set env CLASSPATH .:..\postgresql-9.0-801.jdbc4.jar
    javac SaveQueryImage.java
    jar cfm SaveQueryImage.jar Manifest.txt *.class

And call it from the command-line with something like

    java -jar SaveQueryImage.jar "SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10, 'quad_segs=2'),150, 150, '8BUI',100));" "test.png"

     -- Manifest.txt --
    Class-Path: postgresql-9.0-801.jdbc4.jar
    Main-Class: SaveQueryImage

    // Code for SaveQueryImage.java
    import java.sql.Connection;
    import java.sql.SQLException;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.io.*;

    public class SaveQueryImage {
      public static void main(String[] argv) {
          System.out.println("Checking if Driver is registered with DriverManager.");

          try {
            //java.sql.DriverManager.registerDriver (new org.postgresql.Driver());
            Class.forName("org.postgresql.Driver");
          }
          catch (ClassNotFoundException cnfe) {
            System.out.println("Couldn't find the driver!");
            cnfe.printStackTrace();
            System.exit(1);
          }

          Connection conn = null;

          try {
            conn = DriverManager.getConnection("jdbc:postgresql://localhost:5432/mydb","myuser", "mypwd");
            conn.setAutoCommit(false);

            PreparedStatement sGetImg = conn.prepareStatement(argv[0]);

            ResultSet rs = sGetImg.executeQuery();

    		FileOutputStream fout;
    		try
    		{
    			rs.next();
    			/** Output to file name requested by user **/
    			fout = new FileOutputStream(new File(argv[1]) );
    			fout.write(rs.getBytes(1));
    			fout.close();
    		}
    		catch(Exception e)
    		{
    			System.out.println("Can't create file");
    			e.printStackTrace();
    		}

            rs.close();
    		sGetImg.close();
            conn.close();
          }
          catch (SQLException se) {
            System.out.println("Couldn't connect: print out a stack trace and exit.");
            se.printStackTrace();
            System.exit(1);
          }
      }
    }

### 10.3.4. Use PLPython to dump out images via SQL

This is a plpython stored function that creates a file in the server directory for each record. Requires you have plpython installed. Should work fine with both plpythonu and plpython3u.

    CREATE OR REPLACE FUNCTION write_file (param_bytes bytea, param_filepath text)
    RETURNS text
    AS $$
    f = open(param_filepath, 'wb+')
    f.write(param_bytes)
    return param_filepath
    $$ LANGUAGE plpythonu;

    --write out 5 images to the PostgreSQL server in varying sizes
    -- note the postgresql daemon account needs to have write access to folder
    -- this echos back the file names created;
     SELECT write_file(ST_AsPNG(
    	ST_AsRaster(ST_Buffer(ST_Point(1,5),j*5, 'quad_segs=2'),150*j, 150*j, '8BUI',100)),
    	 'C:/temp/slices'|| j || '.png')
    	 FROM generate_series(1,5) As j;

         write_file
    ---------------------
     C:/temp/slices1.png
     C:/temp/slices2.png
     C:/temp/slices3.png
     C:/temp/slices4.png
     C:/temp/slices5.png

### 10.3.5. Outputting Rasters with PSQL

Sadly PSQL doesn't have easy to use built-in functionality for outputting binaries. This is a bit of a hack that piggy backs on PostgreSQL somewhat legacy large object support. To use first launch your psql commandline connected to your database.

Unlike the python approach, this approach creates the file on your local computer.

    SELECT oid, lowrite(lo_open(oid, 131072), png) As num_bytes
     FROM
     ( VALUES (lo_create(0),
       ST_AsPNG( (SELECT rast FROM aerials.boston WHERE rid=1) )
      ) ) As v(oid,png);
    -- you'll get an output something like --
       oid   | num_bytes
    ---------+-----------
     2630819 |     74860

    -- next note the oid and do this replacing the c:/test.png to file path location
    -- on your local computer
     \lo_export 2630819 'C:/temp/aerial_samp.png'

    -- this deletes the file from large object storage on db
    SELECT lo_unlink(2630819);

# Chapter 11. Raster Reference

The functions given below are the ones which a user of PostGIS Raster is likely to need and which are currently available in PostGIS Raster. There are other functions which are required support functions to the raster objects which are not of use to a general user.

`raster` is a new PostGIS type for storing and analyzing raster data.

For loading rasters from raster files please refer to Section 10.1, “Loading and Creating Rasters”

For the examples in this reference we will be using a raster table of dummy rasters - Formed with the following code

    CREATE TABLE dummy_rast(rid integer, rast raster);
    INSERT INTO dummy_rast(rid, rast)
    VALUES (1,
    ('01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0000' -- nBands (uint16 0)
    ||
    '0000000000000040' -- scaleX (float64 2)
    ||
    '0000000000000840' -- scaleY (float64 3)
    ||
    '000000000000E03F' -- ipX (float64 0.5)
    ||
    '000000000000E03F' -- ipY (float64 0.5)
    ||
    '0000000000000000' -- skewX (float64 0)
    ||
    '0000000000000000' -- skewY (float64 0)
    ||
    '00000000' -- SRID (int32 0)
    ||
    '0A00' -- width (uint16 10)
    ||
    '1400' -- height (uint16 20)
    )::raster
    ),
    -- Raster: 5 x 5 pixels, 3 bands, PT_8BUI pixel type, NODATA = 0
    (2,  ('01000003009A9999999999A93F9A9999999999A9BF000000E02B274A' ||
    '41000000007719564100000000000000000000000000000000FFFFFFFF050005000400FDFEFDFEFEFDFEFEFDF9FAFEF' ||
    'EFCF9FBFDFEFEFDFCFAFEFEFE04004E627AADD16076B4F9FE6370A9F5FE59637AB0E54F58617087040046566487A1506CA2E3FA5A6CAFFBFE4D566DA4CB3E454C5665')::raster);

## 11.1. Raster Support Data types

Abstract

This section lists the PostgreSQL data types specifically created to support raster functionality.

## Name

geomval — A spatial datatype with two fields - geom (holding a geometry object) and val (holding a double precision pixel value from a raster band).

## Description

geomval is a compound data type consisting of a geometry object referenced by the .geom field and val, a double precision value that represents the pixel value at a particular geometric location in a raster band. It is used by the ST_DumpAsPolygon and Raster intersection family of functions as an output type to explode a raster band into geometry polygons.

## See Also

Section 13.6, “PostGIS Geometry / Geography / Raster Dump Functions”

## Name

addbandarg — A composite type used as input into the ST_AddBand function defining the attributes and initial value of the new band.

## Description

A composite type used as input into the ST_AddBand function defining the attributes and initial value of the new band.

`index integer`

  1-based value indicating the position where the new band will be added amongst the raster's bands. If NULL, the new band will be added at the end of the raster's bands.

`pixeltype text`

  Pixel type of the new band. One of defined pixel types as described in ST_BandPixelType.

`initialvalue double precision`

  Initial value that all pixels of new band will be set to.

`nodataval double precision`

  NODATA value of the new band. If NULL, the new band will not have a NODATA value assigned.

## See Also

ST_AddBand

## Name

rastbandarg — A composite type for use when needing to express a raster and a band index of that raster.

## Description

A composite type for use when needing to express a raster and a band index of that raster.

`rast raster`

  The raster in question/

`nband integer`

  1-based value indicating the band of raster

## See Also

ST_MapAlgebra (callback function version)

## Name

raster — raster spatial data type.

## Description

raster is a spatial data type used to represent raster data such as those imported from JPEGs, TIFFs, PNGs, digital elevation models. Each raster has 1 or more bands each having a set of pixel values. Rasters can be georeferenced.

Requires PostGIS be compiled with GDAL support. Currently rasters can be implicitly converted to geometry type, but the conversion returns the ST_ConvexHull of the raster. This auto casting may be removed in the near future so don't rely on it.

## Casting Behavior

This section lists the automatic as well as explicit casts allowed for this data type

Cast To | Behavior
geometry | automatic

## See Also

Chapter 11, Raster Reference

## Name

reclassarg — A composite type used as input into the ST_Reclass function defining the behavior of reclassification.

## Description

A composite type used as input into the ST_Reclass function defining the behavior of reclassification.

`nband integer`

  The band number of band to reclassify.

`reclassexpr text`

  range expression consisting of comma delimited range:map_range mappings. : to define mapping that defines how to map old band values to new band values. ( means >, ) means less than, ] < or equal, [ means > or equal

      1. [a-b] = a <= x <= b

      2. (a-b] = a < x <= b

      3. [a-b) = a <= x < b

      4. (a-b) = a < x < b

  ( notation is optional so a-b means the same as (a-b)

`pixeltype text`

  One of defined pixel types as described in ST_BandPixelType

`nodataval double precision`

  Value to treat as no data. For image outputs that support transparency, these will be blank.

## Example: Reclassify band 2 as an 8BUI where 255 is nodata value

    SELECT ROW(2, '0-100:1-10, 101-500:11-150,501 - 10000: 151-254', '8BUI', 255)::reclassarg;

## Example: Reclassify band 1 as an 1BB and no nodata value defined

    SELECT ROW(1, '0-100]:0, (100-255:1', '1BB', NULL)::reclassarg;

## See Also

ST_Reclass

## Name

summarystats — A composite type returned by the ST_SummaryStats and ST_SummaryStatsAgg functions.

## Description

A composite type returned by the ST_SummaryStats and ST_SummaryStatsAgg functions.

count integer

  Number of pixels counted for the summary statistics.

sum double precision

  Sum of all counted pixel values.

mean double precision

  Arithmetic mean of all counted pixel values.

stddev double precision

  Standard deviation of all counted pixel values.

min double precision

  Minimum value of counted pixel values.

max double precision

  Maximum value of counted pixel values.

## See Also

ST_SummaryStats, ST_SummaryStatsAgg

## Name

unionarg — A composite type used as input into the ST_Union function defining the bands to be processed and behavior of the UNION operation.

## Description

A composite type used as input into the ST_Union function defining the bands to be processed and behavior of the UNION operation.

`nband integer`

  1-based value indicating the band of each input raster to be processed.

`uniontype text`

  Type of UNION operation. One of defined types as described in ST_Union.

## See Also

ST_Union

## 11.2. Raster Management

## Name

AddRasterConstraints — Adds raster constraints to a loaded raster table for a specific column that constrains spatial ref, scaling, blocksize, alignment, bands, band type and a flag to denote if raster column is regularly blocked. The table must be loaded with data for the constraints to be inferred. Returns true if the constraint setting was accomplished and issues a notice otherwise.

## Synopsis

`boolean AddRasterConstraints(` name rasttable, name rastcolumn, boolean srid=true, boolean scale_x=true, boolean scale_y=true, boolean blocksize_x=true, boolean blocksize_y=true, boolean same_alignment=true, boolean regular_blocking=false, boolean num_bands=true , boolean pixel_types=true , boolean nodata_values=true , boolean out_db=true , boolean extent=true `)`;

`boolean AddRasterConstraints(` name rasttable, name rastcolumn, text[] VARIADIC constraints`)`;

`boolean AddRasterConstraints(` name rastschema, name rasttable, name rastcolumn, text[] VARIADIC constraints`)`;

`boolean AddRasterConstraints(` name rastschema, name rasttable, name rastcolumn, boolean srid=true, boolean scale_x=true, boolean scale_y=true, boolean blocksize_x=true, boolean blocksize_y=true, boolean same_alignment=true, boolean regular_blocking=false, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true , boolean out_db=true , boolean extent=true `)`;

## Description

Generates constraints on a raster column that are used to display information in the `raster_columns` raster catalog. The `rastschema` is the name of the table schema the table resides in. The `srid` must be an integer value reference to an entry in the SPATIAL_REF_SYS table.

`raster2pgsql` loader uses this function to register raster tables

Valid constraint names to pass in: refer to Section 10.2.1, “Raster Columns Catalog” for more details.

- `blocksize` sets both X and Y blocksize

- `blocksize_x` sets X tile (width in pixels of each tile)

- `blocksize_y` sets Y tile (height in pixels of each tile)

- `extent` computes extent of whole table and applies constraint all rasters must be within that extent

- `num_bands` number of bands

- `pixel_types` reads array of pixel types for each band ensure all band n have same pixel type

- `regular_blocking` sets spatially unique (no two rasters can be spatially the same) and coverage tile (raster is aligned to a coverage) constraints

- `same_alignment` ensures they all have same alignment meaning any two tiles you compare will return true for. Refer to ST_SameAlignment.

- `srid` ensures all have same srid

- More -- any listed as inputs into the above functions

This function infers the constraints from the data already present in the table. As such for it to work, you must create the raster column first and then load it with data.

If you need to load more data in your tables after you have already applied constraints, you may want to run the DropRasterConstraints if the extent of your data has changed.

Availability: 2.0.0

## Examples: Apply all possible constraints on column based on data

    CREATE TABLE myrasters(rid SERIAL primary key, rast raster);
    INSERT INTO myrasters(rast)
    SELECT ST_AddBand(ST_MakeEmptyRaster(1000, 1000, 0.3, -0.3, 2, 2, 0, 0,4326), 1, '8BSI'::text, -129, NULL);

    SELECT AddRasterConstraints('myrasters'::name, 'rast'::name);

    -- verify if registered correctly in the raster_columns view --
    SELECT srid, scale_x, scale_y, blocksize_x, blocksize_y, num_bands, pixel_types, nodata_values
        FROM raster_columns
        WHERE r_table_name = 'myrasters';

     srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | pixel_types| nodata_values
    ------+---------+---------+-------------+-------------+-----------+-------------+---------------
     4326 |       2 |       2 |        1000 |        1000 |         1 | {8BSI}      | {0}

## Examples: Apply single constraint

    CREATE TABLE public.myrasters2(rid SERIAL primary key, rast raster);
    INSERT INTO myrasters2(rast)
    SELECT ST_AddBand(ST_MakeEmptyRaster(1000, 1000, 0.3, -0.3, 2, 2, 0, 0,4326), 1, '8BSI'::text, -129, NULL);

    SELECT AddRasterConstraints('public'::name, 'myrasters2'::name, 'rast'::name,'regular_blocking', 'blocksize');
    -- get notice--
    NOTICE:  Adding regular blocking constraint
    NOTICE:  Adding blocksize-X constraint
    NOTICE:  Adding blocksize-Y constraint

## See Also

Section 10.2.1, “Raster Columns Catalog”, ST_AddBand, ST_MakeEmptyRaster, DropRasterConstraints, ST_BandPixelType, ST_SRID

## Name

DropRasterConstraints — Drops PostGIS raster constraints that refer to a raster table column. Useful if you need to reload data or update your raster column data.

## Synopsis

`boolean DropRasterConstraints(` name rasttable, name rastcolumn, boolean srid, boolean scale_x, boolean scale_y, boolean blocksize_x, boolean blocksize_y, boolean same_alignment, boolean regular_blocking, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true, boolean out_db=true , boolean extent=true`)`;

`boolean DropRasterConstraints(` name rastschema, name rasttable, name rastcolumn, boolean srid=true, boolean scale_x=true, boolean scale_y=true, boolean blocksize_x=true, boolean blocksize_y=true, boolean same_alignment=true, boolean regular_blocking=false, boolean num_bands=true, boolean pixel_types=true, boolean nodata_values=true, boolean out_db=true , boolean extent=true`)`;

`boolean DropRasterConstraints(` name rastschema, name rasttable, name rastcolumn, text[] constraints`)`;

## Description

Drops PostGIS raster constraints that refer to a raster table column that were added by AddRasterConstraints. Useful if you need to load more data or update your raster column data. You do not need to do this if you want to get rid of a raster table or a raster column.

To drop a raster table use the standard

    DROP TABLE mytable

To drop just a raster column and leave the rest of the table, use standard SQL

    ALTER TABLE mytable DROP COLUMN rast

the table will disappear from the `raster_columns` catalog if the column or table is dropped. However if only the constraints are dropped, the raster column will still be listed in the `raster_columns` catalog, but there will be no other information about it aside from the column name and table.

Availability: 2.0.0

## Examples

    SELECT DropRasterConstraints ('myrasters','rast');
    ----RESULT output ---
    t

    -- verify change in raster_columns --
    SELECT srid, scale_x, scale_y, blocksize_x, blocksize_y, num_bands, pixel_types, nodata_values
        FROM raster_columns
        WHERE r_table_name = 'myrasters';

     srid | scale_x | scale_y | blocksize_x | blocksize_y | num_bands | pixel_types| nodata_values
    ------+---------+---------+-------------+-------------+-----------+-------------+---------------
        0 |         |         |             |             |           |             |

## See Also

AddRasterConstraints

## Name

AddOverviewConstraints — Tag a raster column as being an overview of another.

## Synopsis

`boolean AddOverviewConstraints(` name ovschema, name ovtable, name ovcolumn, name refschema, name reftable, name refcolumn, int ovfactor`)`;

`boolean AddOverviewConstraints(` name ovtable, name ovcolumn, name reftable, name refcolumn, int ovfactor`)`;

## Description

Adds constraints on a raster column that are used to display information in the `raster_overviews` raster catalog.

The `ovfactor` parameter represents the scale multiplier in the overview column: higher overview factors have lower resolution.

When the `ovschema` and `refschema` parameters are omitted, the first table found scanning the `search_path` will be used.

Availability: 2.0.0

## Examples

    CREATE TABLE res1 AS SELECT
    ST_AddBand(
      ST_MakeEmptyRaster(1000, 1000, 0, 0, 2),
      1, '8BSI'::text, -129, NULL
    ) r1;

    CREATE TABLE res2 AS SELECT
    ST_AddBand(
      ST_MakeEmptyRaster(500, 500, 0, 0, 4),
      1, '8BSI'::text, -129, NULL
    ) r2;

    SELECT AddOverviewConstraints('res2', 'r2', 'res1', 'r1', 2);

    -- verify if registered correctly in the raster_overviews view --
    SELECT o_table_name ot, o_raster_column oc,
           r_table_name rt, r_raster_column rc,
           overview_factor f
    FROM raster_overviews WHERE o_table_name = 'res2';
      ot  | oc |  rt  | rc | f
    ------+----+------+----+---
     res2 | r2 | res1 | r1 | 2
    (1 row)

## See Also

Section 10.2.2, “Raster Overviews”, DropOverviewConstraints, ST_CreateOverview, AddRasterConstraints

## Name

DropOverviewConstraints — Untag a raster column from being an overview of another.

## Synopsis

`boolean DropOverviewConstraints(` name ovschema, name ovtable, name ovcolumn`)`;

`boolean DropOverviewConstraints(` name ovtable, name ovcolumn`)`;

## Description

Remove from a raster column the constraints used to show it as being an overview of another in the `raster_overviews` raster catalog.

When the `ovschema` parameter is omitted, the first table found scanning the `search_path` will be used.

Availability: 2.0.0

## See Also

Section 10.2.2, “Raster Overviews”, AddOverviewConstraints, DropRasterConstraints

## Name

PostGIS_GDAL_Version — Reports the version of the GDAL library in use by PostGIS.

## Synopsis

`text PostGIS_GDAL_Version(` `)`;

## Description

Reports the version of the GDAL library in use by PostGIS. Will also check and report if GDAL can find its data files.

## Examples

    SELECT PostGIS_GDAL_Version();
           postgis_gdal_version
    -----------------------------------
     GDAL 1.11dev, released 2013/04/13

## See Also

postgis.gdal_datapath

## Name

PostGIS_Raster_Lib_Build_Date — Reports full raster library build date.

## Synopsis

`text PostGIS_Raster_Lib_Build_Date(` `)`;

## Description

Reports raster build date

## Examples

    SELECT PostGIS_Raster_Lib_Build_Date();
    postgis_raster_lib_build_date
    -----------------------------
    2010-04-28 21:15:10

## See Also

PostGIS_Raster_Lib_Version

## Name

PostGIS_Raster_Lib_Version — Reports full raster version and build configuration infos.

## Synopsis

`text PostGIS_Raster_Lib_Version(` `)`;

## Description

Reports full raster version and build configuration infos.

## Examples

    SELECT PostGIS_Raster_Lib_Version();
    postgis_raster_lib_version
    -----------------------------
     2.0.0

## See Also

PostGIS_Lib_Version

## Name

ST_GDALDrivers — Returns a list of raster formats supported by PostGIS through GDAL. Only those formats with can_write=True can be used by ST_AsGDALRaster

## Synopsis

`setof record ST_GDALDrivers(` integer OUT idx, text OUT short_name, text OUT long_name, text OUT can_read, text OUT can_write, text OUT create_options`)`;

## Description

Returns a list of raster formats short_name,long_name and creator options of each format supported by GDAL. Use the short_name as input in the `format` parameter of ST_AsGDALRaster. Options vary depending on what drivers your libgdal was compiled with. `create_options` returns an xml formatted set of CreationOptionList/Option consisting of name and optional `type`, `description` and set of `VALUE` for each creator option for the specific driver.

Changed: 2.5.0 - add can_read and can_write columns.

Changed: 2.0.6, 2.1.3 - by default no drivers are enabled, unless GUC or Environment variable gdal_enabled_drivers is set.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: List of Drivers

    SET postgis.gdal_enabled_drivers = 'ENABLE_ALL';
    SELECT short_name, long_name, can_write
    FROM st_gdaldrivers()
    ORDER BY short_name;

       short_name    |                          long_name                          | can_write
    -----------------+-------------------------------------------------------------+-----------
     AAIGrid         | Arc/Info ASCII Grid                                         | t
     ACE2            | ACE2                                                        | f
     ADRG            | ARC Digitized Raster Graphics                               | f
     AIG             | Arc/Info Binary Grid                                        | f
     AirSAR          | AirSAR Polarimetric Image                                   | f
     ARG             | Azavea Raster Grid format                                   | t
     BAG             | Bathymetry Attributed Grid                                  | f
     BIGGIF          | Graphics Interchange Format (.gif)                          | f
     BLX             | Magellan topo (.blx)                                        | t
     BMP             | MS Windows Device Independent Bitmap                        | f
     BSB             | Maptech BSB Nautical Charts                                 | f
     PAux            | PCI .aux Labelled                                           | f
     PCIDSK          | PCIDSK Database File                                        | f
     PCRaster        | PCRaster Raster File                                        | f
     PDF             | Geospatial PDF                                              | f
     PDS             | NASA Planetary Data System                                  | f
     PDS4            | NASA Planetary Data System 4                                | t
     PLMOSAIC        | Planet Labs Mosaics API                                     | f
     PLSCENES        | Planet Labs Scenes API                                      | f
     PNG             | Portable Network Graphics                                   | t
     PNM             | Portable Pixmap Format (netpbm)                             | f
     PRF             | Racurs PHOTOMOD PRF                                         | f
     R               | R Object Data Store                                         | t
     Rasterlite      | Rasterlite                                                  | t
     RDA             | DigitalGlobe Raster Data Access driver                      | f
     RIK             | Swedish Grid RIK (.rik)                                     | f
     RMF             | Raster Matrix Format                                        | f
     ROI_PAC         | ROI_PAC raster                                              | f
     RPFTOC          | Raster Product Format TOC format                            | f
     RRASTER         | R Raster                                                    | f
     RS2             | RadarSat 2 XML Product                                      | f
     RST             | Idrisi Raster A.1                                           | t
     SAFE            | Sentinel-1 SAR SAFE Product                                 | f
     SAGA            | SAGA GIS Binary Grid (.sdat, .sg-grd-z)                     | t
     SAR_CEOS        | CEOS SAR Image                                              | f
     SDTS            | SDTS Raster                                                 | f
     SENTINEL2       | Sentinel 2                                                  | f
     SGI             | SGI Image File Format 1.0                                   | f
     SNODAS          | Snow Data Assimilation System                               | f
     SRP             | Standard Raster Product (ASRP/USRP)                         | f
     SRTMHGT         | SRTMHGT File Format                                         | t
     Terragen        | Terragen heightfield                                        | f
     TIL             | EarthWatch .TIL                                             | f
     TSX             | TerraSAR-X Product                                          | f
     USGSDEM         | USGS Optional ASCII DEM (and CDED)                          | t
     VICAR           | MIPL VICAR file                                             | f
     VRT             | Virtual Raster                                              | t
     WCS             | OGC Web Coverage Service                                    | f
     WMS             | OGC Web Map Service                                         | t
     WMTS            | OGC Web Map Tile Service                                    | t
     XPM             | X11 PixMap Format                                           | t
     XYZ             | ASCII Gridded XYZ                                           | t
     ZMap            | ZMap Plus Grid                                              | t

## Example: List of options for each driver

    -- Output the create options XML column of JPEG as a table  --
    -- Note you can use these creator options in ST_AsGDALRaster options argument
    SELECT (xpath('@name', g.opt))[1]::text As oname,
           (xpath('@type', g.opt))[1]::text As otype,
           (xpath('@description', g.opt))[1]::text As descrip
    FROM (SELECT unnest(xpath('/CreationOptionList/Option', create_options::xml)) As opt
    FROM  st_gdaldrivers()
    WHERE short_name = 'JPEG') As g;

           oname        |  otype  |      descrip
    --------------------+---------+-------------------------------------------------
     PROGRESSIVE        | boolean | whether to generate a progressive JPEG
     QUALITY            | int     | good=100, bad=0, default=75
     WORLDFILE          | boolean | whether to generate a worldfile
     INTERNAL_MASK      | boolean | whether to generate a validity mask
     COMMENT            | string  | Comment
     SOURCE_ICC_PROFILE | string  | ICC profile encoded in Base64
     EXIF_THUMBNAIL     | boolean | whether to generate an EXIF thumbnail(overview).
                                    By default its max dimension will be 128
     THUMBNAIL_WIDTH    | int     | Forced thumbnail width
     THUMBNAIL_HEIGHT   | int     | Forced thumbnail height
    (9 rows)

    -- raw xml output for creator options for GeoTiff --
    SELECT create_options
    FROM st_gdaldrivers()
    WHERE short_name = 'GTiff';

    <CreationOptionList>
        <Option name="COMPRESS" type="string-select">
            <Value>NONE</Value>
            <Value>LZW</Value>
            <Value>PACKBITS</Value>
            <Value>JPEG</Value>
            <Value>CCITTRLE</Value>
            <Value>CCITTFAX3</Value>
            <Value>CCITTFAX4</Value>
            <Value>DEFLATE</Value>
        </Option>
        <Option name="PREDICTOR" type="int" description="Predictor Type"/>
        <Option name="JPEG_QUALITY" type="int" description="JPEG quality 1-100" default="75"/>
        <Option name="ZLEVEL" type="int" description="DEFLATE compression level 1-9" default="6"/>
        <Option name="NBITS" type="int" description="BITS for sub-byte files (1-7), sub-uint16 (9-15), sub-uint32 (17-31)"/>
        <Option name="INTERLEAVE" type="string-select" default="PIXEL">
            <Value>BAND</Value>
            <Value>PIXEL</Value>
        </Option>
        <Option name="TILED" type="boolean" description="Switch to tiled format"/>
        <Option name="TFW" type="boolean" description="Write out world file"/>
        <Option name="RPB" type="boolean" description="Write out .RPB (RPC) file"/>
        <Option name="BLOCKXSIZE" type="int" description="Tile Width"/>
        <Option name="BLOCKYSIZE" type="int" description="Tile/Strip Height"/>
        <Option name="PHOTOMETRIC" type="string-select">
            <Value>MINISBLACK</Value>
            <Value>MINISWHITE</Value>
            <Value>PALETTE</Value>
            <Value>RGB</Value>
            <Value>CMYK</Value>
            <Value>YCBCR</Value>
            <Value>CIELAB</Value>
            <Value>ICCLAB</Value>
            <Value>ITULAB</Value>
        </Option>
        <Option name="SPARSE_OK" type="boolean" description="Can newly created files have missing blocks?" default="FALSE"/>
        <Option name="ALPHA" type="boolean" description="Mark first extrasample as being alpha"/>
        <Option name="PROFILE" type="string-select" default="GDALGeoTIFF">
            <Value>GDALGeoTIFF</Value>
            <Value>GeoTIFF</Value>
            <Value>BASELINE</Value>
        </Option>
        <Option name="PIXELTYPE" type="string-select">
            <Value>DEFAULT</Value>
            <Value>SIGNEDBYTE</Value>
        </Option>
        <Option name="BIGTIFF" type="string-select" description="Force creation of BigTIFF file">
            <Value>YES</Value>
            <Value>NO</Value>
            <Value>IF_NEEDED</Value>
            <Value>IF_SAFER</Value>
        </Option>
        <Option name="ENDIANNESS" type="string-select" default="NATIVE" description="Force endianness of created file. For DEBUG purpose mostly">
            <Value>NATIVE</Value>
            <Value>INVERTED</Value>
            <Value>LITTLE</Value>
            <Value>BIG</Value>
        </Option>
        <Option name="COPY_SRC_OVERVIEWS" type="boolean" default="NO" description="Force copy of overviews of source dataset (CreateCopy())"/>
    </CreationOptionList>

    -- Output the create options XML column for GTiff as a table  --
    SELECT (xpath('@name', g.opt))[1]::text As oname,
           (xpath('@type', g.opt))[1]::text As otype,
           (xpath('@description', g.opt))[1]::text As descrip,
           array_to_string(xpath('Value/text()', g.opt),', ') As vals
    FROM (SELECT unnest(xpath('/CreationOptionList/Option', create_options::xml)) As opt
    FROM  st_gdaldrivers()
    WHERE short_name = 'GTiff') As g;

           oname        |     otype     |                               descrip                                |                                   vals
    --------------------+---------------+----------------------------------------------------------------------+---------------------------------------------------------------------------
     COMPRESS           | string-select |                                                                      | NONE, LZW, PACKBITS, JPEG, CCITTRLE, CCITTFAX3, CCITTFAX4, DEFLATE
     PREDICTOR          | int           | Predictor Type                                                       |
     JPEG_QUALITY       | int           | JPEG quality 1-100                                                   |
     ZLEVEL             | int           | DEFLATE compression level 1-9                                        |
     NBITS              | int           | BITS for sub-byte files (1-7), sub-uint16 (9-15), sub-uint32 (17-31) |
     INTERLEAVE         | string-select |                                                                      | BAND, PIXEL
     TILED              | boolean       | Switch to tiled format                                               |
     TFW                | boolean       | Write out world file                                                 |
     RPB                | boolean       | Write out .RPB (RPC) file                                            |
     BLOCKXSIZE         | int           | Tile Width                                                           |
     BLOCKYSIZE         | int           | Tile/Strip Height                                                    |
     PHOTOMETRIC        | string-select |                                                                      | MINISBLACK, MINISWHITE, PALETTE, RGB, CMYK, YCBCR, CIELAB, ICCLAB, ITULAB
     SPARSE_OK          | boolean       | Can newly created files have missing blocks?                         |
     ALPHA              | boolean       | Mark first extrasample as being alpha                                |
     PROFILE            | string-select |                                                                      | GDALGeoTIFF, GeoTIFF, BASELINE
     PIXELTYPE          | string-select |                                                                      | DEFAULT, SIGNEDBYTE
     BIGTIFF            | string-select | Force creation of BigTIFF file                                       | YES, NO, IF_NEEDED, IF_SAFER
     ENDIANNESS         | string-select | Force endianness of created file. For DEBUG purpose mostly           | NATIVE, INVERTED, LITTLE, BIG
     COPY_SRC_OVERVIEWS | boolean       | Force copy of overviews of source dataset (CreateCopy())             |
    (19 rows)

## See Also

ST_AsGDALRaster, ST_SRID, postgis.gdal_enabled_drivers

## Name

ST_Contour — Generates a set of vector contours from the provided raster band, using the GDAL contouring algorithm.

## Synopsis

`setof record ST_Contour(` raster rast, integer bandnumber=1, double precision level_interval=100.0, double precision level_base=0.0, double precision[] fixed_levels=ARRAY[], boolean polygonize=false`)`;

## Description

Generates a set of vector contours from the provided raster band, using the GDAL contouring algorithm.

When the `fixed_levels` parameter is a non-empty array, the `level_interval` and `level_base` parameters are ignored.

Input parameters are:

`rast`

  The raster to generate the contour of

`bandnumber`

  The band to generate the contour of

`level_interval`

  The elevation interval between contours generated

`level_base`

  The "base" relative to which contour intervals are applied, this is normally zero, but could be different. To generate 10m contours at 5, 15, 25, ... the LEVEL_BASE would be 5.

`fixed_levels`

  The elevation interval between contours generated

`polygonize`

  If `true`, contour polygons will be created, rather than polygon lines.

Return values are a set of records with the following attributes:

`geom`

  The geometry of the contour line.

`id`

  A unique identifier given to the contour line by GDAL.

`value`

  The raster value the line represents. For an elevation DEM input, this would be the elevation of the output contour.

Availability: 3.2.0

## Example

    WITH c AS (
    SELECT (ST_Contour(rast, 1, fixed_levels => ARRAY[100.0, 200.0, 300.0])).*
    FROM dem_grid WHERE rid = 1
    )
    SELECT st_astext(geom), id, value
    FROM c;

## See Also

ST_InterpolateRaster

## Name

ST_InterpolateRaster — Interpolates a gridded surface based on an input set of 3-d points, using the X- and Y-values to position the points on the grid and the Z-value of the points as the surface elevation.

## Synopsis

`raster ST_InterpolateRaster(` geometry input_points, text algorithm_options, raster template, integer template_band_num=1`)`;

## Description

Interpolates a gridded surface based on an input set of 3-d points, using the X- and Y-values to position the points on the grid and the Z-value of the points as the surface elevation. There are five interpolation algorithms available: inverse distance, inverse distance nearest-neighbor, moving average, nearest neighbor, and linear interpolation. See the gdal_grid documentation for more details on the algorithms and their parameters. For more information on how interpolations are calculated, see the GDAL grid tutorial.

Input parameters are:

`input_points`

  The points to drive the interpolation. Any geometry with Z-values is acceptable, all points in the input will be used.

`algorithm_options`

  A string defining the algorithm and algorithm options, in the format used by gdal_grid. For example, for an inverse-distance interpolation with a smoothing of 2, you would use "invdist:smoothing=2.0"

`template`

  A raster template to drive the geometry of the output raster. The width, height, pixel size, spatial extent and pixel type will be read from this template.

`template_band_num`

  By default the first band in the template raster is used to drive the output raster, but that can be adjusted with this parameter.

Availability: 3.2.0

## Example

    SELECT ST_InterpolateRaster(
        'MULTIPOINT(10.5 9.5 1000, 11.5 8.5 1000, 10.5 8.5 500, 11.5 9.5 500)'::geometry,
        'invdist:smoothing:2.0',
        ST_AddBand(ST_MakeEmptyRaster(200, 400, 10, 10, 0.01, -0.005, 0, 0), '16BSI')
    )

## See Also

ST_Contour

## Name

UpdateRasterSRID — Change the SRID of all rasters in the user-specified column and table.

## Synopsis

`raster UpdateRasterSRID(` name schema_name, name table_name, name column_name, integer new_srid`)`;

`raster UpdateRasterSRID(` name table_name, name column_name, integer new_srid`)`;

## Description

Change the SRID of all rasters in the user-specified column and table. The function will drop all appropriate column constraints (extent, alignment and SRID) before changing the SRID of the specified column's rasters.

The data (band pixel values) of the rasters are not touched by this function. Only the raster's metadata is changed.

Availability: 2.1.0

## See Also

UpdateGeometrySRID

## Name

ST_CreateOverview — Create an reduced resolution version of a given raster coverage.

## Synopsis

`regclass ST_CreateOverview(` regclass tab, name col, int factor, text algo='NearestNeighbor'`)`;

## Description

Create an overview table with resampled tiles from the source table. Output tiles will have the same size of input tiles and cover the same spatial extent with a lower resolution (pixel size will be 1/`factor` of the original in both directions).

The overview table will be made available in the `raster_overviews` catalog and will have raster constraints enforced.

Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: GDAL Warp resampling methods for more details.

Availability: 2.2.0

## Example

Output to generally better quality but slower to product format

    SELECT ST_CreateOverview('mydata.mytable'::regclass, 'rast', 2, 'Lanczos');

Output to faster to process default nearest neighbor

    SELECT ST_CreateOverview('mydata.mytable'::regclass, 'rast', 2);

## See Also

ST_Retile, AddOverviewConstraints, AddRasterConstraints, Section 10.2.2, “Raster Overviews”

## 11.3. Raster Constructors

## Name

ST_AddBand — Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.

## Synopsis

`(1) raster ST_AddBand(` raster rast, addbandarg[] addbandargset`)`;

`(2) raster ST_AddBand(` raster rast, integer index, text pixeltype, double precision initialvalue=0, double precision nodataval=NULL`)`;

`(3) raster ST_AddBand(` raster rast, text pixeltype, double precision initialvalue=0, double precision nodataval=NULL`)`;

`(4) raster ST_AddBand(` raster torast, raster fromrast, integer fromband=1, integer torastindex=at_end`)`;

`(5) raster ST_AddBand(` raster torast, raster[] fromrasts, integer fromband=1, integer torastindex=at_end`)`;

`(6) raster ST_AddBand(` raster rast, integer index, text outdbfile, integer[] outdbindex, double precision nodataval=NULL`)`;

`(7) raster ST_AddBand(` raster rast, text outdbfile, integer[] outdbindex, integer index=at_end, double precision nodataval=NULL`)`;

## Description

Returns a raster with a new band added in given position (index), of given type, of given initial value, and of given nodata value. If no index is specified, the band is added to the end. If no `fromband` is specified, band 1 is assumed. Pixel type is a string representation of one of the pixel types specified in ST_BandPixelType. If an existing index is specified all subsequent bands >= that index are incremented by 1. If an initial value greater than the max of the pixel type is specified, then the initial value is set to the highest value allowed by the pixel type.

For the variant that takes an array of addbandarg (Variant 1), a specific addbandarg's index value is relative to the raster at the time when the band described by that addbandarg is being added to the raster. See the Multiple New Bands example below.

For the variant that takes an array of rasters (Variant 5), if `torast` is NULL then the `fromband` band of each raster in the array is accumulated into a new raster.

For the variants that take `outdbfile` (Variants 6 and 7), the value must include the full path to the raster file. The file must also be accessible to the postgres server process.

Enhanced: 2.1.0 support for addbandarg added.

Enhanced: 2.1.0 support for new out-db bands added.

## Examples: Single New Band

    -- Add another band of type 8 bit unsigned integer with pixels initialized to 200
    UPDATE dummy_rast
        SET rast = ST_AddBand(rast,'8BUI'::text,200)
    WHERE rid = 1;

    -- Create an empty raster 100x100 units, with upper left  right at 0, add 2 bands (band 1 is 0/1 boolean bit switch, band2 allows values 0-15)
    -- uses addbandargs
    INSERT INTO dummy_rast(rid,rast)
        VALUES(10, ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 1, -1, 0, 0, 0),
        ARRAY[
            ROW(1, '1BB'::text, 0, NULL),
            ROW(2, '4BUI'::text, 0, NULL)
                ]::addbandarg[]
         )
        );

    -- output meta data of raster bands to verify all is right --
    SELECT  (bmd).*
    FROM (SELECT ST_BandMetaData(rast,generate_series(1,2)) As bmd
        FROM dummy_rast WHERE rid = 10) AS foo;
     --result --
     pixeltype | nodatavalue | isoutdb | path
    -----------+----------------+-------------+---------+------
     1BB       |             | f       |
     4BUI      |             | f       |

    -- output meta data of raster -
    SELECT  (rmd).width, (rmd).height, (rmd).numbands
    FROM (SELECT ST_MetaData(rast) As rmd
        FROM dummy_rast WHERE rid = 10) AS foo;
    -- result --
     upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    ------------+------------+-------+--------+------------+------------+-------+-------+------+----------
              0 |          0 |   100 |    100 |      1 |     -1 |     0 |     0 |   0 |        2

## Examples: Multiple New Bands

    SELECT
        *
    FROM ST_BandMetadata(
        ST_AddBand(
            ST_MakeEmptyRaster(10, 10, 0, 0, 1, -1, 0, 0, 0),
            ARRAY[
                ROW(NULL, '8BUI', 255, 0),
                ROW(NULL, '16BUI', 1, 2),
                ROW(2, '32BUI', 100, 12),
                ROW(2, '32BF', 3.14, -1)
            ]::addbandarg[]
        ),
        ARRAY[]::integer[]
    );

     bandnum | pixeltype | nodatavalue | isoutdb | path
    ---------+-----------+-------------+---------+------
           1 | 8BUI      |           0 | f       |
           2 | 32BF      |          -1 | f       |
           3 | 32BUI     |          12 | f       |
           4 | 16BUI     |           2 | f       |

    -- Aggregate the 1st band of a table of like rasters into a single raster
    -- with as many bands as there are test_types and as many rows (new rasters) as there are mice
    -- NOTE: The ORDER BY test_type is only supported in PostgreSQL 9.0+
    -- for 8.4 and below it usually works to order your data in a subselect (but not guaranteed)
    -- The resulting raster will have a band for each test_type alphabetical by test_type
    -- For mouse lovers: No mice were harmed in this exercise
    SELECT
        mouse,
        ST_AddBand(NULL, array_agg(rast ORDER BY test_type), 1) As rast
    FROM mice_studies
    GROUP BY mouse;

## Examples: New Out-db band

    SELECT
        *
    FROM ST_BandMetadata(
        ST_AddBand(
            ST_MakeEmptyRaster(10, 10, 0, 0, 1, -1, 0, 0, 0),
            '/home/raster/mytestraster.tif'::text, NULL::int[]
        ),
        ARRAY[]::integer[]
    );

     bandnum | pixeltype | nodatavalue | isoutdb | path
    ---------+-----------+-------------+---------+------
           1 | 8BUI      |             | t       | /home/raster/mytestraster.tif
           2 | 8BUI      |             | t       | /home/raster/mytestraster.tif
           3 | 8BUI      |             | t       | /home/raster/mytestraster.tif

## See Also

ST_BandMetaData, ST_BandPixelType, ST_MakeEmptyRaster, ST_MetaData, ST_NumBands, ST_Reclass

## Name

ST_AsRaster — Converts a PostGIS geometry to a PostGIS raster.

## Synopsis

`raster ST_AsRaster(` geometry geom, raster ref, text pixeltype, double precision value=1, double precision nodataval=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, raster ref, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, double precision scalex, double precision scaley, double precision gridx, double precision gridy, text pixeltype, double precision value=1, double precision nodataval=0, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, double precision scalex, double precision scaley, double precision gridx=NULL, double precision gridy=NULL, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, double precision scalex, double precision scaley, text pixeltype, double precision value=1, double precision nodataval=0, double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, double precision scalex, double precision scaley, text[] pixeltype, double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, integer width, integer height, double precision gridx, double precision gridy, text pixeltype, double precision value=1, double precision nodataval=0, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, integer width, integer height, double precision gridx=NULL, double precision gridy=NULL, text[] pixeltype=ARRAY['8BUI'], double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, integer width, integer height, text pixeltype, double precision value=1, double precision nodataval=0, double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

`raster ST_AsRaster(` geometry geom, integer width, integer height, text[] pixeltype, double precision[] value=ARRAY[1], double precision[] nodataval=ARRAY[0], double precision upperleftx=NULL, double precision upperlefty=NULL, double precision skewx=0, double precision skewy=0, boolean touched=false`)`;

## Description

Converts a PostGIS geometry to a PostGIS raster. The many variants offers three groups of possibilities for setting the alignment and pixelsize of the resulting raster.

The first group, composed of the two first variants, produce a raster having the same alignment (`scalex`, `scaley`, `gridx` and `gridy`), pixel type and nodata value as the provided reference raster. You generally pass this reference raster by joining the table containing the geometry with the table containing the reference raster.

The second group, composed of four variants, let you set the dimensions of the raster by providing the parameters of a pixel size (`scalex` & `scaley` and `skewx` & `skewy`). The `width` & `height` of the resulting raster will be adjusted to fit the extent of the geometry. In most cases, you must cast integer `scalex` & `scaley` arguments to double precision so that PostgreSQL choose the right variant.

The third group, composed of four variants, let you fix the dimensions of the raster by providing the dimensions of the raster (`width` & `height`). The parameters of the pixel size (`scalex` & `scaley` and `skewx` & `skewy`) of the resulting raster will be adjusted to fit the extent of the geometry.

The two first variants of each of those two last groups let you specify the alignment with an arbitrary corner of the alignment grid (`gridx` & `gridy`) and the two last variants takes the upper left corner (`upperleftx` & `upperlefty`).

Each group of variant allows producing a one band raster or a multiple bands raster. To produce a multiple bands raster, you must provide an array of pixel types (`pixeltype[]`), an array of initial values (`value`) and an array of nodata values (`nodataval`). If not provided pixeltyped defaults to 8BUI, values to 1 and nodataval to 0.

The output raster will be in the same spatial reference as the source geometry. The only exception is for variants with a reference raster. In this case the resulting raster will get the same SRID as the reference raster.

The optional `touched` parameter defaults to false and maps to the GDAL ALL_TOUCHED rasterization option, which determines if pixels touched by lines or polygons will be burned. Not just those on the line render path, or whose center point is within the polygon.

This is particularly useful for rendering jpegs and pngs of geometries directly from the database when using in combination with ST_AsPNG and other ST_AsGDALRaster family of functions.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

Not yet capable of rendering complex geometry types such as curves, TINS, and PolyhedralSurfaces, but should be able too once GDAL can.

## Examples: Output geometries as PNG files

black circle

    -- this will output a black circle taking up 150 x 150 pixels --
    SELECT ST_AsPNG(ST_AsRaster(ST_Buffer(ST_Point(1,5),10),150, 150));

example from buffer rendered with just PostGIS

    -- the bands map to RGB bands - the value (118,154,118) - teal  --
    SELECT ST_AsPNG(
        ST_AsRaster(
            ST_Buffer(
                ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 10,'join=bevel'),
                200,200,ARRAY['8BUI', '8BUI', '8BUI'], ARRAY[118,154,118], ARRAY[0,0,0]));

## See Also

ST_BandPixelType, ST_Buffer, ST_GDALDrivers, ST_AsGDALRaster, ST_AsPNG, ST_AsJPEG, ST_SRID

## Name

ST_Band — Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.

## Synopsis

`raster ST_Band(` raster rast, integer[] nbands = ARRAY[1]`)`;

`raster ST_Band(` raster rast, integer nband`)`;

`raster ST_Band(` raster rast, text nbands, character delimiter=,`)`;

## Description

Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters or export of only selected bands of a raster or rearranging the order of bands in a raster. If no band is specified or any of specified bands does not exist in the raster, then all bands are returned. Used as a helper function in various functions such as for deleting a band.

For the `nbands` as text variant of function, the default delimiter is `,` which means you can ask for `'1,2,3'` and if you wanted to use a different delimiter you would do `ST_Band(rast, '1@2@3', '@')`. For asking for multiple bands, we strongly suggest you use the array form of this function e.g. `ST_Band(rast, '{1,2,3}'::int[]);` since the `text` list of bands form may be removed in future versions of PostGIS.

Availability: 2.0.0

## Examples

    -- Make 2 new rasters: 1 containing band 1 of dummy, second containing band 2 of dummy and then reclassified as a 2BUI
    SELECT ST_NumBands(rast1) As numb1, ST_BandPixelType(rast1) As pix1,
     ST_NumBands(rast2) As numb2,  ST_BandPixelType(rast2) As pix2
    FROM (
        SELECT ST_Band(rast) As rast1, ST_Reclass(ST_Band(rast,3), '100-200):1, [200-254:2', '2BUI') As rast2
            FROM dummy_rast
            WHERE rid = 2) As foo;

     numb1 | pix1 | numb2 | pix2
    -------+------+-------+------
         1 | 8BUI |     1 | 2BUI

    -- Return bands 2 and 3. Using array cast syntax
    SELECT ST_NumBands(ST_Band(rast, '{2,3}'::int[])) As num_bands
        FROM dummy_rast WHERE rid=2;

    num_bands
    ----------
    2

    -- Return bands 2 and 3. Use array to define bands
    SELECT ST_NumBands(ST_Band(rast, ARRAY[2,3])) As num_bands
        FROM dummy_rast
    WHERE rid=2;

original (column rast) | dupe_band | sing_band

    --Make a new raster with 2nd band of original and 1st band repeated twice,
    and another with just the third band
    SELECT rast, ST_Band(rast, ARRAY[2,1,1]) As dupe_band,
        ST_Band(rast, 3) As sing_band
    FROM samples.than_chunked
    WHERE rid=35;

## See Also

ST_AddBand, ST_NumBands, ST_Reclass, Chapter 11, Raster Reference

## Name

ST_MakeEmptyCoverage — Cover georeferenced area with a grid of empty raster tiles.

## Synopsis

`raster ST_MakeEmptyCoverage(` integer tilewidth, integer tileheight, integer width, integer height, double precision upperleftx, double precision upperlefty, double precision scalex, double precision scaley, double precision skewx, double precision skewy, integer srid=unknown`)`;

## Description

Create a set of raster tiles with ST_MakeEmptyRaster. Grid dimension is `width` & `height`. Tile dimension is `tilewidth` & `tileheight`. The covered georeferenced area is from upper left corner (`upperleftx`, `upperlefty`) to lower right corner (`upperleftx` + `width` * `scalex`, `upperlefty` + `height` * `scaley`).

Note that scaley is generally negative for rasters and scalex is generally positive. So lower right corner will have a lower y value and higher x value than the upper left corner.

Availability: 2.4.0

## Examples Basic

Create 16 tiles in a 4x4 grid to cover the WGS84 area from upper left corner (22, 77) to lower right corner (55, 33).

    SELECT (ST_MetaData(tile)).* FROM ST_MakeEmptyCoverage(1, 1, 4, 4, 22, 33, (55 - 22)/(4)::float, (33 - 77)/(4)::float, 0., 0., 4326) tile;

     upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    -------------------------------------------------------------------------------------
             22 |         33 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          30.25 |         33 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
           38.5 |         33 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          46.75 |         33 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
             22 |         22 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          30.25 |         22 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
           38.5 |         22 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          46.75 |         22 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
             22 |         11 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          30.25 |         11 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
           38.5 |         11 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          46.75 |         11 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
             22 |          0 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          30.25 |          0 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
           38.5 |          0 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0
          46.75 |          0 |     1 |      1 |   8.25 |    -11 |     0 |     0 | 4326 |        0

## See Also

ST_MakeEmptyRaster

## Name

ST_MakeEmptyRaster — Returns an empty raster (having no bands) of given dimensions (width & height), upperleft X and Y, pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid). If a raster is passed in, returns a new raster with the same size, alignment and SRID. If srid is left out, the spatial ref is set to unknown (0).

## Synopsis

`raster ST_MakeEmptyRaster(` raster rast`)`;

`raster ST_MakeEmptyRaster(` integer width, integer height, float8 upperleftx, float8 upperlefty, float8 scalex, float8 scaley, float8 skewx, float8 skewy, integer srid=unknown`)`;

`raster ST_MakeEmptyRaster(` integer width, integer height, float8 upperleftx, float8 upperlefty, float8 pixelsize`)`;

## Description

Returns an empty raster (having no band) of given dimensions (width & height) and georeferenced in spatial (or world) coordinates with upper left X (upperleftx), upper left Y (upperlefty), pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid).

The last version use a single parameter to specify the pixel size (pixelsize). scalex is set to this argument and scaley is set to the negative value of this argument. skewx and skewy are set to 0.

If an existing raster is passed in, it returns a new raster with the same meta data settings (without the bands).

If no srid is specified it defaults to 0. After you create an empty raster you probably want to add bands to it and maybe edit it. Refer to ST_AddBand to define bands and ST_SetValue to set initial pixel values.

## Examples

    INSERT INTO dummy_rast(rid,rast)
    VALUES(3, ST_MakeEmptyRaster( 100, 100, 0.0005, 0.0005, 1, 1, 0, 0, 4326) );

    --use an existing raster as template for new raster
    INSERT INTO dummy_rast(rid,rast)
    SELECT 4, ST_MakeEmptyRaster(rast)
    FROM dummy_rast WHERE rid = 3;

    -- output meta data of rasters we just added
    SELECT rid, (md).*
    FROM (SELECT rid, ST_MetaData(rast) As md
        FROM dummy_rast
        WHERE rid IN(3,4)) As foo;

    -- output --
     rid | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    -----+------------+------------+-------+--------+------------+------------+-------+-------+------+----------
       3 |     0.0005 |     0.0005 |   100 |    100 |          1 |          1 |    0  |     0 | 4326 |        0
       4 |     0.0005 |     0.0005 |   100 |    100 |          1 |          1 |    0  |     0 | 4326 |        0

## See Also

ST_AddBand, ST_MetaData, ST_ScaleX, ST_ScaleY, ST_SetValue, ST_SkewX, , ST_SkewY

## Name

ST_Tile — Returns a set of rasters resulting from the split of the input raster based upon the desired dimensions of the output rasters.

## Synopsis

`setof raster ST_Tile(` raster rast, int[] nband, integer width, integer height, boolean padwithnodata=FALSE, double precision nodataval=NULL`)`;

`setof raster ST_Tile(` raster rast, integer nband, integer width, integer height, boolean padwithnodata=FALSE, double precision nodataval=NULL`)`;

`setof raster ST_Tile(` raster rast, integer width, integer height, boolean padwithnodata=FALSE, double precision nodataval=NULL`)`;

## Description

Returns a set of rasters resulting from the split of the input raster based upon the desired dimensions of the output rasters.

If `padwithnodata` = FALSE, edge tiles on the right and bottom sides of the raster may have different dimensions than the rest of the tiles. If `padwithnodata` = TRUE, all tiles will have the same dimensions with the possibility that edge tiles being padded with NODATA values. If raster band(s) do not have NODATA value(s) specified, one can be specified by setting `nodataval`.

If a specified band of the input raster is out-of-db, the corresponding band in the output rasters will also be out-of-db.

Availability: 2.1.0

## Examples

    WITH foo AS (
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 1, 0), 2, '8BUI', 10, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, 0, 1, -1, 0, 0, 0), 1, '8BUI', 2, 0), 2, '8BUI', 20, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, 0, 1, -1, 0, 0, 0), 1, '8BUI', 3, 0), 2, '8BUI', 30, 0) AS rast UNION ALL

        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, -3, 1, -1, 0, 0, 0), 1, '8BUI', 4, 0), 2, '8BUI', 40, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, -3, 1, -1, 0, 0, 0), 1, '8BUI', 5, 0), 2, '8BUI', 50, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, -3, 1, -1, 0, 0, 0), 1, '8BUI', 6, 0), 2, '8BUI', 60, 0) AS rast UNION ALL

        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, -6, 1, -1, 0, 0, 0), 1, '8BUI', 7, 0), 2, '8BUI', 70, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, -6, 1, -1, 0, 0, 0), 1, '8BUI', 8, 0), 2, '8BUI', 80, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, -6, 1, -1, 0, 0, 0), 1, '8BUI', 9, 0), 2, '8BUI', 90, 0) AS rast
    ), bar AS (
        SELECT ST_Union(rast) AS rast FROM foo
    ), baz AS (
        SELECT ST_Tile(rast, 3, 3, TRUE) AS rast FROM bar
    )
    SELECT
        ST_DumpValues(rast)
    FROM baz;

                  st_dumpvalues
    ------------------------------------------
     (1,"{{1,1,1},{1,1,1},{1,1,1}}")
     (2,"{{10,10,10},{10,10,10},{10,10,10}}")
     (1,"{{2,2,2},{2,2,2},{2,2,2}}")
     (2,"{{20,20,20},{20,20,20},{20,20,20}}")
     (1,"{{3,3,3},{3,3,3},{3,3,3}}")
     (2,"{{30,30,30},{30,30,30},{30,30,30}}")
     (1,"{{4,4,4},{4,4,4},{4,4,4}}")
     (2,"{{40,40,40},{40,40,40},{40,40,40}}")
     (1,"{{5,5,5},{5,5,5},{5,5,5}}")
     (2,"{{50,50,50},{50,50,50},{50,50,50}}")
     (1,"{{6,6,6},{6,6,6},{6,6,6}}")
     (2,"{{60,60,60},{60,60,60},{60,60,60}}")
     (1,"{{7,7,7},{7,7,7},{7,7,7}}")
     (2,"{{70,70,70},{70,70,70},{70,70,70}}")
     (1,"{{8,8,8},{8,8,8},{8,8,8}}")
     (2,"{{80,80,80},{80,80,80},{80,80,80}}")
     (1,"{{9,9,9},{9,9,9},{9,9,9}}")
     (2,"{{90,90,90},{90,90,90},{90,90,90}}")
    (18 rows)

    WITH foo AS (
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 1, 0), 2, '8BUI', 10, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, 0, 1, -1, 0, 0, 0), 1, '8BUI', 2, 0), 2, '8BUI', 20, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, 0, 1, -1, 0, 0, 0), 1, '8BUI', 3, 0), 2, '8BUI', 30, 0) AS rast UNION ALL

        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, -3, 1, -1, 0, 0, 0), 1, '8BUI', 4, 0), 2, '8BUI', 40, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, -3, 1, -1, 0, 0, 0), 1, '8BUI', 5, 0), 2, '8BUI', 50, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, -3, 1, -1, 0, 0, 0), 1, '8BUI', 6, 0), 2, '8BUI', 60, 0) AS rast UNION ALL

        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, -6, 1, -1, 0, 0, 0), 1, '8BUI', 7, 0), 2, '8BUI', 70, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 3, -6, 1, -1, 0, 0, 0), 1, '8BUI', 8, 0), 2, '8BUI', 80, 0) AS rast UNION ALL
        SELECT ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 6, -6, 1, -1, 0, 0, 0), 1, '8BUI', 9, 0), 2, '8BUI', 90, 0) AS rast
    ), bar AS (
        SELECT ST_Union(rast) AS rast FROM foo
    ), baz AS (
        SELECT ST_Tile(rast, 3, 3, 2) AS rast FROM bar
    )
    SELECT
        ST_DumpValues(rast)
    FROM baz;

                  st_dumpvalues
    ------------------------------------------
     (1,"{{10,10,10},{10,10,10},{10,10,10}}")
     (1,"{{20,20,20},{20,20,20},{20,20,20}}")
     (1,"{{30,30,30},{30,30,30},{30,30,30}}")
     (1,"{{40,40,40},{40,40,40},{40,40,40}}")
     (1,"{{50,50,50},{50,50,50},{50,50,50}}")
     (1,"{{60,60,60},{60,60,60},{60,60,60}}")
     (1,"{{70,70,70},{70,70,70},{70,70,70}}")
     (1,"{{80,80,80},{80,80,80},{80,80,80}}")
     (1,"{{90,90,90},{90,90,90},{90,90,90}}")
    (9 rows)

## See Also

ST_Union, ST_Retile

## Name

ST_Retile — Return a set of configured tiles from an arbitrarily tiled raster coverage.

## Synopsis

`SETOF raster ST_Retile(` regclass tab, name col, geometry ext, float8 sfx, float8 sfy, int tw, int th, text algo='NearestNeighbor'`)`;

## Description

Return a set of tiles having the specified scale (`sfx`, `sfy`) and max size (`tw`, `th`) and covering the specified extent (`ext`) with data coming from the specified raster coverage (`tab`, `col`).

Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: GDAL Warp resampling methods for more details.

Availability: 2.2.0

## See Also

ST_CreateOverview

## Name

ST_FromGDALRaster — Returns a raster from a supported GDAL raster file.

## Synopsis

`raster ST_FromGDALRaster(` bytea gdaldata, integer srid=NULL`)`;

## Description

Returns a raster from a supported GDAL raster file. `gdaldata` is of type bytea and should be the contents of the GDAL raster file.

If `srid` is NULL, the function will try to automatically assign the SRID from the GDAL raster. If `srid` is provided, the value provided will override any automatically assigned SRID.

Availability: 2.1.0

## Examples

    WITH foo AS (
        SELECT ST_AsPNG(ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 0.1, -0.1, 0, 0, 4326), 1, '8BUI', 1, 0), 2, '8BUI', 2, 0), 3, '8BUI', 3, 0)) AS png
    ),
    bar AS (
        SELECT 1 AS rid, ST_FromGDALRaster(png) AS rast FROM foo
        UNION ALL
        SELECT 2 AS rid, ST_FromGDALRaster(png, 3310) AS rast FROM foo
    )
    SELECT
        rid,
        ST_Metadata(rast) AS metadata,
        ST_SummaryStats(rast, 1) AS stats1,
        ST_SummaryStats(rast, 2) AS stats2,
        ST_SummaryStats(rast, 3) AS stats3
    FROM bar
    ORDER BY rid;

     rid |         metadata          |    stats1     |    stats2     |     stats3
    -----+---------------------------+---------------+---------------+----------------
       1 | (0,0,2,2,1,-1,0,0,0,3)    | (4,4,1,0,1,1) | (4,8,2,0,2,2) | (4,12,3,0,3,3)
       2 | (0,0,2,2,1,-1,0,0,3310,3) | (4,4,1,0,1,1) | (4,8,2,0,2,2) | (4,12,3,0,3,3)
    (2 rows)

## See Also

ST_AsGDALRaster

## 11.4. Raster Accessors

## Name

ST_GeoReference — Returns the georeference meta data in GDAL or ESRI format as commonly seen in a world file. Default is GDAL.

## Synopsis

`text ST_GeoReference(` raster rast, text format=GDAL`)`;

## Description

Returns the georeference meta data including carriage return in GDAL or ESRI format as commonly seen in a world file. Default is GDAL if no type specified. type is string 'GDAL' or 'ESRI'.

Difference between format representations is as follows:

`GDAL`:

    scalex
    skewy
    skewx
    scaley
    upperleftx
    upperlefty

`ESRI`:

    scalex
    skewy
    skewx
    scaley
    upperleftx + scalex*0.5
    upperlefty + scaley*0.5

## Examples

    SELECT ST_GeoReference(rast, 'ESRI') As esri_ref, ST_GeoReference(rast, 'GDAL') As gdal_ref
     FROM dummy_rast WHERE rid=1;

       esri_ref   |   gdal_ref
    --------------+--------------
     2.0000000000 | 2.0000000000
     0.0000000000 : 0.0000000000
     0.0000000000 : 0.0000000000
     3.0000000000 : 3.0000000000
     1.5000000000 : 0.5000000000
     2.0000000000 : 0.5000000000

## See Also

ST_SetGeoReference, ST_ScaleX, ST_ScaleY

## Name

ST_Height — Returns the height of the raster in pixels.

## Synopsis

`integer ST_Height(` raster rast`)`;

## Description

Returns the height of the raster.

## Examples

    SELECT rid, ST_Height(rast) As rastheight
    FROM dummy_rast;

     rid | rastheight
    -----+------------
       1 |         20
       2 |          5

## See Also

ST_Width

## Name

ST_IsEmpty — Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.

## Synopsis

`boolean ST_IsEmpty(` raster rast`)`;

## Description

Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.

Availability: 2.0.0

## Examples

    SELECT ST_IsEmpty(ST_MakeEmptyRaster(100, 100, 0, 0, 0, 0, 0, 0))
    st_isempty |
    -----------+
    f          |

    SELECT ST_IsEmpty(ST_MakeEmptyRaster(0, 0, 0, 0, 0, 0, 0, 0))
    st_isempty |
    -----------+
    t          |

## See Also

ST_HasNoBand

## Name

ST_MemSize — Returns the amount of space (in bytes) the raster takes.

## Synopsis

`integer ST_MemSize(` raster rast`)`;

## Description

Returns the amount of space (in bytes) the raster takes.

This is a nice compliment to PostgreSQL built in functions pg_column_size, pg_size_pretty, pg_relation_size, pg_total_relation_size.

pg_relation_size which gives the byte size of a table may return byte size lower than ST_MemSize. This is because pg_relation_size does not add toasted table contribution and large geometries are stored in TOAST tables. pg_column_size might return lower because it returns the compressed size. pg_total_relation_size - includes, the table, the toasted tables, and the indexes.

Availability: 2.2.0

## Examples

            SELECT ST_MemSize(ST_AsRaster(ST_Buffer(ST_Point(1,5),10,1000),150, 150, '8BUI')) As rast_mem;

            rast_mem
            --------
            22568

## See Also

## Name

ST_MetaData — Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc.

## Synopsis

`record ST_MetaData(` raster rast`)`;

## Description

Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc. Columns returned: upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands

## Examples

    SELECT rid, (foo.md).*
     FROM (SELECT rid, ST_MetaData(rast) As md
    FROM dummy_rast) As foo;

     rid | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
     ----+------------+------------+-------+--------+--------+-----------+-------+-------+------+-------
       1 |        0.5 |        0.5 |    10 |     20 |      2 |      3 |     0 |     0 |    0 |        0
       2 | 3427927.75 |    5793244 |     5 |      5 |   0.05 |  -0.05 |     0 |     0 |    0 |        3

## See Also

ST_BandMetaData, ST_NumBands

## Name

ST_NumBands — Returns the number of bands in the raster object.

## Synopsis

`integer ST_NumBands(` raster rast`)`;

## Description

Returns the number of bands in the raster object.

## Examples

    SELECT rid, ST_NumBands(rast) As numbands
    FROM dummy_rast;

    rid | numbands
    ----+----------
      1 |        0
      2 |        3

## See Also

ST_Value

## Name

ST_PixelHeight — Returns the pixel height in geometric units of the spatial reference system.

## Synopsis

`double precision ST_PixelHeight(` raster rast`)`;

## Description

Returns the height of a pixel in geometric units of the spatial reference system. In the common case where there is no skew, the pixel height is just the scale ratio between geometric coordinates and raster pixels.

Refer to ST_PixelWidth for a diagrammatic visualization of the relationship.

## Examples: Rasters with no skew

    SELECT ST_Height(rast) As rastheight, ST_PixelHeight(rast) As pixheight,
     ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
            ST_SkewY(rast) As skewy
    FROM dummy_rast;

     rastheight | pixheight | scalex | scaley | skewx | skewy
    ------------+-----------+--------+--------+-------+----------
             20 |         3 |      2 |      3 |     0 |        0
              5 |      0.05 |   0.05 |  -0.05 |     0 |        0

## Examples: Rasters with skew different than 0

    SELECT ST_Height(rast) As rastheight, ST_PixelHeight(rast) As pixheight,
     ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
            ST_SkewY(rast) As skewy
    FROM (SELECT ST_SetSKew(rast,0.5,0.5) As rast
            FROM dummy_rast) As skewed;

    rastheight |     pixheight     | scalex | scaley | skewx | skewy
    -----------+-------------------+--------+--------+-------+----------
            20 |  3.04138126514911 |      2 |      3 |   0.5 |      0.5
             5 | 0.502493781056044 |   0.05 |  -0.05 |   0.5 |      0.5

## See Also

ST_PixelWidth, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_PixelWidth — Returns the pixel width in geometric units of the spatial reference system.

## Synopsis

`double precision ST_PixelWidth(` raster rast`)`;

## Description

Returns the width of a pixel in geometric units of the spatial reference system. In the common case where there is no skew, the pixel width is just the scale ratio between geometric coordinates and raster pixels.

The following diagram demonstrates the relationship:

Pixel Width: Pixel size in the i direction

Pixel Height: Pixel size in the j direction

## Examples: Rasters with no skew

    SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
        ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
        ST_SkewY(rast) As skewy
        FROM dummy_rast;

        rastwidth | pixwidth | scalex | scaley | skewx | skewy
        -----------+----------+--------+--------+-------+----------
        10 |        2 |      2 |      3 |     0 |        0
         5 |     0.05 |   0.05 |  -0.05 |     0 |        0

## Examples: Rasters with skew different than 0

    SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
        ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
        ST_SkewY(rast) As skewy
        FROM (SELECT ST_SetSkew(rast,0.5,0.5) As rast
        FROM dummy_rast) As skewed;

        rastwidth |     pixwidth      | scalex | scaley | skewx | skewy
        -----------+-------------------+--------+--------+-------+----------
        10 |  2.06155281280883 |      2 |      3 |   0.5 |      0.5
         5 | 0.502493781056044 |   0.05 |  -0.05 |   0.5 |      0.5

## See Also

ST_PixelHeight, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_ScaleX — Returns the X component of the pixel width in units of coordinate reference system.

## Synopsis

`float8 ST_ScaleX(` raster rast`)`;

## Description

Returns the X component of the pixel width in units of coordinate reference system. Refer to World File for more details.

Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeX.

## Examples

    SELECT rid, ST_ScaleX(rast) As rastpixwidth
    FROM dummy_rast;

     rid | rastpixwidth
    -----+--------------
       1 |            2
       2 |         0.05

## See Also

ST_Width

## Name

ST_ScaleY — Returns the Y component of the pixel height in units of coordinate reference system.

## Synopsis

`float8 ST_ScaleY(` raster rast`)`;

## Description

Returns the Y component of the pixel height in units of coordinate reference system. May be negative. Refer to World File for more details.

Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeY.

## Examples

    SELECT rid, ST_ScaleY(rast) As rastpixheight
    FROM dummy_rast;

     rid | rastpixheight
    -----+---------------
       1 |             3
       2 |         -0.05

## See Also

ST_Height

## Name

ST_RasterToWorldCoord — Returns the raster's upper left corner as geometric X and Y (longitude and latitude) given a column and row. Column and row starts at 1.

## Synopsis

`record ST_RasterToWorldCoord(` raster rast, integer xcolumn, integer yrow`)`;

## Description

Returns the upper left corner as geometric X and Y (longitude and latitude) given a column and row. Returned X and Y are in geometric units of the georeferenced raster. Numbering of column and row starts at 1 but if either parameter is passed a zero, a negative number or a number greater than the respective dimension of the raster, it will return coordinates outside of the raster assuming the raster's grid is applicable outside the raster's bounds.

Availability: 2.1.0

## Examples

    -- non-skewed raster
    SELECT
        rid,
        (ST_RasterToWorldCoord(rast,1, 1)).*,
        (ST_RasterToWorldCoord(rast,2, 2)).*
    FROM dummy_rast

     rid | longitude  | latitude | longitude |  latitude
    -----+------------+----------+-----------+------------
       1 |        0.5 |      0.5 |       2.5 |        3.5
       2 | 3427927.75 |  5793244 | 3427927.8 | 5793243.95

    -- skewed raster
    SELECT
        rid,
        (ST_RasterToWorldCoord(rast, 1, 1)).*,
        (ST_RasterToWorldCoord(rast, 2, 3)).*
    FROM (
        SELECT
            rid,
            ST_SetSkew(rast, 100.5, 0) As rast
        FROM dummy_rast
    ) As foo

     rid | longitude  | latitude | longitude | latitude
    -----+------------+----------+-----------+-----------
       1 |        0.5 |      0.5 |     203.5 |       6.5
       2 | 3427927.75 |  5793244 | 3428128.8 | 5793243.9

## See Also

ST_RasterToWorldCoordX, ST_RasterToWorldCoordY, ST_SetSkew

## Name

ST_RasterToWorldCoordX — Returns the geometric X coordinate upper left of a raster, column and row. Numbering of columns and rows starts at 1.

## Synopsis

`float8 ST_RasterToWorldCoordX(` raster rast, integer xcolumn`)`;

`float8 ST_RasterToWorldCoordX(` raster rast, integer xcolumn, integer yrow`)`;

## Description

Returns the upper left X coordinate of a raster column row in geometric units of the georeferenced raster. Numbering of columns and rows starts at 1 but if you pass in a negative number or number higher than number of columns in raster, it will give you coordinates outside of the raster file to left or right with the assumption that the skew and pixel sizes are same as selected raster.

For non-skewed rasters, providing the X column is sufficient. For skewed rasters, the georeferenced coordinate is a function of the ST_ScaleX and ST_SkewX and row and column. An error will be raised if you give just the X column for a skewed raster.

Changed: 2.1.0 In prior versions, this was called ST_Raster2WorldCoordX

## Examples

    -- non-skewed raster providing column is sufficient
    SELECT rid, ST_RasterToWorldCoordX(rast,1) As x1coord,
        ST_RasterToWorldCoordX(rast,2) As x2coord,
        ST_ScaleX(rast) As pixelx
    FROM dummy_rast;

     rid |  x1coord   |  x2coord  | pixelx
    -----+------------+-----------+--------
       1 |        0.5 |       2.5 |      2
       2 | 3427927.75 | 3427927.8 |   0.05

    -- for fun lets skew it
    SELECT rid, ST_RasterToWorldCoordX(rast, 1, 1) As x1coord,
        ST_RasterToWorldCoordX(rast, 2, 3) As x2coord,
        ST_ScaleX(rast) As pixelx
    FROM (SELECT rid, ST_SetSkew(rast, 100.5, 0) As rast FROM dummy_rast) As foo;

     rid |  x1coord   |  x2coord  | pixelx
    -----+------------+-----------+--------
       1 |        0.5 |     203.5 |      2
       2 | 3427927.75 | 3428128.8 |   0.05

## See Also

ST_ScaleX, ST_RasterToWorldCoordY, ST_SetSkew, ST_SkewX

## Name

ST_RasterToWorldCoordY — Returns the geometric Y coordinate upper left corner of a raster, column and row. Numbering of columns and rows starts at 1.

## Synopsis

`float8 ST_RasterToWorldCoordY(` raster rast, integer yrow`)`;

`float8 ST_RasterToWorldCoordY(` raster rast, integer xcolumn, integer yrow`)`;

## Description

Returns the upper left Y coordinate of a raster column row in geometric units of the georeferenced raster. Numbering of columns and rows starts at 1 but if you pass in a negative number or number higher than number of columns/rows in raster, it will give you coordinates outside of the raster file to left or right with the assumption that the skew and pixel sizes are same as selected raster tile.

For non-skewed rasters, providing the Y column is sufficient. For skewed rasters, the georeferenced coordinate is a function of the ST_ScaleY and ST_SkewY and row and column. An error will be raised if you give just the Y row for a skewed raster.

Changed: 2.1.0 In prior versions, this was called ST_Raster2WorldCoordY

## Examples

    -- non-skewed raster providing row is sufficient
    SELECT rid, ST_RasterToWorldCoordY(rast,1) As y1coord,
        ST_RasterToWorldCoordY(rast,3) As y2coord,
        ST_ScaleY(rast) As pixely
    FROM dummy_rast;

     rid | y1coord |  y2coord  | pixely
    -----+---------+-----------+--------
       1 |     0.5 |       6.5 |      3
       2 | 5793244 | 5793243.9 |  -0.05

    -- for fun lets skew it
    SELECT rid, ST_RasterToWorldCoordY(rast,1,1) As y1coord,
        ST_RasterToWorldCoordY(rast,2,3) As y2coord,
        ST_ScaleY(rast) As pixely
    FROM (SELECT rid, ST_SetSkew(rast,0,100.5) As rast FROM dummy_rast) As foo;

     rid | y1coord |  y2coord  | pixely
    -----+---------+-----------+--------
       1 |     0.5 |       107 |      3
       2 | 5793244 | 5793344.4 |  -0.05

## See Also

ST_ScaleY, ST_RasterToWorldCoordX, ST_SetSkew, ST_SkewY

## Name

ST_Rotation — Returns the rotation of the raster in radian.

## Synopsis

`float8 ST_Rotation(` raster rast`)`;

## Description

Returns the uniform rotation of the raster in radian. If a raster does not have uniform rotation, NaN is returned. Refer to World File for more details.

## Examples

    SELECT rid, ST_Rotation(ST_SetScale(ST_SetSkew(rast, sqrt(2)), sqrt(2))) as rot FROM dummy_rast;

     rid |        rot
    -----+-------------------
       1 | 0.785398163397448
       2 | 0.785398163397448

## See Also

ST_SetRotation, ST_SetScale, ST_SetSkew

## Name

ST_SkewX — Returns the georeference X skew (or rotation parameter).

## Synopsis

`float8 ST_SkewX(` raster rast`)`;

## Description

Returns the georeference X skew (or rotation parameter). Refer to World File for more details.

## Examples

    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast;

     rid | skewx | skewy |       georef
    -----+-------+-------+--------------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000
                         :
       2 |     0 |     0 | 0.0500000000
                         : 0.0000000000
                         : 0.0000000000
                         : -0.0500000000
                         : 3427927.7500000000
                         : 5793244.0000000000

## See Also

ST_GeoReference, ST_SkewY, ST_SetSkew

## Name

ST_SkewY — Returns the georeference Y skew (or rotation parameter).

## Synopsis

`float8 ST_SkewY(` raster rast`)`;

## Description

Returns the georeference Y skew (or rotation parameter). Refer to World File for more details.

## Examples

    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast;

     rid | skewx | skewy |       georef
    -----+-------+-------+--------------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000
                         :
       2 |     0 |     0 | 0.0500000000
                         : 0.0000000000
                         : 0.0000000000
                         : -0.0500000000
                         : 3427927.7500000000
                         : 5793244.0000000000

## See Also

ST_GeoReference, ST_SkewX, ST_SetSkew

## Name

ST_SRID — Returns the spatial reference identifier of the raster as defined in spatial_ref_sys table.

## Synopsis

`integer ST_SRID(` raster rast`)`;

## Description

Returns the spatial reference identifier of the raster object as defined in the spatial_ref_sys table.

From PostGIS 2.0+ the srid of a non-georeferenced raster/geometry is 0 instead of the prior -1.

## Examples

    SELECT ST_SRID(rast) As srid
    FROM dummy_rast WHERE rid=1;

    srid
    ----------------
    0

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SRID

## Name

ST_Summary — Returns a text summary of the contents of the raster.

## Synopsis

`text ST_Summary(` raster rast`)`;

## Description

Returns a text summary of the contents of the raster.

Availability: 2.1.0

## Examples

    SELECT ST_Summary(
        ST_AddBand(
            ST_AddBand(
                ST_AddBand(
                    ST_MakeEmptyRaster(10, 10, 0, 0, 1, -1, 0, 0, 0)
                    , 1, '8BUI', 1, 0
                )
                , 2, '32BF', 0, -9999
            )
            , 3, '16BSI', 0, NULL
        )
    );

                                st_summary
    ------------------------------------------------------------------
     Raster of 10x10 pixels has 3 bands and extent of BOX(0 -10,10 0)+
         band 1 of pixtype 8BUI is in-db with NODATA value of 0      +
         band 2 of pixtype 32BF is in-db with NODATA value of -9999  +
         band 3 of pixtype 16BSI is in-db with no NODATA value
    (1 row)

## See Also

ST_MetaData, ST_BandMetaData, ST_Summary ST_Extent

## Name

ST_UpperLeftX — Returns the upper left X coordinate of raster in projected spatial ref.

## Synopsis

`float8 ST_UpperLeftX(` raster rast`)`;

## Description

Returns the upper left X coordinate of raster in projected spatial ref.

## Examples

    SELECt rid, ST_UpperLeftX(rast) As ulx
    FROM dummy_rast;

     rid |    ulx
    -----+------------
       1 |        0.5
       2 | 3427927.75

## See Also

ST_UpperLeftY, ST_GeoReference, Box3D

## Name

ST_UpperLeftY — Returns the upper left Y coordinate of raster in projected spatial ref.

## Synopsis

`float8 ST_UpperLeftY(` raster rast`)`;

## Description

Returns the upper left Y coordinate of raster in projected spatial ref.

## Examples

    SELECT rid, ST_UpperLeftY(rast) As uly
    FROM dummy_rast;

     rid |   uly
    -----+---------
       1 |     0.5
       2 | 5793244

## See Also

ST_UpperLeftX, ST_GeoReference, Box3D

## Name

ST_Width — Returns the width of the raster in pixels.

## Synopsis

`integer ST_Width(` raster rast`)`;

## Description

Returns the width of the raster in pixels.

## Examples

    SELECT ST_Width(rast) As rastwidth
    FROM dummy_rast WHERE rid=1;

    rastwidth
    ----------------
    10

## See Also

ST_Height

## Name

ST_WorldToRasterCoord — Returns the upper left corner as column and row given geometric X and Y (longitude and latitude) or a point geometry expressed in the spatial reference coordinate system of the raster.

## Synopsis

`record ST_WorldToRasterCoord(` raster rast, geometry pt`)`;

`record ST_WorldToRasterCoord(` raster rast, double precision longitude, double precision latitude`)`;

## Description

Returns the upper left corner as column and row given geometric X and Y (longitude and latitude) or a point geometry. This function works regardless of whether or not the geometric X and Y or point geometry is outside the extent of the raster. Geometric X and Y must be expressed in the spatial reference coordinate system of the raster.

Availability: 2.1.0

## Examples

    SELECT
        rid,
        (ST_WorldToRasterCoord(rast,3427927.8,20.5)).*,
        (ST_WorldToRasterCoord(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast)))).*
    FROM dummy_rast;

     rid | columnx |   rowy    | columnx |   rowy
    -----+---------+-----------+---------+-----------
       1 | 1713964 |         7 | 1713964 |         7
       2 |       2 | 115864471 |       2 | 115864471

## See Also

ST_WorldToRasterCoordX, ST_WorldToRasterCoordY, ST_RasterToWorldCoordX, ST_RasterToWorldCoordY, ST_SRID

## Name

ST_WorldToRasterCoordX — Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

## Synopsis

`integer ST_WorldToRasterCoordX(` raster rast, geometry pt`)`;

`integer ST_WorldToRasterCoordX(` raster rast, double precision xw`)`;

`integer ST_WorldToRasterCoordX(` raster rast, double precision xw, double precision yw`)`;

## Description

Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw). A point, or (both xw and yw world coordinates are required if a raster is skewed). If a raster is not skewed then xw is sufficient. World coordinates are in the spatial reference coordinate system of the raster.

Changed: 2.1.0 In prior versions, this was called ST_World2RasterCoordX

## Examples

    SELECT rid, ST_WorldToRasterCoordX(rast,3427927.8) As xcoord,
            ST_WorldToRasterCoordX(rast,3427927.8,20.5) As xcoord_xwyw,
            ST_WorldToRasterCoordX(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast))) As ptxcoord
    FROM dummy_rast;

     rid | xcoord  |  xcoord_xwyw   | ptxcoord
    -----+---------+---------+----------
       1 | 1713964 | 1713964 |  1713964
       2 |       1 |       1 |        1

## See Also

ST_RasterToWorldCoordX, ST_RasterToWorldCoordY, ST_SRID

## Name

ST_WorldToRasterCoordY — Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

## Synopsis

`integer ST_WorldToRasterCoordY(` raster rast, geometry pt`)`;

`integer ST_WorldToRasterCoordY(` raster rast, double precision xw`)`;

`integer ST_WorldToRasterCoordY(` raster rast, double precision xw, double precision yw`)`;

## Description

Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw). A point, or (both xw and yw world coordinates are required if a raster is skewed). If a raster is not skewed then xw is sufficient. World coordinates are in the spatial reference coordinate system of the raster.

Changed: 2.1.0 In prior versions, this was called ST_World2RasterCoordY

## Examples

    SELECT rid, ST_WorldToRasterCoordY(rast,20.5) As ycoord,
            ST_WorldToRasterCoordY(rast,3427927.8,20.5) As ycoord_xwyw,
            ST_WorldToRasterCoordY(rast,ST_GeomFromText('POINT(3427927.8 20.5)',ST_SRID(rast))) As ptycoord
    FROM dummy_rast;

     rid |  ycoord   | ycoord_xwyw | ptycoord
    -----+-----------+-------------+-----------
       1 |         7 |           7 |         7
       2 | 115864471 |   115864471 | 115864471

## See Also

ST_RasterToWorldCoordX, ST_RasterToWorldCoordY, ST_SRID

## 11.5. Raster Band Accessors

## Name

ST_BandMetaData — Returns basic meta data for a specific raster band. band num 1 is assumed if none-specified.

## Synopsis

`(1) record ST_BandMetaData(` raster rast, integer band=1`)`;

`(2) record ST_BandMetaData(` raster rast, integer[] band`)`;

## Description

Returns basic meta data about a raster band. Columns returned: pixeltype, nodatavalue, isoutdb, path, outdbbandnum, filesize, filetimestamp.

If raster contains no bands then an error is thrown.

If band has no NODATA value, nodatavalue are NULL.

If isoutdb is False, path, outdbbandnum, filesize and filetimestamp are NULL. If outdb access is disabled, filesize and filetimestamp will also be NULL.

Enhanced: 2.5.0 to include outdbbandnum, filesize and filetimestamp for outdb rasters.

## Examples: Variant 1

    SELECT
        rid,
        (foo.md).*
    FROM (
        SELECT
            rid,
            ST_BandMetaData(rast, 1) AS md
        FROM dummy_rast
        WHERE rid=2
    ) As foo;

     rid | pixeltype | nodatavalue | isoutdb | path | outdbbandnum
    -----+-----------+---- --------+---------+------+--------------
       2 | 8BUI      |           0 | f       |      |

## Examples: Variant 2

    WITH foo AS (
        SELECT
            ST_AddBand(NULL::raster, '/home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif', NULL::int[]) AS rast
    )
    SELECT
        *
    FROM ST_BandMetadata(
        (SELECT rast FROM foo),
        ARRAY[1,3,2]::int[]
    );

     bandnum | pixeltype | nodatavalue | isoutdb |                                      path                                      | outdbbandnum  | filesize | filetimestamp |
    ---------+-----------+-------------+---------+--------------------------------------------------------------------------------+---------------+----------+---------------+-
           1 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif      |            1  |    12345 |    1521807257 |
           3 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif      |            3  |    12345 |    1521807257 |
           2 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif      |            2  |    12345 |    1521807257 |

## See Also

ST_MetaData, ST_BandPixelType

## Name

ST_BandNoDataValue — Returns the value in a given band that represents no data. If no band num 1 is assumed.

## Synopsis

`double precision ST_BandNoDataValue(` raster rast, integer bandnum=1`)`;

## Description

Returns the value that represents no data for the band

## Examples

    SELECT ST_BandNoDataValue(rast,1) As bnval1,
        ST_BandNoDataValue(rast,2) As bnval2, ST_BandNoDataValue(rast,3) As bnval3
    FROM dummy_rast
    WHERE rid = 2;

     bnval1 | bnval2 | bnval3
    --------+--------+--------
          0 |      0 |      0

## See Also

ST_NumBands

## Name

ST_BandIsNoData — Returns true if the band is filled with only nodata values.

## Synopsis

`boolean ST_BandIsNoData(` raster rast, integer band, boolean forceChecking=true`)`;

`boolean ST_BandIsNoData(` raster rast, boolean forceChecking=true`)`;

## Description

Returns true if the band is filled with only nodata values. Band 1 is assumed if not specified. If the last argument is TRUE, the entire band is checked pixel by pixel. Otherwise, the function simply returns the value of the isnodata flag for the band. The default value for this parameter is FALSE, if not specified.

Availability: 2.0.0

If the flag is dirty (this is, the result is different using TRUE as last parameter and not using it) you should update the raster to set this flag to true, by using ST_SetBandIsNodata(), or ST_SetBandNodataValue() with TRUE as last argument. See ST_SetBandIsNoData.

## Examples

    -- Create dummy table with one raster column
    create table dummy_rast (rid integer, rast raster);

    -- Add raster with two bands, one pixel/band. In the first band, nodatavalue = pixel value = 3.
    -- In the second band, nodatavalue = 13, pixel value = 4
    insert into dummy_rast values(1,
    (
    '01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0200' -- nBands (uint16 0)
    ||
    '17263529ED684A3F' -- scaleX (float64 0.000805965234044584)
    ||
    'F9253529ED684ABF' -- scaleY (float64 -0.00080596523404458)
    ||
    '1C9F33CE69E352C0' -- ipX (float64 -75.5533328537098)
    ||
    '718F0E9A27A44840' -- ipY (float64 49.2824585505576)
    ||
    'ED50EB853EC32B3F' -- skewX (float64 0.000211812383858707)
    ||
    '7550EB853EC32B3F' -- skewY (float64 0.000211812383858704)
    ||
    'E6100000' -- SRID (int32 4326)
    ||
    '0100' -- width (uint16 1)
    ||
    '0100' -- height (uint16 1)
    ||
    '6' -- hasnodatavalue and isnodata value set to true.
    ||
    '2' -- first band type (4BUI)
    ||
    '03' -- novalue==3
    ||
    '03' -- pixel(0,0)==3 (same that nodata)
    ||
    '0' -- hasnodatavalue set to false
    ||
    '5' -- second band type (16BSI)
    ||
    '0D00' -- novalue==13
    ||
    '0400' -- pixel(0,0)==4
    )::raster
    );

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected true
    select st_bandisnodata(rast, 2) from dummy_rast where rid = 1; -- Expected false

## See Also

ST_BandNoDataValue, ST_NumBands, ST_SetBandNoDataValue, ST_SetBandIsNoData

## Name

ST_BandPath — Returns system file path to a band stored in file system. If no bandnum specified, 1 is assumed.

## Synopsis

`text ST_BandPath(` raster rast, integer bandnum=1`)`;

## Description

Returns system file path to a band. Throws an error if called with an in db band.

## Examples

## See Also

## Name

ST_BandFileSize — Returns the file size of a band stored in file system. If no bandnum specified, 1 is assumed.

## Synopsis

`bigint ST_BandFileSize(` raster rast, integer bandnum=1`)`;

## Description

Returns the file size of a band stored in file system. Throws an error if called with an in db band, or if outdb access is not enabled.

This function is typically used in conjunction with ST_BandPath() and ST_BandFileTimestamp() so a client can determine if the filename of a outdb raster as seen by it is the same as the one seen by the server.

Availability: 2.5.0

## Examples

    SELECT ST_BandFileSize(rast,1) FROM dummy_rast WHERE rid = 1;

     st_bandfilesize
    -----------------
              240574

## Name

ST_BandFileTimestamp — Returns the file timestamp of a band stored in file system. If no bandnum specified, 1 is assumed.

## Synopsis

`bigint ST_BandFileTimestamp(` raster rast, integer bandnum=1`)`;

## Description

Returns the file timestamp (number of seconds since Jan 1st 1970 00:00:00 UTC) of a band stored in file system. Throws an error if called with an in db band, or if outdb access is not enabled.

This function is typically used in conjunction with ST_BandPath() and ST_BandFileSize() so a client can determine if the filename of a outdb raster as seen by it is the same as the one seen by the server.

Availability: 2.5.0

## Examples

    SELECT ST_BandFileTimestamp(rast,1) FROM dummy_rast WHERE rid = 1;

     st_bandfiletimestamp
    ----------------------
               1521807257

## Name

ST_BandPixelType — Returns the type of pixel for given band. If no bandnum specified, 1 is assumed.

## Synopsis

`text ST_BandPixelType(` raster rast, integer bandnum=1`)`;

## Description

Returns name describing data type and size of values stored in each cell of given band.

There are 11 pixel types. Pixel Types supported are as follows:

- 1BB - 1-bit boolean

- 2BUI - 2-bit unsigned integer

- 4BUI - 4-bit unsigned integer

- 8BSI - 8-bit signed integer

- 8BUI - 8-bit unsigned integer

- 16BSI - 16-bit signed integer

- 16BUI - 16-bit unsigned integer

- 32BSI - 32-bit signed integer

- 32BUI - 32-bit unsigned integer

- 32BF - 32-bit float

- 64BF - 64-bit float

## Examples

    SELECT ST_BandPixelType(rast,1) As btype1,
        ST_BandPixelType(rast,2) As btype2, ST_BandPixelType(rast,3) As btype3
    FROM dummy_rast
    WHERE rid = 2;

     btype1 | btype2 | btype3
    --------+--------+--------
     8BUI   | 8BUI   | 8BUI

## See Also

ST_NumBands

## Name

ST_MinPossibleValue — Returns the minimum value this pixeltype can store.

## Synopsis

`integer ST_MinPossibleValue(` text pixeltype`)`;

## Description

Returns the minimum value this pixeltype can store.

## Examples

    SELECT ST_MinPossibleValue('16BSI');

     st_minpossiblevalue
    ---------------------
                  -32768

    SELECT ST_MinPossibleValue('8BUI');

     st_minpossiblevalue
    ---------------------
                       0

## See Also

ST_BandPixelType

## Name

ST_HasNoBand — Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.

## Synopsis

`boolean ST_HasNoBand(` raster rast, integer bandnum=1`)`;

## Description

Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.

Availability: 2.0.0

## Examples

    SELECT rid, ST_HasNoBand(rast) As hb1, ST_HasNoBand(rast,2) as hb2,
    ST_HasNoBand(rast,4) as hb4, ST_NumBands(rast) As numbands
    FROM dummy_rast;

    rid | hb1 | hb2 | hb4 | numbands
    -----+-----+-----+-----+----------
    1 | t   | t   | t   |        0
    2 | f   | f   | t   |        3

## See Also

ST_NumBands

## 11.6. Raster Pixel Accessors and Setters

## Name

ST_PixelAsPolygon — Returns the polygon geometry that bounds the pixel for a particular row and column.

## Synopsis

`geometry ST_PixelAsPolygon(` raster rast, integer columnx, integer rowy`)`;

## Description

Returns the polygon geometry that bounds the pixel for a particular row and column.

Availability: 2.0.0

## Examples

    -- get raster pixel polygon
    SELECT i,j, ST_AsText(ST_PixelAsPolygon(foo.rast, i,j)) As b1pgeom
    FROM dummy_rast As foo
        CROSS JOIN generate_series(1,2) As i
        CROSS JOIN generate_series(1,1) As j
    WHERE rid=2;

     i | j |                                                    b1pgeom
    ---+---+-----------------------------------------------------------------------------
     1 | 1 | POLYGON((3427927.75 5793244,3427927.8 5793244,3427927.8 5793243.95,...
     2 | 1 | POLYGON((3427927.8 5793244,3427927.85 5793244,3427927.85 5793243.95, ..

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygons, ST_PixelAsPoint, ST_PixelAsPoints, ST_PixelAsCentroid, ST_PixelAsCentroids, ST_Intersection, ST_AsText

## Name

ST_PixelAsPolygons — Returns the polygon geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.

## Synopsis

`setof record ST_PixelAsPolygons(` raster rast, integer band=1, boolean exclude_nodata_value=TRUE`)`;

## Description

Returns the polygon geometry that bounds every pixel of a raster band along with the value (double precision), the X and the Y raster coordinates (integers) of each pixel.

Return record format: `geom` geometry, `val` double precision, `x` integer, `y` integers.

When `exclude_nodata_value` = TRUE, only those pixels whose values are not NODATA are returned as points.

ST_PixelAsPolygons returns one polygon geometry for every pixel. This is different than ST_DumpAsPolygons where each geometry represents one or more pixels with the same pixel value.

Availability: 2.0.0

Enhanced: 2.1.0 exclude_nodata_value optional argument was added.

Changed: 2.1.1 Changed behavior of exclude_nodata_value.

## Examples

    -- get raster pixel polygon
    SELECT (gv).x, (gv).y, (gv).val, ST_AsText((gv).geom) geom
    FROM (SELECT ST_PixelAsPolygons(
                     ST_SetValue(ST_SetValue(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 0.001, -0.001, 0.001, 0.001, 4269),
                                                        '8BUI'::text, 1, 0),
                                             2, 2, 10),
                                 1, 1, NULL)
    ) gv
    ) foo;

     x | y | val |                geom
    ---+---+-----------------------------------------------------------------------------
     1 | 1 |     | POLYGON((0 0,0.001 0.001,0.002 0,0.001 -0.001,0 0))
     1 | 2 |   1 | POLYGON((0.001 -0.001,0.002 0,0.003 -0.001,0.002 -0.002,0.001 -0.001))
     2 | 1 |   1 | POLYGON((0.001 0.001,0.002 0.002,0.003 0.001,0.002 0,0.001 0.001))
     2 | 2 |  10 | POLYGON((0.002 0,0.003 0.001,0.004 0,0.003 -0.001,0.002 0))

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_PixelAsPoint, ST_PixelAsPoints, ST_PixelAsCentroid, ST_PixelAsCentroids, ST_AsText

## Name

ST_PixelAsPoint — Returns a point geometry of the pixel's upper-left corner.

## Synopsis

`geometry ST_PixelAsPoint(` raster rast, integer columnx, integer rowy`)`;

## Description

Returns a point geometry of the pixel's upper-left corner.

Availability: 2.1.0

## Examples

    SELECT ST_AsText(ST_PixelAsPoint(rast, 1, 1)) FROM dummy_rast WHERE rid = 1;

       st_astext
    ----------------
     POINT(0.5 0.5)

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_PixelAsPolygons, ST_PixelAsPoints, ST_PixelAsCentroid, ST_PixelAsCentroids

## Name

ST_PixelAsPoints — Returns a point geometry for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The coordinates of the point geometry are of the pixel's upper-left corner.

## Synopsis

`setof record ST_PixelAsPoints(` raster rast, integer band=1, boolean exclude_nodata_value=TRUE`)`;

## Description

Returns a point geometry for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The coordinates of the point geometry are of the pixel's upper-left corner.

Return record format: `geom` geometry, `val` double precision, `x` integer, `y` integers.

When `exclude_nodata_value` = TRUE, only those pixels whose values are not NODATA are returned as points.

Availability: 2.1.0

Changed: 2.1.1 Changed behavior of exclude_nodata_value.

## Examples

    SELECT x, y, val, ST_AsText(geom) FROM (SELECT (ST_PixelAsPoints(rast, 1)).* FROM dummy_rast WHERE rid = 2) foo;

     x | y | val |          st_astext
    ---+---+-----+------------------------------
     1 | 1 | 253 | POINT(3427927.75 5793244)
     2 | 1 | 254 | POINT(3427927.8 5793244)
     3 | 1 | 253 | POINT(3427927.85 5793244)
     4 | 1 | 254 | POINT(3427927.9 5793244)
     5 | 1 | 254 | POINT(3427927.95 5793244)
     1 | 2 | 253 | POINT(3427927.75 5793243.95)
     2 | 2 | 254 | POINT(3427927.8 5793243.95)
     3 | 2 | 254 | POINT(3427927.85 5793243.95)
     4 | 2 | 253 | POINT(3427927.9 5793243.95)
     5 | 2 | 249 | POINT(3427927.95 5793243.95)
     1 | 3 | 250 | POINT(3427927.75 5793243.9)
     2 | 3 | 254 | POINT(3427927.8 5793243.9)
     3 | 3 | 254 | POINT(3427927.85 5793243.9)
     4 | 3 | 252 | POINT(3427927.9 5793243.9)
     5 | 3 | 249 | POINT(3427927.95 5793243.9)
     1 | 4 | 251 | POINT(3427927.75 5793243.85)
     2 | 4 | 253 | POINT(3427927.8 5793243.85)
     3 | 4 | 254 | POINT(3427927.85 5793243.85)
     4 | 4 | 254 | POINT(3427927.9 5793243.85)
     5 | 4 | 253 | POINT(3427927.95 5793243.85)
     1 | 5 | 252 | POINT(3427927.75 5793243.8)
     2 | 5 | 250 | POINT(3427927.8 5793243.8)
     3 | 5 | 254 | POINT(3427927.85 5793243.8)
     4 | 5 | 254 | POINT(3427927.9 5793243.8)
     5 | 5 | 254 | POINT(3427927.95 5793243.8)

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_PixelAsPolygons, ST_PixelAsPoint, ST_PixelAsCentroid, ST_PixelAsCentroids

## Name

ST_PixelAsCentroid — Returns the centroid (point geometry) of the area represented by a pixel.

## Synopsis

`geometry ST_PixelAsCentroid(` raster rast, integer x, integer y`)`;

## Description

Returns the centroid (point geometry) of the area represented by a pixel.

Enhanced: 3.2.0 Faster now implemented in C.

Availability: 2.1.0

## Examples

    SELECT ST_AsText(ST_PixelAsCentroid(rast, 1, 1)) FROM dummy_rast WHERE rid = 1;

      st_astext
    --------------
     POINT(1.5 2)

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_PixelAsPolygons, ST_PixelAsPoint, ST_PixelAsPoints, ST_PixelAsCentroids

## Name

ST_PixelAsCentroids — Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.

## Synopsis

`setof record ST_PixelAsCentroids(` raster rast, integer band=1, boolean exclude_nodata_value=TRUE`)`;

## Description

Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.

Return record format: `geom` geometry, `val` double precision, `x` integer, `y` integers.

When `exclude_nodata_value` = TRUE, only those pixels whose values are not NODATA are returned as points.

Enhanced: 3.2.0 Faster now implemented in C.

Changed: 2.1.1 Changed behavior of exclude_nodata_value.

Availability: 2.1.0

## Examples

     --LATERAL syntax requires PostgreSQL 9.3+
    SELECT x, y, val, ST_AsText(geom)
        FROM (SELECT dp.* FROM dummy_rast, LATERAL ST_PixelAsCentroids(rast, 1) AS dp WHERE rid = 2) foo;
     x | y | val |           st_astext
    ---+---+-----+--------------------------------
     1 | 1 | 253 | POINT(3427927.775 5793243.975)
     2 | 1 | 254 | POINT(3427927.825 5793243.975)
     3 | 1 | 253 | POINT(3427927.875 5793243.975)
     4 | 1 | 254 | POINT(3427927.925 5793243.975)
     5 | 1 | 254 | POINT(3427927.975 5793243.975)
     1 | 2 | 253 | POINT(3427927.775 5793243.925)
     2 | 2 | 254 | POINT(3427927.825 5793243.925)
     3 | 2 | 254 | POINT(3427927.875 5793243.925)
     4 | 2 | 253 | POINT(3427927.925 5793243.925)
     5 | 2 | 249 | POINT(3427927.975 5793243.925)
     1 | 3 | 250 | POINT(3427927.775 5793243.875)
     2 | 3 | 254 | POINT(3427927.825 5793243.875)
     3 | 3 | 254 | POINT(3427927.875 5793243.875)
     4 | 3 | 252 | POINT(3427927.925 5793243.875)
     5 | 3 | 249 | POINT(3427927.975 5793243.875)
     1 | 4 | 251 | POINT(3427927.775 5793243.825)
     2 | 4 | 253 | POINT(3427927.825 5793243.825)
     3 | 4 | 254 | POINT(3427927.875 5793243.825)
     4 | 4 | 254 | POINT(3427927.925 5793243.825)
     5 | 4 | 253 | POINT(3427927.975 5793243.825)
     1 | 5 | 252 | POINT(3427927.775 5793243.775)
     2 | 5 | 250 | POINT(3427927.825 5793243.775)
     3 | 5 | 254 | POINT(3427927.875 5793243.775)
     4 | 5 | 254 | POINT(3427927.925 5793243.775)
     5 | 5 | 254 | POINT(3427927.975 5793243.775)

## See Also

ST_DumpAsPolygons, ST_PixelAsPolygon, ST_PixelAsPolygons, ST_PixelAsPoint, ST_PixelAsPoints, ST_PixelAsCentroid

## Name

ST_Value — Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If `exclude_nodata_value` is set to false, then all pixels include `nodata` pixels are considered to intersect and return value. If `exclude_nodata_value` is not passed in then reads it from metadata of raster.

## Synopsis

`double precision ST_Value(` raster rast, geometry pt, boolean exclude_nodata_value=true`)`;

`double precision ST_Value(` raster rast, integer band, geometry pt, boolean exclude_nodata_value=true, text resample='nearest'`)`;

`double precision ST_Value(` raster rast, integer x, integer y, boolean exclude_nodata_value=true`)`;

`double precision ST_Value(` raster rast, integer band, integer x, integer y, boolean exclude_nodata_value=true`)`;

## Description

Returns the value of a given band in a given columnx, rowy pixel or at a given geometry point. Band numbers start at 1 and band is assumed to be 1 if not specified.

If `exclude_nodata_value` is set to true, then only non `nodata` pixels are considered. If `exclude_nodata_value` is set to false, then all pixels are considered.

The allowed values of the `resample` parameter are "nearest" which performs the default nearest-neighbor resampling, and "bilinear" which performs a bilinear interpolation to estimate the value between pixel centers.

Enhanced: 3.2.0 resample optional argument was added.

Enhanced: 2.0.0 exclude_nodata_value optional argument was added.

## Examples

    -- get raster values at particular postgis geometry points
    -- the srid of your geometry should be same as for your raster
    SELECT rid, ST_Value(rast, foo.pt_geom) As b1pval, ST_Value(rast, 2, foo.pt_geom) As b2pval
    FROM dummy_rast CROSS JOIN (SELECT ST_SetSRID(ST_Point(3427927.77, 5793243.76), 0) As pt_geom) As foo
    WHERE rid=2;

     rid | b1pval | b2pval
    -----+--------+--------
       2 |    252 |     79

    -- general fictitious example using a real table
    SELECT rid, ST_Value(rast, 3, sometable.geom) As b3pval
    FROM sometable
    WHERE ST_Intersects(rast,sometable.geom);

    SELECT rid, ST_Value(rast, 1, 1, 1) As b1pval,
        ST_Value(rast, 2, 1, 1) As b2pval, ST_Value(rast, 3, 1, 1) As b3pval
    FROM dummy_rast
    WHERE rid=2;

     rid | b1pval | b2pval | b3pval
    -----+--------+--------+--------
       2 |    253 |     78 |     70

    --- Get all values in bands 1,2,3 of each pixel --
    SELECT x, y, ST_Value(rast, 1, x, y) As b1val,
        ST_Value(rast, 2, x, y) As b2val, ST_Value(rast, 3, x, y) As b3val
    FROM dummy_rast CROSS JOIN
    generate_series(1, 1000) As x CROSS JOIN generate_series(1, 1000) As y
    WHERE rid =  2 AND x <= ST_Width(rast) AND y <= ST_Height(rast);

     x | y | b1val | b2val | b3val
    ---+---+-------+-------+-------
     1 | 1 |   253 |    78 |    70
     1 | 2 |   253 |    96 |    80
     1 | 3 |   250 |    99 |    90
     1 | 4 |   251 |    89 |    77
     1 | 5 |   252 |    79 |    62
     2 | 1 |   254 |    98 |    86
     2 | 2 |   254 |   118 |   108
     :
     :

    --- Get all values in bands 1,2,3 of each pixel same as above but returning the upper left point point of each pixel --
    SELECT ST_AsText(ST_SetSRID(
        ST_Point(ST_UpperLeftX(rast) + ST_ScaleX(rast)*x,
            ST_UpperLeftY(rast) + ST_ScaleY(rast)*y),
            ST_SRID(rast))) As uplpt
        , ST_Value(rast, 1, x, y) As b1val,
        ST_Value(rast, 2, x, y) As b2val, ST_Value(rast, 3, x, y) As b3val
    FROM dummy_rast CROSS JOIN
    generate_series(1,1000) As x CROSS JOIN generate_series(1,1000) As y
    WHERE rid =  2 AND x <= ST_Width(rast) AND y <= ST_Height(rast);

                uplpt            | b1val | b2val | b3val
    -----------------------------+-------+-------+-------
     POINT(3427929.25 5793245.5) |   253 |    78 |    70
     POINT(3427929.25 5793247)   |   253 |    96 |    80
     POINT(3427929.25 5793248.5) |   250 |    99 |    90
    :

    --- Get a polygon formed by union of all pixels
        that fall in a particular value range and intersect particular polygon --
    SELECT ST_AsText(ST_Union(pixpolyg)) As shadow
    FROM (SELECT ST_Translate(ST_MakeEnvelope(
            ST_UpperLeftX(rast), ST_UpperLeftY(rast),
                ST_UpperLeftX(rast) + ST_ScaleX(rast),
                ST_UpperLeftY(rast) + ST_ScaleY(rast), 0
                ), ST_ScaleX(rast)*x, ST_ScaleY(rast)*y
            ) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
        FROM dummy_rast CROSS JOIN
    generate_series(1,1000) As x CROSS JOIN generate_series(1,1000) As y
    WHERE rid =  2
        AND x <= ST_Width(rast) AND y <= ST_Height(rast)) As foo
    WHERE
        ST_Intersects(
            pixpolyg,
            ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
            ) AND b2val != 254;

            shadow
    ------------------------------------------------------------------------------------
     MULTIPOLYGON(((3427928 5793243.9,3427928 5793243.85,3427927.95 5793243.85,3427927.95 5793243.9,
     3427927.95 5793243.95,3427928 5793243.95,3427928.05 5793243.95,3427928.05 5793243.9,3427928 5793243.9)),((3427927.95 5793243.9,3427927.95 579324
    3.85,3427927.9 5793243.85,3427927.85 5793243.85,3427927.85 5793243.9,3427927.9 5793243.9,3427927.9 5793243.95,
    3427927.95 5793243.95,3427927.95 5793243.9)),((3427927.85 5793243.75,3427927.85 5793243.7,3427927.8 5793243.7,3427927.8 5793243.75
    ,3427927.8 5793243.8,3427927.8 5793243.85,3427927.85 5793243.85,3427927.85 5793243.8,3427927.85 5793243.75)),
    ((3427928.05 5793243.75,3427928.05 5793243.7,3427928 5793243.7,3427927.95 5793243.7,3427927.95 5793243.75,3427927.95 5793243.8,3427
    927.95 5793243.85,3427928 5793243.85,3427928 5793243.8,3427928.05 5793243.8,
    3427928.05 5793243.75)),((3427927.95 5793243.75,3427927.95 5793243.7,3427927.9 5793243.7,3427927.85 5793243.7,
    3427927.85 5793243.75,3427927.85 5793243.8,3427927.85 5793243.85,3427927.9 5793243.85,
    3427927.95 5793243.85,3427927.95 5793243.8,3427927.95 5793243.75)))

    --- Checking all the pixels of a large raster tile can take a long time.
    --- You can dramatically improve speed at some lose of precision by orders of magnitude
    --  by sampling pixels using the step optional parameter of generate_series.
    --  This next example does the same as previous but by checking 1 for every 4 (2x2) pixels and putting in the last checked
    --  putting in the checked pixel as the value for subsequent 4

    SELECT ST_AsText(ST_Union(pixpolyg)) As shadow
    FROM (SELECT ST_Translate(ST_MakeEnvelope(
            ST_UpperLeftX(rast), ST_UpperLeftY(rast),
                ST_UpperLeftX(rast) + ST_ScaleX(rast)*2,
                ST_UpperLeftY(rast) + ST_ScaleY(rast)*2, 0
                ), ST_ScaleX(rast)*x, ST_ScaleY(rast)*y
            ) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
        FROM dummy_rast CROSS JOIN
    generate_series(1,1000,2) As x CROSS JOIN generate_series(1,1000,2) As y
    WHERE rid =  2
        AND x <= ST_Width(rast)  AND y <= ST_Height(rast)  ) As foo
    WHERE
        ST_Intersects(
            pixpolyg,
            ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
            ) AND b2val != 254;

            shadow
    ------------------------------------------------------------------------------------
     MULTIPOLYGON(((3427927.9 5793243.85,3427927.8 5793243.85,3427927.8 5793243.95,
     3427927.9 5793243.95,3427928 5793243.95,3427928.1 5793243.95,3427928.1 5793243.85,3427928 5793243.85,3427927.9 5793243.85)),
     ((3427927.9 5793243.65,3427927.8 5793243.65,3427927.8 5793243.75,3427927.8 5793243.85,3427927.9 5793243.85,
     3427928 5793243.85,3427928 5793243.75,3427928.1 5793243.75,3427928.1 5793243.65,3427928 5793243.65,3427927.9 5793243.65)))

## See Also

ST_SetValue, ST_DumpAsPolygons, ST_NumBands, ST_PixelAsPolygon, ST_ScaleX, ST_ScaleY, ST_UpperLeftX, ST_UpperLeftY, ST_SRID, ST_AsText, ST_Point, ST_MakeEnvelope, ST_Intersects, ST_Intersection

## Name

ST_NearestValue — Returns the nearest non-`NODATA` value of a given band's pixel specified by a columnx and rowy or a geometric point expressed in the same spatial reference coordinate system as the raster.

## Synopsis

`double precision ST_NearestValue(` raster rast, integer bandnum, geometry pt, boolean exclude_nodata_value=true`)`;

`double precision ST_NearestValue(` raster rast, geometry pt, boolean exclude_nodata_value=true`)`;

`double precision ST_NearestValue(` raster rast, integer bandnum, integer columnx, integer rowy, boolean exclude_nodata_value=true`)`;

`double precision ST_NearestValue(` raster rast, integer columnx, integer rowy, boolean exclude_nodata_value=true`)`;

## Description

Returns the nearest non-`NODATA` value of a given band in a given columnx, rowy pixel or at a specific geometric point. If the columnx, rowy pixel or the pixel at the specified geometric point is `NODATA`, the function will find the nearest pixel to the columnx, rowy pixel or geometric point whose value is not `NODATA`.

Band numbers start at 1 and `bandnum` is assumed to be 1 if not specified. If `exclude_nodata_value` is set to false, then all pixels include `nodata` pixels are considered to intersect and return value. If `exclude_nodata_value` is not passed in then reads it from metadata of raster.

Availability: 2.1.0

ST_NearestValue is a drop-in replacement for ST_Value.

## Examples

    -- pixel 2x2 has value
    SELECT
        ST_Value(rast, 2, 2) AS value,
        ST_NearestValue(rast, 2, 2) AS nearestvalue
    FROM (
        SELECT
            ST_SetValue(
                ST_SetValue(
                    ST_SetValue(
                        ST_SetValue(
                            ST_SetValue(
                                ST_AddBand(
                                    ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                                    '8BUI'::text, 1, 0
                                ),
                                1, 1, 0.
                            ),
                            2, 3, 0.
                        ),
                        3, 5, 0.
                    ),
                    4, 2, 0.
                ),
                5, 4, 0.
            ) AS rast
    ) AS foo

     value | nearestvalue
    -------+--------------
         1 |            1

    -- pixel 2x3 is NODATA
    SELECT
        ST_Value(rast, 2, 3) AS value,
        ST_NearestValue(rast, 2, 3) AS nearestvalue
    FROM (
        SELECT
            ST_SetValue(
                ST_SetValue(
                    ST_SetValue(
                        ST_SetValue(
                            ST_SetValue(
                                ST_AddBand(
                                    ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                                    '8BUI'::text, 1, 0
                                ),
                                1, 1, 0.
                            ),
                            2, 3, 0.
                        ),
                        3, 5, 0.
                    ),
                    4, 2, 0.
                ),
                5, 4, 0.
            ) AS rast
    ) AS foo

     value | nearestvalue
    -------+--------------
           |            1

## See Also

ST_Neighborhood, ST_Value

## Name

ST_SetZ — Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the Z dimension using the requested resample algorithm.

## Synopsis

`geometry ST_SetZ(` raster rast, geometry geom, text resample=nearest, integer band=1`)`;

## Description

Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the Z dimensions using the requested resample algorithm.

The `resample` parameter can be set to "nearest" to copy the values from the cell each vertex falls within, or "bilinear" to use bilinear interpolation to calculate a value that takes neighboring cells into account also.

Availability: 3.2.0

## Examples

    --
    -- 2x2 test raster with values
    --
    -- 10 50
    -- 40 20
    --
    WITH test_raster AS (
    SELECT
    ST_SetValues(
      ST_AddBand(
        ST_MakeEmptyRaster(width => 2, height => 2,
          upperleftx => 0, upperlefty => 2,
          scalex => 1.0, scaley => -1.0,
          skewx => 0, skewy => 0, srid => 4326),
        index => 1, pixeltype => '16BSI',
        initialvalue => 0,
        nodataval => -999),
      1,1,1,
      newvalueset =>ARRAY[ARRAY[10.0::float8, 50.0::float8], ARRAY[40.0::float8, 20.0::float8]]) AS rast
    )
    SELECT
    ST_AsText(
      ST_SetZ(
        rast,
        band => 1,
        geom => 'SRID=4326;LINESTRING(1.0 1.9, 1.0 0.2)'::geometry,
        resample => 'bilinear'
    ))
    FROM test_raster

                st_astext
    ----------------------------------
     LINESTRING Z (1 1.9 38,1 0.2 27)

## See Also

ST_Value, ST_SetM

## Name

ST_SetM — Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimension using the requested resample algorithm.

## Synopsis

`geometry ST_SetM(` raster rast, geometry geom, text resample=nearest, integer band=1`)`;

## Description

Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimensions using the requested resample algorithm.

The `resample` parameter can be set to "nearest" to copy the values from the cell each vertex falls within, or "bilinear" to use bilinear interpolation to calculate a value that takes neighboring cells into account also.

Availability: 3.2.0

## Examples

    --
    -- 2x2 test raster with values
    --
    -- 10 50
    -- 40 20
    --
    WITH test_raster AS (
    SELECT
    ST_SetValues(
      ST_AddBand(
        ST_MakeEmptyRaster(width => 2, height => 2,
          upperleftx => 0, upperlefty => 2,
          scalex => 1.0, scaley => -1.0,
          skewx => 0, skewy => 0, srid => 4326),
        index => 1, pixeltype => '16BSI',
        initialvalue => 0,
        nodataval => -999),
      1,1,1,
      newvalueset =>ARRAY[ARRAY[10.0::float8, 50.0::float8], ARRAY[40.0::float8, 20.0::float8]]) AS rast
    )
    SELECT
    ST_AsText(
      ST_SetM(
        rast,
        band => 1,
        geom => 'SRID=4326;LINESTRING(1.0 1.9, 1.0 0.2)'::geometry,
        resample => 'bilinear'
    ))
    FROM test_raster

                st_astext
    ----------------------------------
     LINESTRING M (1 1.9 38,1 0.2 27)

## See Also

ST_Value, ST_SetZ

## Name

ST_Neighborhood — Returns a 2-D double precision array of the non-`NODATA` values around a given band's pixel specified by either a columnX and rowY or a geometric point expressed in the same spatial reference coordinate system as the raster.

## Synopsis

`double precision[][] ST_Neighborhood(` raster rast, integer bandnum, integer columnX, integer rowY, integer distanceX, integer distanceY, boolean exclude_nodata_value=true`)`;

`double precision[][] ST_Neighborhood(` raster rast, integer columnX, integer rowY, integer distanceX, integer distanceY, boolean exclude_nodata_value=true`)`;

`double precision[][] ST_Neighborhood(` raster rast, integer bandnum, geometry pt, integer distanceX, integer distanceY, boolean exclude_nodata_value=true`)`;

`double precision[][] ST_Neighborhood(` raster rast, geometry pt, integer distanceX, integer distanceY, boolean exclude_nodata_value=true`)`;

## Description

Returns a 2-D double precision array of the non-`NODATA` values around a given band's pixel specified by either a columnX and rowY or a geometric point expressed in the same spatial reference coordinate system as the raster. The `distanceX` and `distanceY` parameters define the number of pixels around the specified pixel in the X and Y axes, e.g. I want all values within 3 pixel distance along the X axis and 2 pixel distance along the Y axis around my pixel of interest. The center value of the 2-D array will be the value at the pixel specified by the columnX and rowY or the geometric point.

Band numbers start at 1 and `bandnum` is assumed to be 1 if not specified. If `exclude_nodata_value` is set to false, then all pixels include `nodata` pixels are considered to intersect and return value. If `exclude_nodata_value` is not passed in then reads it from metadata of raster.

The number of elements along each axis of the returning 2-D array is 2 * (`distanceX`|`distanceY`) + 1. So for a `distanceX` and `distanceY` of 1, the returning array will be 3x3.

The 2-D array output can be passed to any of the raster processing builtin functions, e.g. ST_Min4ma, ST_Sum4ma, ST_Mean4ma.

Availability: 2.1.0

## Examples

    -- pixel 2x2 has value
    SELECT
        ST_Neighborhood(rast, 2, 2, 1, 1)
    FROM (
        SELECT
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                    '8BUI'::text, 1, 0
                ),
                1, 1, 1, ARRAY[
                    [0, 1, 1, 1, 1],
                    [1, 1, 1, 0, 1],
                    [1, 0, 1, 1, 1],
                    [1, 1, 1, 1, 0],
                    [1, 1, 0, 1, 1]
                ]::double precision[],
                1
            ) AS rast
    ) AS foo

             st_neighborhood
    ---------------------------------
    {{NULL,1,1},{1,1,1},{1,NULL,1}}

    -- pixel 2x3 is NODATA
    SELECT
        ST_Neighborhood(rast, 2, 3, 1, 1)
    FROM (
        SELECT
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                    '8BUI'::text, 1, 0
                ),
                1, 1, 1, ARRAY[
                    [0, 1, 1, 1, 1],
                    [1, 1, 1, 0, 1],
                    [1, 0, 1, 1, 1],
                    [1, 1, 1, 1, 0],
                    [1, 1, 0, 1, 1]
                ]::double precision[],
                1
            ) AS rast
    ) AS foo

           st_neighborhood
    ------------------------------
     {{1,1,1},{1,NULL,1},{1,1,1}}

    -- pixel 3x3 has value
    -- exclude_nodata_value = FALSE
    SELECT
        ST_Neighborhood(rast, 3, 3, 1, 1, false)
    FROM ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                    '8BUI'::text, 1, 0
                ),
                1, 1, 1, ARRAY[
                    [0, 1, 1, 1, 1],
                    [1, 1, 1, 0, 1],
                    [1, 0, 1, 1, 1],
                    [1, 1, 1, 1, 0],
                    [1, 1, 0, 1, 1]
                ]::double precision[],
                1
            ) AS rast

          st_neighborhood
    ---------------------------
    {{1,1,0},{0,1,1},{1,1,1}}

## See Also

ST_NearestValue, ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_SetValue — Returns modified raster resulting from setting the value of a given band in a given columnx, rowy pixel or the pixels that intersect a particular geometry. Band numbers start at 1 and assumed to be 1 if not specified.

## Synopsis

`raster ST_SetValue(` raster rast, integer bandnum, geometry geom, double precision newvalue`)`;

`raster ST_SetValue(` raster rast, geometry geom, double precision newvalue`)`;

`raster ST_SetValue(` raster rast, integer bandnum, integer columnx, integer rowy, double precision newvalue`)`;

`raster ST_SetValue(` raster rast, integer columnx, integer rowy, double precision newvalue`)`;

## Description

Returns modified raster resulting from setting the specified pixels' values to new value for the designated band given the raster's row and column or a geometry. If no band is specified, then band 1 is assumed.

Enhanced: 2.1.0 Geometry variant of ST_SetValue() now supports any geometry type, not just point. The geometry variant is a wrapper around the geomval[] variant of ST_SetValues()

## Examples

                    -- Geometry example
    SELECT (foo.geomval).val, ST_AsText(ST_Union((foo.geomval).geom))
    FROM (SELECT ST_DumpAsPolygons(
            ST_SetValue(rast,1,
                    ST_Point(3427927.75, 5793243.95),
                    50)
                ) As geomval
    FROM dummy_rast
    where rid = 2) As foo
    WHERE (foo.geomval).val < 250
    GROUP BY (foo.geomval).val;

     val |                                                     st_astext
    -----+-------------------------------------------------------------------
      50 | POLYGON((3427927.75 5793244,3427927.75 5793243.95,3427927.8 579324 ...
     249 | POLYGON((3427927.95 5793243.95,3427927.95 5793243.85,3427928 57932 ...

    -- Store the changed raster --
        UPDATE dummy_rast SET rast = ST_SetValue(rast,1, ST_Point(3427927.75, 5793243.95),100)
            WHERE rid = 2   ;

## See Also

ST_Value, ST_DumpAsPolygons

## Name

ST_SetValues — Returns modified raster resulting from setting the values of a given band.

## Synopsis

`raster ST_SetValues(` raster rast, integer nband, integer columnx, integer rowy, double precision[][] newvalueset, boolean[][] noset=NULL, boolean keepnodata=FALSE`)`;

`raster ST_SetValues(` raster rast, integer nband, integer columnx, integer rowy, double precision[][] newvalueset, double precision nosetvalue, boolean keepnodata=FALSE`)`;

`raster ST_SetValues(` raster rast, integer nband, integer columnx, integer rowy, integer width, integer height, double precision newvalue, boolean keepnodata=FALSE`)`;

`raster ST_SetValues(` raster rast, integer columnx, integer rowy, integer width, integer height, double precision newvalue, boolean keepnodata=FALSE`)`;

`raster ST_SetValues(` raster rast, integer nband, geomval[] geomvalset, boolean keepnodata=FALSE`)`;

## Description

Returns modified raster resulting from setting specified pixels to new value(s) for the designated band. `columnx` and `rowy` are 1-indexed.

If `keepnodata` is TRUE, those pixels whose values are NODATA will not be set with the corresponding value in `newvalueset`.

For Variant 1, the specific pixels to be set are determined by the `columnx`, `rowy` pixel coordinates and the dimensions of the `newvalueset` array. `noset` can be used to prevent pixels with values present in `newvalueset` from being set (due to PostgreSQL not permitting ragged/jagged arrays). See example Variant 1.

Variant 2 is like Variant 1 but with a simple double precision `nosetvalue` instead of a boolean `noset` array. Elements in `newvalueset` with the `nosetvalue` value with be skipped. See example Variant 2.

For Variant 3, the specific pixels to be set are determined by the `columnx`, `rowy` pixel coordinates, `width` and `height`. See example Variant 3.

Variant 4 is the same as Variant 3 with the exception that it assumes that the first band's pixels of `rast` will be set.

For Variant 5, an array of geomval is used to determine the specific pixels to be set. If all the geometries in the array are of type POINT or MULTIPOINT, the function uses a shortcut where the longitude and latitude of each point is used to set a pixel directly. Otherwise, the geometries are converted to rasters and then iterated through in one pass. See example Variant 5.

Availability: 2.1.0

## Examples: Variant 1

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 1 | 1 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 2, 2, ARRAY[[9, 9], [9, 9]]::double precision[][]
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   1
     1 | 2 |   1
     1 | 3 |   1
     2 | 1 |   1
     2 | 2 |   9
     2 | 3 |   9
     3 | 1 |   1
     3 | 2 |   9
     3 | 3 |   9

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 9 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 9 |   | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 9 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 1, 1, ARRAY[[9, 9, 9], [9, NULL, 9], [9, 9, 9]]::double precision[][]
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   9
     1 | 2 |   9
     1 | 3 |   9
     2 | 1 |   9
     2 | 2 |
     2 | 3 |   9
     3 | 1 |   9
     3 | 2 |   9
     3 | 3 |   9

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 9 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 |   | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 9 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 1, 1,
                    ARRAY[[9, 9, 9], [9, NULL, 9], [9, 9, 9]]::double precision[][],
                    ARRAY[[false], [true]]::boolean[][]
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   9
     1 | 2 |   1
     1 | 3 |   9
     2 | 1 |   9
     2 | 2 |
     2 | 3 |   9
     3 | 1 |   9
     3 | 2 |   9
     3 | 3 |   9

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    |   | 1 | 1 |          |   | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 |   | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 9 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_SetValue(
                    ST_AddBand(
                        ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                        1, '8BUI', 1, 0
                    ),
                    1, 1, 1, NULL
                ),
                1, 1, 1,
                    ARRAY[[9, 9, 9], [9, NULL, 9], [9, 9, 9]]::double precision[][],
                    ARRAY[[false], [true]]::boolean[][],
                    TRUE
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |
     1 | 2 |   1
     1 | 3 |   9
     2 | 1 |   9
     2 | 2 |
     2 | 3 |   9
     3 | 1 |   9
     3 | 2 |   9
     3 | 3 |   9

## Examples: Variant 2

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 1 | 1 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 1, 1, ARRAY[[-1, -1, -1], [-1, 9, 9], [-1, 9, 9]]::double precision[][], -1
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   1
     1 | 2 |   1
     1 | 3 |   1
     2 | 1 |   1
     2 | 2 |   9
     2 | 3 |   9
     3 | 1 |   1
     3 | 2 |   9
     3 | 3 |   9

    /*
    This example is like the previous one.  Instead of nosetvalue = -1, nosetvalue = NULL

    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 1 | 1 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 1, 1, ARRAY[[NULL, NULL, NULL], [NULL, 9, 9], [NULL, 9, 9]]::double precision[][], NULL::double precision
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   1
     1 | 2 |   1
     1 | 3 |   1
     2 | 1 |   1
     2 | 2 |   9
     2 | 3 |   9
     3 | 1 |   1
     3 | 2 |   9
     3 | 3 |   9

## Examples: Variant 3

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 1 | 1 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |    =>    | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                    1, '8BUI', 1, 0
                ),
                1, 2, 2, 2, 2, 9
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   1
     1 | 2 |   1
     1 | 3 |   1
     2 | 1 |   1
     2 | 2 |   9
     2 | 3 |   9
     3 | 1 |   1
     3 | 2 |   9
     3 | 3 |   9

    /*
    The ST_SetValues() does the following...

    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 1 | 1 |
    + - + - + - +          + - + - + - +
    | 1 |   | 1 |    =>    | 1 |   | 9 |
    + - + - + - +          + - + - + - +
    | 1 | 1 | 1 |          | 1 | 9 | 9 |
    + - + - + - +          + - + - + - +
    */
    SELECT
        (poly).x,
        (poly).y,
        (poly).val
    FROM (
    SELECT
        ST_PixelAsPolygons(
            ST_SetValues(
                ST_SetValue(
                    ST_AddBand(
                        ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0),
                        1, '8BUI', 1, 0
                    ),
                    1, 2, 2, NULL
                ),
                1, 2, 2, 2, 2, 9, TRUE
            )
        ) AS poly
    ) foo
    ORDER BY 1, 2;

     x | y | val
    ---+---+-----
     1 | 1 |   1
     1 | 2 |   1
     1 | 3 |   1
     2 | 1 |   1
     2 | 2 |
     2 | 3 |   9
     3 | 1 |   1
     3 | 2 |   9
     3 | 3 |   9

## Examples: Variant 5

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 0, 0) AS rast
    ), bar AS (
        SELECT 1 AS gid, 'SRID=0;POINT(2.5 -2.5)'::geometry geom UNION ALL
        SELECT 2 AS gid, 'SRID=0;POLYGON((1 -1, 4 -1, 4 -4, 1 -4, 1 -1))'::geometry geom UNION ALL
        SELECT 3 AS gid, 'SRID=0;POLYGON((0 0, 5 0, 5 -1, 1 -1, 1 -4, 0 -4, 0 0))'::geometry geom UNION ALL
        SELECT 4 AS gid, 'SRID=0;MULTIPOINT(0 0, 4 4, 4 -4)'::geometry
    )
    SELECT
        rid, gid, ST_DumpValues(ST_SetValue(rast, 1, geom, gid))
    FROM foo t1
    CROSS JOIN bar t2
    ORDER BY rid, gid;

     rid | gid |                                                                st_dumpvalues
    -----+-----+---------------------------------------------------------------------------------------------------------------------------------------------
       1 |   1 | (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,1,NULL,NULL},{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL}}")
       1 |   2 | (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,2,2,2,NULL},{NULL,2,2,2,NULL},{NULL,2,2,2,NULL},{NULL,NULL,NULL,NULL,NULL}}")
       1 |   3 | (1,"{{3,3,3,3,3},{3,NULL,NULL,NULL,NULL},{3,NULL,NULL,NULL,NULL},{3,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL}}")
       1 |   4 | (1,"{{4,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,NULL},{NULL,NULL,NULL,NULL,4}}")
    (4 rows)

The following shows that geomvals later in the array can overwrite prior geomvals

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 0, 0) AS rast
    ), bar AS (
        SELECT 1 AS gid, 'SRID=0;POINT(2.5 -2.5)'::geometry geom UNION ALL
        SELECT 2 AS gid, 'SRID=0;POLYGON((1 -1, 4 -1, 4 -4, 1 -4, 1 -1))'::geometry geom UNION ALL
        SELECT 3 AS gid, 'SRID=0;POLYGON((0 0, 5 0, 5 -1, 1 -1, 1 -4, 0 -4, 0 0))'::geometry geom UNION ALL
        SELECT 4 AS gid, 'SRID=0;MULTIPOINT(0 0, 4 4, 4 -4)'::geometry
    )
    SELECT
        t1.rid, t2.gid, t3.gid, ST_DumpValues(ST_SetValues(rast, 1, ARRAY[ROW(t2.geom, t2.gid), ROW(t3.geom, t3.gid)]::geomval[]))
    FROM foo t1
    CROSS JOIN bar t2
    CROSS JOIN bar t3
    WHERE t2.gid = 1
        AND t3.gid = 2
    ORDER BY t1.rid, t2.gid, t3.gid;

     rid | gid | gid |                                                    st_dumpvalues
    -----+-----+-----+---------------------------------------------------------------------------------------------------------------------
       1 |   1 |   2 | (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,2,2,2,NULL},{NULL,2,2,2,NULL},{NULL,2,2,2,NULL},{NULL,NULL,NULL,NULL,NULL}}")
    (1 row)

This example is the opposite of the prior example

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 0, 0) AS rast
    ), bar AS (
        SELECT 1 AS gid, 'SRID=0;POINT(2.5 -2.5)'::geometry geom UNION ALL
        SELECT 2 AS gid, 'SRID=0;POLYGON((1 -1, 4 -1, 4 -4, 1 -4, 1 -1))'::geometry geom UNION ALL
        SELECT 3 AS gid, 'SRID=0;POLYGON((0 0, 5 0, 5 -1, 1 -1, 1 -4, 0 -4, 0 0))'::geometry geom UNION ALL
        SELECT 4 AS gid, 'SRID=0;MULTIPOINT(0 0, 4 4, 4 -4)'::geometry
    )
    SELECT
        t1.rid, t2.gid, t3.gid, ST_DumpValues(ST_SetValues(rast, 1, ARRAY[ROW(t2.geom, t2.gid), ROW(t3.geom, t3.gid)]::geomval[]))
    FROM foo t1
    CROSS JOIN bar t2
    CROSS JOIN bar t3
    WHERE t2.gid = 2
        AND t3.gid = 1
    ORDER BY t1.rid, t2.gid, t3.gid;

     rid | gid | gid |                                                    st_dumpvalues
    -----+-----+-----+---------------------------------------------------------------------------------------------------------------------
       1 |   2 |   1 | (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,2,2,2,NULL},{NULL,2,1,2,NULL},{NULL,2,2,2,NULL},{NULL,NULL,NULL,NULL,NULL}}")
    (1 row)

## See Also

ST_Value, ST_SetValue, ST_PixelAsPolygons

## Name

ST_DumpValues — Get the values of the specified band as a 2-dimension array.

## Synopsis

`setof record ST_DumpValues(` raster rast , integer[] nband=NULL , boolean exclude_nodata_value=true `)`;

`double precision[][] ST_DumpValues(` raster rast , integer nband , boolean exclude_nodata_value=true `)`;

## Description

Get the values of the specified band as a 2-dimension array (first index is row, second is column). If `nband` is NULL or not provided, all raster bands are processed.

Availability: 2.1.0

## Examples

    WITH foo AS (
        SELECT ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI'::text, 1, 0), 2, '32BF'::text, 3, -9999), 3, '16BSI', 0, 0) AS rast
    )
    SELECT
        (ST_DumpValues(rast)).*
    FROM foo;

     nband |                       valarray
    -------+------------------------------------------------------
         1 | {{1,1,1},{1,1,1},{1,1,1}}
         2 | {{3,3,3},{3,3,3},{3,3,3}}
         3 | {{NULL,NULL,NULL},{NULL,NULL,NULL},{NULL,NULL,NULL}}
    (3 rows)

    WITH foo AS (
        SELECT ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI'::text, 1, 0), 2, '32BF'::text, 3, -9999), 3, '16BSI', 0, 0) AS rast
    )
    SELECT
        (ST_DumpValues(rast, ARRAY[3, 1])).*
    FROM foo;

     nband |                       valarray
    -------+------------------------------------------------------
         3 | {{NULL,NULL,NULL},{NULL,NULL,NULL},{NULL,NULL,NULL}}
         1 | {{1,1,1},{1,1,1},{1,1,1}}
    (2 rows)

    WITH foo AS (
        SELECT ST_SetValue(ST_AddBand(ST_MakeEmptyRaster(3, 3, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 1, 0), 1, 2, 5) AS rast
    )
    SELECT
        (ST_DumpValues(rast, 1))[2][1]
    FROM foo;

     st_dumpvalues
    ---------------
                 5
    (1 row)

## See Also

ST_Value, ST_SetValue, ST_SetValues

## Name

ST_PixelOfValue — Get the columnx, rowy coordinates of the pixel whose value equals the search value.

## Synopsis

`setof record ST_PixelOfValue(` raster rast , integer nband , double precision[] search , boolean exclude_nodata_value=true `)`;

`setof record ST_PixelOfValue(` raster rast , double precision[] search , boolean exclude_nodata_value=true `)`;

`setof record ST_PixelOfValue(` raster rast , integer nband , double precision search , boolean exclude_nodata_value=true `)`;

`setof record ST_PixelOfValue(` raster rast , double precision search , boolean exclude_nodata_value=true `)`;

## Description

Get the columnx, rowy coordinates of the pixel whose value equals the search value. If no band is specified, then band 1 is assumed.

Availability: 2.1.0

## Examples

    SELECT
        (pixels).*
    FROM (
        SELECT
            ST_PixelOfValue(
                ST_SetValue(
                    ST_SetValue(
                        ST_SetValue(
                            ST_SetValue(
                                ST_SetValue(
                                    ST_AddBand(
                                        ST_MakeEmptyRaster(5, 5, -2, 2, 1, -1, 0, 0, 0),
                                        '8BUI'::text, 1, 0
                                    ),
                                    1, 1, 0
                                ),
                                2, 3, 0
                            ),
                            3, 5, 0
                        ),
                        4, 2, 0
                    ),
                    5, 4, 255
                )
            , 1, ARRAY[1, 255]) AS pixels
    ) AS foo

     val | x | y
    -----+---+---
       1 | 1 | 2
       1 | 1 | 3
       1 | 1 | 4
       1 | 1 | 5
       1 | 2 | 1
       1 | 2 | 2
       1 | 2 | 4
       1 | 2 | 5
       1 | 3 | 1
       1 | 3 | 2
       1 | 3 | 3
       1 | 3 | 4
       1 | 4 | 1
       1 | 4 | 3
       1 | 4 | 4
       1 | 4 | 5
       1 | 5 | 1
       1 | 5 | 2
       1 | 5 | 3
     255 | 5 | 4
       1 | 5 | 5

## 11.7. Raster Editors

## Name

ST_SetGeoReference — Set Georeference 6 georeference parameters in a single call. Numbers should be separated by white space. Accepts inputs in GDAL or ESRI format. Default is GDAL.

## Synopsis

`raster ST_SetGeoReference(` raster rast, text georefcoords, text format=GDAL`)`;

`raster ST_SetGeoReference(` raster rast, double precision upperleftx, double precision upperlefty, double precision scalex, double precision scaley, double precision skewx, double precision skewy`)`;

## Description

Set Georeference 6 georeference parameters in a single call. Accepts inputs in 'GDAL' or 'ESRI' format. Default is GDAL. If 6 coordinates are not provided will return null.

Difference between format representations is as follows:

`GDAL`:

    scalex skewy skewx scaley upperleftx upperlefty

`ESRI`:

    scalex skewy skewx scaley upperleftx + scalex*0.5 upperlefty + scaley*0.5

If the raster has out-db bands, changing the georeference may result in incorrect access of the band's externally stored data.

Enhanced: 2.1.0 Addition of ST_SetGeoReference(raster, double precision, ...) variant

## Examples

    WITH foo AS (
        SELECT ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0) AS rast
    )
    SELECT
        0 AS rid, (ST_Metadata(rast)).*
    FROM foo
    UNION ALL
    SELECT
        1, (ST_Metadata(ST_SetGeoReference(rast, '10 0 0 -10 0.1 0.1', 'GDAL'))).*
    FROM foo
    UNION ALL
    SELECT
        2, (ST_Metadata(ST_SetGeoReference(rast, '10 0 0 -10 5.1 -4.9', 'ESRI'))).*
    FROM foo
    UNION ALL
    SELECT
        3, (ST_Metadata(ST_SetGeoReference(rast, 1, 1, 10, -10, 0.001, 0.001))).*
    FROM foo

     rid |     upperleftx     |     upperlefty     | width | height | scalex | scaley | skewx | skewy | srid | numbands
    -----+--------------------+--------------------+-------+--------+--------+--------+-------+-------+------+----------
       0 |                  0 |                  0 |     5 |      5 |      1 |     -1 |     0 |     0 |    0 |        0
       1 |                0.1 |                0.1 |     5 |      5 |     10 |    -10 |     0 |     0 |    0 |        0
       2 | 0.0999999999999996 | 0.0999999999999996 |     5 |      5 |     10 |    -10 |     0 |     0 |    0 |        0
       3 |                  1 |                  1 |     5 |      5 |     10 |    -10 | 0.001 | 0.001 |    0 |        0

## See Also

ST_GeoReference, ST_ScaleX, ST_ScaleY, ST_UpperLeftX, ST_UpperLeftY

## Name

ST_SetRotation — Set the rotation of the raster in radian.

## Synopsis

`raster ST_SetRotation(` raster rast, float8 rotation`)`;

## Description

Uniformly rotate the raster. Rotation is in radian. Refer to World File for more details.

## Examples

    SELECT
      ST_ScaleX(rast1), ST_ScaleY(rast1), ST_SkewX(rast1), ST_SkewY(rast1),
      ST_ScaleX(rast2), ST_ScaleY(rast2), ST_SkewX(rast2), ST_SkewY(rast2)
    FROM (
      SELECT ST_SetRotation(rast, 15) AS rast1, rast as rast2 FROM dummy_rast
    ) AS foo;
          st_scalex      |      st_scaley      |      st_skewx      |      st_skewy      | st_scalex | st_scaley | st_skewx | st_skewy
    ---------------------+---------------------+--------------------+--------------------+-----------+-----------+----------+----------
       -1.51937582571764 |   -2.27906373857646 |   1.95086352047135 |   1.30057568031423 |         2 |         3 |        0 |        0
     -0.0379843956429411 | -0.0379843956429411 | 0.0325143920078558 | 0.0325143920078558 |      0.05 |     -0.05 |        0 |        0

## See Also

ST_Rotation, ST_ScaleX, ST_ScaleY, ST_SkewX, ST_SkewY

## Name

ST_SetScale — Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height.

## Synopsis

`raster ST_SetScale(` raster rast, float8 xy`)`;

`raster ST_SetScale(` raster rast, float8 x, float8 y`)`;

## Description

Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height. If only one unit passed in, assumed X and Y are the same number.

ST_SetScale is different from ST_Rescale in that ST_SetScale do not resample the raster to match the raster extent. It only changes the metadata (or georeference) of the raster to correct an originally mis-specified scaling. ST_Rescale results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetScale do not modify the width, nor the height of the raster.

Changed: 2.0.0 In WKTRaster versions this was called ST_SetPixelSize. This was changed in 2.0.0.

## Examples

    UPDATE dummy_rast
        SET rast = ST_SetScale(rast, 1.5)
    WHERE rid = 2;

    SELECT ST_ScaleX(rast) As pixx, ST_ScaleY(rast) As pixy, Box3D(rast) As newbox
    FROM dummy_rast
    WHERE rid = 2;

     pixx | pixy |                    newbox
    ------+------+----------------------------------------------
      1.5 |  1.5 | BOX(3427927.75 5793244 0, 3427935.25 5793251.5 0)

    UPDATE dummy_rast
        SET rast = ST_SetScale(rast, 1.5, 0.55)
    WHERE rid = 2;

    SELECT ST_ScaleX(rast) As pixx, ST_ScaleY(rast) As pixy, Box3D(rast) As newbox
    FROM dummy_rast
    WHERE rid = 2;

     pixx | pixy |                   newbox
    ------+------+--------------------------------------------
      1.5 | 0.55 | BOX(3427927.75 5793244 0,3427935.25 5793247 0)

## See Also

ST_ScaleX, ST_ScaleY, Box3D

## Name

ST_SetSkew — Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value.

## Synopsis

`raster ST_SetSkew(` raster rast, float8 skewxy`)`;

`raster ST_SetSkew(` raster rast, float8 skewx, float8 skewy`)`;

## Description

Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value. Refer to World File for more details.

## Examples

    -- Example 1
    UPDATE dummy_rast SET rast = ST_SetSkew(rast,1,2) WHERE rid = 1;
    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast WHERE rid = 1;

    rid | skewx | skewy |    georef
    ----+-------+-------+--------------
      1 |     1 |     2 | 2.0000000000
                        : 2.0000000000
                        : 1.0000000000
                        : 3.0000000000
                        : 0.5000000000
                        : 0.5000000000

    -- Example 2 set both to same number:
    UPDATE dummy_rast SET rast = ST_SetSkew(rast,0) WHERE rid = 1;
    SELECT rid, ST_SkewX(rast) As skewx, ST_SkewY(rast) As skewy,
        ST_GeoReference(rast) as georef
    FROM dummy_rast WHERE rid = 1;

     rid | skewx | skewy |    georef
    -----+-------+-------+--------------
       1 |     0 |     0 | 2.0000000000
                         : 0.0000000000
                         : 0.0000000000
                         : 3.0000000000
                         : 0.5000000000
                         : 0.5000000000

## See Also

ST_GeoReference, ST_SetGeoReference, ST_SkewX, ST_SkewY

## Name

ST_SetSRID — Sets the SRID of a raster to a particular integer srid defined in the spatial_ref_sys table.

## Synopsis

`raster ST_SetSRID(` raster rast, integer srid`)`;

## Description

Sets the SRID on a raster to a particular integer value.

This function does not transform the raster in any way - it simply sets meta data defining the spatial ref of the coordinate reference system that it's currently in. Useful for transformations later.

## See Also

Section 4.5, “Spatial Reference Systems”, ST_SRID

## Name

ST_SetUpperLeft — Sets the value of the upper left corner of the pixel of the raster to projected X and Y coordinates.

## Synopsis

`raster ST_SetUpperLeft(` raster rast, double precision x, double precision y`)`;

## Description

Set the value of the upper left corner of raster to the projected X and Y coordinates

## Examples

    SELECT ST_SetUpperLeft(rast,-71.01,42.37)
    FROM dummy_rast
    WHERE rid = 2;

## See Also

ST_UpperLeftX, ST_UpperLeftY

## Name

ST_Resample — Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster.

## Synopsis

`raster ST_Resample(` raster rast, integer width, integer height, double precision gridx=NULL, double precision gridy=NULL, double precision skewx=0, double precision skewy=0, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Resample(` raster rast, double precision scalex=0, double precision scaley=0, double precision gridx=NULL, double precision gridy=NULL, double precision skewx=0, double precision skewy=0, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Resample(` raster rast, raster ref, text algorithm=NearestNeighbor, double precision maxerr=0.125, boolean usescale=true`)`;

`raster ST_Resample(` raster rast, raster ref, boolean usescale, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Resample a raster using a specified resampling algorithm, new dimensions (width & height), a grid corner (gridx & gridy) and a set of raster georeferencing attributes (scalex, scaley, skewx & skewy) defined or borrowed from another raster. If using a reference raster, the two rasters must have the same SRID.

New pixel values are computed using one of the following resampling algorithms:

- NearestNeighbor (english or american spelling)

- Bilinear

- Cubic

- CubicSpline

- Lanczos

- Max

- Min

The default is NearestNeighbor which is the fastest but results in the worst interpolation.

A maxerror percent of 0.125 is used if no `maxerr` is specified.

Refer to: GDAL Warp resampling methods for more details.

Availability: 2.0.0 Requires GDAL 1.6.1+

Enhanced: 3.4.0 max and min resampling options added

## Examples

    SELECT
        ST_Width(orig) AS orig_width,
        ST_Width(reduce_100) AS new_width
    FROM (
        SELECT
            rast AS orig,
            ST_Resample(rast,100,100) AS reduce_100
        FROM aerials.boston
        WHERE ST_Intersects(rast,
            ST_Transform(
                ST_MakeEnvelope(-71.128, 42.2392,-71.1277, 42.2397, 4326),26986)
        )
        LIMIT 1
    ) AS foo;

     orig_width | new_width
    ------------+-------------
            200 |         100

## See Also

ST_Rescale, ST_Resize, ST_Transform

## Name

ST_Rescale — Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline, Lanczos, Max or Min resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_Rescale(` raster rast, double precision scalexy, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Rescale(` raster rast, double precision scalex, double precision scaley, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using one of the following resampling algorithms:

- NearestNeighbor (english or american spelling)

- Bilinear

- Cubic

- CubicSpline

- Lanczos

- Max

- Min

The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`scalex` and `scaley` define the new pixel size. scaley must often be negative to get well oriented raster.

When the new scalex or scaley is not a divisor of the raster width or height, the extent of the resulting raster is expanded to encompass the extent of the provided raster. If you want to be sure to retain exact input extent see ST_Resize

`maxerr` is the threshold for transformation approximation by the resampling algorithm (in pixel units). A default of 0.125 is used if no `maxerr` is specified, which is the same value used in GDAL gdalwarp utility. If set to zero, no approximation takes place.

Refer to: GDAL Warp resampling methods for more details.

ST_Rescale is different from ST_SetScale in that ST_SetScale do not resample the raster to match the raster extent. ST_SetScale only changes the metadata (or georeference) of the raster to correct an originally mis-specified scaling. ST_Rescale results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetScale do not modify the width, nor the height of the raster.

Availability: 2.0.0 Requires GDAL 1.6.1+

Enhanced: 3.4.0 max and min resampling options added

Changed: 2.1.0 Works on rasters with no SRID

## Examples

A simple example rescaling a raster from a pixel size of 0.001 degree to a pixel size of 0.0015 degree.

    -- the original raster pixel size
    SELECT ST_PixelWidth(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0)) width

       width
    ----------
    0.001

    -- the rescaled raster raster pixel size
    SELECT ST_PixelWidth(ST_Rescale(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015)) width

       width
    ----------
    0.0015

## See Also

ST_Resize, ST_Resample, ST_SetScale, ST_ScaleX, ST_ScaleY, ST_Transform

## Name

ST_Reskew — Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_Reskew(` raster rast, double precision skewxy, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Reskew(` raster rast, double precision skewx, double precision skewy, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`skewx` and `skewy` define the new skew.

The extent of the new raster will encompass the extent of the provided raster.

A maxerror percent of 0.125 if no `maxerr` is specified.

Refer to: GDAL Warp resampling methods for more details.

ST_Reskew is different from ST_SetSkew in that ST_SetSkew do not resample the raster to match the raster extent. ST_SetSkew only changes the metadata (or georeference) of the raster to correct an originally mis-specified skew. ST_Reskew results in a raster having different width and height computed to fit the geographic extent of the input raster. ST_SetSkew do not modify the width, nor the height of the raster.

Availability: 2.0.0 Requires GDAL 1.6.1+

Changed: 2.1.0 Works on rasters with no SRID

## Examples

A simple example reskewing a raster from a skew of 0.0 to a skew of 0.0015.

    -- the original raster non-rotated
    SELECT ST_Rotation(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0));

    -- result
    0

    -- the reskewed raster raster rotation
    SELECT ST_Rotation(ST_Reskew(ST_AddBand(ST_MakeEmptyRaster(100, 100, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0015));

    -- result
    -0.982793723247329

## See Also

ST_Resample, ST_Rescale, ST_SetSkew, ST_SetRotation, ST_SkewX, ST_SkewY, ST_Transform

## Name

ST_SnapToGrid — Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.

## Synopsis

`raster ST_SnapToGrid(` raster rast, double precision gridx, double precision gridy, text algorithm=NearestNeighbor, double precision maxerr=0.125, double precision scalex=DEFAULT 0, double precision scaley=DEFAULT 0`)`;

`raster ST_SnapToGrid(` raster rast, double precision gridx, double precision gridy, double precision scalex, double precision scaley, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_SnapToGrid(` raster rast, double precision gridx, double precision gridy, double precision scalexy, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Resample a raster by snapping it to a grid defined by an arbitrary pixel corner (gridx & gridy) and optionally a pixel size (scalex & scaley). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

`gridx` and `gridy` define any arbitrary pixel corner of the new grid. This is not necessarily the upper left corner of the new raster and it does not have to be inside or on the edge of the new raster extent.

You can optionally define the pixel size of the new grid with `scalex` and `scaley`.

The extent of the new raster will encompass the extent of the provided raster.

A maxerror percent of 0.125 if no `maxerr` is specified.

Refer to: GDAL Warp resampling methods for more details.

Use ST_Resample if you need more control over the grid parameters.

Availability: 2.0.0 Requires GDAL 1.6.1+

Changed: 2.1.0 Works on rasters with no SRID

## Examples

A simple example snapping a raster to a slightly different grid.

    -- the original raster upper left X
    SELECT ST_UpperLeftX(ST_AddBand(ST_MakeEmptyRaster(10, 10, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0));
    -- result
    0

    -- the upper left of raster after snapping
    SELECT ST_UpperLeftX(ST_SnapToGrid(ST_AddBand(ST_MakeEmptyRaster(10, 10, 0, 0, 0.001, -0.001, 0, 0, 4269), '8BUI'::text, 1, 0), 0.0002, 0.0002));

    --result
    -0.0008

## See Also

ST_Resample, ST_Rescale, ST_UpperLeftX, ST_UpperLeftY

## Name

ST_Resize — Resize a raster to a new width/height

## Synopsis

`raster ST_Resize(` raster rast, integer width, integer height, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Resize(` raster rast, double precision percentwidth, double precision percentheight, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Resize(` raster rast, text width, text height, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Resize a raster to a new width/height. The new width/height can be specified in exact number of pixels or a percentage of the raster's width/height. The extent of the the new raster will be the same as the extent of the provided raster.

New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. The default is NearestNeighbor which is the fastest but results in the worst interpolation.

Variant 1 expects the actual width/height of the output raster.

Variant 2 expects decimal values between zero (0) and one (1) indicating the percentage of the input raster's width/height.

Variant 3 takes either the actual width/height of the output raster or a textual percentage ("20%") indicating the percentage of the input raster's width/height.

Availability: 2.1.0 Requires GDAL 1.6.1+

## Examples

    WITH foo AS(
    SELECT
        1 AS rid,
        ST_Resize(
            ST_AddBand(
                ST_MakeEmptyRaster(1000, 1000, 0, 0, 1, -1, 0, 0, 0)
                , 1, '8BUI', 255, 0
            )
        , '50%', '500') AS rast
    UNION ALL
    SELECT
        2 AS rid,
        ST_Resize(
            ST_AddBand(
                ST_MakeEmptyRaster(1000, 1000, 0, 0, 1, -1, 0, 0, 0)
                , 1, '8BUI', 255, 0
            )
        , 500, 100) AS rast
    UNION ALL
    SELECT
        3 AS rid,
        ST_Resize(
            ST_AddBand(
                ST_MakeEmptyRaster(1000, 1000, 0, 0, 1, -1, 0, 0, 0)
                , 1, '8BUI', 255, 0
            )
        , 0.25, 0.9) AS rast
    ), bar AS (
        SELECT rid, ST_Metadata(rast) AS meta, rast FROM foo
    )
    SELECT rid, (meta).* FROM bar

     rid | upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    -----+------------+------------+-------+--------+--------+--------+-------+-------+------+----------
       1 |          0 |          0 |   500 |    500 |      1 |     -1 |     0 |     0 |    0 |        1
       2 |          0 |          0 |   500 |    100 |      1 |     -1 |     0 |     0 |    0 |        1
       3 |          0 |          0 |   250 |    900 |      1 |     -1 |     0 |     0 |    0 |        1
    (3 rows)

## See Also

ST_Resample, ST_Rescale, ST_Reskew, ST_SnapToGrid

## Name

ST_Transform — Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.

## Synopsis

`raster ST_Transform(` raster rast, integer srid, text algorithm=NearestNeighbor, double precision maxerr=0.125, double precision scalex, double precision scaley`)`;

`raster ST_Transform(` raster rast, integer srid, double precision scalex, double precision scaley, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

`raster ST_Transform(` raster rast, raster alignto, text algorithm=NearestNeighbor, double precision maxerr=0.125`)`;

## Description

Reprojects a raster in a known spatial reference system to another known spatial reference system using specified pixel warping algorithm. Uses 'NearestNeighbor' if no algorithm is specified and maxerror percent of 0.125 if no maxerr is specified.

Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: GDAL Warp resampling methods for more details.

ST_Transform is often confused with ST_SetSRID(). ST_Transform actually changes the coordinates of a raster (and resamples the pixel values) from one spatial reference system to another, while ST_SetSRID() simply changes the SRID identifier of the raster.

Unlike the other variants, Variant 3 requires a reference raster as `alignto`. The transformed raster will be transformed to the spatial reference system (SRID) of the reference raster and be aligned (ST_SameAlignment = TRUE) to the reference raster.

If you find your transformation support is not working right, you may need to set the environment variable PROJSO to the .so or .dll projection library your PostGIS is using. This just needs to have the name of the file. So for example on windows, you would in Control Panel -> System -> Environment Variables add a system variable called `PROJSO` and set it to `libproj.dll` (if you are using proj 4.6.1). You'll have to restart your PostgreSQL service/daemon after this change.

When transforming a coverage of tiles, you almost always want to use a reference raster to insure same alignment and no gaps in your tiles as demonstrated in example: Variant 3.

Availability: 2.0.0 Requires GDAL 1.6.1+

Enhanced: 2.1.0 Addition of ST_Transform(rast, alignto) variant

## Examples

    SELECT ST_Width(mass_stm) As w_before, ST_Width(wgs_84) As w_after,
      ST_Height(mass_stm) As h_before, ST_Height(wgs_84) As h_after
        FROM
        ( SELECT rast As mass_stm, ST_Transform(rast,4326) As wgs_84
      ,  ST_Transform(rast,4326, 'Bilinear') AS wgs_84_bilin
            FROM aerials.o_2_boston
                WHERE ST_Intersects(rast,
                    ST_Transform(ST_MakeEnvelope(-71.128, 42.2392,-71.1277, 42.2397, 4326),26986) )
            LIMIT 1) As foo;

     w_before | w_after | h_before | h_after
    ----------+---------+----------+---------
          200 |     228 |      200 |     170

original mass state plane meters (mass_stm) | After transform to wgs 84 long lat (wgs_84) | After transform to wgs 84 long lat with bilinear algorithm instead of NN default (wgs_84_bilin)

## Examples: Variant 3

The following shows the difference between using ST_Transform(raster, srid) and ST_Transform(raster, alignto)

    WITH foo AS (
        SELECT 0 AS rid, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 1, 0) AS rast UNION ALL
        SELECT 1, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 2, 0) AS rast UNION ALL
        SELECT 2, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 600000, 100, -100, 0, 0, 2163), 1, '16BUI', 3, 0) AS rast UNION ALL

        SELECT 3, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 10, 0) AS rast UNION ALL
        SELECT 4, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 20, 0) AS rast UNION ALL
        SELECT 5, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 599800, 100, -100, 0, 0, 2163), 1, '16BUI', 30, 0) AS rast UNION ALL

        SELECT 6, ST_AddBand(ST_MakeEmptyRaster(2, 2, -500000, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 100, 0) AS rast UNION ALL
        SELECT 7, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499800, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 200, 0) AS rast UNION ALL
        SELECT 8, ST_AddBand(ST_MakeEmptyRaster(2, 2, -499600, 599600, 100, -100, 0, 0, 2163), 1, '16BUI', 300, 0) AS rast
    ), bar AS (
        SELECT
            ST_Transform(rast, 4269) AS alignto
        FROM foo
        LIMIT 1
    ), baz AS (
        SELECT
            rid,
            rast,
            ST_Transform(rast, 4269) AS not_aligned,
            ST_Transform(rast, alignto) AS aligned
        FROM foo
        CROSS JOIN bar
    )
    SELECT
        ST_SameAlignment(rast) AS rast,
        ST_SameAlignment(not_aligned) AS not_aligned,
        ST_SameAlignment(aligned) AS aligned
    FROM baz

     rast | not_aligned | aligned
    ------+-------------+---------
     t    | f           | t

not_aligned | aligned

## See Also

ST_Transform, ST_SetSRID

## 11.8. Raster Band Editors

## Name

ST_SetBandNoDataValue — Sets the value for the given band that represents no data. Band 1 is assumed if no band is specified. To mark a band as having no nodata value, set the nodata value = NULL.

## Synopsis

`raster ST_SetBandNoDataValue(` raster rast, double precision nodatavalue`)`;

`raster ST_SetBandNoDataValue(` raster rast, integer band, double precision nodatavalue, boolean forcechecking=false`)`;

## Description

Sets the value that represents no data for the band. Band 1 is assumed if not specified. This will affect results from ST_Polygon, ST_DumpAsPolygons, and the ST_PixelAs...() functions.

## Examples

    -- change just first band no data value
    UPDATE dummy_rast
        SET rast = ST_SetBandNoDataValue(rast,1, 254)
    WHERE rid = 2;

    -- change no data band value of bands 1,2,3
    UPDATE dummy_rast
        SET rast =
            ST_SetBandNoDataValue(
                ST_SetBandNoDataValue(
                    ST_SetBandNoDataValue(
                        rast,1, 254)
                    ,2,99),
                    3,108)
            WHERE rid = 2;

    -- wipe out the nodata value this will ensure all pixels are considered for all processing functions
    UPDATE dummy_rast
        SET rast = ST_SetBandNoDataValue(rast,1, NULL)
    WHERE rid = 2;

## See Also

ST_BandNoDataValue, ST_NumBands

## Name

ST_SetBandIsNoData — Sets the isnodata flag of the band to TRUE.

## Synopsis

`raster ST_SetBandIsNoData(` raster rast, integer band=1`)`;

## Description

Sets the isnodata flag for the band to true. Band 1 is assumed if not specified. This function should be called only when the flag is considered dirty. That is, when the result calling ST_BandIsNoData is different using TRUE as last argument and without using it

Availability: 2.0.0

## Examples

    -- Create dummy table with one raster column
    create table dummy_rast (rid integer, rast raster);

    -- Add raster with two bands, one pixel/band. In the first band, nodatavalue = pixel value = 3.
    -- In the second band, nodatavalue = 13, pixel value = 4
    insert into dummy_rast values(1,
    (
    '01' -- little endian (uint8 ndr)
    ||
    '0000' -- version (uint16 0)
    ||
    '0200' -- nBands (uint16 0)
    ||
    '17263529ED684A3F' -- scaleX (float64 0.000805965234044584)
    ||
    'F9253529ED684ABF' -- scaleY (float64 -0.00080596523404458)
    ||
    '1C9F33CE69E352C0' -- ipX (float64 -75.5533328537098)
    ||
    '718F0E9A27A44840' -- ipY (float64 49.2824585505576)
    ||
    'ED50EB853EC32B3F' -- skewX (float64 0.000211812383858707)
    ||
    '7550EB853EC32B3F' -- skewY (float64 0.000211812383858704)
    ||
    'E6100000' -- SRID (int32 4326)
    ||
    '0100' -- width (uint16 1)
    ||
    '0100' -- height (uint16 1)
    ||
    '4' -- hasnodatavalue set to true, isnodata value set to false (when it should be true)
    ||
    '2' -- first band type (4BUI)
    ||
    '03' -- novalue==3
    ||
    '03' -- pixel(0,0)==3 (same that nodata)
    ||
    '0' -- hasnodatavalue set to false
    ||
    '5' -- second band type (16BSI)
    ||
    '0D00' -- novalue==13
    ||
    '0400' -- pixel(0,0)==4
    )::raster
    );

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected false
    select st_bandisnodata(rast, 1, TRUE) from dummy_rast where rid = 1; -- Expected true

    -- The isnodata flag is dirty. We are going to set it to true
    update dummy_rast set rast = st_setbandisnodata(rast, 1) where rid = 1;

    select st_bandisnodata(rast, 1) from dummy_rast where rid = 1; -- Expected true

## See Also

ST_BandNoDataValue, ST_NumBands, ST_SetBandNoDataValue, ST_BandIsNoData

## Name

ST_SetBandPath — Update the external path and band number of an out-db band

## Synopsis

`raster ST_SetBandPath(` raster rast, integer band, text outdbpath, integer outdbindex, boolean force=false`)`;

## Description

Updates an out-db band's external raster file path and external band number.

If `force` is set to true, no tests are done to ensure compatibility (e.g. alignment, pixel support) between the external raster file and the PostGIS raster. This mode is intended for file system changes where the external raster resides.

Availability: 2.5.0

## Examples

    WITH foo AS (
        SELECT
            ST_AddBand(NULL::raster, '/home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif', NULL::int[]) AS rast
    )
    SELECT
        1 AS query,
        *
    FROM ST_BandMetadata(
        (SELECT rast FROM foo),
        ARRAY[1,3,2]::int[]
    )
    UNION ALL
    SELECT
        2,
        *
    FROM ST_BandMetadata(
        (
            SELECT
                ST_SetBandPath(
                    rast,
                    2,
                    '/home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected2.tif',
                    1
                ) AS rast
            FROM foo
        ),
        ARRAY[1,3,2]::int[]
    )
    ORDER BY 1, 2;

     query | bandnum | pixeltype | nodatavalue | isoutdb |                                      path                                       | outdbbandnum
    -------+---------+-----------+-------------+---------+---------------------------------------------------------------------------------+--------------
         1 |       1 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            1
         1 |       2 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            2
         1 |       3 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            3
         2 |       1 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            1
         2 |       2 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected2.tif      |            1
         2 |       3 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            3

## See Also

ST_BandMetaData, ST_SetBandIndex

## Name

ST_SetBandIndex — Update the external band number of an out-db band

## Synopsis

`raster ST_SetBandIndex(` raster rast, integer band, integer outdbindex, boolean force=false`)`;

## Description

Updates an out-db band's external band number. This does not touch the external raster file associated with the out-db band

If `force` is set to true, no tests are done to ensure compatibility (e.g. alignment, pixel support) between the external raster file and the PostGIS raster. This mode is intended for where bands are moved around in the external raster file.

Internally, this method replaces the PostGIS raster's band at index `band` with a new band instead of updating the existing path information.

Availability: 2.5.0

## Examples

    WITH foo AS (
        SELECT
            ST_AddBand(NULL::raster, '/home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif', NULL::int[]) AS rast
    )
    SELECT
        1 AS query,
        *
    FROM ST_BandMetadata(
        (SELECT rast FROM foo),
        ARRAY[1,3,2]::int[]
    )
    UNION ALL
    SELECT
        2,
        *
    FROM ST_BandMetadata(
        (
            SELECT
                ST_SetBandIndex(
                    rast,
                    2,
                    1
                ) AS rast
            FROM foo
        ),
        ARRAY[1,3,2]::int[]
    )
    ORDER BY 1, 2;

     query | bandnum | pixeltype | nodatavalue | isoutdb |                                      path                                       | outdbbandnum
    -------+---------+-----------+-------------+---------+---------------------------------------------------------------------------------+--------------
         1 |       1 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            1
         1 |       2 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            2
         1 |       3 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            3
         2 |       1 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            1
         2 |       2 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            1
         2 |       3 | 8BUI      |             | t       | /home/pele/devel/geo/postgis-git/raster/test/regress/loader/Projected.tif       |            3

## See Also

ST_BandMetaData, ST_SetBandPath

## 11.9. Raster Band Statistics and Analytics

## Name

ST_Count — Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.

## Synopsis

`bigint ST_Count(` raster rast, integer nband=1, boolean exclude_nodata_value=true`)`;

`bigint ST_Count(` raster rast, boolean exclude_nodata_value`)`;

## Description

Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified `nband` defaults to 1.

If `exclude_nodata_value` is set to true, will only count pixels with value not equal to the `nodata` value of the raster. Set `exclude_nodata_value` to false to get count all pixels

Changed: 3.1.0 - The ST_Count(rastertable, rastercolumn, ...) variants removed. Use ST_CountAgg instead.

Availability: 2.0.0

## Examples

    --example will count all pixels not 249 and one will count all pixels.  --
    SELECT rid, ST_Count(ST_SetBandNoDataValue(rast,249)) As exclude_nodata,
            ST_Count(ST_SetBandNoDataValue(rast,249),false) As include_nodata
        FROM dummy_rast WHERE rid=2;

    rid | exclude_nodata | include_nodata
    -----+----------------+----------------
       2 |             23 |             25

## See Also

ST_CountAgg, ST_SummaryStats, ST_SetBandNoDataValue

## Name

ST_CountAgg — Aggregate. Returns the number of pixels in a given band of a set of rasters. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the NODATA value.

## Synopsis

`bigint ST_CountAgg(` raster rast, integer nband, boolean exclude_nodata_value, double precision sample_percent`)`;

`bigint ST_CountAgg(` raster rast, integer nband, boolean exclude_nodata_value`)`;

`bigint ST_CountAgg(` raster rast, boolean exclude_nodata_value`)`;

## Description

Returns the number of pixels in a given band of a set of rasters. If no band is specified `nband` defaults to 1.

If `exclude_nodata_value` is set to true, will only count pixels with value not equal to the `NODATA` value of the raster. Set `exclude_nodata_value` to false to get count all pixels

By default will sample all pixels. To get faster response, set `sample_percent` to value between zero (0) and one (1)

Availability: 2.2.0

## Examples

    WITH foo AS (
        SELECT
            rast.rast
        FROM (
            SELECT ST_SetValue(
                ST_SetValue(
                    ST_SetValue(
                        ST_AddBand(
                            ST_MakeEmptyRaster(10, 10, 10, 10, 2, 2, 0, 0,0)
                            , 1, '64BF', 0, 0
                        )
                        , 1, 1, 1, -10
                    )
                    , 1, 5, 4, 0
                )
                , 1, 5, 5, 3.14159
            ) AS rast
        ) AS rast
        FULL JOIN (
            SELECT generate_series(1, 10) AS id
        ) AS id
            ON 1 = 1
    )
    SELECT
        ST_CountAgg(rast, 1, TRUE)
    FROM foo;

     st_countagg
    -------------
              20
    (1 row)

## See Also

ST_Count, ST_SummaryStats, ST_SetBandNoDataValue

## Name

ST_Histogram — Returns a set of record summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.

## Synopsis

`SETOF record ST_Histogram(` raster rast, integer nband=1, boolean exclude_nodata_value=true, integer bins=autocomputed, double precision[] width=NULL, boolean right=false`)`;

`SETOF record ST_Histogram(` raster rast, integer nband, integer bins, double precision[] width=NULL, boolean right=false`)`;

`SETOF record ST_Histogram(` raster rast, integer nband, boolean exclude_nodata_value, integer bins, boolean right`)`;

`SETOF record ST_Histogram(` raster rast, integer nband, integer bins, boolean right`)`;

## Description

Returns set of records consisting of min, max, count, percent for a given raster band for each bin. If no band is specified `nband` defaults to 1.

By default only considers pixel values not equal to the `nodata` value . Set `exclude_nodata_value` to false to get count all pixels.

`width`

  width: an array indicating the width of each category/bin. If the number of bins is greater than the number of widths, the widths are repeated.

  Example: 9 bins, widths are [a, b, c] will have the output be [a, b, c, a, b, c, a, b, c]

`bins`

  Number of breakouts -- this is the number of records you'll get back from the function if specified. If not specified then the number of breakouts is autocomputed.

`right`

  compute the histogram from the right rather than from the left (default). This changes the criteria for evaluating a value x from [a, b) to (a, b]

Changed: 3.1.0 Removed ST_Histogram(table_name, column_name) variant.

Availability: 2.0.0

## Example: Single raster tile - compute histograms for bands 1, 2, 3 and autocompute bins

    SELECT band, (stats).*
    FROM (SELECT rid, band, ST_Histogram(rast, band) As stats
        FROM dummy_rast CROSS JOIN generate_series(1,3) As band
         WHERE rid=2) As foo;

     band |  min  |  max  | count | percent
    ------+-------+-------+-------+---------
        1 |   249 |   250 |     2 |    0.08
        1 |   250 |   251 |     2 |    0.08
        1 |   251 |   252 |     1 |    0.04
        1 |   252 |   253 |     2 |    0.08
        1 |   253 |   254 |    18 |    0.72
        2 |    78 | 113.2 |    11 |    0.44
        2 | 113.2 | 148.4 |     4 |    0.16
        2 | 148.4 | 183.6 |     4 |    0.16
        2 | 183.6 | 218.8 |     1 |    0.04
        2 | 218.8 |   254 |     5 |     0.2
        3 |    62 | 100.4 |    11 |    0.44
        3 | 100.4 | 138.8 |     5 |     0.2
        3 | 138.8 | 177.2 |     4 |    0.16
        3 | 177.2 | 215.6 |     1 |    0.04
        3 | 215.6 |   254 |     4 |    0.16

## Example: Just band 2 but for 6 bins

    SELECT (stats).*
    FROM (SELECT rid, ST_Histogram(rast, 2,6) As stats
        FROM dummy_rast
         WHERE rid=2) As foo;

        min     |    max     | count | percent
    ------------+------------+-------+---------
             78 | 107.333333 |     9 |    0.36
     107.333333 | 136.666667 |     6 |    0.24
     136.666667 |        166 |     0 |       0
            166 | 195.333333 |     4 |    0.16
     195.333333 | 224.666667 |     1 |    0.04
     224.666667 |        254 |     5 |     0.2
    (6 rows)

    -- Same as previous but we explicitly control the pixel value range of each bin.
    SELECT (stats).*
    FROM (SELECT rid, ST_Histogram(rast, 2,6,ARRAY[0.5,1,4,100,5]) As stats
        FROM dummy_rast
         WHERE rid=2) As foo;

      min  |  max  | count | percent
    -------+-------+-------+----------
        78 |  78.5 |     1 |     0.08
      78.5 |  79.5 |     1 |     0.04
      79.5 |  83.5 |     0 |        0
      83.5 | 183.5 |    17 |   0.0068
     183.5 | 188.5 |     0 |        0
     188.5 |   254 |     6 | 0.003664
    (6 rows)

## See Also

ST_Count, ST_SummaryStats, ST_SummaryStatsAgg

## Name

ST_Quantile — Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.

## Synopsis

`SETOF record ST_Quantile(` raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] quantiles=NULL`)`;

`SETOF record ST_Quantile(` raster rast, double precision[] quantiles`)`;

`SETOF record ST_Quantile(` raster rast, integer nband, double precision[] quantiles`)`;

`double precision ST_Quantile(` raster rast, double precision quantile`)`;

`double precision ST_Quantile(` raster rast, boolean exclude_nodata_value, double precision quantile=NULL`)`;

`double precision ST_Quantile(` raster rast, integer nband, double precision quantile`)`;

`double precision ST_Quantile(` raster rast, integer nband, boolean exclude_nodata_value, double precision quantile`)`;

`double precision ST_Quantile(` raster rast, integer nband, double precision quantile`)`;

## Description

Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.

If `exclude_nodata_value` is set to false, will also count pixels with no data.

Changed: 3.1.0 Removed ST_Quantile(table_name, column_name) variant.

Availability: 2.0.0

## Examples

    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
    --Example will consider only pixels of band 1 that are not 249 and in named quantiles --

    SELECT (pvq).*
    FROM (SELECT ST_Quantile(rast, ARRAY[0.25,0.75]) As pvq
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvq).quantile;

     quantile | value
    ----------+-------
         0.25 |   253
         0.75 |   254

    SELECT ST_Quantile(rast, 0.75) As value
        FROM dummy_rast WHERE rid=2;

    value
    ------
      254

    --real live example.  Quantile of all pixels in band 2 intersecting a geometry
    SELECT rid, (ST_Quantile(rast,2)).* As pvc
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                )
    ORDER BY value, quantile,rid
    ;

     rid | quantile | value
    -----+----------+-------
       1 |        0 |     0
       2 |        0 |     0
      14 |        0 |     1
      15 |        0 |     2
      14 |     0.25 |    37
       1 |     0.25 |    42
      15 |     0.25 |    47
       2 |     0.25 |    50
      14 |      0.5 |    56
       1 |      0.5 |    64
      15 |      0.5 |    66
       2 |      0.5 |    77
      14 |     0.75 |    81
      15 |     0.75 |    87
       1 |     0.75 |    94
       2 |     0.75 |   106
      14 |        1 |   199
       1 |        1 |   244
       2 |        1 |   255
      15 |        1 |   255

## See Also

ST_Count, ST_SummaryStats, ST_SummaryStatsAgg, ST_SetBandNoDataValue

## Name

ST_SummaryStats — Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.

## Synopsis

`summarystats ST_SummaryStats(` raster rast, boolean exclude_nodata_value`)`;

`summarystats ST_SummaryStats(` raster rast, integer nband, boolean exclude_nodata_value`)`;

## Description

Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. If no band is specified `nband` defaults to 1.

By default only considers pixel values not equal to the `nodata` value. Set `exclude_nodata_value` to false to get count of all pixels.

By default will sample all pixels. To get faster response, set `sample_percent` to lower than 1

Changed: 3.1.0 ST_SummaryStats(rastertable, rastercolumn, ...) variants are removed. Use ST_SummaryStatsAgg instead.

Availability: 2.0.0

## Example: Single raster tile

    SELECT rid, band, (stats).*
    FROM (SELECT rid, band, ST_SummaryStats(rast, band) As stats
        FROM dummy_rast CROSS JOIN generate_series(1,3) As band
         WHERE rid=2) As foo;

     rid | band | count | sum  |    mean    |  stddev   | min | max
    -----+------+-------+------+------------+-----------+-----+-----
       2 |    1 |    23 | 5821 | 253.086957 |  1.248061 | 250 | 254
       2 |    2 |    25 | 3682 |     147.28 | 59.862188 |  78 | 254
       2 |    3 |    25 | 3290 |      131.6 | 61.647384 |  62 | 254

## Example: Summarize pixels that intersect buildings of interest

This example took 574ms on PostGIS windows 64-bit with all of Boston Buildings and aerial Tiles (tiles each 150x150 pixels ~ 134,000 tiles), ~102,000 building records

    WITH
    -- our features of interest
       feat AS (SELECT gid As building_id, geom_26986 As geom FROM buildings AS b
        WHERE gid IN(100, 103,150)
       ),
    -- clip band 2 of raster tiles to boundaries of builds
    -- then get stats for these clipped regions
       b_stats AS
        (SELECT  building_id, (stats).*
    FROM (SELECT building_id, ST_SummaryStats(ST_Clip(rast,2,geom)) As stats
        FROM aerials.boston
            INNER JOIN feat
        ON ST_Intersects(feat.geom,rast)
     ) As foo
     )
    -- finally summarize stats
    SELECT building_id, SUM(count) As num_pixels
      , MIN(min) As min_pval
      ,  MAX(max) As max_pval
      , SUM(mean*count)/SUM(count) As avg_pval
        FROM b_stats
     WHERE count > 0
        GROUP BY building_id
        ORDER BY building_id;
     building_id | num_pixels | min_pval | max_pval |     avg_pval
    -------------+------------+----------+----------+------------------
             100 |       1090 |        1 |      255 | 61.0697247706422
             103 |        655 |        7 |      182 | 70.5038167938931
             150 |        895 |        2 |      252 | 185.642458100559

## Example: Raster coverage

    -- stats for each band --
    SELECT band, (stats).*
    FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band) As stats
        FROM generate_series(1,3) As band) As foo;

     band |  count  |  sum   |       mean       |      stddev      | min | max
    ------+---------+--------+------------------+------------------+-----+-----
        1 | 8450000 | 725799 | 82.7064349112426 | 45.6800222638537 |   0 | 255
        2 | 8450000 | 700487 | 81.4197705325444 | 44.2161184161765 |   0 | 255
        3 | 8450000 | 575943 |  74.682739408284 | 44.2143885481407 |   0 | 255

    -- For a table -- will get better speed if set sampling to less than 100%
    -- Here we set to 25% and get a much faster answer
    SELECT band, (stats).*
    FROM (SELECT band, ST_SummaryStats('o_4_boston','rast', band,true,0.25) As stats
        FROM generate_series(1,3) As band) As foo;

     band |  count  |  sum   |       mean       |      stddev      | min | max
    ------+---------+--------+------------------+------------------+-----+-----
        1 | 2112500 | 180686 | 82.6890480473373 | 45.6961043857248 |   0 | 255
        2 | 2112500 | 174571 |  81.448503668639 | 44.2252623171821 |   0 | 255
        3 | 2112500 | 144364 | 74.6765884023669 | 44.2014869384578 |   0 | 255

## See Also

summarystats, ST_SummaryStatsAgg, ST_Count, ST_Clip

## Name

ST_SummaryStatsAgg — Aggregate. Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a set of raster. Band 1 is assumed is no band is specified.

## Synopsis

`summarystats ST_SummaryStatsAgg(` raster rast, integer nband, boolean exclude_nodata_value, double precision sample_percent`)`;

`summarystats ST_SummaryStatsAgg(` raster rast, boolean exclude_nodata_value, double precision sample_percent`)`;

`summarystats ST_SummaryStatsAgg(` raster rast, integer nband, boolean exclude_nodata_value`)`;

## Description

Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. If no band is specified `nband` defaults to 1.

By default only considers pixel values not equal to the `NODATA` value. Set `exclude_nodata_value` to False to get count of all pixels.

By default will sample all pixels. To get faster response, set `sample_percent` to value between 0 and 1

Availability: 2.2.0

## Examples

    WITH foo AS (
        SELECT
            rast.rast
        FROM (
            SELECT ST_SetValue(
                ST_SetValue(
                    ST_SetValue(
                        ST_AddBand(
                            ST_MakeEmptyRaster(10, 10, 10, 10, 2, 2, 0, 0,0)
                            , 1, '64BF', 0, 0
                        )
                        , 1, 1, 1, -10
                    )
                    , 1, 5, 4, 0
                )
                , 1, 5, 5, 3.14159
            ) AS rast
        ) AS rast
        FULL JOIN (
            SELECT generate_series(1, 10) AS id
        ) AS id
            ON 1 = 1
    )
    SELECT
        (stats).count,
        round((stats).sum::numeric, 3),
        round((stats).mean::numeric, 3),
        round((stats).stddev::numeric, 3),
        round((stats).min::numeric, 3),
        round((stats).max::numeric, 3)
    FROM (
        SELECT
            ST_SummaryStatsAgg(rast, 1, TRUE, 1) AS stats
        FROM foo
    ) bar;

     count |  round  | round  | round |  round  | round
    -------+---------+--------+-------+---------+-------
        20 | -68.584 | -3.429 | 6.571 | -10.000 | 3.142
    (1 row)

## See Also

summarystats, ST_SummaryStats, ST_Count, ST_Clip

## Name

ST_ValueCount — Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.

## Synopsis

`SETOF record ST_ValueCount(` raster rast, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(` raster rast, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(` raster rast, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`bigint ST_ValueCount(` raster rast, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(` raster rast, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(` raster rast, integer nband, double precision searchvalue, double precision roundto=0`)`;

`SETOF record ST_ValueCount(` text rastertable, text rastercolumn, integer nband=1, boolean exclude_nodata_value=true, double precision[] searchvalues=NULL, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(` text rastertable, text rastercolumn, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`SETOF record ST_ValueCount(` text rastertable, text rastercolumn, integer nband, double precision[] searchvalues, double precision roundto=0, double precision OUT value, integer OUT count`)`;

`bigintST_ValueCount(` text rastertable, text rastercolumn, integer nband, boolean exclude_nodata_value, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(` text rastertable, text rastercolumn, double precision searchvalue, double precision roundto=0`)`;

`bigint ST_ValueCount(` text rastertable, text rastercolumn, integer nband, double precision searchvalue, double precision roundto=0`)`;

## Description

Returns a set of records with columns `value` `count` which contain the pixel band value and count of pixels in the raster tile or raster coverage of selected band.

If no band is specified `nband` defaults to 1. If no `searchvalues` are specified, will return all pixel values found in the raster or raster coverage. If one searchvalue is given, will return an integer instead of records denoting the count of pixels having that pixel band value

If `exclude_nodata_value` is set to false, will also count pixels with no data.

Availability: 2.0.0

## Examples

    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,249) WHERE rid=2;
    --Example will count only pixels of band 1 that are not 249. --

    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;

     value | count
    -------+-------
       250 |     2
       251 |     1
       252 |     2
       253 |     6
       254 |    12

    -- Example will coount all pixels of band 1 including 249 --
    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast,1,false) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;

     value | count
    -------+-------
       249 |     2
       250 |     2
       251 |     1
       252 |     2
       253 |     6
       254 |    12

    -- Example will count only non-nodata value pixels of band 2
    SELECT (pvc).*
    FROM (SELECT ST_ValueCount(rast,2) As pvc
        FROM dummy_rast WHERE rid=2) As foo
        ORDER BY (pvc).value;
     value | count
    -------+-------
        78 |     1
        79 |     1
        88 |     1
        89 |     1
        96 |     1
        97 |     1
        98 |     1
        99 |     2
       112 |     2
    :

    --real live example.  Count all the pixels in an aerial raster tile band 2 intersecting a geometry
    -- and return only the pixel band values that have a count > 500
    SELECT (pvc).value, SUM((pvc).count) As total
    FROM (SELECT ST_ValueCount(rast,2) As pvc
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                 )
            ) As foo
        GROUP BY (pvc).value
        HAVING SUM((pvc).count) > 500
        ORDER BY (pvc).value;

     value | total
    -------+-----
        51 | 502
        54 | 521

    -- Just return count of pixels in each raster tile that have value of 100 of tiles that intersect  a specific geometry --
    SELECT rid, ST_ValueCount(rast,2,100) As count
        FROM o_4_boston
            WHERE ST_Intersects(rast,
                ST_GeomFromText('POLYGON((224486 892151,224486 892200,224706 892200,224706 892151,224486 892151))',26986)
                 ) ;

     rid | count
    -----+-------
       1 |    56
       2 |    95
      14 |    37
      15 |    64

## See Also

ST_Count, ST_SetBandNoDataValue

## 11.10. Raster Inputs

## Name

ST_RastFromWKB — Return a raster value from a Well-Known Binary (WKB) raster.

## Synopsis

`raster ST_RastFromWKB(` bytea wkb`)`;

## Description

Given a Well-Known Binary (WKB) raster, return a raster.

Availability: 2.5.0

## Examples

    SELECT (ST_Metadata(
        ST_RastFromWKB(
            '\001\000\000\000\000\000\000\000\000\000\000\000@\000\000\000\000\000\000\010@\000\000\000\000\000\000\340?\000\000\000\000\000\000\340?\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\012\000\000\000\012\000\024\000'::bytea
        )
    )).* AS metadata;

     upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    ------------+------------+-------+--------+--------+--------+-------+-------+------+----------
            0.5 |        0.5 |    10 |     20 |      2 |      3 |     0 |     0 |   10 |        0

## See Also

ST_MetaData, ST_RastFromHexWKB, ST_AsBinary/ST_AsWKB, ST_AsHexWKB

## Name

ST_RastFromHexWKB — Return a raster value from a Hex representation of Well-Known Binary (WKB) raster.

## Synopsis

`raster ST_RastFromHexWKB(` text wkb`)`;

## Description

Given a Well-Known Binary (WKB) raster in Hex representation, return a raster.

Availability: 2.5.0

## Examples

    SELECT (ST_Metadata(
        ST_RastFromHexWKB(
            '010000000000000000000000400000000000000840000000000000E03F000000000000E03F000000000000000000000000000000000A0000000A001400'
        )
    )).* AS metadata;

     upperleftx | upperlefty | width | height | scalex | scaley | skewx | skewy | srid | numbands
    ------------+------------+-------+--------+--------+--------+-------+-------+------+----------
            0.5 |        0.5 |    10 |     20 |      2 |      3 |     0 |     0 |   10 |        0

## See Also

ST_MetaData, ST_RastFromWKB, ST_AsBinary/ST_AsWKB, ST_AsHexWKB

## 11.11. Raster Outputs

## Name

ST_AsBinary/ST_AsWKB — Return the Well-Known Binary (WKB) representation of the raster.

## Synopsis

`bytea ST_AsBinary(` raster rast, boolean outasin=FALSE`)`;

`bytea ST_AsWKB(` raster rast, boolean outasin=FALSE`)`;

## Description

Returns the Binary representation of the raster. If `outasin` is TRUE, out-db bands are treated as in-db. Refer to raster/doc/RFC2-WellKnownBinaryFormat located in the PostGIS source folder for details of the representation.

This is useful in binary cursors to pull data out of the database without converting it to a string representation.

By default, WKB output contains the external file path for out-db bands. If the client does not have access to the raster file underlying an out-db band, set `outasin` to TRUE.

Enhanced: 2.1.0 Addition of `outasin`

Enhanced: 2.5.0 Addition of `ST_AsWKB`

## Examples

    SELECT ST_AsBinary(rast) As rastbin FROM dummy_rast WHERE rid=1;

                         rastbin
    ---------------------------------------------------------------------------------
    \001\000\000\000\000\000\000\000\000\000\000\000@\000\000\000\000\000\000\010@\000\000\000\000\000\000\340?\000\000\000\000\000\000\340?\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\012\000\000\000\012\000\024\000

## See Also

ST_RastFromWKB, ST_AsHexWKB

## Name

ST_AsHexWKB — Return the Well-Known Binary (WKB) in Hex representation of the raster.

## Synopsis

`bytea ST_AsHexWKB(` raster rast, boolean outasin=FALSE`)`;

## Description

Returns the Binary representation in Hex representation of the raster. If `outasin` is TRUE, out-db bands are treated as in-db. Refer to raster/doc/RFC2-WellKnownBinaryFormat located in the PostGIS source folder for details of the representation.

By default, Hex WKB output contains the external file path for out-db bands. If the client does not have access to the raster file underlying an out-db band, set `outasin` to TRUE.

Availability: 2.5.0

## Examples

    SELECT ST_AsHexWKB(rast) As rastbin FROM dummy_rast WHERE rid=1;

                                                            st_ashexwkb
    ----------------------------------------------------------------------------------------------------------------------------
     010000000000000000000000400000000000000840000000000000E03F000000000000E03F000000000000000000000000000000000A0000000A001400

## See Also

ST_RastFromHexWKB, ST_AsBinary/ST_AsWKB

## Name

ST_AsGDALRaster — Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALDrivers() to get a list of formats supported by your library.

## Synopsis

`bytea ST_AsGDALRaster(` raster rast, text format, text[] options=NULL, integer srid=sameassource`)`;

## Description

Returns the raster tile in the designated format. Arguments are itemized below:

- `format` format to output. This is dependent on the drivers compiled in your libgdal library. Generally available are 'JPEG', 'GTIff', 'PNG'. Use ST_GDALDrivers to get a list of formats supported by your library.

- `options` text array of GDAL options. Valid options are dependent on the format. Refer to GDAL Raster format options for more details.

- `srs` The proj4text or srtext (from spatial_ref_sys) to embed in the image

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## JPEG Output Example, multiple tiles as single raster

    SELECT ST_AsGDALRaster(ST_Union(rast), 'JPEG', ARRAY['QUALITY=50']) As rastjpg
    FROM dummy_rast
    WHERE rast && ST_MakeEnvelope(10, 10, 11, 11);

## Using PostgreSQL Large Object Support to export raster

One way to export raster into another format is using PostgreSQL large object export functions. We'lll repeat the prior example but also exporting. Note for this you'll need to have super user access to db since it uses server side lo functions. It will also export to path on server network. If you need export locally, use the psql equivalent lo_ functions which export to the local file system instead of the server file system.

    DROP TABLE IF EXISTS tmp_out ;

    CREATE TABLE tmp_out AS
    SELECT lo_from_bytea(0,
           ST_AsGDALRaster(ST_Union(rast), 'JPEG', ARRAY['QUALITY=50'])
            ) AS loid
      FROM dummy_rast
    WHERE rast && ST_MakeEnvelope(10, 10, 11, 11);

    SELECT lo_export(loid, '/tmp/dummy.jpg')
       FROM tmp_out;

    SELECT lo_unlink(loid)
      FROM tmp_out;

## GTIFF Output Examples

    SELECT ST_AsGDALRaster(rast, 'GTiff') As rastjpg
    FROM dummy_rast WHERE rid=2;

    -- Out GeoTiff with jpeg compression, 90% quality
    SELECT ST_AsGDALRaster(rast, 'GTiff',
      ARRAY['COMPRESS=JPEG', 'JPEG_QUALITY=90'],
      4269) As rasttiff
    FROM dummy_rast WHERE rid=2;

## See Also

Section 10.3, “Building Custom Applications with PostGIS Raster”, ST_GDALDrivers, ST_SRID

## Name

ST_AsJPEG — Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.

## Synopsis

`bytea ST_AsJPEG(` raster rast, text[] options=NULL`)`;

`bytea ST_AsJPEG(` raster rast, integer nband, integer quality`)`;

`bytea ST_AsJPEG(` raster rast, integer nband, text[] options=NULL`)`;

`bytea ST_AsJPEG(` raster rast, integer[] nbands, text[] options=NULL`)`;

`bytea ST_AsJPEG(` raster rast, integer[] nbands, integer quality`)`;

## Description

Returns the selected bands of the raster as a single Joint Photographic Exports Group Image (JPEG). Use ST_AsGDALRaster if you need to export as less common raster types. If no band is specified and 1 or more than 3 bands, then only the first band is used. If 3 bands then all 3 bands are used. There are many variants of the function with many options. These are itemized below:

- `nband` is for single band exports.

- `nbands` is an array of bands to export (note that max is 3 for JPEG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `quality` number from 0 to 100. The higher the number the crisper the image.

- `options` text Array of GDAL options as defined for JPEG (look at create_options for JPEG ST_GDALDrivers). For JPEG valid ones are `PROGRESSIVE` ON or OFF and `QUALITY` a range from 0 to 100 and default to 75. Refer to GDAL Raster format options for more details.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: Output

    -- output first 3 bands 75% quality
    SELECT ST_AsJPEG(rast) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output only first band as 90% quality
    SELECT ST_AsJPEG(rast,1,90) As rastjpg
        FROM dummy_rast WHERE rid=2;

    -- output first 3 bands (but make band 2 Red, band 1 green, and band 3 blue, progressive and 90% quality
    SELECT ST_AsJPEG(rast,ARRAY[2,1,3],ARRAY['QUALITY=90','PROGRESSIVE=ON']) As rastjpg
        FROM dummy_rast WHERE rid=2;

## See Also

Section 10.3, “Building Custom Applications with PostGIS Raster”, ST_GDALDrivers, ST_AsGDALRaster, ST_AsPNG, ST_AsTIFF

## Name

ST_AsPNG — Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.

## Synopsis

`bytea ST_AsPNG(` raster rast, text[] options=NULL`)`;

`bytea ST_AsPNG(` raster rast, integer nband, integer compression`)`;

`bytea ST_AsPNG(` raster rast, integer nband, text[] options=NULL`)`;

`bytea ST_AsPNG(` raster rast, integer[] nbands, integer compression`)`;

`bytea ST_AsPNG(` raster rast, integer[] nbands, text[] options=NULL`)`;

## Description

Returns the selected bands of the raster as a single Portable Network Graphics Image (PNG). Use ST_AsGDALRaster if you need to export as less common raster types. If no band is specified, then the first 3 bands are exported. There are many variants of the function with many options. If no `srid` is specified then then srid of the raster is used. These are itemized below:

- `nband` is for single band exports.

- `nbands` is an array of bands to export (note that max is 4 for PNG) and the order of the bands is RGBA. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `compression` number from 1 to 9. The higher the number the greater the compression.

- `options` text Array of GDAL options as defined for PNG (look at create_options for PNG of ST_GDALDrivers). For PNG valid one is only ZLEVEL (amount of time to spend on compression -- default 6) e.g. ARRAY['ZLEVEL=9']. WORLDFILE is not allowed since the function would have to output two outputs. Refer to GDAL Raster format options for more details.

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples

    SELECT ST_AsPNG(rast) As rastpng
    FROM dummy_rast WHERE rid=2;

    -- export the first 3 bands and map band 3 to Red, band 1 to Green, band 2 to blue
    SELECT ST_AsPNG(rast, ARRAY[3,1,2]) As rastpng
    FROM dummy_rast WHERE rid=2;

## See Also

ST_AsGDALRaster, ST_ColorMap, ST_GDALDrivers, Section 10.3, “Building Custom Applications with PostGIS Raster”

## Name

ST_AsTIFF — Return the raster selected bands as a single TIFF image (byte array). If no band is specified or any of specified bands does not exist in the raster, then will try to use all bands.

## Synopsis

`bytea ST_AsTIFF(` raster rast, text[] options='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(` raster rast, text compression='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(` raster rast, integer[] nbands, text compression='', integer srid=sameassource`)`;

`bytea ST_AsTIFF(` raster rast, integer[] nbands, text[] options, integer srid=sameassource`)`;

## Description

Returns the selected bands of the raster as a single Tagged Image File Format (TIFF). If no band is specified, will try to use all bands. This is a wrapper around ST_AsGDALRaster. Use ST_AsGDALRaster if you need to export as less common raster types. There are many variants of the function with many options. If no spatial reference SRS text is present, the spatial reference of the raster is used. These are itemized below:

- `nbands` is an array of bands to export (note that max is 3 for PNG) and the order of the bands is RGB. e.g ARRAY[3,2,1] means map band 3 to Red, band 2 to green and band 1 to blue

- `compression` Compression expression -- JPEG90 (or some other percent), LZW, JPEG, DEFLATE9.

- `options` text Array of GDAL create options as defined for GTiff (look at create_options for GTiff of ST_GDALDrivers). or refer to GDAL Raster format options for more details.

- `srid` srid of spatial_ref_sys of the raster. This is used to populate the georeference information

Availability: 2.0.0 - requires GDAL >= 1.6.0.

## Examples: Use jpeg compression 90%

    SELECT ST_AsTIFF(rast, 'JPEG90') As rasttiff
    FROM dummy_rast WHERE rid=2;

## See Also

ST_GDALDrivers, ST_AsGDALRaster, ST_SRID

## 11.12. Raster Processing: Map Algebra

## Name

ST_Clip — Returns the raster clipped by the input geometry. If band number is not specified, all bands are processed. If `crop` is not specified or TRUE, the output raster is cropped. If `touched` is set to TRUE, then touched pixels are included, otherwise only if the center of the pixel is in the geometry it is included.

## Synopsis

`raster ST_Clip(` raster rast, integer[] nband, geometry geom, double precision[] nodataval=NULL, boolean crop=TRUE, boolean touched=FALSE`)`;

`raster ST_Clip(` raster rast, integer nband, geometry geom, double precision nodataval, boolean crop=TRUE, boolean touched=FALSE`)`;

`raster ST_Clip(` raster rast, integer nband, geometry geom, boolean crop, boolean touched=FALSE`)`;

`raster ST_Clip(` raster rast, geometry geom, double precision[] nodataval=NULL, boolean crop=TRUE, boolean touched=FALSE`)`;

`raster ST_Clip(` raster rast, geometry geom, double precision nodataval, boolean crop=TRUE, boolean touched=FALSE`)`;

`raster ST_Clip(` raster rast, geometry geom, boolean crop, boolean touched=FALSE`)`;

## Description

Returns a raster that is clipped by the input geometry `geom`. If band index is not specified, all bands are processed.

Rasters resulting from ST_Clip must have a nodata value assigned for areas clipped, one for each band. If none are provided and the input raster do not have a nodata value defined, nodata values of the resulting raster are set to ST_MinPossibleValue(ST_BandPixelType(rast, band)). When the number of nodata value in the array is smaller than the number of band, the last one in the array is used for the remaining bands. If the number of nodata value is greater than the number of band, the extra nodata values are ignored. All variants accepting an array of nodata values also accept a single value which will be assigned to each band.

If `crop` is not specified, true is assumed meaning the output raster is cropped to the intersection of the `geom`and `rast` extents. If `crop` is set to false, the new raster gets the same extent as `rast`. If `touched` is set to true, then all pixels in the `rast` that intersect the geometry are selected.

The default behavior is touched=false, which will only select pixels where the center of the pixel is covered by the geometry.

Enhanced: 3.5.0 - touched argument added.

Availability: 2.0.0

Enhanced: 2.1.0 Rewritten in C

Examples here use Massachusetts aerial data available on MassGIS site MassGIS Aerial Orthos.

## Examples: Comparing selecting all touched vs. not all touched

    SELECT ST_Count(rast) AS count_pixels_in_orig, ST_Count(rast_touched) AS all_touched_pixels, ST_Count(rast_not_touched) AS default_clip
    FROM ST_AsRaster(ST_Letters('R'), scalex => 1.0, scaley => -1.0) AS r(rast)
        INNER JOIN ST_GeomFromText('LINESTRING(0 1, 5 6, 10 10)') AS g(geom)
     ON ST_Intersects(r.rast,g.geom)
     , ST_Clip(r.rast, g.geom, touched => true) AS rast_touched
     , ST_Clip(r.rast, g.geom, touched => false) AS rast_not_touched;

     count_pixels_in_orig | all_touched_pixels | default_clip
    ----------------------+--------------------+--------------
                     2605 |                 16 |           10
    (1 row)

## Examples: 1 band clipping (not touched)

    -- Clip the first band of an aerial tile by a 20 meter buffer.
    SELECT ST_Clip(rast, 1,
            ST_Buffer(ST_Centroid(ST_Envelope(rast)),20)
        ) from aerials.boston
    WHERE rid = 4;

    -- Demonstrate effect of crop on final dimensions of raster
    -- Note how final extent is clipped to that of the geometry
    -- if crop = true
    SELECT ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, true))) As xmax_w_trim,
        ST_XMax(clipper) As xmax_clipper,
        ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, false))) As xmax_wo_trim,
        ST_XMax(ST_Envelope(rast)) As xmax_rast_orig
    FROM (SELECT rast, ST_Buffer(ST_Centroid(ST_Envelope(rast)),6) As clipper
        FROM aerials.boston
    WHERE rid = 6) As foo;

       xmax_w_trim    |   xmax_clipper   |   xmax_wo_trim   |  xmax_rast_orig
    ------------------+------------------+------------------+------------------
     230657.436173996 | 230657.436173996 | 230666.436173996 | 230666.436173996

Full raster tile before clipping | After Clipping

## Examples: 1 band clipping with no crop and add back other bands unchanged

    -- Same example as before, but we need to set crop to false to be able to use ST_AddBand
    -- because ST_AddBand requires all bands be the same Width and height
    SELECT ST_AddBand(ST_Clip(rast, 1,
            ST_Buffer(ST_Centroid(ST_Envelope(rast)),20),false
        ), ARRAY[ST_Band(rast,2),ST_Band(rast,3)] ) from aerials.boston
    WHERE rid = 6;

Full raster tile before clipping | After Clipping - surreal

## Examples: Clip all bands

    -- Clip all bands of an aerial tile by a 20 meter buffer.
    -- Only difference is we don't specify a specific band to clip
    -- so all bands are clipped
    SELECT ST_Clip(rast,
          ST_Buffer(ST_Centroid(ST_Envelope(rast)), 20),
          false
        ) from aerials.boston
    WHERE rid = 4;

Full raster tile before clipping | After Clipping

## See Also

ST_AddBand, ST_Count, ST_MapAlgebra (callback function version), ST_Intersection

## Name

ST_ColorMap — Creates a new raster of up to four 8BUI bands (grayscale, RGB, RGBA) from the source raster and a specified band. Band 1 is assumed if not specified.

## Synopsis

`raster ST_ColorMap(` raster rast, integer nband=1, text colormap=grayscale, text method=INTERPOLATE`)`;

`raster ST_ColorMap(` raster rast, text colormap, text method=INTERPOLATE`)`;

## Description

Apply a `colormap` to the band at `nband` of `rast` resulting a new raster comprised of up to four 8BUI bands. The number of 8BUI bands in the new raster is determined by the number of color components defined in `colormap`.

If `nband` is not specified, then band 1 is assumed.

`colormap` can be a keyword of a pre-defined colormap or a set of lines defining the value and the color components.

Valid pre-defined `colormap` keyword:

- `grayscale` or `greyscale` for a one 8BUI band raster of shades of gray.

- `pseudocolor` for a four 8BUI (RGBA) band raster with colors going from blue to green to red.

- `fire` for a four 8BUI (RGBA) band raster with colors going from black to red to pale yellow.

- `bluered` for a four 8BUI (RGBA) band raster with colors going from blue to pale white to red.

Users can pass a set of entries (one per line) to `colormap` to specify custom colormaps. Each entry generally consists of five values: the pixel value and corresponding Red, Green, Blue, Alpha components (color components between 0 and 255). Percent values can be used instead of pixel values where 0% and 100% are the minimum and maximum values found in the raster band. Values can be separated with commas (','), tabs, colons (':') and/or spaces. The pixel value can be set to nv, null or nodata for the NODATA value. An example is provided below.

    5 0 0 0 255
    4 100:50 55 255
    1 150,100 150 255
    0% 255 255 255 255
    nv 0 0 0 0

The syntax of `colormap` is similar to that of the color-relief mode of GDAL gdaldem.

Valid keywords for `method`:

- `INTERPOLATE` to use linear interpolation to smoothly blend the colors between the given pixel values

- `EXACT` to strictly match only those pixels values found in the colormap. Pixels whose value does not match a colormap entry will be set to 0 0 0 0 (RGBA)

- `NEAREST` to use the colormap entry whose value is closest to the pixel value

A great reference for colormaps is ColorBrewer.

The resulting bands of new raster will have no NODATA value set. Use ST_SetBandNoDataValue to set a NODATA value if one is needed.

Availability: 2.1.0

## Examples

This is a junk table to play with

    -- setup test raster table --
    DROP TABLE IF EXISTS funky_shapes;
    CREATE TABLE funky_shapes(rast raster);

    INSERT INTO funky_shapes(rast)
    WITH ref AS (
        SELECT ST_MakeEmptyRaster( 200, 200, 0, 200, 1, -1, 0, 0) AS rast
    )
    SELECT
        ST_Union(rast)
    FROM (
        SELECT
            ST_AsRaster(
                ST_Rotate(
                    ST_Buffer(
                        ST_GeomFromText('LINESTRING(0 2,50 50,150 150,125 50)'),
                        i*2
                    ),
                    pi() * i * 0.125, ST_Point(50,50)
                ),
                ref.rast, '8BUI'::text, i * 5
            ) AS rast
        FROM ref
        CROSS JOIN generate_series(1, 10, 3) AS i
    ) AS shapes;

    SELECT
        ST_NumBands(rast) As n_orig,
        ST_NumBands(ST_ColorMap(rast,1, 'greyscale')) As ngrey,
        ST_NumBands(ST_ColorMap(rast,1, 'pseudocolor')) As npseudo,
        ST_NumBands(ST_ColorMap(rast,1, 'fire')) As nfire,
        ST_NumBands(ST_ColorMap(rast,1, 'bluered')) As nbluered,
        ST_NumBands(ST_ColorMap(rast,1, '
    100% 255   0   0
     80% 160   0   0
     50% 130   0   0
     30%  30   0   0
     20%  60   0   0
      0%   0   0   0
      nv 255 255 255
        ')) As nred
    FROM funky_shapes;

     n_orig | ngrey | npseudo | nfire | nbluered | nred
    --------+-------+---------+-------+----------+------
          1 |     1 |       4 |     4 |        4 |    3

## Examples: Compare different color map looks using ST_AsPNG

    SELECT
        ST_AsPNG(rast) As orig_png,
        ST_AsPNG(ST_ColorMap(rast,1,'greyscale')) As grey_png,
        ST_AsPNG(ST_ColorMap(rast,1, 'pseudocolor')) As pseudo_png,
        ST_AsPNG(ST_ColorMap(rast,1, 'nfire')) As fire_png,
        ST_AsPNG(ST_ColorMap(rast,1, 'bluered')) As bluered_png,
        ST_AsPNG(ST_ColorMap(rast,1, '
    100% 255   0   0
     80% 160   0   0
     50% 130   0   0
     30%  30   0   0
     20%  60   0   0
      0%   0   0   0
      nv 255 255 255
        ')) As red_png
    FROM funky_shapes;

orig_png | grey_png | pseudo_png
fire_png | bluered_png | red_png

## See Also

ST_AsPNG, ST_AsRaster ST_MapAlgebra (callback function version), ST_Grayscale ST_NumBands, ST_Reclass, ST_SetBandNoDataValue, ST_Union

## Name

ST_Grayscale — Creates a new one-8BUI band raster from the source raster and specified bands representing Red, Green and Blue

## Synopsis

`(1) raster ST_Grayscale(` raster rast, integer redband=1, integer greenband=2, integer blueband=3, text extenttype=INTERSECTION`)`;

`(2) raster ST_Grayscale(` rastbandarg[] rastbandargset, text extenttype=INTERSECTION`)`;

## Description

Create a raster with one 8BUI band given three input bands (from one or more rasters). Any input band whose pixel type is not 8BUI will be reclassified using ST_Reclass.

This function is not like ST_ColorMap with the `grayscale` keyword as ST_ColorMap operates on only one band while this function expects three bands for RGB. This function applies the following equation for converting RGB to Grayscale: 0.2989 * RED + 0.5870 * GREEN + 0.1140 * BLUE

Availability: 2.5.0

## Examples: Variant 1

    SET postgis.gdal_enabled_drivers = 'ENABLE_ALL';
    SET postgis.enable_outdb_rasters = True;

    WITH apple AS (
        SELECT ST_AddBand(
            ST_MakeEmptyRaster(350, 246, 0, 0, 1, -1, 0, 0, 0),
            '/tmp/apple.png'::text,
            NULL::int[]
        ) AS rast
    )
    SELECT
        ST_AsPNG(rast) AS original_png,
        ST_AsPNG(ST_Grayscale(rast)) AS grayscale_png
    FROM apple;

original_png | grayscale_png

## Examples: Variant 2

    SET postgis.gdal_enabled_drivers = 'ENABLE_ALL';
    SET postgis.enable_outdb_rasters = True;

    WITH apple AS (
        SELECT ST_AddBand(
            ST_MakeEmptyRaster(350, 246, 0, 0, 1, -1, 0, 0, 0),
            '/tmp/apple.png'::text,
            NULL::int[]
        ) AS rast
    )
    SELECT
        ST_AsPNG(rast) AS original_png,
        ST_AsPNG(ST_Grayscale(
            ARRAY[
                ROW(rast, 1)::rastbandarg, -- red
                ROW(rast, 2)::rastbandarg, -- green
                ROW(rast, 3)::rastbandarg, -- blue
            ]::rastbandarg[]
        )) AS grayscale_png
    FROM apple;

## See Also

ST_AsPNG, ST_Reclass, ST_ColorMap

## Name

ST_Intersection — Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.

## Synopsis

`setof geomval ST_Intersection(` geometry geom, raster rast, integer band_num=1`)`;

`setof geomval ST_Intersection(` raster rast, geometry geom`)`;

`setof geomval ST_Intersection(` raster rast, integer band, geometry geomin`)`;

`raster ST_Intersection(` raster rast1, raster rast2, double precision[] nodataval`)`;

`raster ST_Intersection(` raster rast1, raster rast2, text returnband, double precision[] nodataval`)`;

`raster ST_Intersection(` raster rast1, integer band1, raster rast2, integer band2, double precision[] nodataval`)`;

`raster ST_Intersection(` raster rast1, integer band1, raster rast2, integer band2, text returnband, double precision[] nodataval`)`;

## Description

Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.

The first three variants, returning a setof geomval, works in vector space. The raster is first vectorized (using ST_DumpAsPolygons) into a set of geomval rows and those rows are then intersected with the geometry using the ST_Intersection (geometry, geometry) PostGIS function. Geometries intersecting only with a nodata value area of a raster returns an empty geometry. They are normally excluded from the results by the proper usage of ST_Intersects in the WHERE clause.

You can access the geometry and the value parts of the resulting set of geomval by surrounding them with parenthesis and adding '.geom' or '.val' at the end of the expression. e.g. (ST_Intersection(rast, geom)).geom

The other variants, returning a raster, works in raster space. They are using the two rasters version of ST_MapAlgebraExpr to perform the intersection.

The extent of the resulting raster corresponds to the geometrical intersection of the two raster extents. The resulting raster includes 'BAND1', 'BAND2' or 'BOTH' bands, following what is passed as the `returnband` parameter. Nodata value areas present in any band results in nodata value areas in every bands of the result. In other words, any pixel intersecting with a nodata value pixel becomes a nodata value pixel in the result.

Rasters resulting from ST_Intersection must have a nodata value assigned for areas not intersecting. You can define or replace the nodata value for any resulting band by providing a `nodataval[]` array of one or two nodata values depending if you request 'BAND1', 'BAND2' or 'BOTH' bands. The first value in the array replace the nodata value in the first band and the second value replace the nodata value in the second band. If one input band do not have a nodata value defined and none are provided as an array, one is chosen using the ST_MinPossibleValue function. All variant accepting an array of nodata value can also accept a single value which will be assigned to each requested band.

In all variants, if no band number is specified band 1 is assumed. If you need an intersection between a raster and geometry that returns a raster, refer to ST_Clip.

To get more control on the resulting extent or on what to return when encountering a nodata value, use the two rasters version of ST_MapAlgebraExpr.

To compute the intersection of a raster band with a geometry in raster space, use ST_Clip. ST_Clip works on multiple bands rasters and does not return a band corresponding to the rasterized geometry.

ST_Intersection should be used in conjunction with ST_Intersects and an index on the raster column and/or the geometry column.

Enhanced: 2.0.0 - Intersection in the raster space was introduced. In earlier pre-2.0.0 versions, only intersection performed in vector space were supported.

## Examples: Geometry, Raster -- resulting in geometry vals

    SELECT
        foo.rid,
        foo.gid,
        ST_AsText((foo.geomval).geom) As geomwkt,
        (foo.geomval).val
    FROM (
        SELECT
            A.rid,
            g.gid,
            ST_Intersection(A.rast, g.geom) As geomval
        FROM dummy_rast AS A
        CROSS JOIN (
            VALUES
                (1, ST_Point(3427928, 5793243.85) ),
                (2, ST_GeomFromText('LINESTRING(3427927.85 5793243.75,3427927.8 5793243.75,3427927.8 5793243.8)')),
                (3, ST_GeomFromText('LINESTRING(1 2, 3 4)'))
        ) As g(gid,geom)
        WHERE A.rid = 2
    ) As foo;

     rid | gid |      geomwkt                                               | val
    -----+-----+---------------------------------------------------------------------------------------------
       2 |   1 | POINT(3427928 5793243.85)                                  | 249
       2 |   1 | POINT(3427928 5793243.85)                                  | 253
       2 |   2 | POINT(3427927.85 5793243.75)                               | 254
       2 |   2 | POINT(3427927.8 5793243.8)                                 | 251
       2 |   2 | POINT(3427927.8 5793243.8)                                 | 253
       2 |   2 | LINESTRING(3427927.8 5793243.75,3427927.8 5793243.8)   | 252
       2 |   2 | MULTILINESTRING((3427927.8 5793243.8,3427927.8 5793243.75),...) | 250
       2 |   3 | GEOMETRYCOLLECTION EMPTY

## See Also

geomval, ST_Intersects, ST_MapAlgebraExpr, ST_Clip, ST_AsText

## Name

ST_MapAlgebra (callback function version) — Callback function version - Returns a one-band raster given one or more input rasters, band indexes and one user-specified callback function.

## Synopsis

`raster ST_MapAlgebra(` rastbandarg[] rastbandargset, regprocedure callbackfunc, text pixeltype=NULL, text extenttype=INTERSECTION, raster customextent=NULL, integer distancex=0, integer distancey=0, text[] VARIADIC userargs=NULL`)`;

`raster ST_MapAlgebra(` raster rast, integer[] nband, regprocedure callbackfunc, text pixeltype=NULL, text extenttype=FIRST, raster customextent=NULL, integer distancex=0, integer distancey=0, text[] VARIADIC userargs=NULL`)`;

`raster ST_MapAlgebra(` raster rast, integer nband, regprocedure callbackfunc, text pixeltype=NULL, text extenttype=FIRST, raster customextent=NULL, integer distancex=0, integer distancey=0, text[] VARIADIC userargs=NULL`)`;

`raster ST_MapAlgebra(` raster rast1, integer nband1, raster rast2, integer nband2, regprocedure callbackfunc, text pixeltype=NULL, text extenttype=INTERSECTION, raster customextent=NULL, integer distancex=0, integer distancey=0, text[] VARIADIC userargs=NULL`)`;

`raster ST_MapAlgebra(` raster rast, integer nband, regprocedure callbackfunc, float8[] mask, boolean weighted, text pixeltype=NULL, text extenttype=INTERSECTION, raster customextent=NULL, text[] VARIADIC userargs=NULL`)`;

## Description

Returns a one-band raster given one or more input rasters, band indexes and one user-specified callback function.

`rast,rast1,rast2, rastbandargset`

  Rasters on which the map algebra process is evaluated.

  `rastbandargset` allows the use of a map algebra operation on many rasters and/or many bands. See example Variant 1.

`nband, nband1, nband2`

  Band numbers of the raster to be evaluated. nband can be an integer or integer[] denoting the bands. nband1 is band on rast1 and nband2 is band on rast2 for the 2 raster/2band case.

`callbackfunc`

  The `callbackfunc` parameter must be the name and signature of an SQL or PL/pgSQL function, cast to a regprocedure. An example PL/pgSQL function example is:

      CREATE OR REPLACE FUNCTION sample_callbackfunc(value double precision[][][], position integer[][], VARIADIC userargs text[])
          RETURNS double precision
          AS $$
          BEGIN
              RETURN 0;
          END;
          $$ LANGUAGE 'plpgsql' IMMUTABLE;

  The `callbackfunc` must have three arguments: a 3-dimension double precision array, a 2-dimension integer array and a variadic 1-dimension text array. The first argument `value` is the set of values (as double precision) from all input rasters. The three dimensions (where indexes are 1-based) are: raster #, row y, column x. The second argument `position` is the set of pixel positions from the output raster and input rasters. The outer dimension (where indexes are 0-based) is the raster #. The position at outer dimension index 0 is the output raster's pixel position. For each outer dimension, there are two elements in the inner dimension for X and Y. The third argument `userargs` is for passing through any user-specified arguments.

  Passing a regprocedure argument to a SQL function requires the full function signature to be passed, then cast to a regprocedure type. To pass the above example PL/pgSQL function as an argument, the SQL for the argument is:

      'sample_callbackfunc(double precision[], integer[], text[])'::regprocedure

  Note that the argument contains the name of the function, the types of the function arguments, quotes around the name and argument types, and a cast to a regprocedure.

`mask`

  An n-dimensional array (matrix) of numbers used to filter what cells get passed to map algebra call-back function. 0 means a neighbor cell value should be treated as no-data and 1 means value should be treated as data. If weight is set to true, then the values, are used as multipliers to multiple the pixel value of that value in the neighborhood position.

`weighted`

  boolean (true/false) to denote if a mask value should be weighted (multiplied by original value) or not (only applies to proto that takes a mask).

`pixeltype`

  If `pixeltype` is passed in, the one band of the new raster will be of that pixeltype. If pixeltype is passed NULL or left out, the new raster band will have the same pixeltype as the specified band of the first raster (for extent types: INTERSECTION, UNION, FIRST, CUSTOM) or the specified band of the appropriate raster (for extent types: SECOND, LAST). If in doubt, always specify `pixeltype`.

  The resulting pixel type of the output raster must be one listed in ST_BandPixelType or left out or set to NULL.

`extenttype`

  Possible values are INTERSECTION (default), UNION, FIRST (default for one raster variants), SECOND, LAST, CUSTOM.

`customextent`

  If `extentype` is CUSTOM, a raster must be provided for `customextent`. See example 4 of Variant 1.

`distancex`

  The distance in pixels from the reference cell in x direction. So width of resulting matrix would be `2*distancex + 1`.If not specified only the reference cell is considered (neighborhood of 0).

`distancey`

  The distance in pixels from reference cell in y direction. Height of resulting matrix would be `2*distancey + 1` .If not specified only the reference cell is considered (neighborhood of 0).

`userargs`

  The third argument to the `callbackfunc` is a variadic text array. All trailing text arguments are passed through to the specified `callbackfunc`, and are contained in the `userargs` argument.

For more information about the VARIADIC keyword, please refer to the PostgreSQL documentation and the "SQL Functions with Variable Numbers of Arguments" section of Query Language (SQL) Functions.

The text[] argument to the `callbackfunc` is required, regardless of whether you choose to pass any arguments to the callback function for processing or not.

Variant 1 accepts an array of `rastbandarg` allowing the use of a map algebra operation on many rasters and/or many bands. See example Variant 1.

Variants 2 and 3 operate upon one or more bands of one raster. See example Variant 2 and 3.

Variant 4 operate upon two rasters with one band per raster. See example Variant 4.

Availability: 2.2.0: Ability to add a mask

Availability: 2.1.0

## Examples: Variant 1

One raster, one band

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            ARRAY[ROW(rast, 1)]::rastbandarg[],
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo

One raster, several bands

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI', 100, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            ARRAY[ROW(rast, 3), ROW(rast, 1), ROW(rast, 3), ROW(rast, 2)]::rastbandarg[],
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo

Several rasters, several bands

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI', 100, 0) AS rast UNION ALL
        SELECT 2 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 1, 1, -1, 0, 0, 0), 1, '16BUI', 2, 0), 2, '8BUI', 20, 0), 3, '32BUI', 300, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            ARRAY[ROW(t1.rast, 3), ROW(t2.rast, 1), ROW(t2.rast, 3), ROW(t1.rast, 2)]::rastbandarg[],
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo t1
    CROSS JOIN foo t2
    WHERE t1.rid = 1
        AND t2.rid = 2

Complete example of tiles of a coverage with neighborhood. This query only works with PostgreSQL 9.1 or higher.

    WITH foo AS (
        SELECT 0 AS rid, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0) AS rast UNION ALL
        SELECT 1, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, 0, 1, -1, 0, 0, 0), 1, '16BUI', 2, 0) AS rast UNION ALL
        SELECT 2, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, 0, 1, -1, 0, 0, 0), 1, '16BUI', 3, 0) AS rast UNION ALL

        SELECT 3, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, -2, 1, -1, 0, 0, 0), 1, '16BUI', 10, 0) AS rast UNION ALL
        SELECT 4, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, -2, 1, -1, 0, 0, 0), 1, '16BUI', 20, 0) AS rast UNION ALL
        SELECT 5, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, -2, 1, -1, 0, 0, 0), 1, '16BUI', 30, 0) AS rast UNION ALL

        SELECT 6, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, -4, 1, -1, 0, 0, 0), 1, '16BUI', 100, 0) AS rast UNION ALL
        SELECT 7, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, -4, 1, -1, 0, 0, 0), 1, '16BUI', 200, 0) AS rast UNION ALL
        SELECT 8, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, -4, 1, -1, 0, 0, 0), 1, '16BUI', 300, 0) AS rast
    )
    SELECT
        t1.rid,
        ST_MapAlgebra(
            ARRAY[ROW(ST_Union(t2.rast), 1)]::rastbandarg[],
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure,
            '32BUI',
            'CUSTOM', t1.rast,
            1, 1
        ) AS rast
    FROM foo t1
    CROSS JOIN foo t2
    WHERE t1.rid = 4
        AND t2.rid BETWEEN 0 AND 8
        AND ST_Intersects(t1.rast, t2.rast)
    GROUP BY t1.rid, t1.rast

Example like the prior one for tiles of a coverage with neighborhood but works with PostgreSQL 9.0.

    WITH src AS (
        SELECT 0 AS rid, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0) AS rast UNION ALL
        SELECT 1, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, 0, 1, -1, 0, 0, 0), 1, '16BUI', 2, 0) AS rast UNION ALL
        SELECT 2, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, 0, 1, -1, 0, 0, 0), 1, '16BUI', 3, 0) AS rast UNION ALL

        SELECT 3, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, -2, 1, -1, 0, 0, 0), 1, '16BUI', 10, 0) AS rast UNION ALL
        SELECT 4, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, -2, 1, -1, 0, 0, 0), 1, '16BUI', 20, 0) AS rast UNION ALL
        SELECT 5, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, -2, 1, -1, 0, 0, 0), 1, '16BUI', 30, 0) AS rast UNION ALL

        SELECT 6, ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, -4, 1, -1, 0, 0, 0), 1, '16BUI', 100, 0) AS rast UNION ALL
        SELECT 7, ST_AddBand(ST_MakeEmptyRaster(2, 2, 2, -4, 1, -1, 0, 0, 0), 1, '16BUI', 200, 0) AS rast UNION ALL
        SELECT 8, ST_AddBand(ST_MakeEmptyRaster(2, 2, 4, -4, 1, -1, 0, 0, 0), 1, '16BUI', 300, 0) AS rast
    )
    WITH foo AS (
        SELECT
            t1.rid,
            ST_Union(t2.rast) AS rast
        FROM src t1
        JOIN src t2
            ON ST_Intersects(t1.rast, t2.rast)
            AND t2.rid BETWEEN 0 AND 8
        WHERE t1.rid = 4
        GROUP BY t1.rid
    ), bar AS (
        SELECT
            t1.rid,
            ST_MapAlgebra(
                ARRAY[ROW(t2.rast, 1)]::rastbandarg[],
                'raster_nmapalgebra_test(double precision[], int[], text[])'::regprocedure,
                '32BUI',
                'CUSTOM', t1.rast,
                1, 1
            ) AS rast
        FROM src t1
        JOIN foo t2
            ON t1.rid = t2.rid
    )
    SELECT
        rid,
        (ST_Metadata(rast)),
        (ST_BandMetadata(rast, 1)),
        ST_Value(rast, 1, 1, 1)
    FROM bar;

## Examples: Variants 2 and 3

One raster, several bands

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI', 100, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            rast, ARRAY[3, 1, 3, 2]::integer[],
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo

One raster, one band

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI', 100, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            rast, 2,
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo

## Examples: Variant 4

Two rasters, two bands

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI', 100, 0) AS rast UNION ALL
        SELECT 2 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 1, 1, -1, 0, 0, 0), 1, '16BUI', 2, 0), 2, '8BUI', 20, 0), 3, '32BUI', 300, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            t1.rast, 2,
            t2.rast, 1,
            'sample_callbackfunc(double precision[], int[], text[])'::regprocedure
        ) AS rast
    FROM foo t1
    CROSS JOIN foo t2
    WHERE t1.rid = 1
        AND t2.rid = 2

## Examples: Using Masks

    WITH foo AS (SELECT
       ST_SetBandNoDataValue(
    ST_SetValue(ST_SetValue(ST_AsRaster(
            ST_Buffer(
                ST_GeomFromText('LINESTRING(50 50,100 90,100 50)'), 5,'join=bevel'),
                200,200,ARRAY['8BUI'], ARRAY[100], ARRAY[0]), ST_Buffer('POINT(70 70)'::geometry,10,'quad_segs=1') ,50),
      'LINESTRING(20 20, 100 100, 150 98)'::geometry,1),0)  AS rast )
    SELECT 'original' AS title, rast
    FROM foo
    UNION ALL
    SELECT 'no mask mean value' AS title, ST_MapAlgebra(rast,1,'ST_mean4ma(double precision[], int[], text[])'::regprocedure) AS rast
    FROM foo
    UNION ALL
    SELECT 'mask only consider neighbors, exclude center' AS title, ST_MapAlgebra(rast,1,'ST_mean4ma(double precision[], int[], text[])'::regprocedure,
        '{{1,1,1}, {1,0,1}, {1,1,1}}'::double precision[], false) As rast
    FROM foo

    UNION ALL
    SELECT 'mask weighted only consider neighbors, exclude center multi other pixel values by 2' AS title, ST_MapAlgebra(rast,1,'ST_mean4ma(double precision[], int[], text[])'::regprocedure,
        '{{2,2,2}, {2,0,2}, {2,2,2}}'::double precision[], true) As rast
    FROM foo;

original | no mask mean value (same as having all 1s in mask matrix)
mask only consider neighbors, exclude center | mask weighted only consider neighbors, exclude center multi other pixel values by 2

## See Also

rastbandarg, ST_Union, ST_MapAlgebra (expression version)

## Name

ST_MapAlgebra (expression version) — Expression version - Returns a one-band raster given one or two input rasters, band indexes and one or more user-specified SQL expressions.

## Synopsis

`raster ST_MapAlgebra(` raster rast, integer nband, text pixeltype, text expression, double precision nodataval=NULL`)`;

`raster ST_MapAlgebra(` raster rast, text pixeltype, text expression, double precision nodataval=NULL`)`;

`raster ST_MapAlgebra(` raster rast1, integer nband1, raster rast2, integer nband2, text expression, text pixeltype=NULL, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

`raster ST_MapAlgebra(` raster rast1, raster rast2, text expression, text pixeltype=NULL, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

## Description

Expression version - Returns a one-band raster given one or two input rasters, band indexes and one or more user-specified SQL expressions.

Availability: 2.1.0

## Description: Variants 1 and 2 (one raster)

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation defined by the `expression` on the input raster (`rast`). If `nband` is not provided, band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input `rast` band.

- Keywords permitted for `expression`

  1. `[rast]` - Pixel value of the pixel of interest

  2. `[rast.val]` - Pixel value of the pixel of interest

  3. `[rast.x]` - 1-based pixel column of the pixel of interest

  4. `[rast.y]` - 1-based pixel row of the pixel of interest

## Description: Variants 3 and 4 (two raster)

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation to the two bands defined by the `expression` on the two input raster bands `rast1`, (`rast2`). If no `band1`, `band2` is specified band 1 is assumed. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster. The resulting raster will have the extent defined by the `extenttype` parameter.

`expression`

  A PostgreSQL algebraic expression involving the two rasters and PostgreSQL defined functions/operators that will define the pixel value when pixels intersect. e.g. (([rast1] + [rast2])/2.0)::integer

`pixeltype`

  The resulting pixel type of the output raster. Must be one listed in ST_BandPixelType, left out or set to NULL. If not passed in or set to NULL, will default to the pixeltype of the first raster.

`extenttype`

  Controls the extent of resulting raster

  1. `INTERSECTION` - The extent of the new raster is the intersection of the two rasters. This is the default.

  2. `UNION` - The extent of the new raster is the union of the two rasters.

  3. `FIRST` - The extent of the new raster is the same as the one of the first raster.

  4. `SECOND` - The extent of the new raster is the same as the one of the second raster.

`nodata1expr`

  An algebraic expression involving only `rast2` or a constant that defines what to return when pixels of `rast1` are nodata values and spatially corresponding rast2 pixels have values.

`nodata2expr`

  An algebraic expression involving only `rast1` or a constant that defines what to return when pixels of `rast2` are nodata values and spatially corresponding rast1 pixels have values.

`nodatanodataval`

  A numeric constant to return when spatially corresponding rast1 and rast2 pixels are both nodata values.

- Keywords permitted in `expression`, `nodata1expr` and `nodata2expr`

  1. `[rast1]` - Pixel value of the pixel of interest from `rast1`

  2. `[rast1.val]` - Pixel value of the pixel of interest from `rast1`

  3. `[rast1.x]` - 1-based pixel column of the pixel of interest from `rast1`

  4. `[rast1.y]` - 1-based pixel row of the pixel of interest from `rast1`

  5. `[rast2]` - Pixel value of the pixel of interest from `rast2`

  6. `[rast2.val]` - Pixel value of the pixel of interest from `rast2`

  7. `[rast2.x]` - 1-based pixel column of the pixel of interest from `rast2`

  8. `[rast2.y]` - 1-based pixel row of the pixel of interest from `rast2`

## Examples: Variants 1 and 2

    WITH foo AS (
        SELECT ST_AddBand(ST_MakeEmptyRaster(10, 10, 0, 0, 1, 1, 0, 0, 0), '32BF'::text, 1, -1) AS rast
    )
    SELECT
        ST_MapAlgebra(rast, 1, NULL, 'ceil([rast]*[rast.x]/[rast.y]+[rast.val])')
    FROM foo;

## Examples: Variant 3 and 4

    WITH foo AS (
        SELECT 1 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 0, 1, -1, 0, 0, 0), 1, '16BUI', 1, 0), 2, '8BUI', 10, 0), 3, '32BUI'::text, 100, 0) AS rast UNION ALL
        SELECT 2 AS rid, ST_AddBand(ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(2, 2, 0, 1, 1, -1, 0, 0, 0), 1, '16BUI', 2, 0), 2, '8BUI', 20, 0), 3, '32BUI'::text, 300, 0) AS rast
    )
    SELECT
        ST_MapAlgebra(
            t1.rast, 2,
            t2.rast, 1,
            '([rast2] + [rast1.val]) / 2'
        ) AS rast
    FROM foo t1
    CROSS JOIN foo t2
    WHERE t1.rid = 1
        AND t2.rid = 2;

## See Also

rastbandarg, ST_Union, ST_MapAlgebra (callback function version)

## Name

ST_MapAlgebraExpr — 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.

## Synopsis

`raster ST_MapAlgebraExpr(` raster rast, integer band, text pixeltype, text expression, double precision nodataval=NULL`)`;

`raster ST_MapAlgebraExpr(` raster rast, text pixeltype, text expression, double precision nodataval=NULL`)`;

## Description

ST_MapAlgebraExpr is deprecated as of 2.1.0. Use ST_MapAlgebra (expression version) instead.

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation defined by the `expression` on the input raster (`rast`). If no `band` is specified band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input `rast` band.

In the expression you can use the term `[rast]` to refer to the pixel value of the original band, `[rast.x]` to refer to the 1-based pixel column index, `[rast.y]` to refer to the 1-based pixel row index.

Availability: 2.0.0

## Examples

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    ALTER TABLE dummy_rast ADD COLUMN map_rast raster;
    UPDATE dummy_rast SET map_rast = ST_MapAlgebraExpr(rast,NULL,'mod([rast]::numeric,2)') WHERE rid = 2;

    SELECT
        ST_Value(rast,1,i,j) As origval,
        ST_Value(map_rast, 1, i, j) As mapval
    FROM dummy_rast
    CROSS JOIN generate_series(1, 3) AS i
    CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         253 |      1
         254 |      0
         253 |      1
         253 |      1
         254 |      0
         254 |      0
         250 |      0
         254 |      0
         254 |      0

Create a new 1 band raster of pixel-type 2BUI from our original that is reclassified and set the nodata value to be 0.

    ALTER TABLE dummy_rast ADD COLUMN map_rast2 raster;
    UPDATE dummy_rast SET
        map_rast2 = ST_MapAlgebraExpr(rast,'2BUI'::text,'CASE WHEN [rast] BETWEEN 100 and 250 THEN 1 WHEN [rast] = 252 THEN 2 WHEN [rast] BETWEEN 253 and 254 THEN 3 ELSE 0 END'::text, '0')
    WHERE rid = 2;

    SELECT DISTINCT
        ST_Value(rast,1,i,j) As origval,
        ST_Value(map_rast2, 1, i, j) As mapval
    FROM dummy_rast
    CROSS JOIN generate_series(1, 5) AS i
    CROSS JOIN generate_series(1,5) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         249 |      1
         250 |      1
         251 |
         252 |      2
         253 |      3
         254 |      3

    SELECT
        ST_BandPixelType(map_rast2) As b1pixtyp
    FROM dummy_rast
    WHERE rid = 2;

     b1pixtyp
    ----------
     2BUI

original (column rast_view) | rast_view_ma

Create a new 3 band raster same pixel type from our original 3 band raster with first band altered by map algebra and remaining 2 bands unaltered.

    SELECT
        ST_AddBand(
            ST_AddBand(
                ST_AddBand(
                    ST_MakeEmptyRaster(rast_view),
                    ST_MapAlgebraExpr(rast_view,1,NULL,'tan([rast])*[rast]')
                ),
                ST_Band(rast_view,2)
            ),
            ST_Band(rast_view, 3)
        )  As rast_view_ma
    FROM wind
    WHERE rid=167;

## See Also

ST_MapAlgebraExpr, ST_MapAlgebraFct, ST_BandPixelType, ST_GeoReference, ST_Value

## Name

ST_MapAlgebraExpr — 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.

## Synopsis

`raster ST_MapAlgebraExpr(` raster rast1, raster rast2, text expression, text pixeltype=same_as_rast1_band, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

`raster ST_MapAlgebraExpr(` raster rast1, integer band1, raster rast2, integer band2, text expression, text pixeltype=same_as_rast1_band, text extenttype=INTERSECTION, text nodata1expr=NULL, text nodata2expr=NULL, double precision nodatanodataval=NULL`)`;

## Description

ST_MapAlgebraExpr is deprecated as of 2.1.0. Use ST_MapAlgebra (expression version) instead.

Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation to the two bands defined by the `expression` on the two input raster bands `rast1`, (`rast2`). If no `band1`, `band2` is specified band 1 is assumed. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster. The resulting raster will have the extent defined by the `extenttype` parameter.

`expression`

  A PostgreSQL algebraic expression involving the two rasters and PostgreSQL defined functions/operators that will define the pixel value when pixels intersect. e.g. (([rast1] + [rast2])/2.0)::integer

`pixeltype`

  The resulting pixel type of the output raster. Must be one listed in ST_BandPixelType, left out or set to NULL. If not passed in or set to NULL, will default to the pixeltype of the first raster.

`extenttype`

  Controls the extent of resulting raster

  1. `INTERSECTION` - The extent of the new raster is the intersection of the two rasters. This is the default.

  2. `UNION` - The extent of the new raster is the union of the two rasters.

  3. `FIRST` - The extent of the new raster is the same as the one of the first raster.

  4. `SECOND` - The extent of the new raster is the same as the one of the second raster.

`nodata1expr`

  An algebraic expression involving only `rast2` or a constant that defines what to return when pixels of `rast1` are nodata values and spatially corresponding rast2 pixels have values.

`nodata2expr`

  An algebraic expression involving only `rast1` or a constant that defines what to return when pixels of `rast2` are nodata values and spatially corresponding rast1 pixels have values.

`nodatanodataval`

  A numeric constant to return when spatially corresponding rast1 and rast2 pixels are both nodata values.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL or no pixel type specified, then the new raster band will have the same pixeltype as the input `rast1` band.

Use the term `[rast1.val]` `[rast2.val]` to refer to the pixel value of the original raster bands and `[rast1.x]`, `[rast1.y]` etc. to refer to the column / row positions of the pixels.

Availability: 2.0.0

## Example: 2 Band Intersection and Union

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    --Create a cool set of rasters --
    DROP TABLE IF EXISTS fun_shapes;
    CREATE TABLE fun_shapes(rid serial PRIMARY KEY, fun_name text, rast raster);

    -- Insert some cool shapes around Boston in Massachusetts state plane meters --
    INSERT INTO fun_shapes(fun_name, rast)
    VALUES ('ref', ST_AsRaster(ST_MakeEnvelope(235229, 899970, 237229, 901930,26986),200,200,'8BUI',0,0));

    INSERT INTO fun_shapes(fun_name,rast)
    WITH ref(rast) AS (SELECT rast FROM fun_shapes WHERE fun_name = 'ref' )
    SELECT 'area' AS fun_name, ST_AsRaster(ST_Buffer(ST_SetSRID(ST_Point(236229, 900930),26986), 1000),
                ref.rast,'8BUI', 10, 0) As rast
    FROM ref
    UNION ALL
    SELECT 'rand bubbles',
                ST_AsRaster(
                (SELECT ST_Collect(geom)
        FROM (SELECT ST_Buffer(ST_SetSRID(ST_Point(236229 + i*random()*100, 900930 + j*random()*100),26986), random()*20) As geom
                FROM generate_series(1,10) As i, generate_series(1,10) As j
                ) As foo ), ref.rast,'8BUI', 200, 0)
    FROM ref;

    --map them -
    SELECT  ST_MapAlgebraExpr(
            area.rast, bub.rast, '[rast2.val]', '8BUI', 'INTERSECTION', '[rast2.val]', '[rast1.val]') As interrast,
            ST_MapAlgebraExpr(
                area.rast, bub.rast, '[rast2.val]', '8BUI', 'UNION', '[rast2.val]', '[rast1.val]') As unionrast
    FROM
      (SELECT rast FROM fun_shapes WHERE
     fun_name = 'area') As area
    CROSS JOIN  (SELECT rast
    FROM fun_shapes WHERE
     fun_name = 'rand bubbles') As bub

mapalgebra intersection | map algebra union

## Example: Overlaying rasters on a canvas as separate bands

    -- we use ST_AsPNG to render the image so all single band ones look grey --
    WITH mygeoms
        AS ( SELECT 2 As bnum, ST_Buffer(ST_Point(1,5),10) As geom
                UNION ALL
                SELECT 3 AS bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 10,'join=bevel') As geom
                UNION ALL
                SELECT 1 As bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(60 50,150 150,150 50)'), 5,'join=bevel') As geom
                ),
       -- define our canvas to be 1 to 1 pixel to geometry
       canvas
        AS (SELECT ST_AddBand(ST_MakeEmptyRaster(200,
            200,
            ST_XMin(e)::integer, ST_YMax(e)::integer, 1, -1, 0, 0) , '8BUI'::text,0) As rast
            FROM (SELECT ST_Extent(geom) As e,
                        Max(ST_SRID(geom)) As srid
                        from mygeoms
                        ) As foo
                ),
       rbands AS (SELECT ARRAY(SELECT ST_MapAlgebraExpr(canvas.rast, ST_AsRaster(m.geom, canvas.rast, '8BUI', 100),
                     '[rast2.val]', '8BUI', 'FIRST', '[rast2.val]', '[rast1.val]') As rast
                    FROM mygeoms AS m CROSS JOIN canvas
                    ORDER BY m.bnum) As rasts
                    )
              SELECT rasts[1] As rast1 , rasts[2] As rast2, rasts[3] As rast3, ST_AddBand(
                        ST_AddBand(rasts[1],rasts[2]), rasts[3]) As final_rast
                FROM rbands;

rast1 | rast2
rast3 | final_rast

## Example: Overlay 2 meter boundary of select parcels over an aerial imagery

    -- Create new 3 band raster composed of first 2 clipped bands, and overlay of 3rd band with our geometry
    -- This query took 3.6 seconds on PostGIS windows 64-bit install
    WITH pr AS
    -- Note the order of operation: we clip all the rasters to dimensions of our region
    (SELECT ST_Clip(rast,ST_Expand(geom,50) ) As rast, g.geom
        FROM aerials.o_2_boston AS r INNER JOIN
    -- union our parcels of interest so they form a single geometry we can later intersect with
            (SELECT ST_Union(ST_Transform(geom,26986)) AS geom
              FROM landparcels WHERE pid IN('0303890000', '0303900000')) As g
            ON ST_Intersects(rast::geometry, ST_Expand(g.geom,50))
    ),
    -- we then union the raster shards together
    -- ST_Union on raster is kinda of slow but much faster the smaller you can get the rasters
    -- therefore we want to clip first and then union
    prunion AS
    (SELECT ST_AddBand(NULL, ARRAY[ST_Union(rast,1),ST_Union(rast,2),ST_Union(rast,3)] ) As clipped,geom
    FROM pr
    GROUP BY geom)
    -- return our final raster which is the unioned shard with
    -- with the overlay of our parcel boundaries
    -- add first 2 bands, then mapalgebra of 3rd band + geometry
    SELECT ST_AddBand(ST_Band(clipped,ARRAY[1,2])
        , ST_MapAlgebraExpr(ST_Band(clipped,3), ST_AsRaster(ST_Buffer(ST_Boundary(geom),2),clipped, '8BUI',250),
         '[rast2.val]', '8BUI', 'FIRST', '[rast2.val]', '[rast1.val]') ) As rast
    FROM prunion;

The blue lines are the boundaries of select parcels

## See Also

ST_MapAlgebraExpr, ST_AddBand, ST_AsPNG, ST_AsRaster, ST_MapAlgebraFct, ST_BandPixelType, ST_GeoReference, ST_Value, ST_Union, ST_Union

## Name

ST_MapAlgebraFct — 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.

## Synopsis

`raster ST_MapAlgebraFct(` raster rast, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(` raster rast, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(` raster rast, text pixeltype, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(` raster rast, text pixeltype, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(` raster rast, integer band, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(` raster rast, integer band, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

`raster ST_MapAlgebraFct(` raster rast, integer band, text pixeltype, regprocedure onerasteruserfunc`)`;

`raster ST_MapAlgebraFct(` raster rast, integer band, text pixeltype, regprocedure onerasteruserfunc, text[] VARIADIC args`)`;

## Description

ST_MapAlgebraFct is deprecated as of 2.1.0. Use ST_MapAlgebra (callback function version) instead.

Creates a new one band raster formed by applying a valid PostgreSQL function specified by the `onerasteruserfunc` on the input raster (`rast`). If no `band` is specified, band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input `rast` band.

The `onerasteruserfunc` parameter must be the name and signature of a SQL or PL/pgSQL function, cast to a regprocedure. A very simple and quite useless PL/pgSQL function example is:

    CREATE OR REPLACE FUNCTION simple_function(pixel FLOAT, pos INTEGER[], VARIADIC args TEXT[])
        RETURNS FLOAT
        AS $$ BEGIN
            RETURN 0.0;
        END; $$
        LANGUAGE 'plpgsql' IMMUTABLE;

The `userfunction` may accept two or three arguments: a float value, an optional integer array, and a variadic text array. The first argument is the value of an individual raster cell (regardless of the raster datatype). The second argument is the position of the current processing cell in the form '{x,y}'. The third argument indicates that all remaining parameters to ST_MapAlgebraFct shall be passed through to the `userfunction`.

Passing a regprodedure argument to a SQL function requires the full function signature to be passed, then cast to a regprocedure type. To pass the above example PL/pgSQL function as an argument, the SQL for the argument is:

    'simple_function(float,integer[],text[])'::regprocedure

Note that the argument contains the name of the function, the types of the function arguments, quotes around the name and argument types, and a cast to a regprocedure.

The third argument to the `userfunction` is a variadic text array. All trailing text arguments to any ST_MapAlgebraFct call are passed through to the specified `userfunction`, and are contained in the `args` argument.

For more information about the VARIADIC keyword, please refer to the PostgreSQL documentation and the "SQL Functions with Variable Numbers of Arguments" section of Query Language (SQL) Functions.

The text[] argument to the `userfunction` is required, regardless of whether you choose to pass any arguments to your user function for processing or not.

Availability: 2.0.0

## Examples

Create a new 1 band raster from our original that is a function of modulo 2 of the original raster band.

    ALTER TABLE dummy_rast ADD COLUMN map_rast raster;
    CREATE FUNCTION mod_fct(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS $$
    BEGIN
        RETURN pixel::integer % 2;
    END;
    $$
    LANGUAGE 'plpgsql' IMMUTABLE;

    UPDATE dummy_rast SET map_rast = ST_MapAlgebraFct(rast,NULL,'mod_fct(float,integer[],text[])'::regprocedure) WHERE rid = 2;

    SELECT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         253 |      1
         254 |      0
         253 |      1
         253 |      1
         254 |      0
         254 |      0
         250 |      0
         254 |      0
         254 |      0

Create a new 1 band raster of pixel-type 2BUI from our original that is reclassified and set the nodata value to a passed parameter to the user function (0).

    ALTER TABLE dummy_rast ADD COLUMN map_rast2 raster;
    CREATE FUNCTION classify_fct(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS
    $$
    DECLARE
        nodata float := 0;
    BEGIN
        IF NOT args[1] IS NULL THEN
            nodata := args[1];
        END IF;
        IF pixel < 251 THEN
            RETURN 1;
        ELSIF pixel = 252 THEN
            RETURN 2;
        ELSIF pixel > 252 THEN
            RETURN 3;
        ELSE
            RETURN nodata;
        END IF;
    END;
    $$
    LANGUAGE 'plpgsql';
    UPDATE dummy_rast SET map_rast2 = ST_MapAlgebraFct(rast,'2BUI','classify_fct(float,integer[],text[])'::regprocedure, '0') WHERE rid = 2;

    SELECT DISTINCT ST_Value(rast,1,i,j) As origval, ST_Value(map_rast2, 1, i, j) As mapval
    FROM dummy_rast CROSS JOIN generate_series(1, 5) AS i CROSS JOIN generate_series(1,5) AS j
    WHERE rid = 2;

     origval | mapval
    ---------+--------
         249 |      1
         250 |      1
         251 |
         252 |      2
         253 |      3
         254 |      3

    SELECT ST_BandPixelType(map_rast2) As b1pixtyp
    FROM dummy_rast WHERE rid = 2;

     b1pixtyp
    ----------
     2BUI

original (column rast-view) | rast_view_ma

Create a new 3 band raster same pixel type from our original 3 band raster with first band altered by map algebra and remaining 2 bands unaltered.

    CREATE FUNCTION rast_plus_tan(pixel float, pos integer[], variadic args text[])
    RETURNS float
    AS
    $$
    BEGIN
        RETURN tan(pixel) * pixel;
    END;
    $$
    LANGUAGE 'plpgsql';

    SELECT ST_AddBand(
        ST_AddBand(
            ST_AddBand(
                ST_MakeEmptyRaster(rast_view),
                ST_MapAlgebraFct(rast_view,1,NULL,'rast_plus_tan(float,integer[],text[])'::regprocedure)
            ),
            ST_Band(rast_view,2)
        ),
        ST_Band(rast_view, 3) As rast_view_ma
    )
    FROM wind
    WHERE rid=167;

## See Also

ST_MapAlgebraExpr, ST_BandPixelType, ST_GeoReference, ST_SetValue

## Name

ST_MapAlgebraFct — 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.

## Synopsis

`raster ST_MapAlgebraFct(` raster rast1, raster rast2, regprocedure tworastuserfunc, text pixeltype=same_as_rast1, text extenttype=INTERSECTION, text[] VARIADIC userargs`)`;

`raster ST_MapAlgebraFct(` raster rast1, integer band1, raster rast2, integer band2, regprocedure tworastuserfunc, text pixeltype=same_as_rast1, text extenttype=INTERSECTION, text[] VARIADIC userargs`)`;

## Description

ST_MapAlgebraFct is deprecated as of 2.1.0. Use ST_MapAlgebra (callback function version) instead.

Creates a new one band raster formed by applying a valid PostgreSQL function specified by the `tworastuserfunc` on the input raster `rast1`, `rast2`. If no `band1` or `band2` is specified, band 1 is assumed. The new raster will have the same georeference, width, and height as the original rasters but will only have one band.

If `pixeltype` is passed in, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL or left out, then the new raster band will have the same pixeltype as the input `rast1` band.

The `tworastuserfunc` parameter must be the name and signature of an SQL or PL/pgSQL function, cast to a regprocedure. An example PL/pgSQL function example is:

    CREATE OR REPLACE FUNCTION simple_function_for_two_rasters(pixel1 FLOAT, pixel2 FLOAT, pos INTEGER[], VARIADIC args TEXT[])
        RETURNS FLOAT
        AS $$ BEGIN
            RETURN 0.0;
        END; $$
        LANGUAGE 'plpgsql' IMMUTABLE;

The `tworastuserfunc` may accept three or four arguments: a double precision value, a double precision value, an optional integer array, and a variadic text array. The first argument is the value of an individual raster cell in `rast1` (regardless of the raster datatype). The second argument is an individual raster cell value in `rast2`. The third argument is the position of the current processing cell in the form '{x,y}'. The fourth argument indicates that all remaining parameters to ST_MapAlgebraFct shall be passed through to the `tworastuserfunc`.

Passing a regprodedure argument to a SQL function requires the full function signature to be passed, then cast to a regprocedure type. To pass the above example PL/pgSQL function as an argument, the SQL for the argument is:

    'simple_function(double precision, double precision, integer[], text[])'::regprocedure

Note that the argument contains the name of the function, the types of the function arguments, quotes around the name and argument types, and a cast to a regprocedure.

The fourth argument to the `tworastuserfunc` is a variadic text array. All trailing text arguments to any ST_MapAlgebraFct call are passed through to the specified `tworastuserfunc`, and are contained in the `userargs` argument.

For more information about the VARIADIC keyword, please refer to the PostgreSQL documentation and the "SQL Functions with Variable Numbers of Arguments" section of Query Language (SQL) Functions.

The text[] argument to the `tworastuserfunc` is required, regardless of whether you choose to pass any arguments to your user function for processing or not.

Availability: 2.0.0

## Example: Overlaying rasters on a canvas as separate bands

    -- define our user defined function --
    CREATE OR REPLACE FUNCTION raster_mapalgebra_union(
        rast1 double precision,
        rast2 double precision,
        pos integer[],
        VARIADIC userargs text[]
    )
        RETURNS double precision
        AS $$
        DECLARE
        BEGIN
            CASE
                WHEN rast1 IS NOT NULL AND rast2 IS NOT NULL THEN
                    RETURN ((rast1 + rast2)/2.);
                WHEN rast1 IS NULL AND rast2 IS NULL THEN
                    RETURN NULL;
                WHEN rast1 IS NULL THEN
                    RETURN rast2;
                ELSE
                    RETURN rast1;
            END CASE;

            RETURN NULL;
        END;
        $$ LANGUAGE 'plpgsql' IMMUTABLE COST 1000;

    -- prep our test table of rasters
    DROP TABLE IF EXISTS map_shapes;
    CREATE TABLE map_shapes(rid serial PRIMARY KEY, rast raster, bnum integer, descrip text);
    INSERT INTO map_shapes(rast,bnum, descrip)
    WITH mygeoms
        AS ( SELECT 2 As bnum, ST_Buffer(ST_Point(90,90),30) As geom, 'circle' As descrip
                UNION ALL
                SELECT 3 AS bnum,
                    ST_Buffer(ST_GeomFromText('LINESTRING(50 50,150 150,150 50)'), 15) As geom, 'big road' As descrip
                UNION ALL
                SELECT 1 As bnum,
                    ST_Translate(ST_Buffer(ST_GeomFromText('LINESTRING(60 50,150 150,150 50)'), 8,'join=bevel'), 10,-6) As geom, 'small road' As descrip
                ),
       -- define our canvas to be 1 to 1 pixel to geometry
       canvas
        AS ( SELECT ST_AddBand(ST_MakeEmptyRaster(250,
            250,
            ST_XMin(e)::integer, ST_YMax(e)::integer, 1, -1, 0, 0 ) , '8BUI'::text,0) As rast
            FROM (SELECT ST_Extent(geom) As e,
                        Max(ST_SRID(geom)) As srid
                        from mygeoms
                        ) As foo
                )
    -- return our rasters aligned with our canvas
    SELECT ST_AsRaster(m.geom, canvas.rast, '8BUI', 240) As rast, bnum, descrip
                    FROM mygeoms AS m CROSS JOIN canvas
    UNION ALL
    SELECT canvas.rast, 4, 'canvas'
    FROM canvas;

    -- Map algebra on single band rasters and then collect with ST_AddBand
    INSERT INTO map_shapes(rast,bnum,descrip)
    SELECT ST_AddBand(ST_AddBand(rasts[1], rasts[2]),rasts[3]), 4, 'map bands overlay fct union (canvas)'
        FROM (SELECT ARRAY(SELECT ST_MapAlgebraFct(m1.rast, m2.rast,
                'raster_mapalgebra_union(double precision, double precision, integer[], text[])'::regprocedure, '8BUI', 'FIRST')
                    FROM map_shapes As m1 CROSS JOIN map_shapes As m2
        WHERE m1.descrip = 'canvas' AND m2.descrip <> 'canvas' ORDER BY m2.bnum) As rasts) As foo;

map bands overlay (canvas) (R: small road, G: circle, B: big road)

## User Defined function that takes extra args

    CREATE OR REPLACE FUNCTION raster_mapalgebra_userargs(
        rast1 double precision,
        rast2 double precision,
        pos integer[],
        VARIADIC userargs text[]
    )
        RETURNS double precision
        AS $$
        DECLARE
        BEGIN
            CASE
                WHEN rast1 IS NOT NULL AND rast2 IS NOT NULL THEN
                    RETURN least(userargs[1]::integer,(rast1 + rast2)/2.);
                WHEN rast1 IS NULL AND rast2 IS NULL THEN
                    RETURN userargs[2]::integer;
                WHEN rast1 IS NULL THEN
                    RETURN greatest(rast2,random()*userargs[3]::integer)::integer;
                ELSE
                    RETURN greatest(rast1, random()*userargs[4]::integer)::integer;
            END CASE;

            RETURN NULL;
        END;
        $$ LANGUAGE 'plpgsql' VOLATILE COST 1000;

    SELECT ST_MapAlgebraFct(m1.rast, 1, m1.rast, 3,
                'raster_mapalgebra_userargs(double precision, double precision, integer[], text[])'::regprocedure,
                    '8BUI', 'INTERSECT', '100','200','200','0')
                    FROM map_shapes As m1
        WHERE m1.descrip = 'map bands overlay fct union (canvas)';

user defined with extra args and different bands from same raster

## See Also

ST_MapAlgebraExpr, ST_BandPixelType, ST_GeoReference, ST_SetValue

## Name

ST_MapAlgebraFctNgb — 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.

## Synopsis

`raster ST_MapAlgebraFctNgb(` raster rast, integer band, text pixeltype, integer ngbwidth, integer ngbheight, regprocedure onerastngbuserfunc, text nodatamode, text[] VARIADIC args`)`;

## Description

ST_MapAlgebraFctNgb is deprecated as of 2.1.0. Use ST_MapAlgebra (callback function version) instead.

(one raster version) Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band. The user function takes the neighborhood of pixel values as an array of numbers, for each pixel, returns the result from the user function, replacing pixel value of currently inspected pixel with the function result.

`rast`

  Raster on which the user function is evaluated.

`band`

  Band number of the raster to be evaluated. Default to 1.

`pixeltype`

  The resulting pixel type of the output raster. Must be one listed in ST_BandPixelType or left out or set to NULL. If not passed in or set to NULL, will default to the pixeltype of the `rast`. Results are truncated if they are larger than what is allowed for the pixeltype.

`ngbwidth`

  The width of the neighborhood, in cells.

`ngbheight`

  The height of the neighborhood, in cells.

`onerastngbuserfunc`

  PLPGSQL/psql user function to apply to neighborhood pixels of a single band of a raster. The first element is a 2-dimensional array of numbers representing the rectangular pixel neighborhood

`nodatamode`

  Defines what value to pass to the function for a neighborhood pixel that is nodata or NULL

  'ignore': any NODATA values encountered in the neighborhood are ignored by the computation -- this flag must be sent to the user callback function, and the user function decides how to ignore it.

  'NULL': any NODATA values encountered in the neighborhood will cause the resulting pixel to be NULL -- the user callback function is skipped in this case.

  'value': any NODATA values encountered in the neighborhood are replaced by the reference pixel (the one in the center of the neighborhood). Note that if this value is NODATA, the behavior is the same as 'NULL' (for the affected neighborhood)

`args`

  Arguments to pass into the user function.

Availability: 2.0.0

## Examples

Examples utilize the katrina raster loaded as a single tile described in http://trac.osgeo.org/gdal/wiki/frmts_wtkraster.html and then prepared in the ST_Rescale examples

    --
    -- A simple 'callback' user function that averages up all the values in a neighborhood.
    --
    CREATE OR REPLACE FUNCTION rast_avg(matrix float[][], nodatamode text, variadic args text[])
        RETURNS float AS
        $$
        DECLARE
            _matrix float[][];
            x1 integer;
            x2 integer;
            y1 integer;
            y2 integer;
            sum float;
        BEGIN
            _matrix := matrix;
            sum := 0;
            FOR x in array_lower(matrix, 1)..array_upper(matrix, 1) LOOP
                FOR y in array_lower(matrix, 2)..array_upper(matrix, 2) LOOP
                    sum := sum + _matrix[x][y];
                END LOOP;
            END LOOP;
            RETURN (sum*1.0/(array_upper(matrix,1)*array_upper(matrix,2) ))::integer ;
        END;
        $$
    LANGUAGE 'plpgsql' IMMUTABLE COST 1000;

    -- now we apply to our raster averaging pixels within 2 pixels of each other in X and Y direction --
    SELECT ST_MapAlgebraFctNgb(rast, 1,  '8BUI', 4,4,
            'rast_avg(float[][], text, text[])'::regprocedure, 'NULL', NULL) As nn_with_border
        FROM katrinas_rescaled
        limit 1;

First band of our raster | new raster after averaging pixels within 4x4 pixels of each other

## See Also

ST_MapAlgebraFct, ST_MapAlgebraExpr, ST_Rescale

## Name

ST_Reclass — Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.

## Synopsis

`raster ST_Reclass(` raster rast, integer nband, text reclassexpr, text pixeltype, double precision nodataval=NULL`)`;

`raster ST_Reclass(` raster rast, reclassarg[] VARIADIC reclassargset`)`;

`raster ST_Reclass(` raster rast, text reclassexpr, text pixeltype`)`;

## Description

Creates a new raster formed by applying a valid PostgreSQL algebraic operation defined by the `reclassexpr` on the input raster (`rast`). If no `band` is specified band 1 is assumed. The new raster will have the same georeference, width, and height as the original raster. Bands not designated will come back unchanged. Refer to reclassarg for description of valid reclassification expressions.

The bands of the new raster will have pixel type of `pixeltype`. If `reclassargset` is passed in then each reclassarg defines behavior of each band generated.

Availability: 2.0.0

## Examples Basic

Create a new raster from the original where band 2 is converted from 8BUI to 4BUI and all values from 101-254 are set to nodata value.

    ALTER TABLE dummy_rast ADD COLUMN reclass_rast raster;
    UPDATE dummy_rast SET reclass_rast = ST_Reclass(rast,2,'0-87:1-10, 88-100:11-15, 101-254:0-0', '4BUI',0) WHERE rid = 2;

    SELECT i as col, j as row, ST_Value(rast,2,i,j) As origval,
        ST_Value(reclass_rast, 2, i, j) As reclassval,
        ST_Value(reclass_rast, 2, i, j, false) As reclassval_include_nodata
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

     col | row | origval | reclassval | reclassval_include_nodata
    -----+-----+---------+------------+---------------------------
       1 |   1 |      78 |          9 |                         9
       2 |   1 |      98 |         14 |                        14
       3 |   1 |     122 |            |                         0
       1 |   2 |      96 |         14 |                        14
       2 |   2 |     118 |            |                         0
       3 |   2 |     180 |            |                         0
       1 |   3 |      99 |         15 |                        15
       2 |   3 |     112 |            |                         0
       3 |   3 |     169 |            |                         0

## Example: Advanced using multiple reclassargs

Create a new raster from the original where band 1,2,3 is converted to 1BB,4BUI, 4BUI respectively and reclassified. Note this uses the variadic `reclassarg` argument which can take as input an indefinite number of reclassargs (theoretically as many bands as you have)

    UPDATE dummy_rast SET reclass_rast =
        ST_Reclass(rast,
            ROW(2,'0-87]:1-10, (87-100]:11-15, (101-254]:0-0', '4BUI',NULL)::reclassarg,
            ROW(1,'0-253]:1, 254:0', '1BB', NULL)::reclassarg,
            ROW(3,'0-70]:1, (70-86:2, [86-150):3, [150-255:4', '4BUI', NULL)::reclassarg
            ) WHERE rid = 2;

    SELECT i as col, j as row,ST_Value(rast,1,i,j) As ov1,  ST_Value(reclass_rast, 1, i, j) As rv1,
        ST_Value(rast,2,i,j) As ov2, ST_Value(reclass_rast, 2, i, j) As rv2,
        ST_Value(rast,3,i,j) As ov3, ST_Value(reclass_rast, 3, i, j) As rv3
    FROM dummy_rast CROSS JOIN generate_series(1, 3) AS i CROSS JOIN generate_series(1,3) AS j
    WHERE rid = 2;

    col | row | ov1 | rv1 | ov2 | rv2 | ov3 | rv3
    ----+-----+-----+-----+-----+-----+-----+-----
      1 |   1 | 253 |   1 |  78 |   9 |  70 |   1
      2 |   1 | 254 |   0 |  98 |  14 |  86 |   3
      3 |   1 | 253 |   1 | 122 |   0 | 100 |   3
      1 |   2 | 253 |   1 |  96 |  14 |  80 |   2
      2 |   2 | 254 |   0 | 118 |   0 | 108 |   3
      3 |   2 | 254 |   0 | 180 |   0 | 162 |   4
      1 |   3 | 250 |   1 |  99 |  15 |  90 |   3
      2 |   3 | 254 |   0 | 112 |   0 | 108 |   3
      3 |   3 | 254 |   0 | 169 |   0 | 175 |   4

## Example: Advanced Map a single band 32BF raster to multiple viewable bands

Create a new 3 band (8BUI,8BUI,8BUI viewable raster) from a raster that has only one 32bf band

    ALTER TABLE wind ADD COLUMN rast_view raster;
    UPDATE wind
        set rast_view = ST_AddBand( NULL,
            ARRAY[
        ST_Reclass(rast, 1,'0.1-10]:1-10,9-10]:11,(11-33:0'::text, '8BUI'::text,0),
        ST_Reclass(rast,1, '11-33):0-255,[0-32:0,(34-1000:0'::text, '8BUI'::text,0),
        ST_Reclass(rast,1,'0-32]:0,(32-100:100-255'::text, '8BUI'::text,0)
        ]
        );

## See Also

ST_AddBand, ST_Band, ST_BandPixelType, ST_MakeEmptyRaster, reclassarg, ST_Value

## Name

ST_Union — Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.

## Synopsis

`raster ST_Union(` setof raster rast`)`;

`raster ST_Union(` setof raster rast, unionarg[] unionargset`)`;

`raster ST_Union(` setof raster rast, integer nband`)`;

`raster ST_Union(` setof raster rast, text uniontype`)`;

`raster ST_Union(` setof raster rast, integer nband, text uniontype`)`;

## Description

Returns the union of a set of raster tiles into a single raster composed of at least one band. The resulting raster's extent is the extent of the whole set. In the case of intersection, the resulting value is defined by `uniontype` which is one of the following: LAST (default), FIRST, MIN, MAX, COUNT, SUM, MEAN, RANGE.

In order for rasters to be unioned, they must all have the same alignment. Use ST_SameAlignment and ST_NotSameAlignmentReason for more details and help. One way to fix alignment issues is to use ST_Resample and use the same reference raster for alignment.

Availability: 2.0.0

Enhanced: 2.1.0 Improved Speed (fully C-Based).

Availability: 2.1.0 ST_Union(rast, unionarg) variant was introduced.

Enhanced: 2.1.0 ST_Union(rast) (variant 1) unions all bands of all input rasters. Prior versions of PostGIS assumed the first band.

Enhanced: 2.1.0 ST_Union(rast, uniontype) (variant 4) unions all bands of all input rasters.

## Examples: Reconstitute a single band chunked raster tile

    -- this creates a single band from first band of raster tiles
    -- that form the original file system tile
    SELECT filename, ST_Union(rast,1) As file_rast
    FROM sometable WHERE filename IN('dem01', 'dem02') GROUP BY filename;

## Examples: Return a multi-band raster that is the union of tiles intersecting geometry

    -- this creates a multi band raster collecting all the tiles that intersect a line
    -- Note: In 2.0, this would have just returned a single band raster
    -- , new union works on all bands by default
    -- this is equivalent to unionarg: ARRAY[ROW(1, 'LAST'), ROW(2, 'LAST'), ROW(3, 'LAST')]::unionarg[]
    SELECT ST_Union(rast)
    FROM aerials.boston
    WHERE ST_Intersects(rast,  ST_GeomFromText('LINESTRING(230486 887771, 230500 88772)',26986) );

## Examples: Return a multi-band raster that is the union of tiles intersecting geometry

Here we use the longer syntax if we only wanted a subset of bands or we want to change order of bands

    -- this creates a multi band raster collecting all the tiles that intersect a line
    SELECT ST_Union(rast,ARRAY[ROW(2, 'LAST'), ROW(1, 'LAST'), ROW(3, 'LAST')]::unionarg[])
    FROM aerials.boston
    WHERE ST_Intersects(rast,  ST_GeomFromText('LINESTRING(230486 887771, 230500 88772)',26986) );

## See Also

unionarg, ST_Envelope, ST_ConvexHull, ST_Clip, ST_Union

## 11.13. Built-in Map Algebra Callback Functions

## Name

ST_Distinct4ma — Raster processing function that calculates the number of unique pixel values in a neighborhood.

## Synopsis

`float8 ST_Distinct4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Distinct4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the number of unique pixel values in a neighborhood of pixels.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_distinct4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |        3
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_InvDistWeight4ma — Raster processing function that interpolates a pixel's value from the pixel's neighborhood.

## Synopsis

`double precision ST_InvDistWeight4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate an interpolated value for a pixel using the Inverse Distance Weighted method.

There are two optional parameters that can be passed through `userargs`. The first parameter is the power factor (variable k in the equation below) between 0 and 1 used in the Inverse Distance Weighted equation. If not specified, default value is 1. The second parameter is the weight percentage applied only when the value of the pixel of interest is included with the interpolated value from the neighborhood. If not specified and the pixel of interest has a value, that value is returned.

The basic inverse distance weight equation is:

k = power factor, a real number between 0 and 1

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Availability: 2.1.0

## Examples

    -- NEEDS EXAMPLE

## See Also

ST_MapAlgebra (callback function version), ST_MinDist4ma

## Name

ST_Max4ma — Raster processing function that calculates the maximum pixel value in a neighborhood.

## Synopsis

`float8 ST_Max4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Max4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the maximum pixel value in a neighborhood of pixels.

For Variant 2, a substitution value for NODATA pixels can be specified by passing that value to userargs.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_max4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |      254
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Sum4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_Mean4ma — Raster processing function that calculates the mean pixel value in a neighborhood.

## Synopsis

`float8 ST_Mean4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Mean4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the mean pixel value in a neighborhood of pixels.

For Variant 2, a substitution value for NODATA pixels can be specified by passing that value to userargs.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples: Variant 1

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_mean4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid |     st_value
    -----+------------------
       2 | 253.222229003906
    (1 row)

## Examples: Variant 2

    SELECT
        rid,
        st_value(
                  ST_MapAlgebra(rast, 1, 'st_mean4ma(double precision[][][], integer[][], text[])'::regprocedure,'32BF', 'FIRST', NULL, 1, 1)
           ,  2, 2)
      FROM dummy_rast
       WHERE rid = 2;
     rid |     st_value
    -----+------------------
       2 | 253.222229003906
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Range4ma, ST_StdDev4ma

## Name

ST_Min4ma — Raster processing function that calculates the minimum pixel value in a neighborhood.

## Synopsis

`float8 ST_Min4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Min4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the minimum pixel value in a neighborhood of pixels.

For Variant 2, a substitution value for NODATA pixels can be specified by passing that value to userargs.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_min4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |      250
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_MinDist4ma — Raster processing function that returns the minimum distance (in number of pixels) between the pixel of interest and a neighboring pixel with value.

## Synopsis

`double precision ST_MinDist4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Return the shortest distance (in number of pixels) between the pixel of interest and the closest pixel with value in the neighborhood.

The intent of this function is to provide an informative data point that helps infer the usefulness of the pixel of interest's interpolated value from ST_InvDistWeight4ma. This function is particularly useful when the neighborhood is sparsely populated.

This function is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Availability: 2.1.0

## Examples

    -- NEEDS EXAMPLE

## See Also

ST_MapAlgebra (callback function version), ST_InvDistWeight4ma

## Name

ST_Range4ma — Raster processing function that calculates the range of pixel values in a neighborhood.

## Synopsis

`float8 ST_Range4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Range4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the range of pixel values in a neighborhood of pixels.

For Variant 2, a substitution value for NODATA pixels can be specified by passing that value to userargs.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_range4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |        4
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_StdDev4ma — Raster processing function that calculates the standard deviation of pixel values in a neighborhood.

## Synopsis

`float8 ST_StdDev4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_StdDev4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the standard deviation of pixel values in a neighborhood of pixels.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_stddev4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid |     st_value
    -----+------------------
       2 | 1.30170822143555
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma, ST_StdDev4ma

## Name

ST_Sum4ma — Raster processing function that calculates the sum of all pixel values in a neighborhood.

## Synopsis

`float8 ST_Sum4ma(` float8[][] matrix, text nodatamode, text[] VARIADIC args`)`;

`double precision ST_Sum4ma(` double precision[][][] value, integer[][] pos, text[] VARIADIC userargs`)`;

## Description

Calculate the sum of all pixel values in a neighborhood of pixels.

For Variant 2, a substitution value for NODATA pixels can be specified by passing that value to userargs.

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

## Examples

    SELECT
        rid,
        st_value(
            st_mapalgebrafctngb(rast, 1, '32BF', 1, 1, 'st_sum4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
        )
    FROM dummy_rast
    WHERE rid = 2;
     rid | st_value
    -----+----------
       2 |     2279
    (1 row)

## See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Mean4ma, ST_Range4ma, ST_Distinct4ma, ST_StdDev4ma

## 11.14. Raster Processing: DEM (Elevation)

## Name

ST_Aspect — Returns the aspect (in degrees by default) of an elevation raster band. Useful for analyzing terrain.

## Synopsis

`raster ST_Aspect(` raster rast, integer band=1, text pixeltype=32BF, text units=DEGREES, boolean interpolate_nodata=FALSE`)`;

`raster ST_Aspect(` raster rast, integer band, raster customextent, text pixeltype=32BF, text units=DEGREES, boolean interpolate_nodata=FALSE`)`;

## Description

Returns the aspect (in degrees by default) of an elevation raster band. Utilizes map algebra and applies the aspect equation to neighboring pixels.

`units` indicates the units of the aspect. Possible values are: RADIANS, DEGREES (default).

When `units` = RADIANS, values are between 0 and 2 * pi radians measured clockwise from North.

When `units` = DEGREES, values are between 0 and 360 degrees measured clockwise from North.

If slope of pixel is zero, aspect of pixel is -1.

For more information about Slope, Aspect and Hillshade, please refer to ESRI - How hillshade works and ERDAS Field Guide - Aspect Images.

Availability: 2.0.0

Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional `interpolate_nodata` function parameter

Changed: 2.1.0 In prior versions, return values were in radians. Now, return values default to degrees

## Examples: Variant 1

    WITH foo AS (
        SELECT ST_SetValues(
            ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999),
            1, 1, 1, ARRAY[
                [1, 1, 1, 1, 1],
                [1, 2, 2, 2, 1],
                [1, 2, 3, 2, 1],
                [1, 2, 2, 2, 1],
                [1, 1, 1, 1, 1]
            ]::double precision[][]
        ) AS rast
    )
    SELECT
        ST_DumpValues(ST_Aspect(rast, 1, '32BF'))
    FROM foo

                                                                                                        st_dumpvalues

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    ----------------------------------
     (1,"{{315,341.565063476562,0,18.4349479675293,45},{288.434936523438,315,0,45,71.5650482177734},{270,270,-1,90,90},{251.565048217773,225,180,135,108.434951782227},{225,198.43495178
    2227,180,161.565048217773,135}}")
    (1 row)

## Examples: Variant 2

Complete example of tiles of a coverage. This query only works with PostgreSQL 9.1 or higher.

    WITH foo AS (
        SELECT ST_Tile(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(6, 6, 0, 0, 1, -1, 0, 0, 0),
                    1, '32BF', 0, -9999
                ),
                1, 1, 1, ARRAY[
                    [1, 1, 1, 1, 1, 1],
                    [1, 1, 1, 1, 2, 1],
                    [1, 2, 2, 3, 3, 1],
                    [1, 1, 3, 2, 1, 1],
                    [1, 2, 2, 1, 2, 1],
                    [1, 1, 1, 1, 1, 1]
                ]::double precision[]
            ),
            2, 2
        ) AS rast
    )
    SELECT
        t1.rast,
        ST_Aspect(ST_Union(t2.rast), 1, t1.rast)
    FROM foo t1
    CROSS JOIN foo t2
    WHERE ST_Intersects(t1.rast, t2.rast)
    GROUP BY t1.rast;

## See Also

ST_MapAlgebra (callback function version), ST_TRI, ST_TPI, ST_Roughness, ST_HillShade, ST_Slope

## Name

ST_HillShade — Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.

## Synopsis

`raster ST_HillShade(` raster rast, integer band=1, text pixeltype=32BF, double precision azimuth=315, double precision altitude=45, double precision max_bright=255, double precision scale=1.0, boolean interpolate_nodata=FALSE`)`;

`raster ST_HillShade(` raster rast, integer band, raster customextent, text pixeltype=32BF, double precision azimuth=315, double precision altitude=45, double precision max_bright=255, double precision scale=1.0, boolean interpolate_nodata=FALSE`)`;

## Description

Returns the hypothetical illumination of an elevation raster band using the azimuth, altitude, brightness, and scale inputs. Utilizes map algebra and applies the hill shade equation to neighboring pixels. Return pixel values are between 0 and 255.

`azimuth` is a value between 0 and 360 degrees measured clockwise from North.

`altitude` is a value between 0 and 90 degrees where 0 degrees is at the horizon and 90 degrees is directly overhead.

`max_bright` is a value between 0 and 255 with 0 as no brightness and 255 as max brightness.

`scale` is the ratio of vertical units to horizontal. For Feet:LatLon use scale=370400, for Meters:LatLon use scale=111120.

If `interpolate_nodata` is TRUE, values for NODATA pixels from the input raster will be interpolated using ST_InvDistWeight4ma before computing the hillshade illumination.

For more information about Hillshade, please refer to How hillshade works.

Availability: 2.0.0

Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional `interpolate_nodata` function parameter

Changed: 2.1.0 In prior versions, azimuth and altitude were expressed in radians. Now, azimuth and altitude are expressed in degrees

## Examples: Variant 1

    WITH foo AS (
        SELECT ST_SetValues(
            ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999),
            1, 1, 1, ARRAY[
                [1, 1, 1, 1, 1],
                [1, 2, 2, 2, 1],
                [1, 2, 3, 2, 1],
                [1, 2, 2, 2, 1],
                [1, 1, 1, 1, 1]
            ]::double precision[][]
        ) AS rast
    )
    SELECT
        ST_DumpValues(ST_Hillshade(rast, 1, '32BF'))
    FROM foo

                                                                                                                           st_dumpvalues

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    -----------------------------------------------------------------------
     (1,"{{NULL,NULL,NULL,NULL,NULL},{NULL,251.32763671875,220.749786376953,147.224319458008,NULL},{NULL,220.749786376953,180.312225341797,67.7497863769531,NULL},{NULL,147.224319458008
    ,67.7497863769531,43.1210060119629,NULL},{NULL,NULL,NULL,NULL,NULL}}")
    (1 row)

## Examples: Variant 2

Complete example of tiles of a coverage. This query only works with PostgreSQL 9.1 or higher.

    WITH foo AS (
        SELECT ST_Tile(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(6, 6, 0, 0, 1, -1, 0, 0, 0),
                    1, '32BF', 0, -9999
                ),
                1, 1, 1, ARRAY[
                    [1, 1, 1, 1, 1, 1],
                    [1, 1, 1, 1, 2, 1],
                    [1, 2, 2, 3, 3, 1],
                    [1, 1, 3, 2, 1, 1],
                    [1, 2, 2, 1, 2, 1],
                    [1, 1, 1, 1, 1, 1]
                ]::double precision[]
            ),
            2, 2
        ) AS rast
    )
    SELECT
        t1.rast,
        ST_Hillshade(ST_Union(t2.rast), 1, t1.rast)
    FROM foo t1
    CROSS JOIN foo t2
    WHERE ST_Intersects(t1.rast, t2.rast)
    GROUP BY t1.rast;

## See Also

ST_MapAlgebra (callback function version), ST_TRI, ST_TPI, ST_Roughness, ST_Aspect, ST_Slope

## Name

ST_Roughness — Returns a raster with the calculated "roughness" of a DEM.

## Synopsis

`raster ST_Roughness(` raster rast, integer nband, raster customextent, text pixeltype="32BF" , boolean interpolate_nodata=FALSE `)`;

## Description

Calculates the "roughness" of a DEM, by subtracting the maximum from the minimum for a given area.

Availability: 2.1.0

## Examples

    -- needs examples

## See Also

ST_MapAlgebra (callback function version), ST_TRI, ST_TPI, ST_Slope, ST_HillShade, ST_Aspect

## Name

ST_Slope — Returns the slope (in degrees by default) of an elevation raster band. Useful for analyzing terrain.

## Synopsis

`raster ST_Slope(` raster rast, integer nband=1, text pixeltype=32BF, text units=DEGREES, double precision scale=1.0, boolean interpolate_nodata=FALSE`)`;

`raster ST_Slope(` raster rast, integer nband, raster customextent, text pixeltype=32BF, text units=DEGREES, double precision scale=1.0, boolean interpolate_nodata=FALSE`)`;

## Description

Returns the slope (in degrees by default) of an elevation raster band. Utilizes map algebra and applies the slope equation to neighboring pixels.

`units` indicates the units of the slope. Possible values are: RADIANS, DEGREES (default), PERCENT.

`scale` is the ratio of vertical units to horizontal. For Feet:LatLon use scale=370400, for Meters:LatLon use scale=111120.

If `interpolate_nodata` is TRUE, values for NODATA pixels from the input raster will be interpolated using ST_InvDistWeight4ma before computing the surface slope.

For more information about Slope, Aspect and Hillshade, please refer to ESRI - How hillshade works and ERDAS Field Guide - Slope Images.

Availability: 2.0.0

Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional `units`, `scale`, `interpolate_nodata` function parameters

Changed: 2.1.0 In prior versions, return values were in radians. Now, return values default to degrees

## Examples: Variant 1

    WITH foo AS (
        SELECT ST_SetValues(
            ST_AddBand(ST_MakeEmptyRaster(5, 5, 0, 0, 1, -1, 0, 0, 0), 1, '32BF', 0, -9999),
            1, 1, 1, ARRAY[
                [1, 1, 1, 1, 1],
                [1, 2, 2, 2, 1],
                [1, 2, 3, 2, 1],
                [1, 2, 2, 2, 1],
                [1, 1, 1, 1, 1]
            ]::double precision[][]
        ) AS rast
    )
    SELECT
        ST_DumpValues(ST_Slope(rast, 1, '32BF'))
    FROM foo

                                st_dumpvalues

    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    ---------------------------------------------------------------------
     (1,"{{10.0249881744385,21.5681285858154,26.5650520324707,21.5681285858154,10.0249881744385},{21.5681285858154,35.2643890380859,36.8698959350586,35.2643890380859,21.5681285858154},
    {26.5650520324707,36.8698959350586,0,36.8698959350586,26.5650520324707},{21.5681285858154,35.2643890380859,36.8698959350586,35.2643890380859,21.5681285858154},{10.0249881744385,21.
    5681285858154,26.5650520324707,21.5681285858154,10.0249881744385}}")
    (1 row)

## Examples: Variant 2

Complete example of tiles of a coverage. This query only works with PostgreSQL 9.1 or higher.

    WITH foo AS (
        SELECT ST_Tile(
            ST_SetValues(
                ST_AddBand(
                    ST_MakeEmptyRaster(6, 6, 0, 0, 1, -1, 0, 0, 0),
                    1, '32BF', 0, -9999
                ),
                1, 1, 1, ARRAY[
                    [1, 1, 1, 1, 1, 1],
                    [1, 1, 1, 1, 2, 1],
                    [1, 2, 2, 3, 3, 1],
                    [1, 1, 3, 2, 1, 1],
                    [1, 2, 2, 1, 2, 1],
                    [1, 1, 1, 1, 1, 1]
                ]::double precision[]
            ),
            2, 2
        ) AS rast
    )
    SELECT
        t1.rast,
        ST_Slope(ST_Union(t2.rast), 1, t1.rast)
    FROM foo t1
    CROSS JOIN foo t2
    WHERE ST_Intersects(t1.rast, t2.rast)
    GROUP BY t1.rast;

## See Also

ST_MapAlgebra (callback function version), ST_TRI, ST_TPI, ST_Roughness, ST_HillShade, ST_Aspect

## Name

ST_TPI — Returns a raster with the calculated Topographic Position Index.

## Synopsis

`raster ST_TPI(` raster rast, integer nband, raster customextent, text pixeltype="32BF" , boolean interpolate_nodata=FALSE `)`;

## Description

Calculates the Topographic Position Index, which is defined as the focal mean with radius of one minus the center cell.

This function only supports a focalmean radius of one.

Availability: 2.1.0

## Examples

    -- needs examples

## See Also

ST_MapAlgebra (callback function version), ST_TRI, ST_Roughness, ST_Slope, ST_HillShade, ST_Aspect

## Name

ST_TRI — Returns a raster with the calculated Terrain Ruggedness Index.

## Synopsis

`raster ST_TRI(` raster rast, integer nband, raster customextent, text pixeltype="32BF" , boolean interpolate_nodata=FALSE `)`;

## Description

Terrain Ruggedness Index is calculated by comparing a central pixel with its neighbors, taking the absolute values of the differences, and averaging the result.

This function only supports a focalmean radius of one.

Availability: 2.1.0

## Examples

    -- needs examples

## See Also

ST_MapAlgebra (callback function version), ST_Roughness, ST_TPI, ST_Slope, ST_HillShade, ST_Aspect

## 11.15. Raster Processing: Raster to Geometry

## Name

Box3D — Returns the box 3d representation of the enclosing box of the raster.

## Synopsis

`box3d Box3D(` raster rast`)`;

## Description

Returns the box representing the extent of the raster.

The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MAXX`, `MAXY`))

Changed: 2.0.0 In pre-2.0 versions, there used to be a box2d instead of box3d. Since box2d is a deprecated type, this was changed to box3d.

## Examples

    SELECT
        rid,
        Box3D(rast) AS rastbox
    FROM dummy_rast;

    rid |        rastbox
    ----+-------------------------------------------------
    1   | BOX3D(0.5 0.5 0,20.5 60.5 0)
    2   | BOX3D(3427927.75 5793243.5 0,3427928 5793244 0)

## See Also

ST_Envelope

## Name

ST_ConvexHull — Return the convex hull geometry of the raster including pixel values equal to BandNoDataValue. For regular shaped and non-skewed rasters, this gives the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.

## Synopsis

`geometry ST_ConvexHull(` raster rast`)`;

## Description

Return the convex hull geometry of the raster including the NoDataBandValue band pixels. For regular shaped and non-skewed rasters, this gives more or less the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.

ST_Envelope floors the coordinates and hence add a little buffer around the raster so the answer is subtly different from ST_ConvexHull which does not floor.

## Examples

Refer to PostGIS Raster Specification for a diagram of this.

    -- Note envelope and convexhull are more or less the same
    SELECT ST_AsText(ST_ConvexHull(rast)) As convhull,
        ST_AsText(ST_Envelope(rast)) As env
    FROM dummy_rast WHERE rid=1;

                            convhull                        |                env
    --------------------------------------------------------+------------------------------------
     POLYGON((0.5 0.5,20.5 0.5,20.5 60.5,0.5 60.5,0.5 0.5)) | POLYGON((0 0,20 0,20 60,0 60,0 0))

    -- now we skew the raster
    -- note how the convex hull and envelope are now different
    SELECT ST_AsText(ST_ConvexHull(rast)) As convhull,
        ST_AsText(ST_Envelope(rast)) As env
    FROM (SELECT ST_SetRotation(rast, 0.1, 0.1) As rast
        FROM dummy_rast WHERE rid=1) As foo;

                            convhull                        |                env
    --------------------------------------------------------+------------------------------------
     POLYGON((0.5 0.5,20.5 1.5,22.5 61.5,2.5 60.5,0.5 0.5)) | POLYGON((0 0,22 0,22 61,0 61,0 0))

## See Also

ST_Envelope, ST_MinConvexHull, ST_ConvexHull, ST_AsText

## Name

ST_DumpAsPolygons — Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.

## Synopsis

`setof geomval ST_DumpAsPolygons(` raster rast, integer band_num=1, boolean exclude_nodata_value=TRUE`)`;

## Description

This is a set-returning function (SRF). It returns a set of geomval rows, formed by a geometry (geom) and a pixel band value (val). Each polygon is the union of all pixels for that band that have the same pixel value denoted by val.

ST_DumpAsPolygon is useful for polygonizing rasters. It is the reverse of a GROUP BY in that it creates new rows. For example it can be used to expand a single raster into multiple POLYGONS/MULTIPOLYGONS.

Changed 3.3.0, validation and fixing is disabled to improve performance. May result invalid geometries.

Availability: Requires GDAL 1.7 or higher.

If there is a no data value set for a band, pixels with that value will not be returned except in the case of exclude_nodata_value=false.

If you only care about count of pixels with a given value in a raster, it is faster to use ST_ValueCount.

This is different than ST_PixelAsPolygons where one geometry is returned for each pixel regardless of pixel value.

## Examples

     -- this syntax requires PostgreSQL 9.3+
    SELECT val, ST_AsText(geom) As geomwkt
    FROM (
    SELECT dp.*
    FROM dummy_rast, LATERAL ST_DumpAsPolygons(rast) AS dp
    WHERE rid = 2
    ) As foo
    WHERE val BETWEEN 249 and 251
    ORDER BY val;

     val |                                                       geomwkt
    -----+--------------------------------------------------------------------------
     249 | POLYGON((3427927.95 5793243.95,3427927.95 5793243.85,3427928 5793243.85,
            3427928 5793243.95,3427927.95 5793243.95))
     250 | POLYGON((3427927.75 5793243.9,3427927.75 5793243.85,3427927.8 5793243.85,
            3427927.8 5793243.9,3427927.75 5793243.9))
     250 | POLYGON((3427927.8 5793243.8,3427927.8 5793243.75,3427927.85 5793243.75,
            3427927.85 5793243.8, 3427927.8 5793243.8))
     251 | POLYGON((3427927.75 5793243.85,3427927.75 5793243.8,3427927.8 5793243.8,
            3427927.8 5793243.85,3427927.75 5793243.85))

## See Also

geomval, ST_Value, ST_Polygon, ST_ValueCount

## Name

ST_Envelope — Returns the polygon representation of the extent of the raster.

## Synopsis

`geometry ST_Envelope(` raster rast`)`;

## Description

Returns the polygon representation of the extent of the raster in spatial coordinate units defined by srid. It is a float8 minimum bounding box represented as a polygon.

The polygon is defined by the corner points of the bounding box ((`MINX`, `MINY`), (`MINX`, `MAXY`), (`MAXX`, `MAXY`), (`MAXX`, `MINY`), (`MINX`, `MINY`))

## Examples

    SELECT rid, ST_AsText(ST_Envelope(rast)) As envgeomwkt
    FROM dummy_rast;

     rid |                                         envgeomwkt
    -----+--------------------------------------------------------------------
       1 | POLYGON((0 0,20 0,20 60,0 60,0 0))
       2 | POLYGON((3427927 5793243,3427928 5793243,
            3427928 5793244,3427927 5793244, 3427927 5793243))

## See Also

ST_Envelope, ST_AsText, ST_SRID

## Name

ST_MinConvexHull — Return the convex hull geometry of the raster excluding NODATA pixels.

## Synopsis

`geometry ST_MinConvexHull(` raster rast, integer nband=NULL`)`;

## Description

Return the convex hull geometry of the raster excluding NODATA pixels. If `nband` is NULL, all bands of the raster are considered.

Availability: 2.1.0

## Examples

    WITH foo AS (
        SELECT
            ST_SetValues(
                ST_SetValues(
                    ST_AddBand(ST_AddBand(ST_MakeEmptyRaster(9, 9, 0, 0, 1, -1, 0, 0, 0), 1, '8BUI', 0, 0), 2, '8BUI', 1, 0),
                    1, 1, 1,
                    ARRAY[
                        [0, 0, 0, 0, 0, 0, 0, 0, 0],
                        [0, 0, 0, 0, 0, 0, 0, 0, 0],
                        [0, 0, 0, 0, 0, 0, 0, 0, 0],
                        [0, 0, 0, 1, 0, 0, 0, 0, 1],
                        [0, 0, 0, 1, 1, 0, 0, 0, 0],
                        [0, 0, 0, 1, 0, 0, 0, 0, 0],
                        [0, 0, 0, 0, 0, 0, 0, 0, 0],
                        [0, 0, 0, 0, 0, 0, 0, 0, 0],
                        [0, 0, 0, 0, 0, 0, 0, 0, 0]
                    ]::double precision[][]
                ),
                2, 1, 1,
                ARRAY[
                    [0, 0, 0, 0, 0, 0, 0, 0, 0],
                    [0, 0, 0, 0, 0, 0, 0, 0, 0],
                    [0, 0, 0, 0, 0, 0, 0, 0, 0],
                    [1, 0, 0, 0, 0, 1, 0, 0, 0],
                    [0, 0, 0, 0, 1, 1, 0, 0, 0],
                    [0, 0, 0, 0, 0, 1, 0, 0, 0],
                    [0, 0, 0, 0, 0, 0, 0, 0, 0],
                    [0, 0, 0, 0, 0, 0, 0, 0, 0],
                    [0, 0, 1, 0, 0, 0, 0, 0, 0]
                ]::double precision[][]
            ) AS rast
    )
    SELECT
        ST_AsText(ST_ConvexHull(rast)) AS hull,
        ST_AsText(ST_MinConvexHull(rast)) AS mhull,
        ST_AsText(ST_MinConvexHull(rast, 1)) AS mhull_1,
        ST_AsText(ST_MinConvexHull(rast, 2)) AS mhull_2
    FROM foo

                   hull               |                mhull                |               mhull_1               |               mhull_2
    ----------------------------------+-------------------------------------+-------------------------------------+-------------------------------------
     POLYGON((0 0,9 0,9 -9,0 -9,0 0)) | POLYGON((0 -3,9 -3,9 -9,0 -9,0 -3)) | POLYGON((3 -3,9 -3,9 -6,3 -6,3 -3)) | POLYGON((0 -3,6 -3,6 -9,0 -9,0 -3))

## See Also

ST_Envelope, ST_ConvexHull, ST_ConvexHull, ST_AsText

## Name

ST_Polygon — Returns a multipolygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.

## Synopsis

`geometry ST_Polygon(` raster rast, integer band_num=1`)`;

## Description

Changed 3.3.0, validation and fixing is disabled to improve performance. May result invalid geometries.

Availability: 0.1.6 Requires GDAL 1.7 or higher.

Enhanced: 2.1.0 Improved Speed (fully C-Based) and the returning multipolygon is ensured to be valid.

Changed: 2.1.0 In prior versions would sometimes return a polygon, changed to always return multipolygon.

## Examples

    -- by default no data band value is 0 or not set, so polygon will return a square polygon
    SELECT ST_AsText(ST_Polygon(rast)) As geomwkt
    FROM dummy_rast
    WHERE rid = 2;

    geomwkt
    --------------------------------------------
    MULTIPOLYGON(((3427927.75 5793244,3427928 5793244,3427928 5793243.75,3427927.75 5793243.75,3427927.75 5793244)))

    -- now we change the no data value of first band
    UPDATE dummy_rast SET rast = ST_SetBandNoDataValue(rast,1,254)
    WHERE rid = 2;
    SELECt rid, ST_BandNoDataValue(rast)
    from dummy_rast where rid = 2;

    -- ST_Polygon excludes the pixel value 254 and returns a multipolygon
    SELECT ST_AsText(ST_Polygon(rast)) As geomwkt
    FROM dummy_rast
    WHERE rid = 2;

    geomwkt
    ---------------------------------------------------------
    MULTIPOLYGON(((3427927.9 5793243.95,3427927.85 5793243.95,3427927.85 5793244,3427927.9 5793244,3427927.9 5793243.95)),((3427928 5793243.85,3427928 5793243.8,3427927.95 5793243.8,3427927.95 5793243.85,3427927.9 5793243.85,3427927.9 5793243.9,3427927.9 5793243.95,3427927.95 5793243.95,3427928 5793243.95,3427928 5793243.85)),((3427927.8 5793243.75,3427927.75 5793243.75,3427927.75 5793243.8,3427927.75 5793243.85,3427927.75 5793243.9,3427927.75 5793244,3427927.8 5793244,3427927.8 5793243.9,3427927.8 5793243.85,3427927.85 5793243.85,3427927.85 5793243.8,3427927.85 5793243.75,3427927.8 5793243.75)))

    -- Or if you want the no data value different for just one time

    SELECT ST_AsText(
        ST_Polygon(
            ST_SetBandNoDataValue(rast,1,252)
            )
        ) As geomwkt
    FROM dummy_rast
    WHERE rid =2;

    geomwkt
    ---------------------------------
    MULTIPOLYGON(((3427928 5793243.85,3427928 5793243.8,3427928 5793243.75,3427927.85 5793243.75,3427927.8 5793243.75,3427927.8 5793243.8,3427927.75 5793243.8,3427927.75 5793243.85,3427927.75 5793243.9,3427927.75 5793244,3427927.8 5793244,3427927.85 5793244,3427927.9 5793244,3427928 5793244,3427928 5793243.95,3427928 5793243.85),(3427927.9 5793243.9,3427927.9 5793243.85,3427927.95 5793243.85,3427927.95 5793243.9,3427927.9 5793243.9)))

## See Also

ST_Value, ST_DumpAsPolygons

## 11.16. Raster Operators

## Name

&& — Returns `TRUE` if A's bounding box intersects B's bounding box.

## Synopsis

`boolean &&(` raster A , raster B `)`;

`boolean &&(` raster A , geometry B `)`;

`boolean &&(` geometry B , raster A `)`;

## Description

The `&&` operator returns `TRUE` if the bounding box of raster/geometr A intersects the bounding box of raster/geometr B.

This operand will make use of any indexes that may be available on the rasters.

Availability: 2.0.0

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast && B.rast As intersect
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B LIMIT 3;

     a_rid | b_rid | intersect
    -------+-------+---------
         2 |     2 | t
         2 |     3 | f
         2 |     1 | f

## Name

&< — Returns `TRUE` if A's bounding box is to the left of B's.

## Synopsis

`boolean &<(` raster A , raster B `)`;

## Description

The `&<` operator returns `TRUE` if the bounding box of raster A overlaps or is to the left of the bounding box of raster B, or more accurately, overlaps or is NOT to the right of the bounding box of raster B.

This operand will make use of any indexes that may be available on the rasters.

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast &< B.rast As overleft
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

    a_rid | b_rid | overleft
    ------+-------+----------
        2 |     2 | t
        2 |     3 | f
        2 |     1 | f
        3 |     2 | t
        3 |     3 | t
        3 |     1 | f
        1 |     2 | t
        1 |     3 | t
        1 |     1 | t

## Name

&> — Returns `TRUE` if A's bounding box is to the right of B's.

## Synopsis

`boolean &>(` raster A , raster B `)`;

## Description

The `&>` operator returns `TRUE` if the bounding box of raster A overlaps or is to the right of the bounding box of raster B, or more accurately, overlaps or is NOT to the left of the bounding box of raster B.

This operand will make use of any indexes that may be available on the geometries.

## Examples

    SELECT A.rid As a_rid, B.rid As b_rid, A.rast &> B.rast As overright
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

     a_rid | b_rid | overright
    -------+-------+----------
         2 |     2 | t
         2 |     3 | t
         2 |     1 | t
         3 |     2 | f
         3 |     3 | t
         3 |     1 | f
         1 |     2 | f
         1 |     3 | t
         1 |     1 | t

## Name

= — Returns `TRUE` if A's bounding box is the same as B's. Uses double precision bounding box.

## Synopsis

`boolean =(` raster A , raster B `)`;

## Description

The `=` operator returns `TRUE` if the bounding box of raster A is the same as the bounding box of raster B. PostgreSQL uses the =, <, and > operators defined for rasters to perform internal orderings and comparison of rasters (ie. in a GROUP BY or ORDER BY clause).

This operand will NOT make use of any indexes that may be available on the rasters. Use ~= instead. This operator exists mostly so one can group by the raster column.

Availability: 2.1.0

## See Also

~=

## Name

@ — Returns `TRUE` if A's bounding box is contained by B's. Uses double precision bounding box.

## Synopsis

`boolean @(` raster A , raster B `)`;

`boolean @(` geometry A , raster B `)`;

`boolean @(` raster B , geometry A `)`;

## Description

The `@` operator returns `TRUE` if the bounding box of raster/geometry A is contained by bounding box of raster/geometr B.

This operand will use spatial indexes on the rasters.

Availability: 2.0.0 raster @ raster, raster @ geometry introduced

Availability: 2.0.5 geometry @ raster introduced

## See Also

~

## Name

~= — Returns `TRUE` if A's bounding box is the same as B's.

## Synopsis

`boolean ~=(` raster A , raster B `)`;

## Description

The `~=` operator returns `TRUE` if the bounding box of raster A is the same as the bounding box of raster B.

This operand will make use of any indexes that may be available on the rasters.

Availability: 2.0.0

## Examples

Very useful usecase is for taking two sets of single band rasters that are of the same chunk but represent different themes and creating a multi-band raster

    SELECT ST_AddBand(prec.rast, alt.rast) As new_rast
        FROM prec INNER JOIN alt ON (prec.rast ~= alt.rast);

## See Also

ST_AddBand, =

## Name

~ — Returns `TRUE` if A's bounding box is contains B's. Uses double precision bounding box.

## Synopsis

`boolean ~(` raster A , raster B `)`;

`boolean ~(` geometry A , raster B `)`;

`boolean ~(` raster B , geometry A `)`;

## Description

The `~` operator returns `TRUE` if the bounding box of raster/geometry A is contains bounding box of raster/geometr B.

This operand will use spatial indexes on the rasters.

Availability: 2.0.0

## See Also

@

## 11.17. Raster and Raster Band Spatial Relationships

## Name

ST_Contains — Return true if no points of raster rastB lie in the exterior of raster rastA and at least one point of the interior of rastB lies in the interior of rastA.

## Synopsis

`boolean ST_Contains(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Contains(` raster rastA , raster rastB `)`;

## Description

Raster rastA contains rastB if and only if no points of rastB lie in the exterior of rastA and at least one point of the interior of rastB lies in the interior of rastA. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Contains(ST_Polygon(raster), geometry) or ST_Contains(geometry, ST_Polygon(raster)).

ST_Contains() is the inverse of ST_Within(). So, ST_Contains(rastA, rastB) implies ST_Within(rastB, rastA).

Availability: 2.1.0

## Examples

    -- specified band numbers
    SELECT r1.rid, r2.rid, ST_Contains(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 1;

    NOTICE:  The first raster provided has no bands
     rid | rid | st_contains
    -----+-----+-------------
       1 |   1 |
       1 |   2 | f

    -- no band numbers specified
    SELECT r1.rid, r2.rid, ST_Contains(r1.rast, r2.rast) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 1;
     rid | rid | st_contains
    -----+-----+-------------
       1 |   1 | t
       1 |   2 | f

## See Also

ST_Intersects, ST_Within

## Name

ST_ContainsProperly — Return true if rastB intersects the interior of rastA but not the boundary or exterior of rastA.

## Synopsis

`boolean ST_ContainsProperly(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_ContainsProperly(` raster rastA , raster rastB `)`;

## Description

Raster rastA contains properly rastB if rastB intersects the interior of rastA but not the boundary or exterior of rastA. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

Raster rastA does not contain properly itself but does contain itself.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_ContainsProperly(ST_Polygon(raster), geometry) or ST_ContainsProperly(geometry, ST_Polygon(raster)).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_ContainsProperly(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_containsproperly
    -----+-----+---------------------
       2 |   1 | f
       2 |   2 | f

## See Also

ST_Intersects, ST_Contains

## Name

ST_Covers — Return true if no points of raster rastB lie outside raster rastA.

## Synopsis

`boolean ST_Covers(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Covers(` raster rastA , raster rastB `)`;

## Description

Raster rastA covers rastB if and only if no points of rastB lie in the exterior of rastA. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Covers(ST_Polygon(raster), geometry) or ST_Covers(geometry, ST_Polygon(raster)).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_Covers(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_covers
    -----+-----+-----------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Intersects, ST_CoveredBy

## Name

ST_CoveredBy — Return true if no points of raster rastA lie outside raster rastB.

## Synopsis

`boolean ST_CoveredBy(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_CoveredBy(` raster rastA , raster rastB `)`;

## Description

Raster rastA is covered by rastB if and only if no points of rastA lie in the exterior of rastB. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_CoveredBy(ST_Polygon(raster), geometry) or ST_CoveredBy(geometry, ST_Polygon(raster)).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_CoveredBy(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_coveredby
    -----+-----+--------------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Intersects, ST_Covers

## Name

ST_Disjoint — Return true if raster rastA does not spatially intersect rastB.

## Synopsis

`boolean ST_Disjoint(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Disjoint(` raster rastA , raster rastB `)`;

## Description

Raster rastA and rastB are disjointed if they do not share any space together. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function does NOT use any indexes.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Disjoint(ST_Polygon(raster), geometry).

Availability: 2.1.0

## Examples

    -- rid = 1 has no bands, hence the NOTICE and the NULL value for st_disjoint
    SELECT r1.rid, r2.rid, ST_Disjoint(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

    NOTICE:  The second raster provided has no bands
     rid | rid | st_disjoint
    -----+-----+-------------
       2 |   1 |
       2 |   2 | f

    -- this time, without specifying band numbers
    SELECT r1.rid, r2.rid, ST_Disjoint(r1.rast, r2.rast) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_disjoint
    -----+-----+-------------
       2 |   1 | t
       2 |   2 | f

## See Also

ST_Intersects

## Name

ST_Intersects — Return true if raster rastA spatially intersects raster rastB.

## Synopsis

`boolean ST_Intersects(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Intersects(` raster rastA , raster rastB `)`;

`boolean ST_Intersects(` raster rast , integer nband , geometry geommin `)`;

`boolean ST_Intersects(` raster rast , geometry geommin , integer nband=NULL `)`;

`boolean ST_Intersects(` geometry geommin , raster rast , integer nband=NULL `)`;

## Description

Return true if raster rastA spatially intersects raster rastB. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

Enhanced: 2.0.0 support raster/raster intersects was introduced.

Changed: 2.1.0 The behavior of the ST_Intersects(raster, geometry) variants changed to match that of ST_Intersects(geometry, raster).

## Examples

    -- different bands of same raster
    SELECT ST_Intersects(rast, 2, rast, 3) FROM dummy_rast WHERE rid = 2;

     st_intersects
    ---------------
     t

## See Also

ST_Intersection, ST_Disjoint

## Name

ST_Overlaps — Return true if raster rastA and rastB intersect but one does not completely contain the other.

## Synopsis

`boolean ST_Overlaps(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Overlaps(` raster rastA , raster rastB `)`;

## Description

Return true if raster rastA spatially overlaps raster rastB. This means that rastA and rastB intersect but one does not completely contain the other. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Overlaps(ST_Polygon(raster), geometry).

Availability: 2.1.0

## Examples

    -- comparing different bands of same raster
    SELECT ST_Overlaps(rast, 1, rast, 2) FROM dummy_rast WHERE rid = 2;

     st_overlaps
    -------------
     f

## See Also

ST_Intersects

## Name

ST_Touches — Return true if raster rastA and rastB have at least one point in common but their interiors do not intersect.

## Synopsis

`boolean ST_Touches(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Touches(` raster rastA , raster rastB `)`;

## Description

Return true if raster rastA spatially touches raster rastB. This means that rastA and rastB have at least one point in common but their interiors do not intersect. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Touches(ST_Polygon(raster), geometry).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_Touches(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_touches
    -----+-----+------------
       2 |   1 | f
       2 |   2 | f

## See Also

ST_Intersects

## Name

ST_SameAlignment — Returns true if rasters have same skew, scale, spatial ref, and offset (pixels can be put on same grid without cutting into pixels) and false if they don't with notice detailing issue.

## Synopsis

`boolean ST_SameAlignment(` raster rastA , raster rastB `)`;

`boolean ST_SameAlignment(` double precision ulx1 , double precision uly1 , double precision scalex1 , double precision scaley1 , double precision skewx1 , double precision skewy1 , double precision ulx2 , double precision uly2 , double precision scalex2 , double precision scaley2 , double precision skewx2 , double precision skewy2 `)`;

`boolean ST_SameAlignment(` raster set rastfield `)`;

## Description

Non-Aggregate version (Variants 1 and 2): Returns true if the two rasters (either provided directly or made using the values for upperleft, scale, skew and srid) have the same scale, skew, srid and at least one of any of the four corners of any pixel of one raster falls on any corner of the grid of the other raster. Returns false if they don't and a NOTICE detailing the alignment issue.

Aggregate version (Variant 3): From a set of rasters, returns true if all rasters in the set are aligned. The ST_SameAlignment() function is an "aggregate" function in the terminology of PostgreSQL. That means that it operates on rows of data, in the same way the SUM() and AVG() functions do.

Availability: 2.0.0

Enhanced: 2.1.0 addition of Aggegrate variant

## Examples: Rasters

    SELECT ST_SameAlignment(
        ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0),
        ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0)
    ) as sm;

    sm
    ----
    t

    SELECT ST_SameAlignment(A.rast,b.rast)
     FROM dummy_rast AS A CROSS JOIN dummy_rast AS B;

     NOTICE:  The two rasters provided have different SRIDs
    NOTICE:  The two rasters provided have different SRIDs
     st_samealignment
    ------------------
     t
     f
     f
     f

## See Also

Section 10.1, “Loading and Creating Rasters”, ST_NotSameAlignmentReason, ST_MakeEmptyRaster

## Name

ST_NotSameAlignmentReason — Returns text stating if rasters are aligned and if not aligned, a reason why.

## Synopsis

`text ST_NotSameAlignmentReason(` raster rastA, raster rastB`)`;

## Description

Returns text stating if rasters are aligned and if not aligned, a reason why.

If there are several reasons why the rasters are not aligned, only one reason (the first test to fail) will be returned.

Availability: 2.1.0

## Examples

    SELECT
        ST_SameAlignment(
            ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0),
            ST_MakeEmptyRaster(1, 1, 0, 0, 1.1, 1.1, 0, 0)
        ),
        ST_NotSameAlignmentReason(
            ST_MakeEmptyRaster(1, 1, 0, 0, 1, 1, 0, 0),
            ST_MakeEmptyRaster(1, 1, 0, 0, 1.1, 1.1, 0, 0)
        )
    ;

     st_samealignment |            st_notsamealignmentreason
    ------------------+-------------------------------------------------
     f                | The rasters have different scales on the X axis
    (1 row)

## See Also

Section 10.1, “Loading and Creating Rasters”, ST_SameAlignment

## Name

ST_Within — Return true if no points of raster rastA lie in the exterior of raster rastB and at least one point of the interior of rastA lies in the interior of rastB.

## Synopsis

`boolean ST_Within(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Within(` raster rastA , raster rastB `)`;

## Description

Raster rastA is within rastB if and only if no points of rastA lie in the exterior of rastB and at least one point of the interior of rastA lies in the interior of rastB. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This operand will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Within(ST_Polygon(raster), geometry) or ST_Within(geometry, ST_Polygon(raster)).

ST_Within() is the inverse of ST_Contains(). So, ST_Within(rastA, rastB) implies ST_Contains(rastB, rastA).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_Within(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_within
    -----+-----+-----------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Intersects, ST_Contains, ST_DWithin, ST_DFullyWithin

## Name

ST_DWithin — Return true if rasters rastA and rastB are within the specified distance of each other.

## Synopsis

`boolean ST_DWithin(` raster rastA , integer nbandA , raster rastB , integer nbandB , double precision distance_of_srid `)`;

`boolean ST_DWithin(` raster rastA , raster rastB , double precision distance_of_srid `)`;

## Description

Return true if rasters rastA and rastB are within the specified distance of each other. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

The distance is specified in units defined by the spatial reference system of the rasters. For this function to make sense, the source rasters must both be of the same coordinate projection, having the same SRID.

This operand will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_DWithin(ST_Polygon(raster), geometry).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_DWithin(r1.rast, 1, r2.rast, 1, 3.14) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_dwithin
    -----+-----+------------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Within, ST_DFullyWithin

## Name

ST_DFullyWithin — Return true if rasters rastA and rastB are fully within the specified distance of each other.

## Synopsis

`boolean ST_DFullyWithin(` raster rastA , integer nbandA , raster rastB , integer nbandB , double precision distance_of_srid `)`;

`boolean ST_DFullyWithin(` raster rastA , raster rastB , double precision distance_of_srid `)`;

## Description

Return true if rasters rastA and rastB are fully within the specified distance of each other. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

The distance is specified in units defined by the spatial reference system of the rasters. For this function to make sense, the source rasters must both be of the same coordinate projection, having the same SRID.

This operand will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_DFullyWithin(ST_Polygon(raster), geometry).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_DFullyWithin(r1.rast, 1, r2.rast, 1, 3.14) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_dfullywithin
    -----+-----+-----------------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Within, ST_DWithin

## 11.18. Raster Tips

Abstract

This section documents various gotchas and tips related to PostGIS Raster.

### 11.18.1. Out-DB Rasters

#### 11.18.1.1. Directory containing many files

When GDAL opens a file, GDAL eagerly scans the directory of that file to build a catalog of other files. If this directory contains many files (e.g. thousands, millions), opening that file becomes extremely slow (especially if that file happens to be on a network drive such as NFS).

To control this behavior, GDAL provides the following environment variable: GDAL_DISABLE_READDIR_ON_OPEN. Set `GDAL_DISABLE_READDIR_ON_OPEN` to `TRUE` to disable directory scanning.

In Ubuntu (and assuming you are using PostgreSQL's packages for Ubuntu), `GDAL_DISABLE_READDIR_ON_OPEN` can be set in /etc/postgresql/POSTGRESQL_VERSION/CLUSTER_NAME/environment (where POSTGRESQL_VERSION is the version of PostgreSQL, e.g. 9.6 and CLUSTER_NAME is the name of the cluster, e.g. maindb). You can also set PostGIS environment variables here as well.

    # environment variables for postmaster process
    # This file has the same syntax as postgresql.conf:
    #  VARIABLE = simple_value
    #  VARIABLE2 = 'any value!'
    # I. e. you need to enclose any value which does not only consist of letters,
    # numbers, and '-', '_', '.' in single quotes. Shell commands are not
    # evaluated.
    POSTGIS_GDAL_ENABLED_DRIVERS = 'ENABLE_ALL'

    POSTGIS_ENABLE_OUTDB_RASTERS = 1

    GDAL_DISABLE_READDIR_ON_OPEN = 'TRUE'

#### 11.18.1.2. Maximum Number of Open Files

The maximum number of open files permitted by Linux and PostgreSQL are typically conservative (typically 1024 open files per process) given the assumption that the system is consumed by human users. For Out-DB Rasters, a single valid query can easily exceed this limit (e.g. a dataset of 10 year's worth of rasters with one raster for each day containing minimum and maximum temperatures and we want to know the absolute min and max value for a pixel in that dataset).

The easiest change to make is the following PostgreSQL setting: max_files_per_process. The default is set to 1000, which is far too low for Out-DB Rasters. A safe starting value could be 65536 but this really depends on your datasets and the queries run against those datasets. This setting can only be made on server start and probably only in the PostgreSQL configuration file (e.g. /etc/postgresql/POSTGRESQL_VERSION/CLUSTER_NAME/postgresql.conf in Ubuntu environments).

    ...
    # - Kernel Resource Usage -

    max_files_per_process = 65536           # min 25
                                            # (change requires restart)
    ...

The major change to make is the Linux kernel's open files limits. There are two parts to this:

- Maximum number of open files for the entire system

- Maximum number of open files per process

##### 11.18.1.2.1. Maximum number of open files for the entire system

You can inspect the current maximum number of open files for the entire system with the following example:

    $ sysctl -a | grep fs.file-max
    fs.file-max = 131072

If the value returned is not large enough, add a file to /etc/sysctl.d/ as per the following example:

    $ echo "fs.file-max = 6145324" >> /etc/sysctl.d/fs.conf

    $ cat /etc/sysctl.d/fs.conf
    fs.file-max = 6145324

    $ sysctl -p --system
    * Applying /etc/sysctl.d/fs.conf ...
    fs.file-max = 2097152
    * Applying /etc/sysctl.conf ...

    $ sysctl -a | grep fs.file-max
    fs.file-max = 6145324

##### 11.18.1.2.2. Maximum number of open files per process

We need to increase the maximum number of open files per process for the PostgreSQL server processes.

To see what the current PostgreSQL service processes are using for maximum number of open files, do as per the following example (make sure to have PostgreSQL running):

    $ ps aux | grep postgres
    postgres 31713  0.0  0.4 179012 17564 pts/0    S    Dec26   0:03 /home/dustymugs/devel/postgresql/sandbox/10/usr/local/bin/postgres -D /home/dustymugs/devel/postgresql/sandbox/10/pgdata
    postgres 31716  0.0  0.8 179776 33632 ?        Ss   Dec26   0:01 postgres: checkpointer process
    postgres 31717  0.0  0.2 179144  9416 ?        Ss   Dec26   0:05 postgres: writer process
    postgres 31718  0.0  0.2 179012  8708 ?        Ss   Dec26   0:06 postgres: wal writer process
    postgres 31719  0.0  0.1 179568  7252 ?        Ss   Dec26   0:03 postgres: autovacuum launcher process
    postgres 31720  0.0  0.1  34228  4124 ?        Ss   Dec26   0:09 postgres: stats collector process
    postgres 31721  0.0  0.1 179308  6052 ?        Ss   Dec26   0:00 postgres: bgworker: logical replication launcher

    $ cat /proc/31718/limits
    Limit                     Soft Limit           Hard Limit           Units
    Max cpu time              unlimited            unlimited            seconds
    Max file size             unlimited            unlimited            bytes
    Max data size             unlimited            unlimited            bytes
    Max stack size            8388608              unlimited            bytes
    Max core file size        0                    unlimited            bytes
    Max resident set          unlimited            unlimited            bytes
    Max processes             15738                15738                processes
    Max open files            1024                 4096                 files
    Max locked memory         65536                65536                bytes
    Max address space         unlimited            unlimited            bytes
    Max file locks            unlimited            unlimited            locks
    Max pending signals       15738                15738                signals
    Max msgqueue size         819200               819200               bytes
    Max nice priority         0                    0
    Max realtime priority     0                    0
    Max realtime timeout      unlimited            unlimited            us

In the example above, we inspected the open files limit for Process 31718. It doesn't matter which PostgreSQL process, any of them will do. The response we are interested in is Max open files.

We want to increase Soft Limit and Hard Limit of Max open files to be greater than the value we specified for the PostgreSQL setting `max_files_per_process`. In our example, we set `max_files_per_process` to 65536.

In Ubuntu (and assuming you are using PostgreSQL's packages for Ubuntu), the easiest way to change the Soft Limit and Hard Limit is to edit /etc/init.d/postgresql (SysV) or /lib/systemd/system/postgresql*.service (systemd).

Let's first address the SysV Ubuntu case where we add ulimit -H -n 262144 and ulimit -n 131072 to /etc/init.d/postgresql.

    ...
    case "$1" in
        start|stop|restart|reload)
            if [ "$1" = "start" ]; then
                create_socket_directory
            fi
        if [ -z "`pg_lsclusters -h`" ]; then
            log_warning_msg 'No PostgreSQL clusters exist; see "man pg_createcluster"'
            exit 0
        fi

        ulimit -H -n 262144
        ulimit -n 131072

        for v in $versions; do
            $1 $v || EXIT=$?
        done
        exit ${EXIT:-0}
            ;;
        status)
    ...

Now to address the systemd Ubuntu case. We will add LimitNOFILE=131072 to every /lib/systemd/system/postgresql*.service file in the [Service] section.

    ...
    [Service]

    LimitNOFILE=131072

    ...

    [Install]
    WantedBy=multi-user.target
    ...

After making the necessary systemd changes, make sure to reload the daemon

    systemctl daemon-reload

# Chapter 12. PostGIS Extras

This chapter documents features found in the extras folder of the PostGIS source tarballs and source repository. These are not always packaged with PostGIS binary releases, but are usually PL/pgSQL based or standard shell scripts that can be run as is.

## 12.1. Address Standardizer

This is a fork of the PAGC standardizer (original code for this portion was PAGC PostgreSQL Address Standardizer).

The address standardizer is a single line address parser that takes an input address and normalizes it based on a set of rules stored in a table and helper lex and gaz tables.

The code is built into a single PostgreSQL extension library called `address_standardizer` which can be installed with `CREATE EXTENSION address_standardizer;`. In addition to the address_standardizer extension, a sample data extension called `address_standardizer_data_us` extensions is built, which contains gaz, lex, and rules tables for US data. This extensions can be installed via: `CREATE EXTENSION address_standardizer_data_us;`

The code for this extension can be found in the PostGIS `extensions/address_standardizer` and is currently self-contained.

For installation instructions refer to: Section 2.3, “Installing and Using the address standardizer”.

### 12.1.1. How the Parser Works

The parser works from right to left looking first at the macro elements for postcode, state/province, city, and then looks micro elements to determine if we are dealing with a house number street or intersection or landmark. It currently does not look for a country code or name, but that could be introduced in the future.

Country code

  Assumed to be US or CA based on: postcode as US or Canada state/province as US or Canada else US

Postcode/zipcode

  These are recognized using Perl compatible regular expressions. These regexs are currently in the parseaddress-api.c and are relatively simple to make changes to if needed.

State/province

  These are recognized using Perl compatible regular expressions. These regexs are currently in the parseaddress-api.c but could get moved into includes in the future for easier maintenance.

### 12.1.2. Address Standardizer Types

Abstract

This section lists the PostgreSQL data types installed by Address Standardizer extension. Note we describe the casting behavior of these which is very important especially when designing your own functions.

## Name

stdaddr — A composite type that consists of the elements of an address. This is the return type for `standardize_address` function.

## Description

A composite type that consists of elements of an address. This is the return type for standardize_address function. Some descriptions for elements are borrowed from PAGC Postal Attributes.

The token numbers denote the output reference number in the rules table.

This method needs address_standardizer extension.

`building`

  is text (token number `0`): Refers to building number or name. Unparsed building identifiers and types. Generally blank for most addresses.

`house_num`

  is a text (token number `1`): This is the street number on a street. Example 75 in `75 State Street`.

`predir`

  is text (token number `2`): STREET NAME PRE-DIRECTIONAL such as North, South, East, West etc.

`qual`

  is text (token number `3`): STREET NAME PRE-MODIFIER Example OLD in `3715 OLD HIGHWAY 99`.

`pretype`

  is text (token number `4`): STREET PREFIX TYPE

`name`

  is text (token number `5`): STREET NAME

`suftype`

  is text (token number `6`): STREET POST TYPE e.g. St, Ave, Cir. A street type following the root street name. Example STREET in `75 State Street`.

`sufdir`

  is text (token number `7`): STREET POST-DIRECTIONAL A directional modifier that follows the street name.. Example WEST in `3715 TENTH AVENUE WEST`.

`ruralroute`

  is text (token number `8`): RURAL ROUTE . Example 7 in `RR 7`.

`extra`

  is text: Extra information like Floor number.

`city`

  is text (token number `10`): Example Boston.

`state`

  is text (token number `11`): Example `MASSACHUSETTS`

`country`

  is text (token number `12`): Example `USA`

`postcode`

  is text POSTAL CODE (ZIP CODE) (token number `13`): Example `02109`

`box`

  is text POSTAL BOX NUMBER (token number `14 and 15`): Example `02109`

`unit`

  is text Apartment number or Suite Number (token number `17`): Example 3B in `APT 3B`.

### 12.1.3. Address Standardizer Tables

Abstract

This section lists the PostgreSQL table formats used by the address_standardizer for normalizing addresses. Note that these tables do not need to be named the same as what is referenced here. You can have different lex, gaz, rules tables for each country for example or for your custom geocoder. The names of these tables get passed into the address standardizer functions.

The packaged extension `address_standardizer_data_us` contains data for standardizing US addresses.

## Name

rules table — The rules table contains a set of rules that maps address input sequence tokens to standardized output sequence. A rule is defined as a set of input tokens followed by -1 (terminator) followed by set of output tokens followed by -1 followed by number denoting kind of rule followed by ranking of rule.

## Description

A rules table must have at least the following columns, though you are allowed to add more for your own uses.

`id`

  Primary key of table

`rule`

  text field denoting the rule. Details at PAGC Address Standardizer Rule records.

  A rule consists of a set of non-negative integers representing input tokens, terminated by a -1, followed by an equal number of non-negative integers representing postal attributes, terminated by a -1, followed by an integer representing a rule type, followed by an integer representing the rank of the rule. The rules are ranked from 0 (lowest) to 17 (highest).

  So for example the rule `2 0 2 22 3 -1 5 5 6 7 3 -1 2 6` maps to sequence of output tokens TYPE NUMBER TYPE DIRECT QUALIF to the output sequence STREET STREET SUFTYP SUFDIR QUALIF. The rule is an ARC_C rule of rank 6.

  Numbers for corresponding output tokens are listed in stdaddr.

## Input Tokens

Each rule starts with a set of input tokens followed by a terminator `-1`. Valid input tokens excerpted from PAGC Input Tokens are as follows:

Form-Based Input Tokens

`AMPERS`

  (13). The ampersand (&) is frequently used to abbreviate the word "and".

`DASH`

  (9). A punctuation character.

`DOUBLE`

  (21). A sequence of two letters. Often used as identifiers.

`FRACT`

  (25). Fractions are sometimes used in civic numbers or unit numbers.

`MIXED`

  (23). An alphanumeric string that contains both letters and digits. Used for identifiers.

`NUMBER`

  (0). A string of digits.

`ORD`

  (15). Representations such as First or 1st. Often used in street names.

`ORD`

  (18). A single letter.

`WORD`

  (1). A word is a string of letters of arbitrary length. A single letter can be both a SINGLE and a WORD.

Function-based Input Tokens

`BOXH`

  (14). Words used to denote post office boxes. For example Box or PO Box.

`BUILDH`

  (19). Words used to denote buildings or building complexes, usually as a prefix. For example: Tower in Tower 7A.

`BUILDT`

  (24). Words and abbreviations used to denote buildings or building complexes, usually as a suffix. For example: Shopping Centre.

`DIRECT`

  (22). Words used to denote directions, for example North.

`MILE`

  (20). Words used to denote milepost addresses.

`ROAD`

  (6). Words and abbreviations used to denote highways and roads. For example: the Interstate in Interstate 5

`RR`

  (8). Words and abbreviations used to denote rural routes. RR.

`TYPE`

  (2). Words and abbreviation used to denote street typess. For example: ST or AVE.

`UNITH`

  (16). Words and abbreviation used to denote internal subaddresses. For example, APT or UNIT.

Postal Type Input Tokens

`QUINT`

  (28). A 5 digit number. Identifies a Zip Code

`QUAD`

  (29). A 4 digit number. Identifies ZIP4.

`PCH`

  (27). A 3 character sequence of letter number letter. Identifies an FSA, the first 3 characters of a Canadian postal code.

`PCT`

  (26). A 3 character sequence of number letter number. Identifies an LDU, the last 3 characters of a Canadian postal code.

Stopwords

STOPWORDS combine with WORDS. In rules a string of multiple WORDs and STOPWORDs will be represented by a single WORD token.

`STOPWORD`

  (7). A word with low lexical significance, that can be omitted in parsing. For example: THE.

## Output Tokens

After the first -1 (terminator), follows the output tokens and their order, followed by a terminator `-1`. Numbers for corresponding output tokens are listed in stdaddr. What are allowed is dependent on kind of rule. Output tokens valid for each rule type are listed in the section called “Rule Types and Rank”.

## Rule Types and Rank

The final part of the rule is the rule type which is denoted by one of the following, followed by a rule rank. The rules are ranked from 0 (lowest) to 17 (highest).

`MACRO_C`

(token number = "0"). The class of rules for parsing MACRO clauses such as PLACE STATE ZIP

`MACRO_C` output tokens (excerpted from http://www.pagcgeo.org/docs/html/pagc-12.html#--r-typ--.

`CITY`

  (token number "10"). Example "Albany"

`STATE`

  (token number "11"). Example "NY"

`NATION`

  (token number "12"). This attribute is not used in most reference files. Example "USA"

`POSTAL`

  (token number "13"). (SADS elements "ZIP CODE" , "PLUS 4" ). This attribute is used for both the US Zip and the Canadian Postal Codes.

`MICRO_C`

(token number = "1"). The class of rules for parsing full MICRO clauses (such as House, street, sufdir, predir, pretyp, suftype, qualif) (ie ARC_C plus CIVIC_C). These rules are not used in the build phase.

`MICRO_C` output tokens (excerpted from http://www.pagcgeo.org/docs/html/pagc-12.html#--r-typ--.

`HOUSE`

  is a text (token number `1`): This is the street number on a street. Example 75 in `75 State Street`.

`predir`

  is text (token number `2`): STREET NAME PRE-DIRECTIONAL such as North, South, East, West etc.

`qual`

  is text (token number `3`): STREET NAME PRE-MODIFIER Example OLD in `3715 OLD HIGHWAY 99`.

`pretype`

  is text (token number `4`): STREET PREFIX TYPE

`street`

  is text (token number `5`): STREET NAME

`suftype`

  is text (token number `6`): STREET POST TYPE e.g. St, Ave, Cir. A street type following the root street name. Example STREET in `75 State Street`.

`sufdir`

  is text (token number `7`): STREET POST-DIRECTIONAL A directional modifier that follows the street name.. Example WEST in `3715 TENTH AVENUE WEST`.

`ARC_C`

(token number = "2"). The class of rules for parsing MICRO clauses, excluding the HOUSE attribute. As such uses same set of output tokens as MICRO_C minus the HOUSE token.

`CIVIC_C`

(token number = "3"). The class of rules for parsing the HOUSE attribute.

`EXTRA_C`

(token number = "4"). The class of rules for parsing EXTRA attributes - attributes excluded from geocoding. These rules are not used in the build phase.

`EXTRA_C` output tokens (excerpted from http://www.pagcgeo.org/docs/html/pagc-12.html#--r-typ--.

`BLDNG`

  (token number `0`): Unparsed building identifiers and types.

`BOXH`

  (token number `14`): The BOX in `BOX 3B`

`BOXT`

  (token number `15`): The 3B in `BOX 3B`

`RR`

  (token number `8`): The RR in `RR 7`

`UNITH`

  (token number `16`): The APT in `APT 3B`

`UNITT`

  (token number `17`): The 3B in `APT 3B`

`UNKNWN`

  (token number `9`): An otherwise unclassified output.

## Name

lex table — A lex table is used to classify alphanumeric input and associate that input with (a) input tokens ( See the section called “Input Tokens”) and (b) standardized representations.

## Description

A lex (short for lexicon) table is used to classify alphanumeric input and associate that input with the section called “Input Tokens” and (b) standardized representations. Things you will find in these tables are `ONE` mapped to stdword: `1`.

A lex has at least the following columns in the table. You may add

`id`

  Primary key of table

`seq`

  integer: definition number?

`word`

  text: the input word

`stdword`

  text: the standardized replacement word

`token`

  integer: the kind of word it is. Only if it is used in this context will it be replaced. Refer to PAGC Tokens.

## Name

gaz table — A gaz table is used to standardize place names and associate that input with (a) input tokens ( See the section called “Input Tokens”) and (b) standardized representations.

## Description

A gaz (short for gazeteer) table is used to standardize place names and associate that input with the section called “Input Tokens” and (b) standardized representations. For example if you are in US, you may load these with State Names and associated abbreviations.

A gaz table has at least the following columns in the table. You may add more columns if you wish for your own purposes.

`id`

  Primary key of table

`seq`

  integer: definition number? - identifier used for that instance of the word

`word`

  text: the input word

`stdword`

  text: the standardized replacement word

`token`

  integer: the kind of word it is. Only if it is used in this context will it be replaced. Refer to PAGC Tokens.

### 12.1.4. Address Standardizer Functions

## Name

debug_standardize_address — Returns a json formatted text listing the parse tokens and standardizations

## Synopsis

`text debug_standardize_address(` text lextab, text gaztab, text rultab, text micro, text macro=NULL`)`;

## Description

This is a function for debugging address standardizer rules and lex/gaz mappings. It returns a json formatted text that includes the matching rules, mapping of tokens, and best standardized address stdaddr form of an input address utilizing lex table table name, gaz table, and rules table table names and an address.

For single line addresses use just `micro`

For two line address A `micro` consisting of standard first line of postal address e.g. `house_num street`, and a macro consisting of standard postal second line of an address e.g `city, state postal_code country`.

Elements returned in the json document are

`input_tokens`

  For each word in the input address, returns the position of the word, token categorization of the word, and the standard word it is mapped to. Note that for some input words, you might get back multiple records because some inputs can be categorized as more than one thing.

`rules`

  The set of rules matching the input and the corresponding score for each. The first rule (highest scoring) is what is used for standardization

`stdaddr`

  The standardized address elements stdaddr that would be returned when running standardize_address

Availability: 3.4.0

This method needs address_standardizer extension.

## Examples

Using address_standardizer_data_us extension

    CREATE EXTENSION address_standardizer_data_us; -- only needs to be done once

Variant 1: Single line address and returning the input tokens

    SELECT it->>'pos' AS position, it->>'word' AS word, it->>'stdword' AS standardized_word,
                it->>'token' AS token, it->>'token-code' AS token_code
        FROM jsonb(
                debug_standardize_address('us_lex',
                    'us_gaz', 'us_rules', 'One Devonshire Place, PH 301, Boston, MA 02109')
                     ) AS s, jsonb_array_elements(s->'input_tokens') AS it;

    position |    word    | standardized_word | token  | token_code
    ----------+------------+-------------------+--------+------------
     0        | ONE        | 1                 | NUMBER | 0
     0        | ONE        | 1                 | WORD   | 1
     1        | DEVONSHIRE | DEVONSHIRE        | WORD   | 1
     2        | PLACE      | PLACE             | TYPE   | 2
     3        | PH         | PATH              | TYPE   | 2
     3        | PH         | PENTHOUSE         | UNITT  | 17
     4        | 301        | 301               | NUMBER | 0
    (7 rows)

Variant 2: Multi line address and returning first rule input mappings and score

    SELECT (s->'rules'->0->>'score')::numeric AS score, it->>'pos' AS position,
            it->>'input-word' AS word, it->>'input-token' AS input_token, it->>'mapped-word' AS standardized_word,
                it->>'output-token' AS output_token
        FROM jsonb(
                debug_standardize_address('us_lex',
                    'us_gaz', 'us_rules', 'One Devonshire Place, PH 301', 'Boston, MA 02109')
                     ) AS s, jsonb_array_elements(s->'rules'->0->'rule_tokens') AS it;

     score   | position |    word    | input_token | standardized_word | output_token
    ----------+----------+------------+-------------+-------------------+--------------
     0.876250 | 0        | ONE        | NUMBER      | 1                 | HOUSE
     0.876250 | 1        | DEVONSHIRE | WORD        | DEVONSHIRE        | STREET
     0.876250 | 2        | PLACE      | TYPE        | PLACE             | SUFTYP
     0.876250 | 3        | PH         | UNITT       | PENTHOUSE         | UNITT
     0.876250 | 4        | 301        | NUMBER      | 301               | UNITT
    (5 rows)

## See Also

stdaddr, rules table, lex table, gaz table, Pagc_Normalize_Address

## Name

parse_address — Takes a 1 line address and breaks into parts

## Synopsis

`record parse_address(` text address`)`;

## Description

Returns takes an address as input, and returns a record output consisting of fields num, street, street2, address1, city, state, zip, zipplus, country.

Availability: 2.2.0

This method needs address_standardizer extension.

## Examples

Single Address

    SELECT num, street, city, zip, zipplus
    	FROM parse_address('1 Devonshire Place, Boston, MA 02109-1234') AS a;

     num |      street      |  city  |  zip  | zipplus
    -----+------------------+--------+-------+---------
     1   | Devonshire Place | Boston | 02109 | 1234

Table of addresses

    -- basic table
    CREATE TABLE places(addid serial PRIMARY KEY, address text);

    INSERT INTO places(address)
    VALUES ('529 Main Street, Boston MA, 02129'),
     ('77 Massachusetts Avenue, Cambridge, MA 02139'),
     ('25 Wizard of Oz, Walaford, KS 99912323'),
     ('26 Capen Street, Medford, MA'),
     ('124 Mount Auburn St, Cambridge, Massachusetts 02138'),
     ('950 Main Street, Worcester, MA 01610');

     -- parse the addresses
     -- if you want all fields you can use (a).*
    SELECT addid, (a).num, (a).street, (a).city, (a).state, (a).zip, (a).zipplus
    FROM (SELECT addid, parse_address(address) As a
     FROM places) AS p;

     addid | num |        street        |   city    | state |  zip  | zipplus
    -------+-----+----------------------+-----------+-------+-------+---------
         1 | 529 | Main Street          | Boston    | MA    | 02129 |
         2 | 77  | Massachusetts Avenue | Cambridge | MA    | 02139 |
         3 | 25  | Wizard of Oz         | Walaford  | KS    | 99912 | 323
         4 | 26  | Capen Street         | Medford   | MA    |       |
         5 | 124 | Mount Auburn St      | Cambridge | MA    | 02138 |
         6 | 950 | Main Street          | Worcester | MA    | 01610 |
    (6 rows)

## See Also

## Name

standardize_address — Returns an stdaddr form of an input address utilizing lex, gaz, and rule tables.

## Synopsis

`stdaddr standardize_address(` text lextab, text gaztab, text rultab, text address`)`;

`stdaddr standardize_address(` text lextab, text gaztab, text rultab, text micro, text macro`)`;

## Description

Returns an stdaddr form of an input address utilizing lex table table name, gaz table, and rules table table names and an address.

Variant 1: Takes an address as a single line.

Variant 2: Takes an address as 2 parts. A `micro` consisting of standard first line of postal address e.g. `house_num street`, and a macro consisting of standard postal second line of an address e.g `city, state postal_code country`.

Availability: 2.2.0

This method needs address_standardizer extension.

## Examples

Using address_standardizer_data_us extension

    CREATE EXTENSION address_standardizer_data_us; -- only needs to be done once

Variant 1: Single line address. This doesn't work well with non-US addresses

    SELECT house_num, name, suftype, city, country, state, unit  FROM standardize_address('us_lex',
    			   'us_gaz', 'us_rules', 'One Devonshire Place, PH 301, Boston, MA 02109');

    house_num |    name    | suftype |  city  | country |     state     |      unit
    ----------+------------+---------+--------+---------+---------------+-----------------
    1         | DEVONSHIRE | PLACE   | BOSTON | USA     | MASSACHUSETTS | # PENTHOUSE 301

Using tables packaged with tiger geocoder. This example only works if you installed `postgis_tiger_geocoder`.

    SELECT *  FROM standardize_address('tiger.pagc_lex',
             'tiger.pagc_gaz', 'tiger.pagc_rules', 'One Devonshire Place, PH 301, Boston, MA 02109-1234');

Make easier to read we'll dump output using hstore extension CREATE EXTENSION hstore; you need to install

    SELECT (each(hstore(p))).*
     FROM standardize_address('tiger.pagc_lex', 'tiger.pagc_gaz',
       'tiger.pagc_rules', 'One Devonshire Place, PH 301, Boston, MA 02109') As p;

        key     |      value
    ------------+-----------------
     box        |
     city       | BOSTON
     name       | DEVONSHIRE
     qual       |
     unit       | # PENTHOUSE 301
     extra      |
     state      | MA
     predir     |
     sufdir     |
     country    | USA
     pretype    |
     suftype    | PL
     building   |
     postcode   | 02109
     house_num  | 1
     ruralroute |
    (16 rows)

Variant 2: As a two part Address

    SELECT (each(hstore(p))).*
     FROM standardize_address('tiger.pagc_lex', 'tiger.pagc_gaz',
       'tiger.pagc_rules', 'One Devonshire Place, PH 301', 'Boston, MA 02109, US') As p;

        key     |      value
    ------------+-----------------
     box        |
     city       | BOSTON
     name       | DEVONSHIRE
     qual       |
     unit       | # PENTHOUSE 301
     extra      |
     state      | MA
     predir     |
     sufdir     |
     country    | USA
     pretype    |
     suftype    | PL
     building   |
     postcode   | 02109
     house_num  | 1
     ruralroute |
    (16 rows)

## See Also

stdaddr, rules table, lex table, gaz table, Pagc_Normalize_Address

## 12.2. Tiger Geocoder

Abstract

A plpgsql based geocoder written to work with the TIGER (Topologically Integrated Geographic Encoding and Referencing system ) / Line and Master Address database export released by the US Census Bureau.

There are four components to the geocoder: the data loader functions, the address normalizer, the address geocoder, and the reverse geocoder.

Although it is designed specifically for the US, a lot of the concepts and functions are applicable and can be adapted to work with other country address and road networks.

The script builds a schema called `tiger` to house all the tiger related functions, reusable lookup data such as road type prefixes, suffixes, states, various control tables for managing data load, and skeleton base tables from which all the tiger loaded tables inherit from.

Another schema called `tiger_data` is also created which houses all the census data for each state that the loader downloads from Census site and loads into the database. In the current model, each set of state tables is prefixed with the state code e.g `ma_addr`, `ma_edges` etc with constraints to enforce only that state data. Each of these tables inherits from the tables `addr`, `faces`, `edges`, etc located in the `tiger schema`.

All the geocode functions only reference the base tables, so there is no requirement that the data schema be called `tiger_data` or that data can't be further partitioned into other schemas -- e.g a different schema for each state, as long as all the tables inherit from the tables in the `tiger` schema.

For instructions on how to enable the extension in your database and also to load data using it, refer to Section 2.4.1, “Tiger Geocoder Enabling your PostGIS database”.

If you are using tiger geocoder (tiger_2010), you can upgrade the scripts using the accompanying upgrade_geocoder.bat / .sh scripts in extras/tiger. One major change between `tiger_2010` and `tiger_2011+` is that the `county` and `state` tables are no longer broken out by state. If you have data from tiger_2010 and want to replace with tiger_2015, refer to Section 2.4.4, “Upgrading your Tiger Geocoder Install and Data”

New in PostGIS 2.2.0 release is support for Tiger 2015 data and inclusion of Address Standardizer as part of PostGIS. New in PostGIS 2.1.0 release is ability to install tiger geocoder with PostgreSQL extension model if you are running PostgreSQL 9.1+. Refer to Section 2.4.1, “Tiger Geocoder Enabling your PostGIS database” for details.

The Pagc_Normalize_Address function as a drop in replacement for in-built Normalize_Address. Refer to Section 2.3, “Installing and Using the address standardizer” for compile and installation instructions.

Design:

The goal of this project is to build a fully functional geocoder that can process an arbitrary United States address string and using normalized TIGER census data, produce a point geometry and rating reflecting the location of the given address and likeliness of the location. The higher the rating number the worse the result.

The `reverse_geocode` function, introduced in PostGIS 2.0.0 is useful for deriving the street address and cross streets of a GPS location.

The geocoder should be simple for anyone familiar with PostGIS to install and use, and should be easily installable and usable on all platforms supported by PostGIS.

It should be robust enough to function properly despite formatting and spelling errors.

It should be extensible enough to be used with future data updates, or alternate data sources with a minimum of coding changes.

The `tiger` schema must be added to the database search path for the functions to work properly.

There are a couple other open source geocoders for PostGIS, that unlike tiger geocoder have the advantage of multi-country geocoding support

- Nominatim uses OpenStreetMap gazeteer formatted data. It requires osm2pgsql for loading the data, PostgreSQL 8.4+ and PostGIS 1.5+ to function. It is packaged as a webservice interface and seems designed to be called as a webservice. Just like the tiger geocoder, it has both a geocoder and a reverse geocoder component. From the documentation, it is unclear if it has a pure SQL interface like the tiger geocoder, or if a good deal of the logic is implemented in the web interface.

- GIS Graphy also utilizes PostGIS and like Nominatim works with OpenStreetMap (OSM) data. It comes with a loader to load OSM data and similar to Nominatim is capable of geocoding not just US. Much like Nominatim, it runs as a webservice and relies on Java 1.5, Servlet apps, Solr. GisGraphy is cross-platform and also has a reverse geocoder among some other neat features.

## Name

Drop_Indexes_Generate_Script — Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to `tiger_data` if no schema is specified.

## Synopsis

`text Drop_Indexes_Generate_Script(` text param_schema=tiger_data`)`;

## Description

Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to `tiger_data` if no schema is specified.

This is useful for minimizing index bloat that may confuse the query planner or take up unnecessary space. Use in combination with Install_Missing_Indexes to add just the indexes used by the geocoder.

Availability: 2.0.0

## Examples

    SELECT drop_indexes_generate_script() As actionsql;
    actionsql
    ---------------------------------------------------------
    DROP INDEX tiger.idx_tiger_countysub_lookup_lower_name;
    DROP INDEX tiger.idx_tiger_edges_countyfp;
    DROP INDEX tiger.idx_tiger_faces_countyfp;
    DROP INDEX tiger.tiger_place_the_geom_gist;
    DROP INDEX tiger.tiger_edges_the_geom_gist;
    DROP INDEX tiger.tiger_state_the_geom_gist;
    DROP INDEX tiger.idx_tiger_addr_least_address;
    DROP INDEX tiger.idx_tiger_addr_tlid;
    DROP INDEX tiger.idx_tiger_addr_zip;
    DROP INDEX tiger.idx_tiger_county_countyfp;
    DROP INDEX tiger.idx_tiger_county_lookup_lower_name;
    DROP INDEX tiger.idx_tiger_county_lookup_snd_name;
    DROP INDEX tiger.idx_tiger_county_lower_name;
    DROP INDEX tiger.idx_tiger_county_snd_name;
    DROP INDEX tiger.idx_tiger_county_the_geom_gist;
    DROP INDEX tiger.idx_tiger_countysub_lookup_snd_name;
    DROP INDEX tiger.idx_tiger_cousub_countyfp;
    DROP INDEX tiger.idx_tiger_cousub_cousubfp;
    DROP INDEX tiger.idx_tiger_cousub_lower_name;
    DROP INDEX tiger.idx_tiger_cousub_snd_name;
    DROP INDEX tiger.idx_tiger_cousub_the_geom_gist;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_least_address;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_tlid;
    DROP INDEX tiger_data.idx_tiger_data_ma_addr_zip;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_countyfp;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lookup_lower_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lookup_snd_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_lower_name;
    DROP INDEX tiger_data.idx_tiger_data_ma_county_snd_name;
    :
    :

## See Also

Install_Missing_Indexes, Missing_Indexes_Generate_Script

## Name

Drop_Nation_Tables_Generate_Script — Generates a script that drops all tables in the specified schema that start with `county_all`, `state_all` or state code followed by `county` or `state`.

## Synopsis

`text Drop_Nation_Tables_Generate_Script(` text param_schema=tiger_data`)`;

## Description

Generates a script that drops all tables in the specified schema that start with `county_all`, `state_all` or state code followed by `county` or `state`. This is needed if you are upgrading from `tiger_2010` to `tiger_2011` data.

Availability: 2.1.0

## Examples

    SELECT drop_nation_tables_generate_script();
    DROP TABLE tiger_data.county_all;
    DROP TABLE tiger_data.county_all_lookup;
    DROP TABLE tiger_data.state_all;
    DROP TABLE tiger_data.ma_county;
    DROP TABLE tiger_data.ma_state;

## See Also

Loader_Generate_Nation_Script

## Name

Drop_State_Tables_Generate_Script — Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to `tiger_data` if no schema is specified.

## Synopsis

`text Drop_State_Tables_Generate_Script(` text param_state, text param_schema=tiger_data`)`;

## Description

Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to `tiger_data` if no schema is specified. This function is useful for dropping tables of a state just before you reload a state in case something went wrong during your previous load.

Availability: 2.0.0

## Examples

    SELECT drop_state_tables_generate_script('PA');
    DROP TABLE tiger_data.pa_addr;
    DROP TABLE tiger_data.pa_county;
    DROP TABLE tiger_data.pa_county_lookup;
    DROP TABLE tiger_data.pa_cousub;
    DROP TABLE tiger_data.pa_edges;
    DROP TABLE tiger_data.pa_faces;
    DROP TABLE tiger_data.pa_featnames;
    DROP TABLE tiger_data.pa_place;
    DROP TABLE tiger_data.pa_state;
    DROP TABLE tiger_data.pa_zip_lookup_base;
    DROP TABLE tiger_data.pa_zip_state;
    DROP TABLE tiger_data.pa_zip_state_loc;

## See Also

Loader_Generate_Script

## Name

Geocode — Takes in an address as a string (or other normalized address) and outputs a set of possible locations which include a point geometry in NAD 83 long lat, a normalized address for each, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10, and restrict_region (defaults to NULL)

## Synopsis

`setof record geocode(` varchar address, integer max_results=10, geometry restrict_region=NULL, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

`setof record geocode(` norm_addy in_addy, integer max_results=10, geometry restrict_region=NULL, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

## Description

Takes in an address as a string (or already normalized address) and outputs a set of possible locations which include a point geometry in NAD 83 long lat, a `normalized_address` (addy) for each, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Uses Tiger data (edges,faces,addr), PostgreSQL fuzzy string matching (soundex,levenshtein) and PostGIS line interpolation functions to interpolate address along the Tiger edges. The higher the rating the less likely the geocode is right. The geocoded point is defaulted to offset 10 meters from center-line off to side (L/R) of street address is located on.

Enhanced: 2.0.0 to support Tiger 2010 structured data and revised some logic to improve speed, accuracy of geocoding, and to offset point from centerline to side of street address is located on. The new parameter `max_results` useful for specifying number of best results or just returning the best result.

## Examples: Basic

The below examples timings are on a 3.0 GHZ single processor Windows 7 machine with 2GB ram running PostgreSQL 9.1rc1/PostGIS 2.0 loaded with all of MA,MN,CA, RI state Tiger data loaded.

Exact matches are faster to compute (61ms)

    SELECT g.rating, ST_X(g.geomout) As lon, ST_Y(g.geomout) As lat,
        (addy).address As stno, (addy).streetname As street,
        (addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
        FROM geocode('75 State Street, Boston MA 02109', 1) As g;
     rating |        lon        |      lat       | stno | street | styp |  city  | st |  zip
    --------+-------------------+----------------+------+--------+------+--------+----+-------
          0 | -71.0557505845646 | 42.35897920691 |   75 | State  | St   | Boston | MA | 02109

Even if zip is not passed in the geocoder can guess (took about 122-150 ms)

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
        (addy).address As stno, (addy).streetname As street,
        (addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
        FROM geocode('226 Hanover Street, Boston, MA',1) As g;
     rating |         wktlonlat         | stno | street  | styp |  city  | st |  zip
    --------+---------------------------+------+---------+------+--------+----+-------
          1 | POINT(-71.05528 42.36316) |  226 | Hanover | St   | Boston | MA | 02113

Can handle misspellings and provides more than one possible solution with ratings and takes longer (500ms).

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
        (addy).address As stno, (addy).streetname As street,
        (addy).streettypeabbrev As styp, (addy).location As city, (addy).stateabbrev As st,(addy).zip
        FROM geocode('31 - 37 Stewart Street, Boston, MA 02116',1) As g;
     rating |         wktlonlat         | stno | street | styp |  city  | st |  zip
    --------+---------------------------+------+--------+------+--------+----+-------
         70 | POINT(-71.06466 42.35114) |   31 | Stuart | St   | Boston | MA | 02116

Using to do a batch geocode of addresses. Easiest is to set `max_results=1`. Only process those not yet geocoded (have no rating).

    CREATE TABLE addresses_to_geocode(addid serial PRIMARY KEY, address text,
            lon numeric, lat numeric, new_address text, rating integer);

    INSERT INTO addresses_to_geocode(address)
    VALUES ('529 Main Street, Boston MA, 02129'),
     ('77 Massachusetts Avenue, Cambridge, MA 02139'),
     ('25 Wizard of Oz, Walaford, KS 99912323'),
     ('26 Capen Street, Medford, MA'),
     ('124 Mount Auburn St, Cambridge, Massachusetts 02138'),
     ('950 Main Street, Worcester, MA 01610');

    -- only update the first 3 addresses (323-704 ms -  there are caching and shared memory effects so first geocode you do is always slower) --
    -- for large numbers of addresses you don't want to update all at once
    -- since the whole geocode must commit at once
    -- For this example we rejoin with LEFT JOIN
    -- and set to rating to -1 rating if no match
    -- to ensure we don't regeocode a bad address
    UPDATE addresses_to_geocode
      SET  (rating, new_address, lon, lat)
        = ( COALESCE(g.rating,-1), pprint_addy(g.addy),
           ST_X(g.geomout)::numeric(8,5), ST_Y(g.geomout)::numeric(8,5) )
    FROM (SELECT addid, address
        FROM addresses_to_geocode
        WHERE rating IS NULL ORDER BY addid LIMIT 3) As a
        LEFT JOIN LATERAL geocode(a.address,1) As g ON true
    WHERE a.addid = addresses_to_geocode.addid;

    result
    -----
    Query returned successfully: 3 rows affected, 480 ms execution time.

    SELECT * FROM addresses_to_geocode WHERE rating is not null;

     addid |                   address                    |    lon    |   lat    |                new_address                | rating
    -------+----------------------------------------------+-----------+----------+-------------------------------------------+--------
         1 | 529 Main Street, Boston MA, 02129            | -71.07177 | 42.38357 | 529 Main St, Boston, MA 02129             |      0
         2 | 77 Massachusetts Avenue, Cambridge, MA 02139 | -71.09396 | 42.35961 | 77 Massachusetts Ave, Cambridge, MA 02139 |      0
         3 | 25 Wizard of Oz, Walaford, KS 99912323       | -97.92913 | 38.12717 | Willowbrook, KS 67502                     |    108
    (3 rows)

## Examples: Using Geometry filter

    SELECT g.rating, ST_AsText(ST_SnapToGrid(g.geomout,0.00001)) As wktlonlat,
        (addy).address As stno, (addy).streetname As street,
        (addy).streettypeabbrev As styp,
        (addy).location As city, (addy).stateabbrev As st,(addy).zip
      FROM geocode('100 Federal Street, MA',
            3,
            (SELECT ST_Union(the_geom)
                FROM place WHERE statefp = '25' AND name = 'Lynn')::geometry
            ) As g;

     rating |         wktlonlat         | stno | street  | styp | city | st |  zip
    --------+---------------------------+------+---------+------+------+----+-------
          7 | POINT(-70.96796 42.4659)  |  100 | Federal | St   | Lynn | MA | 01905
         16 | POINT(-70.96786 42.46853) | NULL | Federal | St   | Lynn | MA | 01905
    (2 rows)

    Time: 622.939 ms

## See Also

Normalize_Address, Pprint_Addy, ST_AsText, ST_SnapToGrid, ST_X, ST_Y

## Name

Geocode_Intersection — Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a geomout as the point location in NAD 83 long lat, a `normalized_address` (addy) for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10. Uses Tiger data (edges, faces, addr), PostgreSQL fuzzy string matching (soundex, levenshtein).

## Synopsis

`setof record geocode_intersection(` text roadway1, text roadway2, text in_state, text in_city, text in_zip, integer max_results=10, norm_addy OUT addy, geometry OUT geomout, integer OUT rating`)`;

## Description

Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a point geometry in NAD 83 long lat, a normalized address for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10. Returns `normalized_address` (addy) for each, geomout as the point location in nad 83 long lat, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Uses Tiger data (edges,faces,addr), PostgreSQL fuzzy string matching (soundex,levenshtein)

Availability: 2.0.0

## Examples: Basic

The below examples timings are on a 3.0 GHZ single processor Windows 7 machine with 2GB ram running PostgreSQL 9.0/PostGIS 1.5 loaded with all of MA state Tiger data loaded. Currently a bit slow (3000 ms)

Testing on Windows 2003 64-bit 8GB on PostGIS 2.0 PostgreSQL 64-bit Tiger 2011 data loaded -- (41ms)

    SELECT pprint_addy(addy), st_astext(geomout),rating
                FROM geocode_intersection( 'Haverford St','Germania St', 'MA', 'Boston', '02130',1);
               pprint_addy            |         st_astext          | rating
    ----------------------------------+----------------------------+--------
    98 Haverford St, Boston, MA 02130 | POINT(-71.101375 42.31376) |      0

Even if zip is not passed in the geocoder can guess (took about 3500 ms on the windows 7 box), on the windows 2003 64-bit 741 ms

    SELECT pprint_addy(addy), st_astext(geomout),rating
                    FROM geocode_intersection('Weld', 'School', 'MA', 'Boston');
              pprint_addy          |        st_astext         | rating
    -------------------------------+--------------------------+--------
     98 Weld Ave, Boston, MA 02119 | POINT(-71.099 42.314234) |      3
     99 Weld Ave, Boston, MA 02119 | POINT(-71.099 42.314234) |      3

## See Also

Geocode, Pprint_Addy, ST_AsText

## Name

Get_Geocode_Setting — Returns value of specific setting stored in tiger.geocode_settings table.

## Synopsis

`text Get_Geocode_Setting(` text setting_name`)`;

## Description

Returns value of specific setting stored in tiger.geocode_settings table. Settings allow you to toggle debugging of functions. Later plans will be to control rating with settings. Current list of settings are as follows:

                  name              | setting |  unit   | category  |                                                             short_desc
    --------------------------------+---------+---------+-----------+------------------------------------------------------------------------------------------------------------------------------
     debug_geocode_address          | false   | boolean | debug     | outputs debug information in notice log such as queries when geocode_address is called if true
     debug_geocode_intersection     | false   | boolean | debug     | outputs debug information in notice log such as queries when geocode_intersection is called if true
     debug_normalize_address        | false   | boolean | debug     | outputs debug information in notice log such as queries and intermediate expressions when normalize_address is called if true
     debug_reverse_geocode          | false   | boolean | debug     | if true, outputs debug information in notice log such as queries and intermediate expressions when reverse_geocode
     reverse_geocode_numbered_roads | 0       | integer | rating    | For state and county highways, 0 - no preference in name,
                                                                      1 - prefer the numbered highway name, 2 - prefer local state/county name
     use_pagc_address_parser        | false   | boolean | normalize | If set to true, will try to use the address_standardizer extension (via pagc_normalize_address)
                                                                     instead of tiger normalize_address built one

Changed: 2.2.0 : default settings are now kept in a table called geocode_settings_default. Use customized settingsa are in geocode_settings and only contain those that have been set by user.

Availability: 2.1.0

## Example return debugging setting

    SELECT get_geocode_setting('debug_geocode_address) As result;
    result
    ---------
    false

## See Also

Set_Geocode_Setting

## Name

Get_Tract — Returns census tract or field from tract table of where the geometry is located. Default to returning short name of tract.

## Synopsis

`text get_tract(` geometry loc_geom, text output_field=name`)`;

## Description

Given a geometry will return the census tract location of that geometry. NAD 83 long lat is assumed if no spatial ref sys is specified.

This function uses the census `tract` which is not loaded by default. If you have already loaded your state table, you can load tract as well as bg, and tabblock using the Loader_Generate_Census_Script script. If you have not loaded your state data yet and want these additional tables loaded, do the following
    UPDATE tiger.loader_lookuptables SET load = true WHERE load = false AND lookup_name IN('tract', 'bg', 'tabblock');
then they will be included by the Loader_Generate_Script.

Availability: 2.0.0

## Examples: Basic

    SELECT get_tract(ST_Point(-71.101375, 42.31376) ) As tract_name;
    tract_name
    ---------
    1203.01

    --this one returns the tiger geoid
    SELECT get_tract(ST_Point(-71.101375, 42.31376), 'tract_id' ) As tract_id;
    tract_id
    ---------
    25025120301

## See Also

Geocode>

## Name

Install_Missing_Indexes — Finds all tables with key columns used in geocoder joins and filter conditions that are missing used indexes on those columns and will add them.

## Synopsis

`boolean Install_Missing_Indexes(` `)`;

## Description

Finds all tables in `tiger` and `tiger_data` schemas with key columns used in geocoder joins and filters that are missing indexes on those columns and will output the SQL DDL to define the index for those tables and then execute the generated script. This is a helper function that adds new indexes needed to make queries faster that may have been missing during the load process. This function is a companion to Missing_Indexes_Generate_Script that in addition to generating the create index script, also executes it. It is called as part of the `update_geocode.sql` upgrade script.

Availability: 2.0.0

## Examples

    SELECT install_missing_indexes();
             install_missing_indexes
    -------------------------
     t

## See Also

Loader_Generate_Script, Missing_Indexes_Generate_Script

## Name

Loader_Generate_Census_Script — Generates a shell script for the specified platform for the specified states that will download Tiger census state tract, bg, and tabblocks data tables, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

## Synopsis

`setof text loader_generate_census_script(` text[] param_states, text os`)`;

## Description

Generates a shell script for the specified platform for the specified states that will download Tiger data census state `tract`, block groups `bg`, and `tabblocks` data tables, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

It uses unzip on Linux (7-zip on Windows by default) and wget to do the downloading. It uses Section 4.7.2, “Using the Shapefile Loader” to load in the data. Note the smallest unit it does is a whole state. It will only process the files in the staging and temp folders.

It uses the following control tables to control the process and different OS shell syntax variations.

1. `loader_variables` keeps track of various variables such as census site, year, data and staging schemas

2. `loader_platform` profiles of various platforms and where the various executables are located. Comes with windows and linux. More can be added.

3. `loader_lookuptables` each record defines a kind of table (state, county), whether to process records in it and how to load them in. Defines the steps to import data, stage data, add, removes columns, indexes, and constraints for each. Each table is prefixed with the state and inherits from a table in the tiger schema. e.g. creates `tiger_data.ma_faces` which inherits from `tiger.faces`

Availability: 2.0.0

Loader_Generate_Script includes this logic, but if you installed tiger geocoder prior to PostGIS 2.0.0 alpha5, you'll need to run this on the states you have already done to get these additional tables.

## Examples

Generate script to load up data for select states in Windows shell script format.

    SELECT loader_generate_census_script(ARRAY['MA'], 'windows');
    -- result --
    set STATEDIR="\gisdata\www2.census.gov\geo\pvs\tiger2010st\25_Massachusetts"
    set TMPDIR=\gisdata\temp\
    set UNZIPTOOL="C:\Program Files\7-Zip\7z.exe"
    set WGETTOOL="C:\wget\wget.exe"
    set PGBIN=C:\projects\pg\pg91win\bin\
    set PGPORT=5432
    set PGHOST=localhost
    set PGUSER=postgres
    set PGPASSWORD=yourpasswordhere
    set PGDATABASE=tiger_postgis20
    set PSQL="%PGBIN%psql"
    set SHP2PGSQL="%PGBIN%shp2pgsql"
    cd \gisdata

    %WGETTOOL% http://www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts/25/ --no-parent --relative --accept=*bg10.zip,*tract10.zip,*tabblock10.zip --mirror --reject=html
    del %TMPDIR%\*.* /Q
    %PSQL% -c "DROP SCHEMA tiger_staging CASCADE;"
    %PSQL% -c "CREATE SCHEMA tiger_staging;"
    cd %STATEDIR%
    for /r %%z in (*.zip) do %UNZIPTOOL% e %%z  -o%TMPDIR%
    cd %TMPDIR%
    %PSQL% -c "CREATE TABLE tiger_data.MA_tract(CONSTRAINT pk_MA_tract PRIMARY KEY (tract_id) ) INHERITS(tiger.tract); "
    %SHP2PGSQL% -c -s 4269 -g the_geom   -W "latin1" tl_2010_25_tract10.dbf tiger_staging.ma_tract10 | %PSQL%
    %PSQL% -c "ALTER TABLE tiger_staging.MA_tract10 RENAME geoid10 TO tract_id;  SELECT loader_load_staged_data(lower('MA_tract10'), lower('MA_tract')); "
    %PSQL% -c "CREATE INDEX tiger_data_MA_tract_the_geom_gist ON tiger_data.MA_tract USING gist(the_geom);"
    %PSQL% -c "VACUUM ANALYZE tiger_data.MA_tract;"
    %PSQL% -c "ALTER TABLE tiger_data.MA_tract ADD CONSTRAINT chk_statefp CHECK (statefp = '25');"
    :

Generate sh script

    STATEDIR="/gisdata/www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts"
    TMPDIR="/gisdata/temp/"
    UNZIPTOOL=unzip
    WGETTOOL="/usr/bin/wget"
    export PGBIN=/usr/pgsql-9.0/bin
    export PGPORT=5432
    export PGHOST=localhost
    export PGUSER=postgres
    export PGPASSWORD=yourpasswordhere
    export PGDATABASE=geocoder
    PSQL=${PGBIN}/psql
    SHP2PGSQL=${PGBIN}/shp2pgsql
    cd /gisdata

    wget http://www2.census.gov/geo/pvs/tiger2010st/25_Massachusetts/25/ --no-parent --relative --accept=*bg10.zip,*tract10.zip,*tabblock10.zip --mirror --reject=html
    rm -f ${TMPDIR}/*.*
    ${PSQL} -c "DROP SCHEMA tiger_staging CASCADE;"
    ${PSQL} -c "CREATE SCHEMA tiger_staging;"
    cd $STATEDIR
    for z in *.zip; do $UNZIPTOOL -o -d $TMPDIR $z; done
    :
    :

## See Also

Loader_Generate_Script

## Name

Loader_Generate_Script — Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into `tiger_data` schema. Each state script is returned as a separate record. Latest version supports Tiger 2010 structural changes and also loads census tract, block groups, and blocks tables.

## Synopsis

`setof text loader_generate_script(` text[] param_states, text os`)`;

## Description

Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into `tiger_data` schema. Each state script is returned as a separate record.

It uses unzip on Linux (7-zip on Windows by default) and wget to do the downloading. It uses Section 4.7.2, “Using the Shapefile Loader” to load in the data. Note the smallest unit it does is a whole state, but you can overwrite this by downloading the files yourself. It will only process the files in the staging and temp folders.

It uses the following control tables to control the process and different OS shell syntax variations.

1. `loader_variables` keeps track of various variables such as census site, year, data and staging schemas

2. `loader_platform` profiles of various platforms and where the various executables are located. Comes with windows and linux. More can be added.

3. `loader_lookuptables` each record defines a kind of table (state, county), whether to process records in it and how to load them in. Defines the steps to import data, stage data, add, removes columns, indexes, and constraints for each. Each table is prefixed with the state and inherits from a table in the tiger schema. e.g. creates `tiger_data.ma_faces` which inherits from `tiger.faces`

Availability: 2.0.0 to support Tiger 2010 structured data and load census tract (tract), block groups (bg), and blocks (tabblocks) tables .

If you are using pgAdmin 3, be warned that by default pgAdmin 3 truncates long text. To fix, change File -> Options -> Query Tool -> Query Editor - > Max. characters per column to larger than 50000 characters.

## Examples

Using psql where gistest is your database and `/gisdata/data_load.sh` is the file to create with the shell commands to run.

    psql -U postgres -h localhost -d gistest -A -t \
     -c "SELECT Loader_Generate_Script(ARRAY['MA'], 'gistest')" > /gisdata/data_load.sh;

Generate script to load up data for 2 states in Windows shell script format.

    SELECT loader_generate_script(ARRAY['MA','RI'], 'windows') AS result;
    -- result --
    set TMPDIR=\gisdata\temp\
    set UNZIPTOOL="C:\Program Files\7-Zip\7z.exe"
    set WGETTOOL="C:\wget\wget.exe"
    set PGBIN=C:\Program Files\PostgreSQL\9.4\bin\
    set PGPORT=5432
    set PGHOST=localhost
    set PGUSER=postgres
    set PGPASSWORD=yourpasswordhere
    set PGDATABASE=geocoder
    set PSQL="%PGBIN%psql"
    set SHP2PGSQL="%PGBIN%shp2pgsql"
    cd \gisdata

    cd \gisdata
    %WGETTOOL% ftp://ftp2.census.gov/geo/tiger/TIGER2015/PLACE/tl_*_25_* --no-parent --relative --recursive --level=2 --accept=zip --mirror --reject=html
    cd \gisdata/ftp2.census.gov/geo/tiger/TIGER2015/PLACE
    :
    :

Generate sh script

    SELECT loader_generate_script(ARRAY['MA','RI'], 'sh') AS result;
    -- result --
    TMPDIR="/gisdata/temp/"
    UNZIPTOOL=unzip
    WGETTOOL="/usr/bin/wget"
    export PGBIN=/usr/lib/postgresql/9.4/bin
    -- variables used by psql: https://www.postgresql.org/docs/current/static/libpq-envars.html
    export PGPORT=5432
    export PGHOST=localhost
    export PGUSER=postgres
    export PGPASSWORD=yourpasswordhere
    export PGDATABASE=geocoder
    PSQL=${PGBIN}/psql
    SHP2PGSQL=${PGBIN}/shp2pgsql
    cd /gisdata

    cd /gisdata
    wget ftp://ftp2.census.gov/geo/tiger/TIGER2015/PLACE/tl_*_25_* --no-parent --relative --recursive --level=2 --accept=zip --mirror --reject=html
    cd /gisdata/ftp2.census.gov/geo/tiger/TIGER2015/PLACE
    rm -f ${TMPDIR}/*.*
    :
    :

## See Also

Section 2.4.1, “Tiger Geocoder Enabling your PostGIS database”, Loader_Generate_Nation_Script, Drop_State_Tables_Generate_Script

## Name

Loader_Generate_Nation_Script — Generates a shell script for the specified platform that loads in the county and state lookup tables.

## Synopsis

`text loader_generate_nation_script(` text os`)`;

## Description

Generates a shell script for the specified platform that loads in the `county_all`, `county_all_lookup`, `state_all` tables into `tiger_data` schema. These inherit respectively from the `county`, `county_lookup`, `state` tables in `tiger` schema.

It uses unzip on Linux (7-zip on Windows by default) and wget to do the downloading. It uses Section 4.7.2, “Using the Shapefile Loader” to load in the data.

It uses the following control tables `tiger.loader_platform`, `tiger.loader_variables`, and `tiger.loader_lookuptables` to control the process and different OS shell syntax variations.

1. `loader_variables` keeps track of various variables such as census site, year, data and staging schemas

2. `loader_platform` profiles of various platforms and where the various executables are located. Comes with windows and linux/unix. More can be added.

3. `loader_lookuptables` each record defines a kind of table (state, county), whether to process records in it and how to load them in. Defines the steps to import data, stage data, add, removes columns, indexes, and constraints for each. Each table is prefixed with the state and inherits from a table in the tiger schema. e.g. creates `tiger_data.ma_faces` which inherits from `tiger.faces`

Enhanced: 2.4.1 zip code 5 tabulation area (zcta5) load step was fixed and when enabled, zcta5 data is loaded as a single table called zcta5_all as part of the nation script load.

Availability: 2.1.0

If you want zip code 5 tabulation area (zcta5) to be included in your nation script load, do the following:
    UPDATE tiger.loader_lookuptables SET load = true WHERE table_name = 'zcta510';

If you were running `tiger_2010` version and you want to reload as state with newer tiger data, you'll need to for the very first load generate and run drop statements Drop_Nation_Tables_Generate_Script before you run this script.

## Examples

Generate script script to load nation data Windows.

    SELECT loader_generate_nation_script('windows');

Generate script to load up data for Linux/Unix systems.

    SELECT loader_generate_nation_script('sh');

## See Also

Loader_Generate_Script, Drop_Nation_Tables_Generate_Script

## Name

Missing_Indexes_Generate_Script — Finds all tables with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables.

## Synopsis

`text Missing_Indexes_Generate_Script(` `)`;

## Description

Finds all tables in `tiger` and `tiger_data` schemas with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables. This is a helper function that adds new indexes needed to make queries faster that may have been missing during the load process. As the geocoder is improved, this function will be updated to accommodate new indexes being used. If this function outputs nothing, it means all your tables have what we think are the key indexes already in place.

Availability: 2.0.0

## Examples

    SELECT missing_indexes_generate_script();
    -- output: This was run on a database that was created before many corrections were made to the loading script ---
    CREATE INDEX idx_tiger_county_countyfp ON tiger.county USING btree(countyfp);
    CREATE INDEX idx_tiger_cousub_countyfp ON tiger.cousub USING btree(countyfp);
    CREATE INDEX idx_tiger_edges_tfidr ON tiger.edges USING btree(tfidr);
    CREATE INDEX idx_tiger_edges_tfidl ON tiger.edges USING btree(tfidl);
    CREATE INDEX idx_tiger_zip_lookup_all_zip ON tiger.zip_lookup_all USING btree(zip);
    CREATE INDEX idx_tiger_data_ma_county_countyfp ON tiger_data.ma_county USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_cousub_countyfp ON tiger_data.ma_cousub USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_edges_countyfp ON tiger_data.ma_edges USING btree(countyfp);
    CREATE INDEX idx_tiger_data_ma_faces_countyfp ON tiger_data.ma_faces USING btree(countyfp);

## See Also

Loader_Generate_Script, Install_Missing_Indexes

## Name

Normalize_Address — Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data).

## Synopsis

`norm_addy normalize_address(` varchar in_address`)`;

## Description

Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This is the first step in the geocoding process to get all addresses into normalized postal form. No other data is required aside from what is packaged with the geocoder.

This function just uses the various direction/state/suffix lookup tables preloaded with the tiger_geocoder and located in the `tiger` schema, so it doesn't need you to download tiger census data or any other additional data to make use of it. You may find the need to add more abbreviations or alternative namings to the various lookup tables in the `tiger` schema.

It uses various control lookup tables located in `tiger` schema to normalize the input address.

Fields in the `norm_addy` type object returned by this function in this order where () indicates a field required by the geocoder, [] indicates an optional field:

(address) [predirAbbrev] (streetName) [streetTypeAbbrev] [postdirAbbrev] [internal] [location] [stateAbbrev] [zip] [parsed] [zip4] [address_alphanumeric]

Enhanced: 2.4.0 norm_addy object includes additional fields zip4 and address_alphanumeric.

1. `address` is an integer: The street number

2. `predirAbbrev` is varchar: Directional prefix of road such as N, S, E, W etc. These are controlled using the `direction_lookup` table.

3. `streetName` varchar

4. `streetTypeAbbrev` varchar abbreviated version of street type: e.g. St, Ave, Cir. These are controlled using the `street_type_lookup` table.

5. `postdirAbbrev` varchar abbreviated directional suffice of road N, S, E, W etc. These are controlled using the `direction_lookup` table.

6. `internal` varchar internal address such as an apartment or suite number.

7. `location` varchar usually a city or governing province.

8. `stateAbbrev` varchar two character US State. e.g MA, NY, MI. These are controlled by the `state_lookup` table.

9. `zip` varchar 5-digit zipcode. e.g. 02109.

10. `parsed` boolean - denotes if address was formed from normalize process. The normalize_address function sets this to true before returning the address.

11. `zip4` last 4 digits of a 9 digit zip code. Availability: PostGIS 2.4.0.

12. `address_alphanumeric` Full street number even if it has alpha characters like 17R. Parsing of this is better using Pagc_Normalize_Address function. Availability: PostGIS 2.4.0.

## Examples

Output select fields. Use Pprint_Addy if you want a pretty textual output.

    SELECT address As orig, (g.na).streetname, (g.na).streettypeabbrev
     FROM (SELECT address, normalize_address(address) As na
            FROM addresses_to_geocode) As g;

                            orig                         |  streetname   | streettypeabbrev
    -----------------------------------------------------+---------------+------------------
     28 Capen Street, Medford, MA                        | Capen         | St
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | Mount Auburn  | St
     950 Main Street, Worcester, MA 01610                | Main          | St
     529 Main Street, Boston MA, 02129                   | Main          | St
     77 Massachusetts Avenue, Cambridge, MA 02139        | Massachusetts | Ave
     25 Wizard of Oz, Walaford, KS 99912323              | Wizard of Oz  |

## See Also

Geocode, Pprint_Addy

## Name

Pagc_Normalize_Address — Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data). Requires address_standardizer extension.

## Synopsis

`norm_addy pagc_normalize_address(` varchar in_address`)`;

## Description

Given a textual street address, returns a composite `norm_addy` type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This is the first step in the geocoding process to get all addresses into normalized postal form. No other data is required aside from what is packaged with the geocoder.

This function just uses the various pagc_* lookup tables preloaded with the tiger_geocoder and located in the `tiger` schema, so it doesn't need you to download tiger census data or any other additional data to make use of it. You may find the need to add more abbreviations or alternative namings to the various lookup tables in the `tiger` schema.

It uses various control lookup tables located in `tiger` schema to normalize the input address.

Fields in the `norm_addy` type object returned by this function in this order where () indicates a field required by the geocoder, [] indicates an optional field:

There are slight variations in casing and formatting over the Normalize_Address.

Availability: 2.1.0

This method needs address_standardizer extension.

(address) [predirAbbrev] (streetName) [streetTypeAbbrev] [postdirAbbrev] [internal] [location] [stateAbbrev] [zip]

The native standardaddr of address_standardizer extension is at this time a bit richer than norm_addy since its designed to support international addresses (including country). standardaddr equivalent fields are:

house_num,predir, name, suftype, sufdir, unit, city, state, postcode

Enhanced: 2.4.0 norm_addy object includes additional fields zip4 and address_alphanumeric.

1. `address` is an integer: The street number

2. `predirAbbrev` is varchar: Directional prefix of road such as N, S, E, W etc. These are controlled using the `direction_lookup` table.

3. `streetName` varchar

4. `streetTypeAbbrev` varchar abbreviated version of street type: e.g. St, Ave, Cir. These are controlled using the `street_type_lookup` table.

5. `postdirAbbrev` varchar abbreviated directional suffice of road N, S, E, W etc. These are controlled using the `direction_lookup` table.

6. `internal` varchar internal address such as an apartment or suite number.

7. `location` varchar usually a city or governing province.

8. `stateAbbrev` varchar two character US State. e.g MA, NY, MI. These are controlled by the `state_lookup` table.

9. `zip` varchar 5-digit zipcode. e.g. 02109.

10. `parsed` boolean - denotes if address was formed from normalize process. The normalize_address function sets this to true before returning the address.

11. `zip4` last 4 digits of a 9 digit zip code. Availability: PostGIS 2.4.0.

12. `address_alphanumeric` Full street number even if it has alpha characters like 17R. Parsing of this is better using Pagc_Normalize_Address function. Availability: PostGIS 2.4.0.

## Examples

Single call example

    SELECT addy.*
    FROM pagc_normalize_address('9000 E ROO ST STE 999, Springfield, CO') AS addy;

     address | predirabbrev | streetname | streettypeabbrev | postdirabbrev | internal  |  location   | stateabbrev | zip | parsed
    ---------+--------------+------------+------------------+---------------+-----------+-------------+-------------+-----+--------
        9000 | E            | ROO        | ST               |               | SUITE 999 | SPRINGFIELD | CO          |     | t

Batch call. There are currently speed issues with the way postgis_tiger_geocoder wraps the address_standardizer. These will hopefully be resolved in later editions. To work around them, if you need speed for batch geocoding to call generate a normaddy in batch mode, you are encouraged to directly call the address_standardizer standardize_address function as shown below which is similar exercise to what we did in Normalize_Address that uses data created in Geocode.

    WITH g AS (SELECT address, ROW((sa).house_num, (sa).predir, (sa).name
      , (sa).suftype, (sa).sufdir, (sa).unit , (sa).city, (sa).state, (sa).postcode, true)::norm_addy As na
     FROM (SELECT address, standardize_address('tiger.pagc_lex'
           , 'tiger.pagc_gaz'
           , 'tiger.pagc_rules', address) As sa
            FROM addresses_to_geocode) As g)
    SELECT address As orig, (g.na).streetname, (g.na).streettypeabbrev
     FROM  g;

     orig                                                |  streetname   | streettypeabbrev
    -----------------------------------------------------+---------------+------------------
     529 Main Street, Boston MA, 02129                   | MAIN          | ST
     77 Massachusetts Avenue, Cambridge, MA 02139        | MASSACHUSETTS | AVE
     25 Wizard of Oz, Walaford, KS 99912323              | WIZARD OF     |
     26 Capen Street, Medford, MA                        | CAPEN         | ST
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | MOUNT AUBURN  | ST
     950 Main Street, Worcester, MA 01610                | MAIN          | ST

## See Also

Normalize_Address, Geocode

## Name

Pprint_Addy — Given a `norm_addy` composite type object, returns a pretty print representation of it. Usually used in conjunction with normalize_address.

## Synopsis

`varchar pprint_addy(` norm_addy in_addy`)`;

## Description

Given a `norm_addy` composite type object, returns a pretty print representation of it. No other data is required aside from what is packaged with the geocoder.

Usually used in conjunction with Normalize_Address.

## Examples

Pretty print a single address

    SELECT pprint_addy(normalize_address('202 East Fremont Street, Las Vegas, Nevada 89101')) As pretty_address;
                pretty_address
    ---------------------------------------
     202 E Fremont St, Las Vegas, NV 89101

Pretty print address a table of addresses

    SELECT address As orig, pprint_addy(normalize_address(address)) As pretty_address
            FROM addresses_to_geocode;

                            orig                         |              pretty_address
    -----------------------------------------------------+-------------------------------------------
     529 Main Street, Boston MA, 02129                   | 529 Main St, Boston MA, 02129
     77 Massachusetts Avenue, Cambridge, MA 02139        | 77 Massachusetts Ave, Cambridge, MA 02139
     28 Capen Street, Medford, MA                        | 28 Capen St, Medford, MA
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | 124 Mount Auburn St, Cambridge, MA 02138
     950 Main Street, Worcester, MA 01610                | 950 Main St, Worcester, MA 01610

## See Also

Normalize_Address

## Name

Reverse_Geocode — Takes a geometry point in a known spatial ref sys and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets.

## Synopsis

`record Reverse_Geocode(` geometry pt, boolean include_strnum_range=false, geometry[] OUT intpt, norm_addy[] OUT addy, varchar[] OUT street`)`;

## Description

Takes a geometry point in a known spatial ref and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets. include_strnum_range defaults to false if not passed in. Addresses are sorted according to which road a point is closest to so first address is most likely the right one.

Why do we say theoretical instead of actual addresses. The Tiger data doesn't have real addresses, but just street ranges. As such the theoretical address is an interpolated address based on the street ranges. Like for example interpolating one of my addresses returns a 26 Court St. and 26 Court Sq., though there is no such place as 26 Court Sq. This is because a point may be at a corner of 2 streets and thus the logic interpolates along both streets. The logic also assumes addresses are equally spaced along a street, which of course is wrong since you can have a municipal building taking up a good chunk of the street range and the rest of the buildings are clustered at the end.

Note: Hmm this function relies on Tiger data. If you have not loaded data covering the region of this point, then hmm you will get a record filled with NULLS.

Returned elements of the record are as follows:

1. `intpt` is an array of points: These are the center line points on the street closest to the input point. There are as many points as there are addresses.

2. `addy` is an array of norm_addy (normalized addresses): These are an array of possible addresses that fit the input point. The first one in the array is most likely. Generally there should be only one, except in the case when a point is at the corner of 2 or 3 streets, or the point is somewhere on the road and not off to the side.

3. `street` an array of varchar: These are cross streets (or the street) (streets that intersect or are the street the point is projected to be on).

Enhanced: 2.4.1 if optional zcta5 dataset is loaded, the reverse_geocode function can resolve to state and zip even if the specific state data is not loaded. Refer to Loader_Generate_Nation_Script for details on loading zcta5 data.

Availability: 2.0.0

## Examples

Example of a point at the corner of two streets, but closest to one. This is approximate location of MIT: 77 Massachusetts Ave, Cambridge, MA 02139 Note that although we don't have 3 streets, PostgreSQL will just return null for entries above our upper bound so safe to use. This includes street ranges

    SELECT pprint_addy(r.addy[1]) As st1, pprint_addy(r.addy[2]) As st2, pprint_addy(r.addy[3]) As st3,
                array_to_string(r.street, ',') As cross_streets
            FROM reverse_geocode(ST_GeomFromText('POINT(-71.093902 42.359446)',4269),true) As r;

     result
     ------
          st1                                  | st2 | st3 |               cross_streets
    -------------------------------------------+-----+-----+----------------------------------------------
     67 Massachusetts Ave, Cambridge, MA 02139 |     |     | 67 - 127 Massachusetts Ave,32 - 88 Vassar St

Here we choose not to include the address ranges for the cross streets and picked a location really really close to a corner of 2 streets thus could be known by two different addresses.

    SELECT pprint_addy(r.addy[1]) As st1, pprint_addy(r.addy[2]) As st2,
    pprint_addy(r.addy[3]) As st3, array_to_string(r.street, ',') As cross_str
    FROM reverse_geocode(ST_GeomFromText('POINT(-71.06941 42.34225)',4269)) As r;

    result
    --------
                   st1               |               st2               | st3 | cross_str
    ---------------------------------+---------------------------------+-----+------------------------
     5 Bradford St, Boston, MA 02118 | 49 Waltham St, Boston, MA 02118 |     | Waltham St

For this one we reuse our geocoded example from Geocode and we only want the primary address and at most 2 cross streets.

    SELECT actual_addr, lon, lat, pprint_addy((rg).addy[1]) As int_addr1,
        (rg).street[1] As cross1, (rg).street[2] As cross2
    FROM (SELECT address As actual_addr, lon, lat,
        reverse_geocode( ST_SetSRID(ST_Point(lon,lat),4326) ) As rg
        FROM addresses_to_geocode WHERE rating > -1) As foo;

                         actual_addr                     |    lon    |   lat    |                 int_addr1                 |     cross1      |   cross2
    -----------------------------------------------------+-----------+----------+-------------------------------------------+-----------------+------------
     529 Main Street, Boston MA, 02129                   | -71.07181 | 42.38359 | 527 Main St, Boston, MA 02129             | Medford St      |
     77 Massachusetts Avenue, Cambridge, MA 02139        | -71.09428 | 42.35988 | 77 Massachusetts Ave, Cambridge, MA 02139 | Vassar St       |
     26 Capen Street, Medford, MA                        | -71.12377 | 42.41101 | 9 Edison Ave, Medford, MA 02155           | Capen St        | Tesla Ave
     124 Mount Auburn St, Cambridge, Massachusetts 02138 | -71.12304 | 42.37328 | 3 University Rd, Cambridge, MA 02138      | Mount Auburn St |
     950 Main Street, Worcester, MA 01610                | -71.82368 | 42.24956 | 3 Maywood St, Worcester, MA 01603         | Main St         | Maywood Pl

## See Also

Pprint_Addy, Geocode, Loader_Generate_Nation_Script

## Name

Topology_Load_Tiger — Loads a defined region of tiger data into a PostGIS Topology and transforming the tiger data to spatial reference of the topology and snapping to the precision tolerance of the topology.

## Synopsis

`text Topology_Load_Tiger(` varchar topo_name, varchar region_type, varchar region_id`)`;

## Description

Loads a defined region of tiger data into a PostGIS Topology. The faces, nodes and edges are transformed to the spatial reference system of the target topology and points are snapped to the tolerance of the target topology. The created faces, nodes, edges maintain the same ids as the original Tiger data faces, nodes, edges so that datasets can be in the future be more easily reconciled with tiger data. Returns summary details about the process.

This would be useful for example for redistricting data where you require the newly formed polygons to follow the center lines of streets and for the resulting polygons not to overlap.

This function relies on Tiger data as well as the installation of the PostGIS topology module. For more information, refer to Chapter 9, Topology and Section 2.2.3, “Build configuration”. If you have not loaded data covering the region of interest, then no topology records will be created. This function will also fail if you have not created a topology using the topology functions.

Most topology validation errors are a result of tolerance issues where after transformation the edges points don't quite line up or overlap. To remedy the situation you may want to increase or lower the precision if you get topology validation failures.

Required arguments:

1. `topo_name` The name of an existing PostGIS topology to load data into.

2. `region_type` The type of bounding region. Currently only `place` and `county` are supported. Plan is to have several more. This is the table to look into to define the region bounds. e.g `tiger.place`, `tiger.county`

3. `region_id` This is what TIGER calls the geoid. It is the unique identifier of the region in the table. For place it is the `plcidfp` column in `tiger.place`. For county it is the `cntyidfp` column in `tiger.county`

Availability: 2.0.0

## Example: Boston, Massachusetts Topology

Create a topology for Boston, Massachusetts in Mass State Plane Feet (2249) with tolerance 0.25 feet and then load in Boston city tiger faces, edges, nodes.

    SELECT topology.CreateTopology('topo_boston', 2249, 0.25);
    createtopology
    --------------
       15
    -- 60,902 ms ~ 1 minute on windows 7 desktop running 9.1 (with 5 states tiger data loaded)
    SELECT tiger.topology_load_tiger('topo_boston', 'place', '2507000');
    -- topology_loader_tiger --
    29722 edges holding in temporary. 11108 faces added. 1875 edges of faces added.  20576 nodes added.
    19962 nodes contained in a face.  0 edge start end corrected.  31597 edges added.

    -- 41 ms --
    SELECT topology.TopologySummary('topo_boston');
     -- topologysummary--
    Topology topo_boston (15), SRID 2249, precision 0.25
    20576 nodes, 31597 edges, 11109 faces, 0 topogeoms in 0 layers

    -- 28,797 ms to validate yeh returned no errors --
    SELECT * FROM
        topology.ValidateTopology('topo_boston');

           error       |   id1    |    id2
    -------------------+----------+-----------

## Example: Suffolk, Massachusetts Topology

Create a topology for Suffolk, Massachusetts in Mass State Plane Meters (26986) with tolerance 0.25 meters and then load in Suffolk county tiger faces, edges, nodes.

    SELECT topology.CreateTopology('topo_suffolk', 26986, 0.25);
    -- this took 56,275 ms ~ 1 minute on Windows 7 32-bit with 5 states of tiger loaded
    -- must have been warmed up after loading boston
    SELECT tiger.topology_load_tiger('topo_suffolk', 'county', '25025');
    -- topology_loader_tiger --
     36003 edges holding in temporary. 13518 faces added. 2172 edges of faces added.
     24761 nodes added.  24075 nodes contained in a face.  0 edge start end corrected.  38175 edges added.
    -- 31 ms --
    SELECT topology.TopologySummary('topo_suffolk');
     -- topologysummary--
     Topology topo_suffolk (14), SRID 26986, precision 0.25
    24761 nodes, 38175 edges, 13519 faces, 0 topogeoms in 0 layers

    -- 33,606 ms to validate --
    SELECT * FROM
        topology.ValidateTopology('topo_suffolk');

           error       |   id1    |    id2
    -------------------+----------+-----------
     coincident nodes  | 81045651 |  81064553
     edge crosses node | 81045651 |  85737793
     edge crosses node | 81045651 |  85742215
     edge crosses node | 81045651 | 620628939
     edge crosses node | 81064553 |  85697815
     edge crosses node | 81064553 |  85728168
     edge crosses node | 81064553 |  85733413

## See Also

CreateTopology, CreateTopoGeom, TopologySummary, ValidateTopology

## Name

Set_Geocode_Setting — Sets a setting that affects behavior of geocoder functions.

## Synopsis

`text Set_Geocode_Setting(` text setting_name, text setting_value`)`;

## Description

Sets value of specific setting stored in `tiger.geocode_settings` table. Settings allow you to toggle debugging of functions. Later plans will be to control rating with settings. Current list of settings are listed in Get_Geocode_Setting.

Availability: 2.1.0

## Example return debugging setting

If you run Geocode when this function is true, the NOTICE log will output timing and queries.

    SELECT set_geocode_setting('debug_geocode_address', 'true') As result;
    result
    ---------
    true

## See Also

Get_Geocode_Setting

# Chapter 13. PostGIS Special Functions Index

## 13.1. PostGIS Aggregate Functions

The functions below are spatial aggregate functions that are used in the same way as SQL aggregate function such as `sum` and `average`.

- CG_3DUnion - Perform 3D union using postgis_sfcgal.
- ST_3DExtent - Aggregate function that returns the 3D bounding box of geometries.
- ST_3DUnion - Perform 3D union.
- ST_AsFlatGeobuf - Return a FlatGeobuf representation of a set of rows.
- ST_AsGeobuf - Return a Geobuf representation of a set of rows.
- ST_AsMVT - Aggregate function returning a MVT representation of a set of rows.
- ST_ClusterDBSCAN - Window function that returns a cluster id for each input geometry using the DBSCAN algorithm.
- ST_ClusterIntersecting - Aggregate function that clusters input geometries into connected sets.
- ST_ClusterIntersectingWin - Window function that returns a cluster id for each input geometry, clustering input geometries into connected sets.
- ST_ClusterKMeans - Window function that returns a cluster id for each input geometry using the K-means algorithm.
- ST_ClusterWithin - Aggregate function that clusters geometries by separation distance.
- ST_ClusterWithinWin - Window function that returns a cluster id for each input geometry, clustering using separation distance.
- ST_Collect - Creates a GeometryCollection or Multi* geometry from a set of geometries.
- ST_CoverageInvalidEdges - Window function that finds locations where polygons fail to form a valid coverage.
- ST_CoverageSimplify - Window function that simplifies the edges of a polygonal coverage.
- ST_CoverageUnion - Computes the union of a set of polygons forming a coverage by removing shared edges.
- ST_Extent - Aggregate function that returns the bounding box of geometries.
- ST_MakeLine - Creates a LineString from Point, MultiPoint, or LineString geometries.
- ST_MemUnion - Aggregate function which unions geometries in a memory-efficent but slower way
- ST_Polygonize - Computes a collection of polygons formed from the linework of a set of geometries.
- ST_SameAlignment - Returns true if rasters have same skew, scale, spatial ref, and offset (pixels can be put on same grid without cutting into pixels) and false if they don't with notice detailing issue.
- ST_Union - Computes a geometry representing the point-set union of the input geometries.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- TopoElementArray_Agg - Returns a topoelementarray for a set of element_id, type arrays (topoelements).

## 13.2. PostGIS Window Functions

The functions below are spatial window functions that are used in the same way as SQL window functions such as `row_number()`, `lead()`, and `lag()`. They must be followed by an `OVER()` clause.

- ST_ClusterDBSCAN - Window function that returns a cluster id for each input geometry using the DBSCAN algorithm.
- ST_ClusterIntersectingWin - Window function that returns a cluster id for each input geometry, clustering input geometries into connected sets.
- ST_ClusterKMeans - Window function that returns a cluster id for each input geometry using the K-means algorithm.
- ST_ClusterWithinWin - Window function that returns a cluster id for each input geometry, clustering using separation distance.
- ST_CoverageInvalidEdges - Window function that finds locations where polygons fail to form a valid coverage.
- ST_CoverageSimplify - Window function that simplifies the edges of a polygonal coverage.

## 13.3. PostGIS SQL-MM Compliant Functions

The functions given below are PostGIS functions that conform to the SQL/MM 3 standard

- CG_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- CG_3DDifference - Perform 3D difference
- CG_3DIntersection - Perform 3D intersection
- CG_3DUnion - Perform 3D union using postgis_sfcgal.
- CG_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- ST_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- ST_3DDWithin - Tests if two 3D geometries are within a given 3D distance
- ST_3DDifference - Perform 3D difference
- ST_3DDistance - Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DIntersection - Perform 3D intersection
- ST_3DIntersects - Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)
- ST_3DLength - Returns the 3D length of a linear geometry.
- ST_3DPerimeter - Returns the 3D perimeter of a polygonal geometry.
- ST_3DUnion - Perform 3D union.
- ST_AddEdgeModFace - Add a new edge and, if in doing so it splits a face, modify the original face and add a new face.
- ST_AddEdgeNewFaces - Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces.
- ST_AddIsoEdge - Adds an isolated edge defined by geometry alinestring to a topology connecting two existing isolated nodes anode and anothernode and returns the edge id of the new edge.
- ST_AddIsoNode - Adds an isolated node to a face in a topology and returns the nodeid of the new node. If face is null, the node is still created.
- ST_Area - Returns the area of a polygonal geometry.
- ST_AsBinary - Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Boundary - Returns the boundary of a geometry.
- ST_Buffer - Computes a geometry covering all points within a given distance from a geometry.
- ST_Centroid - Returns the geometric center of a geometry.
- ST_ChangeEdgeGeom - Changes the shape of an edge without affecting the topology structure.
- ST_Contains - Tests if every point of B lies in A, and their interiors have a point in common
- ST_ConvexHull - Computes the convex hull of a geometry.
- ST_CoordDim - Return the coordinate dimension of a geometry.
- ST_CreateTopoGeo - Adds a collection of geometries to a given empty topology and returns a message detailing success.
- ST_Crosses - Tests if two geometries have some, but not all, interior points in common
- ST_CurveN - Returns the Nth component curve geometry of a CompoundCurve.
- ST_CurveToLine - Converts a geometry containing curves to a linear geometry.
- ST_Difference - Computes a geometry representing the part of geometry A that does not intersect geometry B.
- ST_Dimension - Returns the topological dimension of a geometry.
- ST_Disjoint - Tests if two geometries have no points in common
- ST_Distance - Returns the distance between two geometry or geography values.
- ST_EndPoint - Returns the last point of a LineString or CircularLineString.
- ST_Envelope - Returns a geometry representing the bounding box of a geometry.
- ST_Equals - Tests if two geometries include the same set of points
- ST_ExteriorRing - Returns a LineString representing the exterior ring of a Polygon.
- ST_GMLToSQL - Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
- ST_GeomCollFromText - Makes a collection Geometry from collection WKT with the given SRID. If SRID is not given, it defaults to 0.
- ST_GeomFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT).
- ST_GeomFromWKB - Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.
- ST_GeometryFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText
- ST_GeometryN - Return an element of a geometry collection.
- ST_GeometryType - Returns the SQL-MM type of a geometry as text.
- ST_GetFaceEdges - Returns a set of ordered edges that bound aface.
- ST_GetFaceGeometry - Returns the polygon in the given topology with the specified face id.
- ST_InitTopoGeo - Creates a new topology schema and registers it in the topology.topology table.
- ST_InteriorRingN - Returns the Nth interior ring (hole) of a Polygon.
- ST_Intersection - Computes a geometry representing the shared portion of geometries A and B.
- ST_Intersects - Tests if two geometries intersect (they have at least one point in common)
- ST_IsClosed - Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).
- ST_IsEmpty - Tests if a geometry is empty.
- ST_IsRing - Tests if a LineString is closed and simple.
- ST_IsSimple - Tests if a geometry has no points of self-intersection or self-tangency.
- ST_IsValid - Tests if a geometry is well-formed in 2D.
- ST_Length - Returns the 2D length of a linear geometry.
- ST_LineFromText - Makes a Geometry from WKT representation with the given SRID. If SRID is not given, it defaults to 0.
- ST_LineFromWKB - Makes a LINESTRING from WKB with the given SRID
- ST_LinestringFromWKB - Makes a geometry from WKB with the given SRID.
- ST_LocateAlong - Returns the point(s) on a geometry that match a measure value.
- ST_LocateBetween - Returns the portions of a geometry that match a measure range.
- ST_M - Returns the M coordinate of a Point.
- ST_MLineFromText - Return a specified ST_MultiLineString value from WKT representation.
- ST_MPointFromText - Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
- ST_MPolyFromText - Makes a MultiPolygon Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
- ST_ModEdgeHeal - Heals two edges by deleting the node connecting them, modifying the first edgeand deleting the second edge. Returns the id of the deleted node.
- ST_ModEdgeSplit - Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge.
- ST_MoveIsoNode - Moves an isolated node in a topology from one point to another. If new apoint geometry exists as a node an error is thrown. Returns description of move.
- ST_NewEdgeHeal - Heals two edges by deleting the node connecting them, deleting both edges,and replacing them with an edge whose direction is the same as the firstedge provided.
- ST_NewEdgesSplit - Split an edge by creating a new node along an existing edge, deleting the original edge and replacing it with two new edges. Returns the id of the new node created that joins the new edges.
- ST_NumCurves - Return the number of component curves in a CompoundCurve.
- ST_NumGeometries - Returns the number of elements in a geometry collection.
- ST_NumInteriorRings - Returns the number of interior rings (holes) of a Polygon.
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_NumPoints - Returns the number of points in a LineString or CircularString.
- ST_OrderingEquals - Tests if two geometries represent the same geometry and have points in the same directional order
- ST_Overlaps - Tests if two geometries have the same dimension and intersect, but each has at least one point not in the other
- ST_PatchN - Returns the Nth geometry (face) of a PolyhedralSurface.
- ST_Perimeter - Returns the length of the boundary of a polygonal geometry or geography.
- ST_Point - Creates a Point with X, Y and SRID values.
- ST_PointFromText - Makes a point Geometry from WKT with the given SRID. If SRID is not given, it defaults to unknown.
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID
- ST_PointN - Returns the Nth point in the first LineString or circular LineString in a geometry.
- ST_PointOnSurface - Computes a point guaranteed to lie in a polygon, or on a geometry.
- ST_Polygon - Creates a Polygon from a LineString with a specified SRID.
- ST_PolygonFromText - Makes a Geometry from WKT with the given SRID. If SRID is not given, it defaults to 0.
- ST_Relate - Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix
- ST_RemEdgeModFace - Removes an edge, and if the edge separates two facesdeletes one face and modifies the other face to cover the space of both.
- ST_RemEdgeNewFace - Removes an edge and, if the removed edge separated two faces,delete the original faces and replace them with a new face.
- ST_RemoveIsoEdge - Removes an isolated edge and returns description of action. If the edge is not isolated, then an exception is thrown.
- ST_RemoveIsoNode - Removes an isolated node and returns description of action. If the node is not isolated (is start or end of an edge), then an exception is thrown.
- ST_SRID - Returns the spatial reference identifier for a geometry.
- ST_StartPoint - Returns the first point of a LineString.
- ST_SymDifference - Computes a geometry representing the portions of geometries A and B that do not intersect.
- ST_Touches - Tests if two geometries have at least one point in common, but their interiors do not intersect
- ST_Transform - Return a new geometry with coordinates transformed to a different spatial reference system.
- ST_Union - Computes a geometry representing the point-set union of the input geometries.
- ST_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- ST_WKBToSQL - Return a specified ST_Geometry value from Well-Known Binary representation (WKB). This is an alias name for ST_GeomFromWKB that takes no srid
- ST_WKTToSQL - Return a specified ST_Geometry value from Well-Known Text representation (WKT). This is an alias name for ST_GeomFromText
- ST_Within - Tests if every point of A lies in B, and their interiors have a point in common
- ST_X - Returns the X coordinate of a Point.
- ST_Y - Returns the Y coordinate of a Point.
- ST_Z - Returns the Z coordinate of a Point.
- ST_SRID - Returns the spatial reference identifier for a topogeometry.

## 13.4. PostGIS Geography Support Functions

The functions and operators given below are PostGIS functions/operators that take as input or return as output a geography data type object.

Functions with a (T) are not native geodetic functions, and use a ST_Transform call to and from geometry to do the operation. As a result, they may not behave as expected when going over dateline, poles, and for large geometries or geometry pairs that cover more than one UTM zone. Basic transform - (favoring UTM, Lambert Azimuthal (North/South), and falling back on mercator in worst case scenario)

- ST_Area - Returns the area of a polygonal geometry.
- ST_AsBinary - Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Return a geometry or feature in GeoJSON format.
- ST_AsKML - Return the geometry as a KML element.
- ST_AsSVG - Returns SVG path data for a geometry.
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Azimuth - Returns the north-based azimuth of a line between two points.
- ST_Buffer - Computes a geometry covering all points within a given distance from a geometry.
- ST_Centroid - Returns the geometric center of a geometry.
- ST_ClosestPoint - Returns the 2D point on g1 that is closest to g2. This is the first point of the shortest line from one geometry to the other.
- ST_CoveredBy - Tests if every point of A lies in B
- ST_Covers - Tests if every point of B lies in A
- ST_DWithin - Tests if two geometries are within a given distance
- ST_Distance - Returns the distance between two geometry or geography values.
- ST_GeogFromText - Return a specified geography value from Well-Known Text representation or extended (WKT).
- ST_GeogFromWKB - Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
- ST_GeographyFromText - Return a specified geography value from Well-Known Text representation or extended (WKT).
- = - Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.
- ST_Intersection - Computes a geometry representing the shared portion of geometries A and B.
- ST_Intersects - Tests if two geometries intersect (they have at least one point in common)
- ST_Length - Returns the 2D length of a linear geometry.
- ST_LineInterpolatePoint - Returns a point interpolated along a line at a fractional location.
- ST_LineInterpolatePoints - Returns points interpolated along a line at a fractional interval.
- ST_LineLocatePoint - Returns the fractional location of the closest point on a line to a point.
- ST_LineSubstring - Returns the part of a line between two fractional locations.
- ST_Perimeter - Returns the length of the boundary of a polygonal geometry or geography.
- ST_Project - Returns a point projected from a start point by a distance and bearing (azimuth).
- ST_Segmentize - Returns a modified geometry/geography having no segment longer than a given distance.
- ST_ShortestLine - Returns the 2D shortest line between two geometries
- ST_Summary - Returns a text summary of the contents of a geometry.
- <-> - Returns the 2D distance between A and B.
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.

## 13.5. PostGIS Raster Support Functions

The functions and operators given below are PostGIS functions/operators that take as input or return as output a raster data type object. Listed in alphabetical order.

- Box3D - Returns the box 3d representation of the enclosing box of the raster.
- @ - Returns TRUE if A's bounding box is contained by B's. Uses double precision bounding box.
- ~ - Returns TRUE if A's bounding box is contains B's. Uses double precision bounding box.
- = - Returns TRUE if A's bounding box is the same as B's. Uses double precision bounding box.
- && - Returns TRUE if A's bounding box intersects B's bounding box.
- &< - Returns TRUE if A's bounding box is to the left of B's.
- &> - Returns TRUE if A's bounding box is to the right of B's.
- ~= - Returns TRUE if A's bounding box is the same as B's.
- ST_Retile - Return a set of configured tiles from an arbitrarily tiled raster coverage.
- ST_AddBand - Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.
- ST_AsBinary/ST_AsWKB - Return the Well-Known Binary (WKB) representation of the raster.
- ST_AsGDALRaster - Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALDrivers() to get a list of formats supported by your library.
- ST_AsHexWKB - Return the Well-Known Binary (WKB) in Hex representation of the raster.
- ST_AsJPEG - Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.
- ST_AsPNG - Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.
- ST_AsRaster - Converts a PostGIS geometry to a PostGIS raster.
- ST_AsTIFF - Return the raster selected bands as a single TIFF image (byte array). If no band is specified or any of specified bands does not exist in the raster, then will try to use all bands.
- ST_Aspect - Returns the aspect (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_Band - Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.
- ST_BandFileSize - Returns the file size of a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_BandFileTimestamp - Returns the file timestamp of a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_BandIsNoData - Returns true if the band is filled with only nodata values.
- ST_BandMetaData - Returns basic meta data for a specific raster band. band num 1 is assumed if none-specified.
- ST_BandNoDataValue - Returns the value in a given band that represents no data. If no band num 1 is assumed.
- ST_BandPath - Returns system file path to a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_BandPixelType - Returns the type of pixel for given band. If no bandnum specified, 1 is assumed.
- ST_Clip - Returns the raster clipped by the input geometry. If band number is not specified, all bands are processed. If crop is not specified or TRUE, the output raster is cropped. If touched is set to TRUE, then touched pixels are included, otherwise only if the center of the pixel is in the geometry it is included.
- ST_ColorMap - Creates a new raster of up to four 8BUI bands (grayscale, RGB, RGBA) from the source raster and a specified band. Band 1 is assumed if not specified.
- ST_Contains - Return true if no points of raster rastB lie in the exterior of raster rastA and at least one point of the interior of rastB lies in the interior of rastA.
- ST_ContainsProperly - Return true if rastB intersects the interior of rastA but not the boundary or exterior of rastA.
- ST_Contour - Generates a set of vector contours from the provided raster band, using the GDAL contouring algorithm.
- ST_ConvexHull - Return the convex hull geometry of the raster including pixel values equal to BandNoDataValue. For regular shaped and non-skewed rasters, this gives the same result as ST_Envelope so only useful for irregularly shaped or skewed rasters.
- ST_Count - Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.
- ST_CountAgg - Aggregate. Returns the number of pixels in a given band of a set of rasters. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the NODATA value.
- ST_CoveredBy - Return true if no points of raster rastA lie outside raster rastB.
- ST_Covers - Return true if no points of raster rastB lie outside raster rastA.
- ST_DFullyWithin - Return true if rasters rastA and rastB are fully within the specified distance of each other.
- ST_DWithin - Return true if rasters rastA and rastB are within the specified distance of each other.
- ST_Disjoint - Return true if raster rastA does not spatially intersect rastB.
- ST_DumpAsPolygons - Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.
- ST_DumpValues - Get the values of the specified band as a 2-dimension array.
- ST_Envelope - Returns the polygon representation of the extent of the raster.
- ST_FromGDALRaster - Returns a raster from a supported GDAL raster file.
- ST_GeoReference - Returns the georeference meta data in GDAL or ESRI format as commonly seen in a world file. Default is GDAL.
- ST_Grayscale - Creates a new one-8BUI band raster from the source raster and specified bands representing Red, Green and Blue
- ST_HasNoBand - Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
- ST_Height - Returns the height of the raster in pixels.
- ST_HillShade - Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.
- ST_Histogram - Returns a set of record summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.
- ST_InterpolateRaster - Interpolates a gridded surface based on an input set of 3-d points, using the X- and Y-values to position the points on the grid and the Z-value of the points as the surface elevation.
- ST_Intersection - Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.
- ST_Intersects - Return true if raster rastA spatially intersects raster rastB.
- ST_IsEmpty - Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.
- ST_MakeEmptyCoverage - Cover georeferenced area with a grid of empty raster tiles.
- ST_MakeEmptyRaster - Returns an empty raster (having no bands) of given dimensions (width & height), upperleft X and Y, pixel size and rotation (scalex, scaley, skewx & skewy) and reference system (srid). If a raster is passed in, returns a new raster with the same size, alignment and SRID. If srid is left out, the spatial ref is set to unknown (0).
- ST_MapAlgebra (callback function version) - Callback function version - Returns a one-band raster given one or more input rasters, band indexes and one user-specified callback function.
- ST_MapAlgebraExpr - 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.
- ST_MapAlgebraExpr - 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.
- ST_MapAlgebraFct - 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.
- ST_MapAlgebraFct - 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.
- ST_MapAlgebraFctNgb - 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.
- ST_MapAlgebra (expression version) - Expression version - Returns a one-band raster given one or two input rasters, band indexes and one or more user-specified SQL expressions.
- ST_MemSize - Returns the amount of space (in bytes) the raster takes.
- ST_MetaData - Returns basic meta data about a raster object such as pixel size, rotation (skew), upper, lower left, etc.
- ST_MinConvexHull - Return the convex hull geometry of the raster excluding NODATA pixels.
- ST_NearestValue - Returns the nearest non-NODATA value of a given band's pixel specified by a columnx and rowy or a geometric point expressed in the same spatial reference coordinate system as the raster.
- ST_Neighborhood - Returns a 2-D double precision array of the non-NODATA values around a given band's pixel specified by either a columnX and rowY or a geometric point expressed in the same spatial reference coordinate system as the raster.
- ST_NotSameAlignmentReason - Returns text stating if rasters are aligned and if not aligned, a reason why.
- ST_NumBands - Returns the number of bands in the raster object.
- ST_Overlaps - Return true if raster rastA and rastB intersect but one does not completely contain the other.
- ST_PixelAsCentroid - Returns the centroid (point geometry) of the area represented by a pixel.
- ST_PixelAsCentroids - Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.
- ST_PixelAsPoint - Returns a point geometry of the pixel's upper-left corner.
- ST_PixelAsPoints - Returns a point geometry for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The coordinates of the point geometry are of the pixel's upper-left corner.
- ST_PixelAsPolygon - Returns the polygon geometry that bounds the pixel for a particular row and column.
- ST_PixelAsPolygons - Returns the polygon geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.
- ST_PixelHeight - Returns the pixel height in geometric units of the spatial reference system.
- ST_PixelOfValue - Get the columnx, rowy coordinates of the pixel whose value equals the search value.
- ST_PixelWidth - Returns the pixel width in geometric units of the spatial reference system.
- ST_Polygon - Returns a multipolygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.
- ST_Quantile - Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.
- ST_RastFromHexWKB - Return a raster value from a Hex representation of Well-Known Binary (WKB) raster.
- ST_RastFromWKB - Return a raster value from a Well-Known Binary (WKB) raster.
- ST_RasterToWorldCoord - Returns the raster's upper left corner as geometric X and Y (longitude and latitude) given a column and row. Column and row starts at 1.
- ST_RasterToWorldCoordX - Returns the geometric X coordinate upper left of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_RasterToWorldCoordY - Returns the geometric Y coordinate upper left corner of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_Reclass - Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.
- ST_Resample - Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster.
- ST_Rescale - Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline, Lanczos, Max or Min resampling algorithm. Default is NearestNeighbor.
- ST_Resize - Resize a raster to a new width/height
- ST_Reskew - Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Rotation - Returns the rotation of the raster in radian.
- ST_Roughness - Returns a raster with the calculated "roughness" of a DEM.
- ST_SRID - Returns the spatial reference identifier of the raster as defined in spatial_ref_sys table.
- ST_SameAlignment - Returns true if rasters have same skew, scale, spatial ref, and offset (pixels can be put on same grid without cutting into pixels) and false if they don't with notice detailing issue.
- ST_ScaleX - Returns the X component of the pixel width in units of coordinate reference system.
- ST_ScaleY - Returns the Y component of the pixel height in units of coordinate reference system.
- ST_SetBandIndex - Update the external band number of an out-db band
- ST_SetBandIsNoData - Sets the isnodata flag of the band to TRUE.
- ST_SetBandNoDataValue - Sets the value for the given band that represents no data. Band 1 is assumed if no band is specified. To mark a band as having no nodata value, set the nodata value = NULL.
- ST_SetBandPath - Update the external path and band number of an out-db band
- ST_SetGeoReference - Set Georeference 6 georeference parameters in a single call. Numbers should be separated by white space. Accepts inputs in GDAL or ESRI format. Default is GDAL.
- ST_SetM - Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimension using the requested resample algorithm.
- ST_SetRotation - Set the rotation of the raster in radian.
- ST_SetSRID - Sets the SRID of a raster to a particular integer srid defined in the spatial_ref_sys table.
- ST_SetScale - Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height.
- ST_SetSkew - Sets the georeference X and Y skew (or rotation parameter). If only one is passed in, sets X and Y to the same value.
- ST_SetUpperLeft - Sets the value of the upper left corner of the pixel of the raster to projected X and Y coordinates.
- ST_SetValue - Returns modified raster resulting from setting the value of a given band in a given columnx, rowy pixel or the pixels that intersect a particular geometry. Band numbers start at 1 and assumed to be 1 if not specified.
- ST_SetValues - Returns modified raster resulting from setting the values of a given band.
- ST_SetZ - Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the Z dimension using the requested resample algorithm.
- ST_SkewX - Returns the georeference X skew (or rotation parameter).
- ST_SkewY - Returns the georeference Y skew (or rotation parameter).
- ST_Slope - Returns the slope (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_SnapToGrid - Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Summary - Returns a text summary of the contents of the raster.
- ST_SummaryStats - Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.
- ST_SummaryStatsAgg - Aggregate. Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a set of raster. Band 1 is assumed is no band is specified.
- ST_TPI - Returns a raster with the calculated Topographic Position Index.
- ST_TRI - Returns a raster with the calculated Terrain Ruggedness Index.
- ST_Tile - Returns a set of rasters resulting from the split of the input raster based upon the desired dimensions of the output rasters.
- ST_Touches - Return true if raster rastA and rastB have at least one point in common but their interiors do not intersect.
- ST_Transform - Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.
- ST_Union - Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- ST_UpperLeftX - Returns the upper left X coordinate of raster in projected spatial ref.
- ST_UpperLeftY - Returns the upper left Y coordinate of raster in projected spatial ref.
- ST_Value - Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If exclude_nodata_value is set to false, then all pixels include nodata pixels are considered to intersect and return value. If exclude_nodata_value is not passed in then reads it from metadata of raster.
- ST_ValueCount - Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.
- ST_Width - Returns the width of the raster in pixels.
- ST_Within - Return true if no points of raster rastA lie in the exterior of raster rastB and at least one point of the interior of rastA lies in the interior of rastB.
- ST_WorldToRasterCoord - Returns the upper left corner as column and row given geometric X and Y (longitude and latitude) or a point geometry expressed in the spatial reference coordinate system of the raster.
- ST_WorldToRasterCoordX - Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.
- ST_WorldToRasterCoordY - Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.
- UpdateRasterSRID - Change the SRID of all rasters in the user-specified column and table.

## 13.6. PostGIS Geometry / Geography / Raster Dump Functions

The functions given below are PostGIS functions that take as input or return as output a set of or single geometry_dump or geomval data type object.

- ST_DumpAsPolygons - Returns a set of geomval (geom,val) rows, from a given raster band. If no band number is specified, band num defaults to 1.
- ST_Intersection - Returns a raster or a set of geometry-pixelvalue pairs representing the shared portion of two rasters or the geometrical intersection of a vectorization of the raster and a geometry.
- ST_Dump - Returns a set of geometry_dump rows for the components of a geometry.
- ST_DumpPoints - Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_DumpRings - Returns a set of geometry_dump rows for the exterior and interior rings of a Polygon.
- ST_DumpSegments - Returns a set of geometry_dump rows for the segments in a geometry.

## 13.7. PostGIS Box Functions

The functions given below are PostGIS functions that take as input or return as output the box* family of PostGIS spatial types. The box family of types consists of box2d, and box3d

- Box2D - Returns a BOX2D representing the 2D extent of a geometry.
- Box3D - Returns a BOX3D representing the 3D extent of a geometry.
- Box3D - Returns the box 3d representation of the enclosing box of the raster.
- ST_3DExtent - Aggregate function that returns the 3D bounding box of geometries.
- ST_3DMakeBox - Creates a BOX3D defined by two 3D point geometries.
- ST_AsMVTGeom - Transforms a geometry into the coordinate space of a MVT tile.
- ST_AsTWKB - Returns the geometry as TWKB, aka "Tiny Well-Known Binary"
- ST_Box2dFromGeoHash - Return a BOX2D from a GeoHash string.
- ST_ClipByBox2D - Computes the portion of a geometry falling within a rectangle.
- ST_EstimatedExtent - Returns the estimated extent of a spatial table.
- ST_Expand - Returns a bounding box expanded from another bounding box or a geometry.
- ST_Extent - Aggregate function that returns the bounding box of geometries.
- ST_MakeBox2D - Creates a BOX2D defined by two 2D point geometries.
- ST_RemoveIrrelevantPointsForView - Removes points that are irrelevant for rendering a specific rectangluar view of a geometry.
- ST_XMax - Returns the X maxima of a 2D or 3D bounding box or a geometry.
- ST_XMin - Returns the X minima of a 2D or 3D bounding box or a geometry.
- ST_YMax - Returns the Y maxima of a 2D or 3D bounding box or a geometry.
- ST_YMin - Returns the Y minima of a 2D or 3D bounding box or a geometry.
- ST_ZMax - Returns the Z maxima of a 2D or 3D bounding box or a geometry.
- ST_ZMin - Returns the Z minima of a 2D or 3D bounding box or a geometry.
- RemoveUnusedPrimitives - Removes topology primitives which not needed to define existing TopoGeometry objects.
- ValidateTopology - Returns a set of validatetopology_returntype objects detailing issues with topology.
- ~(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).
- ~(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.
- ~(geometry,box2df) - Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).
- @(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.
- @(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.
- @(geometry,box2df) - Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).
- &&(box2df,box2df) - Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.
- &&(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.
- &&(geometry,box2df) - Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).

## 13.8. PostGIS Functions that support 3D

The functions given below are PostGIS functions that do not throw away the Z-Index.

- AddGeometryColumn - Adds a geometry column to an existing table.
- Box3D - Returns a BOX3D representing the 3D extent of a geometry.
- CG_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- CG_3DConvexHull - Computes the 3D convex hull of a geometry.
- CG_3DDifference - Perform 3D difference
- CG_3DIntersection - Perform 3D intersection
- CG_3DUnion - Perform 3D union using postgis_sfcgal.
- CG_ApproximateMedialAxis - Compute the approximate medial axis of an areal geometry.
- CG_ConstrainedDelaunayTriangles - Return a constrained Delaunay triangulation around the given input geometry.
- CG_Extrude - Extrude a surface to a related volume
- CG_ForceLHR - Force LHR orientation
- CG_IsPlanar - Check if a surface is or not planar
- CG_IsSolid - Test if the geometry is a solid. No validity check is performed.
- CG_MakeSolid - Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- CG_Orientation - Determine surface orientation
- CG_StraightSkeleton - Compute a straight skeleton from a geometry
- CG_Tesselate - Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- CG_Visibility - Compute a visibility polygon from a point or a segment in a polygon geometry
- CG_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- DropGeometryColumn - Removes a geometry column from a spatial table.
- GeometryType - Returns the type of a geometry as text.
- ST_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- ST_3DClosestPoint - Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DConvexHull - Computes the 3D convex hull of a geometry.
- ST_3DDFullyWithin - Tests if two 3D geometries are entirely within a given 3D distance
- ST_3DDWithin - Tests if two 3D geometries are within a given 3D distance
- ST_3DDifference - Perform 3D difference
- ST_3DDistance - Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DExtent - Aggregate function that returns the 3D bounding box of geometries.
- ST_3DIntersection - Perform 3D intersection
- ST_3DIntersects - Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)
- ST_3DLength - Returns the 3D length of a linear geometry.
- ST_3DLineInterpolatePoint - Returns a point interpolated along a 3D line at a fractional location.
- ST_3DLongestLine - Returns the 3D longest line between two geometries
- ST_3DMaxDistance - Returns the 3D cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DPerimeter - Returns the 3D perimeter of a polygonal geometry.
- ST_3DShortestLine - Returns the 3D shortest line between two geometries
- ST_3DUnion - Perform 3D union.
- ST_AddMeasure - Interpolates measures along a linear geometry.
- ST_AddPoint - Add a point to a LineString.
- ST_Affine - Apply a 3D affine transformation to a geometry.
- ST_ApproximateMedialAxis - Compute the approximate medial axis of an areal geometry.
- ST_AsBinary - Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Return a geometry or feature in GeoJSON format.
- ST_AsHEXEWKB - Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.
- ST_AsKML - Return the geometry as a KML element.
- ST_AsX3D - Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_Boundary - Returns the boundary of a geometry.
- ST_BoundingDiagonal - Returns the diagonal of a geometry's bounding box.
- ST_CPAWithin - Tests if the closest point of approach of two trajectoriesis within the specified distance.
- ST_ChaikinSmoothing - Returns a smoothed version of a geometry, using the Chaikin algorithm
- ST_ClosestPointOfApproach - Returns a measure at the closest point of approach of two trajectories.
- ST_Collect - Creates a GeometryCollection or Multi* geometry from a set of geometries.
- ST_ConstrainedDelaunayTriangles - Return a constrained Delaunay triangulation around the given input geometry.
- ST_ConvexHull - Computes the convex hull of a geometry.
- ST_CoordDim - Return the coordinate dimension of a geometry.
- ST_CurveN - Returns the Nth component curve geometry of a CompoundCurve.
- ST_CurveToLine - Converts a geometry containing curves to a linear geometry.
- ST_DelaunayTriangles - Returns the Delaunay triangulation of the vertices of a geometry.
- ST_Difference - Computes a geometry representing the part of geometry A that does not intersect geometry B.
- ST_DistanceCPA - Returns the distance between the closest point of approach of two trajectories.
- ST_Dump - Returns a set of geometry_dump rows for the components of a geometry.
- ST_DumpPoints - Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_DumpRings - Returns a set of geometry_dump rows for the exterior and interior rings of a Polygon.
- ST_DumpSegments - Returns a set of geometry_dump rows for the segments in a geometry.
- ST_EndPoint - Returns the last point of a LineString or CircularLineString.
- ST_ExteriorRing - Returns a LineString representing the exterior ring of a Polygon.
- ST_Extrude - Extrude a surface to a related volume
- ST_FlipCoordinates - Returns a version of a geometry with X and Y axis flipped.
- ST_Force2D - Force the geometries into a "2-dimensional mode".
- ST_ForceCurve - Upcast a geometry into its curved type, if applicable.
- ST_ForceLHR - Force LHR orientation
- ST_ForcePolygonCCW - Orients all exterior rings counter-clockwise and all interior rings clockwise.
- ST_ForcePolygonCW - Orients all exterior rings clockwise and all interior rings counter-clockwise.
- ST_ForceRHR - Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
- ST_ForceSFS - Force the geometries to use SFS 1.1 geometry types only.
- ST_Force3D - Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DZ - Force the geometries into XYZ mode.
- ST_Force4D - Force the geometries into XYZM mode.
- ST_ForceCollection - Convert the geometry into a GEOMETRYCOLLECTION.
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromGML - Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeomFromGeoJSON - Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_GeomFromKML - Takes as input KML representation of geometry and outputs a PostGIS geometry object
- ST_GeometricMedian - Returns the geometric median of a MultiPoint.
- ST_GeometryN - Return an element of a geometry collection.
- ST_GeometryType - Returns the SQL-MM type of a geometry as text.
- ST_HasArc - Tests if a geometry contains a circular arc
- ST_HasM - Checks if a geometry has an M (measure) dimension.
- ST_HasZ - Checks if a geometry has a Z dimension.
- ST_InteriorRingN - Returns the Nth interior ring (hole) of a Polygon.
- ST_InterpolatePoint - Returns the interpolated measure of a geometry closest to a point.
- ST_Intersection - Computes a geometry representing the shared portion of geometries A and B.
- ST_IsClosed - Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).
- ST_IsCollection - Tests if a geometry is a geometry collection type.
- ST_IsPlanar - Check if a surface is or not planar
- ST_IsPolygonCCW - Tests if Polygons have exterior rings oriented counter-clockwise and interior rings oriented clockwise.
- ST_IsPolygonCW - Tests if Polygons have exterior rings oriented clockwise and interior rings oriented counter-clockwise.
- ST_IsSimple - Tests if a geometry has no points of self-intersection or self-tangency.
- ST_IsSolid - Test if the geometry is a solid. No validity check is performed.
- ST_IsValidTrajectory - Tests if the geometry is a valid trajectory.
- ST_LengthSpheroid - Returns the 2D or 3D length/perimeter of a lon/lat geometry on a spheroid.
- ST_LineFromMultiPoint - Creates a LineString from a MultiPoint geometry.
- ST_LineInterpolatePoint - Returns a point interpolated along a line at a fractional location.
- ST_LineInterpolatePoints - Returns points interpolated along a line at a fractional interval.
- ST_LineSubstring - Returns the part of a line between two fractional locations.
- ST_LineToCurve - Converts a linear geometry to a curved geometry.
- ST_LocateBetweenElevations - Returns the portions of a geometry that lie in an elevation (Z) range.
- ST_M - Returns the M coordinate of a Point.
- ST_MakeLine - Creates a LineString from Point, MultiPoint, or LineString geometries.
- ST_MakePoint - Creates a 2D, 3DZ or 4D Point.
- ST_MakePolygon - Creates a Polygon from a shell and optional list of holes.
- ST_MakeSolid - Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- ST_MakeValid - Attempts to make an invalid geometry valid without losing vertices.
- ST_MemSize - Returns the amount of memory space a geometry takes.
- ST_MemUnion - Aggregate function which unions geometries in a memory-efficent but slower way
- ST_NDims - Returns the coordinate dimension of a geometry.
- ST_NPoints - Returns the number of points (vertices) in a geometry.
- ST_NRings - Returns the number of rings in a polygonal geometry.
- ST_Node - Nodes a collection of lines.
- ST_NumCurves - Return the number of component curves in a CompoundCurve.
- ST_NumGeometries - Returns the number of elements in a geometry collection.
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_Orientation - Determine surface orientation
- ST_PatchN - Returns the Nth geometry (face) of a PolyhedralSurface.
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID
- ST_PointN - Returns the Nth point in the first LineString or circular LineString in a geometry.
- ST_PointOnSurface - Computes a point guaranteed to lie in a polygon, or on a geometry.
- ST_Points - Returns a MultiPoint containing the coordinates of a geometry.
- ST_Polygon - Creates a Polygon from a LineString with a specified SRID.
- ST_RemovePoint - Remove a point from a linestring.
- ST_RemoveRepeatedPoints - Returns a version of a geometry with duplicate points removed.
- ST_Reverse - Return the geometry with vertex order reversed.
- ST_Rotate - Rotates a geometry about an origin point.
- ST_RotateX - Rotates a geometry about the X axis.
- ST_RotateY - Rotates a geometry about the Y axis.
- ST_RotateZ - Rotates a geometry about the Z axis.
- ST_Scale - Scales a geometry by given factors.
- ST_Scroll - Change start point of a closed LineString.
- ST_SetPoint - Replace point of a linestring with a given point.
- ST_ShiftLongitude - Shifts the longitude coordinates of a geometry between -180..180 and 0..360.
- ST_SnapToGrid - Snap all points of the input geometry to a regular grid.
- ST_StartPoint - Returns the first point of a LineString.
- ST_StraightSkeleton - Compute a straight skeleton from a geometry
- ST_SwapOrdinates - Returns a version of the given geometry with given ordinate values swapped.
- ST_SymDifference - Computes a geometry representing the portions of geometries A and B that do not intersect.
- ST_Tesselate - Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- ST_TransScale - Translates and scales a geometry by given offsets and factors.
- ST_Translate - Translates a geometry by given offsets.
- ST_UnaryUnion - Computes the union of the components of a single geometry.
- ST_Union - Computes a geometry representing the point-set union of the input geometries.
- ST_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- ST_WrapX - Wrap a geometry around an X value.
- ST_X - Returns the X coordinate of a Point.
- ST_XMax - Returns the X maxima of a 2D or 3D bounding box or a geometry.
- ST_XMin - Returns the X minima of a 2D or 3D bounding box or a geometry.
- ST_Y - Returns the Y coordinate of a Point.
- ST_YMax - Returns the Y maxima of a 2D or 3D bounding box or a geometry.
- ST_YMin - Returns the Y minima of a 2D or 3D bounding box or a geometry.
- ST_Z - Returns the Z coordinate of a Point.
- ST_ZMax - Returns the Z maxima of a 2D or 3D bounding box or a geometry.
- ST_ZMin - Returns the Z minima of a 2D or 3D bounding box or a geometry.
- ST_Zmflag - Returns a code indicating the ZM coordinate dimension of a geometry.
- Equals - Returns true if two topogeometries are composed of the same topology primitives.
- Intersects - Returns true if any pair of primitives from the two topogeometries intersect.
- UpdateGeometrySRID - Updates the SRID of all features in a geometry column, and the table metadata.
- &&& - Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.
- &&&(geometry,gidx) - Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).
- &&&(gidx,geometry) - Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.
- &&&(gidx,gidx) - Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.

## 13.9. PostGIS Curved Geometry Support Functions

The functions given below are PostGIS functions that can use CIRCULARSTRING, CURVEPOLYGON, and other curved geometry types

- AddGeometryColumn - Adds a geometry column to an existing table.
- Box2D - Returns a BOX2D representing the 2D extent of a geometry.
- Box3D - Returns a BOX3D representing the 3D extent of a geometry.
- DropGeometryColumn - Removes a geometry column from a spatial table.
- GeometryType - Returns the type of a geometry as text.
- PostGIS_AddBBox - Add bounding box to the geometry.
- PostGIS_DropBBox - Drop the bounding box cache from the geometry.
- PostGIS_HasBBox - Returns TRUE if the bbox of this geometry is cached, FALSE otherwise.
- ST_3DExtent - Aggregate function that returns the 3D bounding box of geometries.
- ST_Affine - Apply a 3D affine transformation to a geometry.
- ST_AsBinary - Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsHEXEWKB - Returns a Geometry in HEXEWKB format (as text) using either little-endian (NDR) or big-endian (XDR) encoding.
- ST_AsSVG - Returns SVG path data for a geometry.
- ST_AsText - Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_ClusterDBSCAN - Window function that returns a cluster id for each input geometry using the DBSCAN algorithm.
- ST_ClusterWithin - Aggregate function that clusters geometries by separation distance.
- ST_ClusterWithinWin - Window function that returns a cluster id for each input geometry, clustering using separation distance.
- ST_Collect - Creates a GeometryCollection or Multi* geometry from a set of geometries.
- ST_CoordDim - Return the coordinate dimension of a geometry.
- ST_CurveToLine - Converts a geometry containing curves to a linear geometry.
- ST_Distance - Returns the distance between two geometry or geography values.
- ST_Dump - Returns a set of geometry_dump rows for the components of a geometry.
- ST_DumpPoints - Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_EndPoint - Returns the last point of a LineString or CircularLineString.
- ST_EstimatedExtent - Returns the estimated extent of a spatial table.
- ST_FlipCoordinates - Returns a version of a geometry with X and Y axis flipped.
- ST_Force2D - Force the geometries into a "2-dimensional mode".
- ST_ForceCurve - Upcast a geometry into its curved type, if applicable.
- ST_ForceSFS - Force the geometries to use SFS 1.1 geometry types only.
- ST_Force3D - Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DM - Force the geometries into XYM mode.
- ST_Force3DZ - Force the geometries into XYZ mode.
- ST_Force4D - Force the geometries into XYZM mode.
- ST_ForceCollection - Convert the geometry into a GEOMETRYCOLLECTION.
- ST_GeoHash - Return a GeoHash representation of the geometry.
- ST_GeogFromWKB - Creates a geography instance from a Well-Known Binary geometry representation (WKB) or extended Well Known Binary (EWKB).
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromText - Return a specified ST_Geometry value from Well-Known Text representation (WKT).
- ST_GeomFromWKB - Creates a geometry instance from a Well-Known Binary geometry representation (WKB) and optional SRID.
- ST_GeometryN - Return an element of a geometry collection.
- = - Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.
- &<| - Returns TRUE if A's bounding box overlaps or is below B's.
- ST_HasArc - Tests if a geometry contains a circular arc
- ST_Intersects - Tests if two geometries intersect (they have at least one point in common)
- ST_IsClosed - Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).
- ST_IsCollection - Tests if a geometry is a geometry collection type.
- ST_IsEmpty - Tests if a geometry is empty.
- ST_LineToCurve - Converts a linear geometry to a curved geometry.
- ST_MemSize - Returns the amount of memory space a geometry takes.
- ST_NPoints - Returns the number of points (vertices) in a geometry.
- ST_NRings - Returns the number of rings in a polygonal geometry.
- ST_PointFromWKB - Makes a geometry from WKB with the given SRID
- ST_PointN - Returns the Nth point in the first LineString or circular LineString in a geometry.
- ST_Points - Returns a MultiPoint containing the coordinates of a geometry.
- ST_Rotate - Rotates a geometry about an origin point.
- ST_RotateZ - Rotates a geometry about the Z axis.
- ST_SRID - Returns the spatial reference identifier for a geometry.
- ST_Scale - Scales a geometry by given factors.
- ST_SetSRID - Set the SRID on a geometry.
- ST_StartPoint - Returns the first point of a LineString.
- ST_Summary - Returns a text summary of the contents of a geometry.
- ST_SwapOrdinates - Returns a version of the given geometry with given ordinate values swapped.
- ST_TransScale - Translates and scales a geometry by given offsets and factors.
- ST_Transform - Return a new geometry with coordinates transformed to a different spatial reference system.
- ST_Translate - Translates a geometry by given offsets.
- ST_XMax - Returns the X maxima of a 2D or 3D bounding box or a geometry.
- ST_XMin - Returns the X minima of a 2D or 3D bounding box or a geometry.
- ST_YMax - Returns the Y maxima of a 2D or 3D bounding box or a geometry.
- ST_YMin - Returns the Y minima of a 2D or 3D bounding box or a geometry.
- ST_ZMax - Returns the Z maxima of a 2D or 3D bounding box or a geometry.
- ST_ZMin - Returns the Z minima of a 2D or 3D bounding box or a geometry.
- ST_Zmflag - Returns a code indicating the ZM coordinate dimension of a geometry.
- UpdateGeometrySRID - Updates the SRID of all features in a geometry column, and the table metadata.
- ~(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).
- ~(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.
- ~(geometry,box2df) - Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- &&& - Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.
- @(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.
- @(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.
- @(geometry,box2df) - Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).
- &&(box2df,box2df) - Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.
- &&(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.
- &&(geometry,box2df) - Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).
- &&&(geometry,gidx) - Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).
- &&&(gidx,geometry) - Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.
- &&&(gidx,gidx) - Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.

## 13.10. PostGIS Polyhedral Surface Support Functions

The functions given below are PostGIS functions that can use POLYHEDRALSURFACE, POLYHEDRALSURFACEM geometries

- Box2D - Returns a BOX2D representing the 2D extent of a geometry.
- Box3D - Returns a BOX3D representing the 3D extent of a geometry.
- CG_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- CG_3DConvexHull - Computes the 3D convex hull of a geometry.
- CG_3DDifference - Perform 3D difference
- CG_3DIntersection - Perform 3D intersection
- CG_3DUnion - Perform 3D union using postgis_sfcgal.
- CG_ApproximateMedialAxis - Compute the approximate medial axis of an areal geometry.
- CG_Extrude - Extrude a surface to a related volume
- CG_ForceLHR - Force LHR orientation
- CG_IsPlanar - Check if a surface is or not planar
- CG_IsSolid - Test if the geometry is a solid. No validity check is performed.
- CG_MakeSolid - Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- CG_StraightSkeleton - Compute a straight skeleton from a geometry
- CG_Tesselate - Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- CG_Visibility - Compute a visibility polygon from a point or a segment in a polygon geometry
- CG_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- GeometryType - Returns the type of a geometry as text.
- ST_3DArea - Computes area of 3D surface geometries. Will return 0 for solids.
- ST_3DClosestPoint - Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DConvexHull - Computes the 3D convex hull of a geometry.
- ST_3DDFullyWithin - Tests if two 3D geometries are entirely within a given 3D distance
- ST_3DDWithin - Tests if two 3D geometries are within a given 3D distance
- ST_3DDifference - Perform 3D difference
- ST_3DDistance - Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DExtent - Aggregate function that returns the 3D bounding box of geometries.
- ST_3DIntersection - Perform 3D intersection
- ST_3DIntersects - Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)
- ST_3DLongestLine - Returns the 3D longest line between two geometries
- ST_3DMaxDistance - Returns the 3D cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DShortestLine - Returns the 3D shortest line between two geometries
- ST_3DUnion - Perform 3D union.
- ST_Affine - Apply a 3D affine transformation to a geometry.
- ST_ApproximateMedialAxis - Compute the approximate medial axis of an areal geometry.
- ST_Area - Returns the area of a polygonal geometry.
- ST_AsBinary - Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Return the geometry as a GML version 2 or 3 element.
- ST_AsX3D - Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_CoordDim - Return the coordinate dimension of a geometry.
- ST_Dimension - Returns the topological dimension of a geometry.
- ST_Dump - Returns a set of geometry_dump rows for the components of a geometry.
- ST_DumpPoints - Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_Expand - Returns a bounding box expanded from another bounding box or a geometry.
- ST_Extent - Aggregate function that returns the bounding box of geometries.
- ST_Extrude - Extrude a surface to a related volume
- ST_FlipCoordinates - Returns a version of a geometry with X and Y axis flipped.
- ST_Force2D - Force the geometries into a "2-dimensional mode".
- ST_ForceLHR - Force LHR orientation
- ST_ForceRHR - Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
- ST_ForceSFS - Force the geometries to use SFS 1.1 geometry types only.
- ST_Force3D - Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DZ - Force the geometries into XYZ mode.
- ST_ForceCollection - Convert the geometry into a GEOMETRYCOLLECTION.
- ST_GeomFromEWKB - Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromGML - Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeometryN - Return an element of a geometry collection.
- ST_GeometryType - Returns the SQL-MM type of a geometry as text.
- = - Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.
- &<| - Returns TRUE if A's bounding box overlaps or is below B's.
- ~= - Returns TRUE if A's bounding box is the same as B's.
- ST_IsClosed - Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).
- ST_IsPlanar - Check if a surface is or not planar
- ST_IsSolid - Test if the geometry is a solid. No validity check is performed.
- ST_MakeSolid - Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- ST_MemSize - Returns the amount of memory space a geometry takes.
- ST_NPoints - Returns the number of points (vertices) in a geometry.
- ST_NumGeometries - Returns the number of elements in a geometry collection.
- ST_NumPatches - Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_PatchN - Returns the Nth geometry (face) of a PolyhedralSurface.
- ST_RemoveRepeatedPoints - Returns a version of a geometry with duplicate points removed.
- ST_Reverse - Return the geometry with vertex order reversed.
- ST_Rotate - Rotates a geometry about an origin point.
- ST_RotateX - Rotates a geometry about the X axis.
- ST_RotateY - Rotates a geometry about the Y axis.
- ST_RotateZ - Rotates a geometry about the Z axis.
- ST_Scale - Scales a geometry by given factors.
- ST_ShiftLongitude - Shifts the longitude coordinates of a geometry between -180..180 and 0..360.
- ST_StraightSkeleton - Compute a straight skeleton from a geometry
- ST_Summary - Returns a text summary of the contents of a geometry.
- ST_SwapOrdinates - Returns a version of the given geometry with given ordinate values swapped.
- ST_Tesselate - Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- ST_Transform - Return a new geometry with coordinates transformed to a different spatial reference system.
- ST_Volume - Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- ~(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).
- ~(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.
- ~(geometry,box2df) - Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).
- && - Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- &&& - Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.
- @(box2df,box2df) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.
- @(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.
- @(geometry,box2df) - Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).
- &&(box2df,box2df) - Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.
- &&(box2df,geometry) - Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.
- &&(geometry,box2df) - Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).
- &&&(geometry,gidx) - Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).
- &&&(gidx,geometry) - Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.
- &&&(gidx,gidx) - Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.

## 13.11. PostGIS Function Support Matrix

Below is an alphabetical listing of spatial specific functions in PostGIS and the kinds of spatial types they work with or OGC/SQL compliance they try to conform to.

- A means the function works with the type or subtype natively.
- A means it works but with a transform cast built-in using cast to geometry, transform to a "best srid" spatial ref and then cast back. Results may not be as expected for large areas or areas at poles and may accumulate floating point junk.
- A means the function works with the type because of a auto-cast to another such as to box3d rather than direct type support.
- A means the function only available if PostGIS compiled with SFCGAL support.
- geom - Basic 2D geometry support (x,y).
- geog - Basic 2D geography support (x,y).
- 2.5D - basic 2D geometries in 3 D/4D space (has Z or M coord).
- PS - Polyhedral surfaces
- T - Triangles and Triangulated Irregular Network surfaces (TIN)

Function | geom | geog | 2.5D | Curves | SQL MM | PS | T
--- | --- | --- | --- | --- | --- | --- | ---
ST_Collect |  |  |  |  |  |  |
ST_LineFromMultiPoint |  |  |  |  |  |  |
ST_MakeEnvelope |  |  |  |  |  |  |
ST_MakeLine |  |  |  |  |  |  |
ST_MakePoint |  |  |  |  |  |  |
ST_MakePointM |  |  |  |  |  |  |
ST_MakePolygon |  |  |  |  |  |  |
ST_Point |  |  |  |  |  |  |
ST_PointZ |  |  |  |  |  |  |
ST_PointM |  |  |  |  |  |  |
ST_PointZM |  |  |  |  |  |  |
ST_Polygon |  |  |  |  |  |  |
ST_TileEnvelope |  |  |  |  |  |  |
ST_HexagonGrid |  |  |  |  |  |  |
ST_Hexagon |  |  |  |  |  |  |
ST_SquareGrid |  |  |  |  |  |  |
ST_Square |  |  |  |  |  |  |
ST_Letters |  |  |  |  |  |  |
GeometryType |  |  |  |  |  |  |
ST_Boundary |  |  |  |  |  |  |
ST_BoundingDiagonal |  |  |  |  |  |  |
ST_CoordDim |  |  |  |  |  |  |
ST_Dimension |  |  |  |  |  |  |
ST_Dump |  |  |  |  |  |  |
ST_DumpPoints |  |  |  |  |  |  |
ST_DumpSegments |  |  |  |  |  |  |
ST_DumpRings |  |  |  |  |  |  |
ST_EndPoint |  |  |  |  |  |  |
ST_Envelope |  |  |  |  |  |  |
ST_ExteriorRing |  |  |  |  |  |  |
ST_GeometryN |  |  |  |  |  |  |
ST_GeometryType |  |  |  |  |  |  |
ST_HasArc |  |  |  |  |  |  |
ST_InteriorRingN |  |  |  |  |  |  |
ST_NumCurves |  |  |  |  |  |  |
ST_CurveN |  |  |  |  |  |  |
ST_IsClosed |  |  |  |  |  |  |
ST_IsCollection |  |  |  |  |  |  |
ST_IsEmpty |  |  |  |  |  |  |
ST_IsPolygonCCW |  |  |  |  |  |  |
ST_IsPolygonCW |  |  |  |  |  |  |
ST_IsRing |  |  |  |  |  |  |
ST_IsSimple |  |  |  |  |  |  |
ST_M |  |  |  |  |  |  |
ST_MemSize |  |  |  |  |  |  |
ST_NDims |  |  |  |  |  |  |
ST_NPoints |  |  |  |  |  |  |
ST_NRings |  |  |  |  |  |  |
ST_NumGeometries |  |  |  |  |  |  |
ST_NumInteriorRings |  |  |  |  |  |  |
ST_NumInteriorRing |  |  |  |  |  |  |
ST_NumPatches |  |  |  |  |  |  |
ST_NumPoints |  |  |  |  |  |  |
ST_PatchN |  |  |  |  |  |  |
ST_PointN |  |  |  |  |  |  |
ST_Points |  |  |  |  |  |  |
ST_StartPoint |  |  |  |  |  |  |
ST_Summary |  |  |  |  |  |  |
ST_X |  |  |  |  |  |  |
ST_Y |  |  |  |  |  |  |
ST_Z |  |  |  |  |  |  |
ST_Zmflag |  |  |  |  |  |  |
ST_HasZ |  |  |  |  |  |  |
ST_HasM |  |  |  |  |  |  |
ST_AddPoint |  |  |  |  |  |  |
ST_CollectionExtract |  |  |  |  |  |  |
ST_CollectionHomogenize |  |  |  |  |  |  |
ST_CurveToLine |  |  |  |  |  |  |
ST_Scroll |  |  |  |  |  |  |
ST_FlipCoordinates |  |  |  |  |  |  |
ST_Force2D |  |  |  |  |  |  |
ST_Force3D |  |  |  |  |  |  |
ST_Force3DZ |  |  |  |  |  |  |
ST_Force3DM |  |  |  |  |  |  |
ST_Force4D |  |  |  |  |  |  |
ST_ForceCollection |  |  |  |  |  |  |
ST_ForceCurve |  |  |  |  |  |  |
ST_ForcePolygonCCW |  |  |  |  |  |  |
ST_ForcePolygonCW |  |  |  |  |  |  |
ST_ForceSFS |  |  |  |  |  |  |
ST_ForceRHR |  |  |  |  |  |  |
ST_LineExtend |  |  |  |  |  |  |
ST_LineToCurve |  |  |  |  |  |  |
ST_Multi |  |  |  |  |  |  |
ST_Normalize |  |  |  |  |  |  |
ST_Project |  |  |  |  |  |  |
ST_QuantizeCoordinates |  |  |  |  |  |  |
ST_RemovePoint |  |  |  |  |  |  |
ST_RemoveRepeatedPoints |  |  |  |  |  |  |
ST_RemoveIrrelevantPointsForView |  |  |  |  |  |  |
ST_RemoveSmallParts |  |  |  |  |  |  |
ST_Reverse |  |  |  |  |  |  |
ST_Segmentize |  |  |  |  |  |  |
ST_SetPoint |  |  |  |  |  |  |
ST_ShiftLongitude |  |  |  |  |  |  |
ST_WrapX |  |  |  |  |  |  |
ST_SnapToGrid |  |  |  |  |  |  |
ST_Snap |  |  |  |  |  |  |
ST_SwapOrdinates |  |  |  |  |  |  |
ST_IsValid |  |  |  |  |  |  |
ST_IsValidDetail |  |  |  |  |  |  |
ST_IsValidReason |  |  |  |  |  |  |
ST_MakeValid |  |  |  |  |  |  |
ST_InverseTransformPipeline |  |  |  |  |  |  |
ST_SetSRID |  |  |  |  |  |  |
ST_SRID |  |  |  |  |  |  |
ST_Transform |  |  |  |  |  |  |
ST_TransformPipeline |  |  |  |  |  |  |
postgis_srs_codes |  |  |  |  |  |  |
postgis_srs |  |  |  |  |  |  |
postgis_srs_all |  |  |  |  |  |  |
postgis_srs_search |  |  |  |  |  |  |
ST_BdPolyFromText |  |  |  |  |  |  |
ST_BdMPolyFromText |  |  |  |  |  |  |
ST_GeogFromText |  |  |  |  |  |  |
ST_GeographyFromText |  |  |  |  |  |  |
ST_GeomCollFromText |  |  |  |  |  |  |
ST_GeomFromEWKT |  |  |  |  |  |  |
ST_GeomFromMARC21 |  |  |  |  |  |  |
ST_GeometryFromText |  |  |  |  |  |  |
ST_GeomFromText |  |  |  |  |  |  |
ST_LineFromText |  |  |  |  |  |  |
ST_MLineFromText |  |  |  |  |  |  |
ST_MPointFromText |  |  |  |  |  |  |
ST_MPolyFromText |  |  |  |  |  |  |
ST_PointFromText |  |  |  |  |  |  |
ST_PolygonFromText |  |  |  |  |  |  |
ST_WKTToSQL |  |  |  |  |  |  |
ST_GeogFromWKB |  |  |  |  |  |  |
ST_GeomFromEWKB |  |  |  |  |  |  |
ST_GeomFromWKB |  |  |  |  |  |  |
ST_LineFromWKB |  |  |  |  |  |  |
ST_LinestringFromWKB |  |  |  |  |  |  |
ST_PointFromWKB |  |  |  |  |  |  |
ST_WKBToSQL |  |  |  |  |  |  |
ST_Box2dFromGeoHash |  |  |  |  |  |  |
ST_GeomFromGeoHash |  |  |  |  |  |  |
ST_GeomFromGML |  |  |  |  |  |  |
ST_GeomFromGeoJSON |  |  |  |  |  |  |
ST_GeomFromKML |  |  |  |  |  |  |
ST_GeomFromTWKB |  |  |  |  |  |  |
ST_GMLToSQL |  |  |  |  |  |  |
ST_LineFromEncodedPolyline |  |  |  |  |  |  |
ST_PointFromGeoHash |  |  |  |  |  |  |
ST_FromFlatGeobufToTable |  |  |  |  |  |  |
ST_FromFlatGeobuf |  |  |  |  |  |  |
ST_AsEWKT |  |  |  |  |  |  |
ST_AsText |  |  |  |  |  |  |
ST_AsBinary |  |  |  |  |  |  |
ST_AsEWKB |  |  |  |  |  |  |
ST_AsHEXEWKB |  |  |  |  |  |  |
ST_AsEncodedPolyline |  |  |  |  |  |  |
ST_AsFlatGeobuf |  |  |  |  |  |  |
ST_AsGeobuf |  |  |  |  |  |  |
ST_AsGeoJSON |  |  |  |  |  |  |
ST_AsGML |  |  |  |  |  |  |
ST_AsKML |  |  |  |  |  |  |
ST_AsLatLonText |  |  |  |  |  |  |
ST_AsMARC21 |  |  |  |  |  |  |
ST_AsMVTGeom |  |  |  |  |  |  |
ST_AsMVT |  |  |  |  |  |  |
ST_AsSVG |  |  |  |  |  |  |
ST_AsTWKB |  |  |  |  |  |  |
ST_AsX3D |  |  |  |  |  |  |
ST_GeoHash |  |  |  |  |  |  |
&& |  |  |  |  |  |  |
&&(geometry,box2df) |  |  |  |  |  |  |
&&(box2df,geometry) |  |  |  |  |  |  |
&&(box2df,box2df) |  |  |  |  |  |  |
&&& |  |  |  |  |  |  |
&&&(geometry,gidx) |  |  |  |  |  |  |
&&&(gidx,geometry) |  |  |  |  |  |  |
&&&(gidx,gidx) |  |  |  |  |  |  |
&< |  |  |  |  |  |  |
&<| |  |  |  |  |  |  |
&> |  |  |  |  |  |  |
<< |  |  |  |  |  |  |
<<| |  |  |  |  |  |  |
= |  |  |  |  |  |  |
>> |  |  |  |  |  |  |
@ |  |  |  |  |  |  |
@(geometry,box2df) |  |  |  |  |  |  |
@(box2df,geometry) |  |  |  |  |  |  |
@(box2df,box2df) |  |  |  |  |  |  |
|&> |  |  |  |  |  |  |
|>> |  |  |  |  |  |  |
~ |  |  |  |  |  |  |
~(geometry,box2df) |  |  |  |  |  |  |
~(box2df,geometry) |  |  |  |  |  |  |
~(box2df,box2df) |  |  |  |  |  |  |
~= |  |  |  |  |  |  |
<-> |  |  |  |  |  |  |
|=| |  |  |  |  |  |  |
<#> |  |  |  |  |  |  |
<<->> |  |  |  |  |  |  |
ST_3DIntersects |  |  |  |  |  |  |
ST_Contains |  |  |  |  |  |  |
ST_ContainsProperly |  |  |  |  |  |  |
ST_CoveredBy |  |  |  |  |  |  |
ST_Covers |  |  |  |  |  |  |
ST_Crosses |  |  |  |  |  |  |
ST_Disjoint |  |  |  |  |  |  |
ST_Equals |  |  |  |  |  |  |
ST_Intersects |  |  |  |  |  |  |
ST_LineCrossingDirection |  |  |  |  |  |  |
ST_OrderingEquals |  |  |  |  |  |  |
ST_Overlaps |  |  |  |  |  |  |
ST_Relate |  |  |  |  |  |  |
ST_RelateMatch |  |  |  |  |  |  |
ST_Touches |  |  |  |  |  |  |
ST_Within |  |  |  |  |  |  |
ST_3DDWithin |  |  |  |  |  |  |
ST_3DDFullyWithin |  |  |  |  |  |  |
ST_DFullyWithin |  |  |  |  |  |  |
ST_DWithin |  |  |  |  |  |  |
ST_PointInsideCircle |  |  |  |  |  |  |
ST_Area |  |  |  |  |  |  |
ST_Azimuth |  |  |  |  |  |  |
ST_Angle |  |  |  |  |  |  |
ST_ClosestPoint |  |  |  |  |  |  |
ST_3DClosestPoint |  |  |  |  |  |  |
ST_Distance |  |  |  |  |  |  |
ST_3DDistance |  |  |  |  |  |  |
ST_DistanceSphere |  |  |  |  |  |  |
ST_DistanceSpheroid |  |  |  |  |  |  |
ST_FrechetDistance |  |  |  |  |  |  |
ST_HausdorffDistance |  |  |  |  |  |  |
ST_Length |  |  |  |  |  |  |
ST_Length2D |  |  |  |  |  |  |
ST_3DLength |  |  |  |  |  |  |
ST_LengthSpheroid |  |  |  |  |  |  |
ST_LongestLine |  |  |  |  |  |  |
ST_3DLongestLine |  |  |  |  |  |  |
ST_MaxDistance |  |  |  |  |  |  |
ST_3DMaxDistance |  |  |  |  |  |  |
ST_MinimumClearance |  |  |  |  |  |  |
ST_MinimumClearanceLine |  |  |  |  |  |  |
ST_Perimeter |  |  |  |  |  |  |
ST_Perimeter2D |  |  |  |  |  |  |
ST_3DPerimeter |  |  |  |  |  |  |
ST_ShortestLine |  |  |  |  |  |  |
ST_3DShortestLine |  |  |  |  |  |  |
ST_ClipByBox2D |  |  |  |  |  |  |
ST_Difference |  |  |  |  |  |  |
ST_Intersection |  |  |  |  |  |  |
ST_MemUnion |  |  |  |  |  |  |
ST_Node |  |  |  |  |  |  |
ST_Split |  |  |  |  |  |  |
ST_Subdivide |  |  |  |  |  |  |
ST_SymDifference |  |  |  |  |  |  |
ST_UnaryUnion |  |  |  |  |  |  |
ST_Union |  |  |  |  |  |  |
ST_Buffer |  |  |  |  |  |  |
ST_BuildArea |  |  |  |  |  |  |
ST_Centroid |  |  |  |  |  |  |
ST_ChaikinSmoothing |  |  |  |  |  |  |
ST_ConcaveHull |  |  |  |  |  |  |
ST_ConvexHull |  |  |  |  |  |  |
ST_DelaunayTriangles |  |  |  |  |  |  |
ST_FilterByM |  |  |  |  |  |  |
ST_GeneratePoints |  |  |  |  |  |  |
ST_GeometricMedian |  |  |  |  |  |  |
ST_LineMerge |  |  |  |  |  |  |
ST_MaximumInscribedCircle |  |  |  |  |  |  |
ST_LargestEmptyCircle |  |  |  |  |  |  |
ST_MinimumBoundingCircle |  |  |  |  |  |  |
ST_MinimumBoundingRadius |  |  |  |  |  |  |
ST_OrientedEnvelope |  |  |  |  |  |  |
ST_OffsetCurve |  |  |  |  |  |  |
ST_PointOnSurface |  |  |  |  |  |  |
ST_Polygonize |  |  |  |  |  |  |
ST_ReducePrecision |  |  |  |  |  |  |
ST_SharedPaths |  |  |  |  |  |  |
ST_Simplify |  |  |  |  |  |  |
ST_SimplifyPreserveTopology |  |  |  |  |  |  |
ST_SimplifyPolygonHull |  |  |  |  |  |  |
ST_SimplifyVW |  |  |  |  |  |  |
ST_SetEffectiveArea |  |  |  |  |  |  |
ST_TriangulatePolygon |  |  |  |  |  |  |
ST_VoronoiLines |  |  |  |  |  |  |
ST_VoronoiPolygons |  |  |  |  |  |  |
ST_CoverageInvalidEdges |  |  |  |  |  |  |
ST_CoverageSimplify |  |  |  |  |  |  |
ST_CoverageUnion |  |  |  |  |  |  |
ST_Affine |  |  |  |  |  |  |
ST_Rotate |  |  |  |  |  |  |
ST_RotateX |  |  |  |  |  |  |
ST_RotateY |  |  |  |  |  |  |
ST_RotateZ |  |  |  |  |  |  |
ST_Scale |  |  |  |  |  |  |
ST_Translate |  |  |  |  |  |  |
ST_TransScale |  |  |  |  |  |  |
ST_ClusterDBSCAN |  |  |  |  |  |  |
ST_ClusterIntersecting |  |  |  |  |  |  |
ST_ClusterIntersectingWin |  |  |  |  |  |  |
ST_ClusterKMeans |  |  |  |  |  |  |
ST_ClusterWithin |  |  |  |  |  |  |
ST_ClusterWithinWin |  |  |  |  |  |  |
Box2D |  |  |  |  |  |  |
Box3D |  |  |  |  |  |  |
ST_EstimatedExtent |  |  |  |  |  |  |
ST_Expand |  |  |  |  |  |  |
ST_Extent |  |  |  |  |  |  |
ST_3DExtent |  |  |  |  |  |  |
ST_MakeBox2D |  |  |  |  |  |  |
ST_3DMakeBox |  |  |  |  |  |  |
ST_XMax |  |  |  |  |  |  |
ST_XMin |  |  |  |  |  |  |
ST_YMax |  |  |  |  |  |  |
ST_YMin |  |  |  |  |  |  |
ST_ZMax |  |  |  |  |  |  |
ST_ZMin |  |  |  |  |  |  |
ST_LineInterpolatePoint |  |  |  |  |  |  |
ST_3DLineInterpolatePoint |  |  |  |  |  |  |
ST_LineInterpolatePoints |  |  |  |  |  |  |
ST_LineLocatePoint |  |  |  |  |  |  |
ST_LineSubstring |  |  |  |  |  |  |
ST_LocateAlong |  |  |  |  |  |  |
ST_LocateBetween |  |  |  |  |  |  |
ST_LocateBetweenElevations |  |  |  |  |  |  |
ST_InterpolatePoint |  |  |  |  |  |  |
ST_AddMeasure |  |  |  |  |  |  |
ST_IsValidTrajectory |  |  |  |  |  |  |
ST_ClosestPointOfApproach |  |  |  |  |  |  |
ST_DistanceCPA |  |  |  |  |  |  |
ST_CPAWithin |  |  |  |  |  |  |
postgis.backend |  |  |  |  |  |  |
postgis.gdal_datapath |  |  |  |  |  |  |
postgis.gdal_enabled_drivers |  |  |  |  |  |  |
postgis.enable_outdb_rasters |  |  |  |  |  |  |
postgis.gdal_vsi_options |  |  |  |  |  |  |
PostGIS_AddBBox |  |  |  |  |  |  |
PostGIS_DropBBox |  |  |  |  |  |  |
PostGIS_HasBBox |  |  |  |  |  |  |
postgis_sfcgal_version |  |  |  |  |  |  |
postgis_sfcgal_full_version |  |  |  |  |  |  |
CG_ForceLHR |  |  |  |  |  |  |
CG_IsPlanar |  |  |  |  |  |  |
CG_IsSolid |  |  |  |  |  |  |
CG_MakeSolid |  |  |  |  |  |  |
CG_Orientation |  |  |  |  |  |  |
CG_Area |  |  |  |  |  |  |
CG_3DArea |  |  |  |  |  |  |
CG_Volume |  |  |  |  |  |  |
ST_ForceLHR |  |  |  |  |  |  |
ST_IsPlanar |  |  |  |  |  |  |
ST_IsSolid |  |  |  |  |  |  |
ST_MakeSolid |  |  |  |  |  |  |
ST_Orientation |  |  |  |  |  |  |
ST_3DArea |  |  |  |  |  |  |
ST_Volume |  |  |  |  |  |  |
CG_Intersection |  |  |  |  |  |  |
CG_Intersects |  |  |  |  |  |  |
CG_3DIntersects |  |  |  |  |  |  |
CG_Difference |  |  |  |  |  |  |
ST_3DDifference |  |  |  |  |  |  |
CG_3DDifference |  |  |  |  |  |  |
CG_Distance |  |  |  |  |  |  |
CG_3DDistance |  |  |  |  |  |  |
ST_3DConvexHull |  |  |  |  |  |  |
CG_3DConvexHull |  |  |  |  |  |  |
ST_3DIntersection |  |  |  |  |  |  |
CG_3DIntersection |  |  |  |  |  |  |
CG_Union |  |  |  |  |  |  |
ST_3DUnion |  |  |  |  |  |  |
CG_3DUnion |  |  |  |  |  |  |
ST_AlphaShape |  |  |  |  |  |  |
CG_AlphaShape |  |  |  |  |  |  |
CG_ApproxConvexPartition |  |  |  |  |  |  |
ST_ApproximateMedialAxis |  |  |  |  |  |  |
CG_ApproximateMedialAxis |  |  |  |  |  |  |
ST_ConstrainedDelaunayTriangles |  |  |  |  |  |  |
CG_ConstrainedDelaunayTriangles |  |  |  |  |  |  |
ST_Extrude |  |  |  |  |  |  |
CG_Extrude |  |  |  |  |  |  |
CG_ExtrudeStraightSkeleton |  |  |  |  |  |  |
CG_GreeneApproxConvexPartition |  |  |  |  |  |  |
ST_MinkowskiSum |  |  |  |  |  |  |
CG_MinkowskiSum |  |  |  |  |  |  |
ST_OptimalAlphaShape |  |  |  |  |  |  |
CG_OptimalAlphaShape |  |  |  |  |  |  |
CG_OptimalConvexPartition |  |  |  |  |  |  |
CG_StraightSkeleton |  |  |  |  |  |  |
ST_StraightSkeleton |  |  |  |  |  |  |
ST_Tesselate |  |  |  |  |  |  |
CG_Tesselate |  |  |  |  |  |  |
CG_Triangulate |  |  |  |  |  |  |
CG_Visibility |  |  |  |  |  |  |
CG_YMonotonePartition |  |  |  |  |  |  |
getfaceedges_returntype |  |  |  |  |  |  |
TopoGeometry |  |  |  |  |  |  |
validatetopology_returntype |  |  |  |  |  |  |
TopoElement |  |  |  |  |  |  |
TopoElementArray |  |  |  |  |  |  |
AddTopoGeometryColumn |  |  |  |  |  |  |
RenameTopoGeometryColumn |  |  |  |  |  |  |
DropTopology |  |  |  |  |  |  |
RenameTopology |  |  |  |  |  |  |
DropTopoGeometryColumn |  |  |  |  |  |  |
Populate_Topology_Layer |  |  |  |  |  |  |
TopologySummary |  |  |  |  |  |  |
ValidateTopology |  |  |  |  |  |  |
ValidateTopologyRelation |  |  |  |  |  |  |
FindTopology |  |  |  |  |  |  |
FindLayer |  |  |  |  |  |  |
CreateTopology |  |  |  |  |  |  |
CopyTopology |  |  |  |  |  |  |
ST_InitTopoGeo |  |  |  |  |  |  |
ST_CreateTopoGeo |  |  |  |  |  |  |
TopoGeo_AddPoint |  |  |  |  |  |  |
TopoGeo_AddLineString |  |  |  |  |  |  |
TopoGeo_AddPolygon |  |  |  |  |  |  |
TopoGeo_LoadGeometry |  |  |  |  |  |  |
ST_AddIsoNode |  |  |  |  |  |  |
ST_AddIsoEdge |  |  |  |  |  |  |
ST_AddEdgeNewFaces |  |  |  |  |  |  |
ST_AddEdgeModFace |  |  |  |  |  |  |
ST_RemEdgeNewFace |  |  |  |  |  |  |
ST_RemEdgeModFace |  |  |  |  |  |  |
ST_ChangeEdgeGeom |  |  |  |  |  |  |
ST_ModEdgeSplit |  |  |  |  |  |  |
ST_ModEdgeHeal |  |  |  |  |  |  |
ST_NewEdgeHeal |  |  |  |  |  |  |
ST_MoveIsoNode |  |  |  |  |  |  |
ST_NewEdgesSplit |  |  |  |  |  |  |
ST_RemoveIsoNode |  |  |  |  |  |  |
ST_RemoveIsoEdge |  |  |  |  |  |  |
GetEdgeByPoint |  |  |  |  |  |  |
GetFaceByPoint |  |  |  |  |  |  |
GetFaceContainingPoint |  |  |  |  |  |  |
GetNodeByPoint |  |  |  |  |  |  |
GetTopologyID |  |  |  |  |  |  |
GetTopologySRID |  |  |  |  |  |  |
GetTopologyName |  |  |  |  |  |  |
ST_GetFaceEdges |  |  |  |  |  |  |
ST_GetFaceGeometry |  |  |  |  |  |  |
GetRingEdges |  |  |  |  |  |  |
GetNodeEdges |  |  |  |  |  |  |
Polygonize |  |  |  |  |  |  |
AddNode |  |  |  |  |  |  |
AddEdge |  |  |  |  |  |  |
AddFace |  |  |  |  |  |  |
ST_Simplify |  |  |  |  |  |  |
RemoveUnusedPrimitives |  |  |  |  |  |  |
CreateTopoGeom |  |  |  |  |  |  |
toTopoGeom |  |  |  |  |  |  |
TopoElementArray_Agg |  |  |  |  |  |  |
TopoElement |  |  |  |  |  |  |
clearTopoGeom |  |  |  |  |  |  |
TopoGeom_addElement |  |  |  |  |  |  |
TopoGeom_remElement |  |  |  |  |  |  |
TopoGeom_addTopoGeom |  |  |  |  |  |  |
toTopoGeom |  |  |  |  |  |  |
GetTopoGeomElementArray |  |  |  |  |  |  |
GetTopoGeomElements |  |  |  |  |  |  |
ST_SRID |  |  |  |  |  |  |
AsGML |  |  |  |  |  |  |
AsTopoJSON |  |  |  |  |  |  |
Equals |  |  |  |  |  |  |
Intersects |  |  |  |  |  |  |
geomval |  |  |  |  |  |  |
addbandarg |  |  |  |  |  |  |
rastbandarg |  |  |  |  |  |  |
raster |  |  |  |  |  |  |
reclassarg |  |  |  |  |  |  |
summarystats |  |  |  |  |  |  |
unionarg |  |  |  |  |  |  |
AddRasterConstraints |  |  |  |  |  |  |
DropRasterConstraints |  |  |  |  |  |  |
AddOverviewConstraints |  |  |  |  |  |  |
DropOverviewConstraints |  |  |  |  |  |  |
PostGIS_GDAL_Version |  |  |  |  |  |  |
PostGIS_Raster_Lib_Build_Date |  |  |  |  |  |  |
PostGIS_Raster_Lib_Version |  |  |  |  |  |  |
ST_GDALDrivers |  |  |  |  |  |  |
ST_Contour |  |  |  |  |  |  |
ST_InterpolateRaster |  |  |  |  |  |  |
UpdateRasterSRID |  |  |  |  |  |  |
ST_CreateOverview |  |  |  |  |  |  |
ST_AddBand |  |  |  |  |  |  |
ST_AsRaster |  |  |  |  |  |  |
ST_Band |  |  |  |  |  |  |
ST_MakeEmptyCoverage |  |  |  |  |  |  |
ST_MakeEmptyRaster |  |  |  |  |  |  |
ST_Tile |  |  |  |  |  |  |
ST_Retile |  |  |  |  |  |  |
ST_FromGDALRaster |  |  |  |  |  |  |
ST_GeoReference |  |  |  |  |  |  |
ST_Height |  |  |  |  |  |  |
ST_IsEmpty |  |  |  |  |  |  |
ST_MemSize |  |  |  |  |  |  |
ST_MetaData |  |  |  |  |  |  |
ST_NumBands |  |  |  |  |  |  |
ST_PixelHeight |  |  |  |  |  |  |
ST_PixelWidth |  |  |  |  |  |  |
ST_ScaleX |  |  |  |  |  |  |
ST_ScaleY |  |  |  |  |  |  |
ST_RasterToWorldCoord |  |  |  |  |  |  |
ST_RasterToWorldCoordX |  |  |  |  |  |  |
ST_RasterToWorldCoordY |  |  |  |  |  |  |
ST_Rotation |  |  |  |  |  |  |
ST_SkewX |  |  |  |  |  |  |
ST_SkewY |  |  |  |  |  |  |
ST_SRID |  |  |  |  |  |  |
ST_Summary |  |  |  |  |  |  |
ST_UpperLeftX |  |  |  |  |  |  |
ST_UpperLeftY |  |  |  |  |  |  |
ST_Width |  |  |  |  |  |  |
ST_WorldToRasterCoord |  |  |  |  |  |  |
ST_WorldToRasterCoordX |  |  |  |  |  |  |
ST_WorldToRasterCoordY |  |  |  |  |  |  |
ST_BandMetaData |  |  |  |  |  |  |
ST_BandNoDataValue |  |  |  |  |  |  |
ST_BandIsNoData |  |  |  |  |  |  |
ST_BandPath |  |  |  |  |  |  |
ST_BandFileSize |  |  |  |  |  |  |
ST_BandFileTimestamp |  |  |  |  |  |  |
ST_BandPixelType |  |  |  |  |  |  |
ST_MinPossibleValue |  |  |  |  |  |  |
ST_HasNoBand |  |  |  |  |  |  |
ST_PixelAsPolygon |  |  |  |  |  |  |
ST_PixelAsPolygons |  |  |  |  |  |  |
ST_PixelAsPoint |  |  |  |  |  |  |
ST_PixelAsPoints |  |  |  |  |  |  |
ST_PixelAsCentroid |  |  |  |  |  |  |
ST_PixelAsCentroids |  |  |  |  |  |  |
ST_Value |  |  |  |  |  |  |
ST_NearestValue |  |  |  |  |  |  |
ST_SetZ |  |  |  |  |  |  |
ST_SetM |  |  |  |  |  |  |
ST_Neighborhood |  |  |  |  |  |  |
ST_SetValue |  |  |  |  |  |  |
ST_SetValues |  |  |  |  |  |  |
ST_DumpValues |  |  |  |  |  |  |
ST_PixelOfValue |  |  |  |  |  |  |
ST_SetGeoReference |  |  |  |  |  |  |
ST_SetRotation |  |  |  |  |  |  |
ST_SetScale |  |  |  |  |  |  |
ST_SetSkew |  |  |  |  |  |  |
ST_SetSRID |  |  |  |  |  |  |
ST_SetUpperLeft |  |  |  |  |  |  |
ST_Resample |  |  |  |  |  |  |
ST_Rescale |  |  |  |  |  |  |
ST_Reskew |  |  |  |  |  |  |
ST_SnapToGrid |  |  |  |  |  |  |
ST_Resize |  |  |  |  |  |  |
ST_Transform |  |  |  |  |  |  |
ST_SetBandNoDataValue |  |  |  |  |  |  |
ST_SetBandIsNoData |  |  |  |  |  |  |
ST_SetBandPath |  |  |  |  |  |  |
ST_SetBandIndex |  |  |  |  |  |  |
ST_Count |  |  |  |  |  |  |
ST_CountAgg |  |  |  |  |  |  |
ST_Histogram |  |  |  |  |  |  |
ST_Quantile |  |  |  |  |  |  |
ST_SummaryStats |  |  |  |  |  |  |
ST_SummaryStatsAgg |  |  |  |  |  |  |
ST_ValueCount |  |  |  |  |  |  |
ST_RastFromWKB |  |  |  |  |  |  |
ST_RastFromHexWKB |  |  |  |  |  |  |
ST_AsBinary/ST_AsWKB |  |  |  |  |  |  |
ST_AsHexWKB |  |  |  |  |  |  |
ST_AsGDALRaster |  |  |  |  |  |  |
ST_AsJPEG |  |  |  |  |  |  |
ST_AsPNG |  |  |  |  |  |  |
ST_AsTIFF |  |  |  |  |  |  |
ST_Clip |  |  |  |  |  |  |
ST_ColorMap |  |  |  |  |  |  |
ST_Grayscale |  |  |  |  |  |  |
ST_Intersection |  |  |  |  |  |  |
ST_MapAlgebra (callback function version) |  |  |  |  |  |  |
ST_MapAlgebra (expression version) |  |  |  |  |  |  |
ST_MapAlgebraExpr |  |  |  |  |  |  |
ST_MapAlgebraExpr |  |  |  |  |  |  |
ST_MapAlgebraFct |  |  |  |  |  |  |
ST_MapAlgebraFct |  |  |  |  |  |  |
ST_MapAlgebraFctNgb |  |  |  |  |  |  |
ST_Reclass |  |  |  |  |  |  |
ST_Union |  |  |  |  |  |  |
ST_Distinct4ma |  |  |  |  |  |  |
ST_InvDistWeight4ma |  |  |  |  |  |  |
ST_Max4ma |  |  |  |  |  |  |
ST_Mean4ma |  |  |  |  |  |  |
ST_Min4ma |  |  |  |  |  |  |
ST_MinDist4ma |  |  |  |  |  |  |
ST_Range4ma |  |  |  |  |  |  |
ST_StdDev4ma |  |  |  |  |  |  |
ST_Sum4ma |  |  |  |  |  |  |
ST_Aspect |  |  |  |  |  |  |
ST_HillShade |  |  |  |  |  |  |
ST_Roughness |  |  |  |  |  |  |
ST_Slope |  |  |  |  |  |  |
ST_TPI |  |  |  |  |  |  |
ST_TRI |  |  |  |  |  |  |
Box3D |  |  |  |  |  |  |
ST_ConvexHull |  |  |  |  |  |  |
ST_DumpAsPolygons |  |  |  |  |  |  |
ST_Envelope |  |  |  |  |  |  |
ST_MinConvexHull |  |  |  |  |  |  |
ST_Polygon |  |  |  |  |  |  |
&& |  |  |  |  |  |  |
&< |  |  |  |  |  |  |
&> |  |  |  |  |  |  |
= |  |  |  |  |  |  |
@ |  |  |  |  |  |  |
~= |  |  |  |  |  |  |
~ |  |  |  |  |  |  |
ST_Contains |  |  |  |  |  |  |
ST_ContainsProperly |  |  |  |  |  |  |
ST_Covers |  |  |  |  |  |  |
ST_CoveredBy |  |  |  |  |  |  |
ST_Disjoint |  |  |  |  |  |  |
ST_Intersects |  |  |  |  |  |  |
ST_Overlaps |  |  |  |  |  |  |
ST_Touches |  |  |  |  |  |  |
ST_SameAlignment |  |  |  |  |  |  |
ST_NotSameAlignmentReason |  |  |  |  |  |  |
ST_Within |  |  |  |  |  |  |
ST_DWithin |  |  |  |  |  |  |
ST_DFullyWithin |  |  |  |  |  |  |
stdaddr |  |  |  |  |  |  |
rules table |  |  |  |  |  |  |
lex table |  |  |  |  |  |  |
gaz table |  |  |  |  |  |  |
debug_standardize_address |  |  |  |  |  |  |
parse_address |  |  |  |  |  |  |
standardize_address |  |  |  |  |  |  |
Drop_Indexes_Generate_Script |  |  |  |  |  |  |
Drop_Nation_Tables_Generate_Script |  |  |  |  |  |  |
Drop_State_Tables_Generate_Script |  |  |  |  |  |  |
Geocode |  |  |  |  |  |  |
Geocode_Intersection |  |  |  |  |  |  |
Get_Geocode_Setting |  |  |  |  |  |  |
Get_Tract |  |  |  |  |  |  |
Install_Missing_Indexes |  |  |  |  |  |  |
Loader_Generate_Census_Script |  |  |  |  |  |  |
Loader_Generate_Script |  |  |  |  |  |  |
Loader_Generate_Nation_Script |  |  |  |  |  |  |
Missing_Indexes_Generate_Script |  |  |  |  |  |  |
Normalize_Address |  |  |  |  |  |  |
Pagc_Normalize_Address |  |  |  |  |  |  |
Pprint_Addy |  |  |  |  |  |  |
Reverse_Geocode |  |  |  |  |  |  |
Topology_Load_Tiger |  |  |  |  |  |  |
Set_Geocode_Setting |  |  |  |  |  |  |

## 13.12. New, Enhanced or changed PostGIS Functions

### 13.12.1. PostGIS Functions new or enhanced in 3.5

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.5

- CG_3DArea - Availability: 3.5.0 Computes area of 3D surface geometries. Will return 0 for solids.
- CG_3DConvexHull - Availability: 3.5.0 Computes the 3D convex hull of a geometry.
- CG_3DDifference - Availability: 3.5.0 Perform 3D difference
- CG_3DDistance - Availability: 3.5.0 Computes the minimum 3D distance between two geometries
- CG_3DIntersection - Availability: 3.5.0 Perform 3D intersection
- CG_3DIntersects - Availability: 3.5.0 Tests if two 3D geometries intersect
- CG_3DUnion - Availability: 3.5.0 Perform 3D union using postgis_sfcgal.
- CG_AlphaShape - Availability: 3.5.0 - requires SFCGAL >= 1.4.1. Computes an Alpha-shape enclosing a geometry
- CG_ApproxConvexPartition - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Computes approximal convex partition of the polygon geometry
- CG_ApproximateMedialAxis - Availability: 3.5.0 Compute the approximate medial axis of an areal geometry.
- CG_Area - Availability: 3.5.0 Calculates the area of a geometry
- CG_Difference - Availability: 3.5.0 Computes the geometric difference between two geometries
- CG_Distance - Availability: 3.5.0 Computes the minimum distance between two geometries
- CG_Extrude - Availability: 3.5.0 Extrude a surface to a related volume
- CG_ExtrudeStraightSkeleton - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Straight Skeleton Extrusion
- CG_ForceLHR - Availability: 3.5.0 Force LHR orientation
- CG_GreeneApproxConvexPartition - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Computes approximal convex partition of the polygon geometry
- CG_Intersection - Availability: 3.5.0 Computes the intersection of two geometries
- CG_Intersects - Availability: 3.5.0 Tests if two geometries intersect (they have at least one point in common)
- CG_IsPlanar - Availability: 3.5.0 Check if a surface is or not planar
- CG_IsSolid - Availability: 3.5.0 Test if the geometry is a solid. No validity check is performed.
- CG_MakeSolid - Availability: 3.5.0 Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- CG_MinkowskiSum - Availability: 3.5.0 Performs Minkowski sum
- CG_OptimalAlphaShape - Availability: 3.5.0 - requires SFCGAL >= 1.4.1. Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.
- CG_OptimalConvexPartition - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Computes an optimal convex partition of the polygon geometry
- CG_Orientation - Availability: 3.5.0 Determine surface orientation
- CG_StraightSkeleton - Availability: 3.5.0 Compute a straight skeleton from a geometry
- CG_Tesselate - Availability: 3.5.0 Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- CG_Triangulate - Availability: 3.5.0 Triangulates a polygonal geometry
- CG_Union - Availability: 3.5.0 Computes the union of two geometries
- CG_Visibility - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Compute a visibility polygon from a point or a segment in a polygon geometry
- CG_Volume - Availability: 3.5.0 Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- CG_YMonotonePartition - Availability: 3.5.0 - requires SFCGAL >= 1.5.0. Computes y-monotone partition of the polygon geometry
- ST_HasM - Availability: 3.5.0 Checks if a geometry has an M (measure) dimension.
- ST_HasZ - Availability: 3.5.0 Checks if a geometry has a Z dimension.
- ST_RemoveIrrelevantPointsForView - Availability: 3.5.0 Removes points that are irrelevant for rendering a specific rectangluar view of a geometry.
- ST_RemoveSmallParts - Availability: 3.5.0 Removes small parts (polygon rings or linestrings) of a geometry.
- TopoGeo_LoadGeometry - Availability: 3.5.0 Load a geometry into an existing topology, snapping and splitting as needed.

Functions enhanced in PostGIS 3.5

- ST_Clip - Enhanced: 3.5.0 - touched argument added. Returns the raster clipped by the input geometry. If band number is not specified, all bands are processed. If crop is not specified or TRUE, the output raster is cropped. If touched is set to TRUE, then touched pixels are included, otherwise only if the center of the pixel is in the geometry it is included.

Functions changed in PostGIS 3.5

- ST_AsGeoJSON - Changed: 3.5.0 allow specifying the column containing the feature id Return a geometry or feature in GeoJSON format.
- ST_DFullyWithin - Changed: 3.5.0 : the logic behind the function now uses a test of containment within a buffer, rather than the ST_MaxDistance algorithm. Results will differ from prior versions, but should be closer to user expectations. Tests if a geometry is entirely inside a distance of another

### 13.12.2. PostGIS Functions new or enhanced in 3.4

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.4

- PostGIS_GEOS_Compiled_Version - Availability: 3.4.0 Returns the version number of the GEOS library against which PostGIS was built.
- PostGIS_PROJ_Compiled_Version - Availability: 3.5.0 Returns the version number of the PROJ library against which PostGIS was built.
- RenameTopoGeometryColumn - Availability: 3.4.0 Renames a topogeometry column
- RenameTopology - Availability: 3.4.0 Renames a topology
- ST_ClusterIntersectingWin - Availability: 3.4.0 Window function that returns a cluster id for each input geometry, clustering input geometries into connected sets.
- ST_ClusterWithinWin - Availability: 3.4.0 Window function that returns a cluster id for each input geometry, clustering using separation distance.
- ST_CoverageInvalidEdges - Availability: 3.4.0 Window function that finds locations where polygons fail to form a valid coverage.
- ST_CoverageSimplify - Availability: 3.4.0 Window function that simplifies the edges of a polygonal coverage.
- ST_CoverageUnion - Availability: 3.4.0 - requires GEOS >= 3.8.0 Computes the union of a set of polygons forming a coverage by removing shared edges.
- ST_InverseTransformPipeline - Availability: 3.4.0 Return a new geometry with coordinates transformed to a different spatial reference system using the inverse of a defined coordinate transformation pipeline.
- ST_LargestEmptyCircle - Availability: 3.4.0. Computes the largest circle not overlapping a geometry.
- ST_LineExtend - Availability: 3.4.0 Returns a line extended forwards and backwards by specified distances.
- ST_TransformPipeline - Availability: 3.4.0 Return a new geometry with coordinates transformed to a different spatial reference system using a defined coordinate transformation pipeline.
- TopoElement - Availability: 3.4.0 Converts a topogeometry to a topoelement.
- debug_standardize_address - Availability: 3.4.0 Returns a json formatted text listing the parse tokens and standardizations
- postgis_srs - Availability: 3.4.0 Return a metadata record for the requested authority and srid.
- postgis_srs_all - Availability: 3.4.0 Return metadata records for every spatial reference system in the underlying Proj database.
- postgis_srs_codes - Availability: 3.4.0 Return the list of SRS codes associated with the given authority.
- postgis_srs_search - Availability: 3.4.0 Return metadata records for projected coordinate systems that have areas of usage that fully contain the bounds parameter.

Functions enhanced in PostGIS 3.4

- PostGIS_Full_Version - Enhanced: 3.4.0 now includes extra PROJ configurations NETWORK_ENABLED, URL_ENDPOINT and DATABASE_PATH of proj.db location Reports full PostGIS version and build configuration infos.
- PostGIS_PROJ_Version - Enhanced: 3.4.0 now includes NETWORK_ENABLED, URL_ENDPOINT and DATABASE_PATH of proj.db location Returns the version number of the PROJ4 library.
- ST_AsSVG - Enhanced: 3.4.0 to support all curve types Returns SVG path data for a geometry.
- ST_ClosestPoint - Enhanced: 3.4.0 - Support for geography. Returns the 2D point on g1 that is closest to g2. This is the first point of the shortest line from one geometry to the other.
- ST_LineSubstring - Enhanced: 3.4.0 - Support for geography was introduced. Returns the part of a line between two fractional locations.
- ST_Project - Enhanced: 3.4.0 Allow geometry arguments and two-point form omitting azimuth. Returns a point projected from a start point by a distance and bearing (azimuth).
- ST_Resample - Enhanced: 3.4.0 max and min resampling options added Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster.
- ST_Rescale - Enhanced: 3.4.0 max and min resampling options added Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline, Lanczos, Max or Min resampling algorithm. Default is NearestNeighbor.
- ST_ShortestLine - Enhanced: 3.4.0 - support for geography. Returns the 2D shortest line between two geometries

Functions changed in PostGIS 3.4

- PostGIS_Extensions_Upgrade - Changed: 3.4.0 to add target_version argument. Packages and upgrades PostGIS extensions (e.g. postgis_raster,postgis_topology, postgis_sfcgal) to given or latest version.

### 13.12.3. PostGIS Functions new or enhanced in 3.3

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.3

- RemoveUnusedPrimitives - Availability: 3.3.0 Removes topology primitives which not needed to define existing TopoGeometry objects.
- ST_3DConvexHull - Availability: 3.3.0 Computes the 3D convex hull of a geometry.
- ST_3DUnion - Availability: 3.3.0 aggregate variant was added Perform 3D union.
- ST_AsMARC21 - Availability: 3.3.0 Returns geometry as a MARC21/XML record with a geographic datafield (034).
- ST_GeomFromMARC21 - Availability: 3.3.0, requires libxml2 2.6+ Takes MARC21/XML geographic data as input and returns a PostGIS geometry object.
- ST_Letters - Availability: 3.3.0 Returns the input letters rendered as geometry with a default start position at the origin and default text height of 100.
- ST_OptimalAlphaShape - Availability: 3.3.0 - requires SFCGAL >= 1.4.1. Computes an Alpha-shape enclosing a geometry using an "optimal" alpha value.
- ST_SimplifyPolygonHull - Availability: 3.3.0. Computes a simplifed topology-preserving outer or inner hull of a polygonal geometry.
- ST_TriangulatePolygon - Availability: 3.3.0. Computes the constrained Delaunay triangulation of polygons
- postgis_sfcgal_full_version - Availability: 3.3.0 Returns the full version of SFCGAL in use including CGAL and Boost versions

Functions enhanced in PostGIS 3.3

- ST_ConcaveHull - Enhanced: 3.3.0, GEOS native implementation enabled for GEOS 3.11+ Computes a possibly concave geometry that contains all input geometry vertices
- ST_LineMerge - Enhanced: 3.3.0 accept a directed parameter. Return the lines formed by sewing together a MultiLineString.

Functions changed in PostGIS 3.3

- PostGIS_Extensions_Upgrade - Changed: 3.3.0 support for upgrades from any PostGIS version. Does not work on all systems. Packages and upgrades PostGIS extensions (e.g. postgis_raster,postgis_topology, postgis_sfcgal) to given or latest version.

### 13.12.4. PostGIS Functions new or enhanced in 3.2

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.2

- FindLayer - Availability: 3.2.0 Returns a topology.layer record by different means.
- FindTopology - Availability: 3.2.0 Returns a topology record by different means.
- GetFaceContainingPoint - Availability: 3.2.0 Finds the face containing a point.
- ST_AsFlatGeobuf - Availability: 3.2.0 Return a FlatGeobuf representation of a set of rows.
- ST_Contour - Availability: 3.2.0 Generates a set of vector contours from the provided raster band, using the GDAL contouring algorithm.
- ST_DumpSegments - Availability: 3.2.0 Returns a set of geometry_dump rows for the segments in a geometry.
- ST_FromFlatGeobuf - Availability: 3.2.0 Reads FlatGeobuf data.
- ST_FromFlatGeobufToTable - Availability: 3.2.0 Creates a table based on the structure of FlatGeobuf data.
- ST_InterpolateRaster - Availability: 3.2.0 Interpolates a gridded surface based on an input set of 3-d points, using the X- and Y-values to position the points on the grid and the Z-value of the points as the surface elevation.
- ST_SRID - Availability: 3.2.0 Returns the spatial reference identifier for a topogeometry.
- ST_Scroll - Availability: 3.2.0 Change start point of a closed LineString.
- ST_SetM - Availability: 3.2.0 Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the M dimension using the requested resample algorithm.
- ST_SetZ - Availability: 3.2.0 Returns a geometry with the same X/Y coordinates as the input geometry, and values from the raster copied into the Z dimension using the requested resample algorithm.
- TopoGeom_addTopoGeom - Availability: 3.2 Adds element of a TopoGeometry to the definition of another TopoGeometry.
- ValidateTopologyRelation - Availability: 3.2.0 Returns info about invalid topology relation records
- postgis.gdal_vsi_options - Availability: 3.2.0 A string configuration to set options used when working with an out-db raster.

Functions enhanced in PostGIS 3.2

- GetFaceByPoint - Enhanced: 3.2.0 more efficient implementation and clearer contract, stops working with invalid topologies. Finds face intersecting a given point.
- ST_ClusterKMeans - Enhanced: 3.2.0 Support for max_radius Window function that returns a cluster id for each input geometry using the K-means algorithm.
- ST_MakeValid - Enhanced: 3.2.0, added algorithm options, 'linework' and 'structure' which requires GEOS >= 3.10.0. Attempts to make an invalid geometry valid without losing vertices.
- ST_PixelAsCentroid - Enhanced: 3.2.0 Faster now implemented in C. Returns the centroid (point geometry) of the area represented by a pixel.
- ST_PixelAsCentroids - Enhanced: 3.2.0 Faster now implemented in C. Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.
- ST_Point - Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry. Creates a Point with X, Y and SRID values.
- ST_PointM - Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry. Creates a Point with X, Y, M and SRID values.
- ST_PointZ - Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry. Creates a Point with X, Y, Z and SRID values.
- ST_PointZM - Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry. Creates a Point with X, Y, Z, M and SRID values.
- ST_RemovePoint - Enhanced: 3.2.0 Remove a point from a linestring.
- ST_RemoveRepeatedPoints - Enhanced: 3.2.0 Returns a version of a geometry with duplicate points removed.
- ST_StartPoint - Enhanced: 3.2.0 returns a point for all geometries. Prior behavior returns NULLs if input was not a LineString. Returns the first point of a LineString.
- ST_Value - Enhanced: 3.2.0 resample optional argument was added. Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If exclude_nodata_value is set to false, then all pixels include nodata pixels are considered to intersect and return value. If exclude_nodata_value is not passed in then reads it from metadata of raster.
- TopoGeo_AddLineString - Enhanced: 3.2.0 added support for returning signed identifier. Adds a linestring to an existing topology using a tolerance and possibly splitting existing edges/faces.

Functions changed in PostGIS 3.2

- ST_Boundary - Changed: 3.2.0 support for TIN, does not use geos, does not linearize curves Returns the boundary of a geometry.
- ValidateTopology - Changed: 3.2.0 added optional bbox parameter, perform face labeling and edge linking checks. Returns a set of validatetopology_returntype objects detailing issues with topology.

### 13.12.5. PostGIS Functions new or enhanced in 3.1

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.1

- ST_Hexagon - Availability: 3.1.0 Returns a single hexagon, using the provided edge size and cell coordinate within the hexagon grid space.
- ST_HexagonGrid - Availability: 3.1.0 Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.
- ST_MaximumInscribedCircle - Availability: 3.1.0. Computes the largest circle contained within a geometry.
- ST_ReducePrecision - Availability: 3.1.0. Returns a valid geometry with points rounded to a grid tolerance.
- ST_Square - Availability: 3.1.0 Returns a single square, using the provided edge size and cell coordinate within the square grid space.
- ST_SquareGrid - Availability: 3.1.0 Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.

Functions enhanced in PostGIS 3.1

- ST_AsEWKT - Enhanced: 3.1.0 support for optional precision parameter. Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_ClusterKMeans - Enhanced: 3.1.0 Support for 3D geometries and weights Window function that returns a cluster id for each input geometry using the K-means algorithm.
- ST_Difference - Enhanced: 3.1.0 accept a gridSize parameter. Computes a geometry representing the part of geometry A that does not intersect geometry B.
- ST_Intersection - Enhanced: 3.1.0 accept a gridSize parameter Computes a geometry representing the shared portion of geometries A and B.
- ST_MakeValid - Enhanced: 3.1.0, added removal of Coordinates with NaN values. Attempts to make an invalid geometry valid without losing vertices.
- ST_Subdivide - Enhanced: 3.1.0 accept a gridSize parameter. Computes a rectilinear subdivision of a geometry.
- ST_SymDifference - Enhanced: 3.1.0 accept a gridSize parameter. Computes a geometry representing the portions of geometries A and B that do not intersect.
- ST_TileEnvelope - Enhanced: 3.1.0 Added margin parameter. Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.
- ST_UnaryUnion - Enhanced: 3.1.0 accept a gridSize parameter. Computes the union of the components of a single geometry.
- ST_Union - Enhanced: 3.1.0 accept a gridSize parameter. Computes a geometry representing the point-set union of the input geometries.

Functions changed in PostGIS 3.1

- ST_Count - Changed: 3.1.0 - The ST_Count(rastertable, rastercolumn, ...) variants removed. Use instead. Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.
- ST_Force3D - Changed: 3.1.0. Added support for supplying a non-zero Z value. Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DM - Changed: 3.1.0. Added support for supplying a non-zero M value. Force the geometries into XYM mode.
- ST_Force3DZ - Changed: 3.1.0. Added support for supplying a non-zero Z value. Force the geometries into XYZ mode.
- ST_Force4D - Changed: 3.1.0. Added support for supplying non-zero Z and M values. Force the geometries into XYZM mode.
- ST_Histogram - Changed: 3.1.0 Removed ST_Histogram(table_name, column_name) variant. Returns a set of record summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.
- ST_Quantile - Changed: 3.1.0 Removed ST_Quantile(table_name, column_name) variant. Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.
- ST_SummaryStats - Changed: 3.1.0 ST_SummaryStats(rastertable, rastercolumn, ...) variants are removed. Use instead. Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.

### 13.12.6. PostGIS Functions new or enhanced in 3.0

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 3.0

- CG_ConstrainedDelaunayTriangles - Availability: 3.0.0 Return a constrained Delaunay triangulation around the given input geometry.
- ST_3DLineInterpolatePoint - Availability: 3.0.0 Returns a point interpolated along a 3D line at a fractional location.
- ST_ConstrainedDelaunayTriangles - Availability: 3.0.0 Return a constrained Delaunay triangulation around the given input geometry.
- ST_TileEnvelope - Availability: 3.0.0 Creates a rectangular Polygon in Web Mercator (SRID:3857) using the XYZ tile system.

Functions enhanced in PostGIS 3.0

- ST_AsMVT - Enhanced: 3.0 - added support for Feature ID. Aggregate function returning a MVT representation of a set of rows.
- ST_Contains - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if every point of B lies in A, and their interiors have a point in common
- ST_ContainsProperly - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if every point of B lies in the interior of A
- ST_CoveredBy - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if every point of A lies in B
- ST_Covers - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if every point of B lies in A
- ST_Crosses - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries have some, but not all, interior points in common
- ST_CurveToLine - Enhanced: 3.0.0 implemented a minimum number of segments per linearized arc to prevent topological collapse. Converts a geometry containing curves to a linear geometry.
- ST_Disjoint - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries have no points in common
- ST_Equals - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries include the same set of points
- ST_GeneratePoints - Enhanced: 3.0.0, added seed parameter Generates a multipoint of random points contained in a Polygon or MultiPolygon.
- ST_GeomFromGeoJSON - Enhanced: 3.0.0 parsed geometry defaults to SRID=4326 if not specified otherwise. Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_LocateBetween - Enhanced: 3.0.0 - added support for POLYGON, TIN, TRIANGLE. Returns the portions of a geometry that match a measure range.
- ST_LocateBetweenElevations - Enhanced: 3.0.0 - added support for POLYGON, TIN, TRIANGLE. Returns the portions of a geometry that lie in an elevation (Z) range.
- ST_Overlaps - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries have the same dimension and intersect, but each has at least one point not in the other
- ST_Relate - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix
- ST_Segmentize - Enhanced: 3.0.0 Segmentize geometry now produces equal-length subsegments Returns a modified geometry/geography having no segment longer than a given distance.
- ST_Touches - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if two geometries have at least one point in common, but their interiors do not intersect
- ST_Within - Enhanced: 3.0.0 enabled support for GEOMETRYCOLLECTION Tests if every point of A lies in B, and their interiors have a point in common

Functions changed in PostGIS 3.0

- PostGIS_Extensions_Upgrade - Changed: 3.0.0 to repackage loose extensions and support postgis_raster. Packages and upgrades PostGIS extensions (e.g. postgis_raster,postgis_topology, postgis_sfcgal) to given or latest version.
- ST_3DDistance - Changed: 3.0.0 - SFCGAL version removed Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DIntersects - Changed: 3.0.0 SFCGAL backend removed, GEOS backend supports TINs. Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)
- ST_Area - Changed: 3.0.0 - does not depend on SFCGAL anymore. Returns the area of a polygonal geometry.
- ST_AsGeoJSON - Changed: 3.0.0 support records as input Return a geometry or feature in GeoJSON format.
- ST_AsGeoJSON - Changed: 3.0.0 output SRID if not EPSG:4326. Return a geometry or feature in GeoJSON format.
- ST_AsKML - Changed: 3.0.0 - Removed the "versioned" variant signature Return the geometry as a KML element.
- ST_Distance - Changed: 3.0.0 - does not depend on SFCGAL anymore. Returns the distance between two geometry or geography values.
- ST_Intersection - Changed: 3.0.0 does not depend on SFCGAL. Computes a geometry representing the shared portion of geometries A and B.
- ST_Intersects - Changed: 3.0.0 SFCGAL version removed and native support for 2D TINS added. Tests if two geometries intersect (they have at least one point in common)
- ST_Union - Changed: 3.0.0 does not depend on SFCGAL. Computes a geometry representing the point-set union of the input geometries.

### 13.12.7. PostGIS Functions new or enhanced in 2.5

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.5

- ST_QuantizeCoordinates - Availability: 2.5.0 Sets least significant bits of coordinates to zero
- PostGIS_Extensions_Upgrade - Availability: 2.5.0 Packages and upgrades PostGIS extensions (e.g. postgis_raster,postgis_topology, postgis_sfcgal) to given or latest version.
- ST_Angle - Availability: 2.5.0 Returns the angle between two vectors defined by 3 or 4 points, or 2 lines.
- ST_AsHexWKB - Availability: 2.5.0 Return the Well-Known Binary (WKB) in Hex representation of the raster.
- ST_BandFileSize - Availability: 2.5.0 Returns the file size of a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_BandFileTimestamp - Availability: 2.5.0 Returns the file timestamp of a band stored in file system. If no bandnum specified, 1 is assumed.
- ST_ChaikinSmoothing - Availability: 2.5.0 Returns a smoothed version of a geometry, using the Chaikin algorithm
- ST_FilterByM - Availability: 2.5.0 Removes vertices based on their M value
- ST_Grayscale - Availability: 2.5.0 Creates a new one-8BUI band raster from the source raster and specified bands representing Red, Green and Blue
- ST_LineInterpolatePoints - Availability: 2.5.0 Returns points interpolated along a line at a fractional interval.
- ST_OrientedEnvelope - Availability: 2.5.0. Returns a minimum-area rectangle containing a geometry.
- ST_RastFromHexWKB - Availability: 2.5.0 Return a raster value from a Hex representation of Well-Known Binary (WKB) raster.
- ST_RastFromWKB - Availability: 2.5.0 Return a raster value from a Well-Known Binary (WKB) raster.
- ST_SetBandIndex - Availability: 2.5.0 Update the external band number of an out-db band
- ST_SetBandPath - Availability: 2.5.0 Update the external path and band number of an out-db band

Functions enhanced in PostGIS 2.5

- ST_GeometricMedian - Enhanced: 2.5.0 Added support for M as weight of points. Returns the geometric median of a MultiPoint.
- ST_AsBinary/ST_AsWKB - Enhanced: 2.5.0 Addition of ST_AsWKB Return the Well-Known Binary (WKB) representation of the raster.
- ST_AsMVT - Enhanced: 2.5.0 - added support parallel query. Aggregate function returning a MVT representation of a set of rows.
- ST_AsText - Enhanced: 2.5 - optional parameter precision introduced. Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_BandMetaData - Enhanced: 2.5.0 to include outdbbandnum, filesize and filetimestamp for outdb rasters. Returns basic meta data for a specific raster band. band num 1 is assumed if none-specified.
- ST_Buffer - Enhanced: 2.5.0 - ST_Buffer geometry support was enhanced to allow for side buffering specification side=both|left|right. Computes a geometry covering all points within a given distance from a geometry.
- ST_GeomFromGeoJSON - Enhanced: 2.5.0 can now accept json and jsonb as inputs. Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_Intersects - Enhanced: 2.5.0 Supports GEOMETRYCOLLECTION. Tests if two geometries intersect (they have at least one point in common)
- ST_OffsetCurve - Enhanced: 2.5 - added support for GEOMETRYCOLLECTION and MULTILINESTRING Returns an offset line at a given distance and side from an input line.
- ST_Scale - Enhanced: 2.5.0 support for scaling relative to a local origin (origin parameter) was introduced. Scales a geometry by given factors.
- ST_Split - Enhanced: 2.5.0 support for splitting a polygon by a multiline was introduced. Returns a collection of geometries created by splitting a geometry by another geometry.
- ST_Subdivide - Enhanced: 2.5.0 reuses existing points on polygon split, vertex count is lowered from 8 to 5. Computes a rectilinear subdivision of a geometry.

Functions changed in PostGIS 2.5

- ST_GDALDrivers - Changed: 2.5.0 - add can_read and can_write columns. Returns a list of raster formats supported by PostGIS through GDAL. Only those formats with can_write=True can be used by ST_AsGDALRaster

### 13.12.8. PostGIS Functions new or enhanced in 2.4

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.4

- ST_ForcePolygonCCW - Availability: 2.4.0 Orients all exterior rings counter-clockwise and all interior rings clockwise.
- ST_ForcePolygonCW - Availability: 2.4.0 Orients all exterior rings clockwise and all interior rings counter-clockwise.
- ST_IsPolygonCCW - Availability: 2.4.0 Tests if Polygons have exterior rings oriented counter-clockwise and interior rings oriented clockwise.
- ST_IsPolygonCW - Availability: 2.4.0 Tests if Polygons have exterior rings oriented clockwise and interior rings oriented counter-clockwise.
- ST_AsGeobuf - Availability: 2.4.0 Return a Geobuf representation of a set of rows.
- ST_AsMVT - Availability: 2.4.0 Aggregate function returning a MVT representation of a set of rows.
- ST_AsMVTGeom - Availability: 2.4.0 Transforms a geometry into the coordinate space of a MVT tile.
- ST_Centroid - Availability: 2.4.0 support for geography was introduced. Returns the geometric center of a geometry.
- ST_FrechetDistance - Availability: 2.4.0 - requires GEOS >= 3.7.0 Returns the Fréchet distance between two geometries.
- ST_MakeEmptyCoverage - Availability: 2.4.0 Cover georeferenced area with a grid of empty raster tiles.

Functions enhanced in PostGIS 2.4

- Loader_Generate_Nation_Script - Enhanced: 2.4.1 zip code 5 tabulation area (zcta5) load step was fixed and when enabled, zcta5 data is loaded as a single table called zcta5_all as part of the nation script load. Generates a shell script for the specified platform that loads in the county and state lookup tables.
- Normalize_Address - Enhanced: 2.4.0 norm_addy object includes additional fields zip4 and address_alphanumeric. Given a textual street address, returns a composite norm_addy type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data).
- Pagc_Normalize_Address - Enhanced: 2.4.0 norm_addy object includes additional fields zip4 and address_alphanumeric. Given a textual street address, returns a composite norm_addy type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data). Requires address_standardizer extension.
- Reverse_Geocode - Enhanced: 2.4.1 if optional zcta5 dataset is loaded, the reverse_geocode function can resolve to state and zip even if the specific state data is not loaded. Refer to for details on loading zcta5 data. Takes a geometry point in a known spatial ref sys and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets.
- ST_AsTWKB - Enhanced: 2.4.0 memory and speed improvements. Returns the geometry as TWKB, aka "Tiny Well-Known Binary"
- ST_Covers - Enhanced: 2.4.0 Support for polygon in polygon and line in polygon added for geography type Tests if every point of B lies in A
- ST_CurveToLine - Enhanced: 2.4.0 added support for max-deviation and max-angle tolerance, and for symmetric output. Converts a geometry containing curves to a linear geometry.
- ST_Project - Enhanced: 2.4.0 Allow negative distance and non-normalized azimuth. Returns a point projected from a start point by a distance and bearing (azimuth).
- ST_Reverse - Enhanced: 2.4.0 support for curves was introduced. Return the geometry with vertex order reversed.

Functions changed in PostGIS 2.4

- = - Changed: 2.4.0, in prior versions this was bounding box equality not a geometric equality. If you need bounding box equality, use instead. Returns TRUE if the coordinates and coordinate order geometry/geography A are the same as the coordinates and coordinate order of geometry/geography B.
- ST_Node - Changed: 2.4.0 this function uses GEOSNode internally instead of GEOSUnaryUnion. This may cause the resulting linestrings to have a different order and direction compared to PostGIS < 2.4. Nodes a collection of lines.

### 13.12.9. PostGIS Functions new or enhanced in 2.3

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.3

- ST_GeometricMedian - Availability: 2.3.0 Returns the geometric median of a MultiPoint.
- &&&(geometry,gidx) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a geometry's (cached) n-D bounding box intersects a n-D float precision bounding box (GIDX).
- &&&(gidx,geometry) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a n-D float precision bounding box (GIDX) intersects a geometry's (cached) n-D bounding box.
- &&&(gidx,gidx) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if two n-D float precision bounding boxes (GIDX) intersect each other.
- &&(box2df,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if two 2D float precision bounding boxes (BOX2DF) intersect each other.
- &&(box2df,geometry) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a 2D float precision bounding box (BOX2DF) intersects a geometry's (cached) 2D bounding box.
- &&(geometry,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a geometry's (cached) 2D bounding box intersects a 2D float precision bounding box (BOX2DF).
- @(box2df,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into another 2D float precision bounding box.
- @(box2df,geometry) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a 2D float precision bounding box (BOX2DF) is contained into a geometry's 2D bounding box.
- @(geometry,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a geometry's 2D bounding box is contained into a 2D float precision bounding box (BOX2DF).
- Populate_Topology_Layer - Availability: 2.3.0 Adds missing entries to topology.layer table by reading metadata from topo tables.
- ST_ClusterDBSCAN - Availability: 2.3.0 Window function that returns a cluster id for each input geometry using the DBSCAN algorithm.
- ST_ClusterKMeans - Availability: 2.3.0 Window function that returns a cluster id for each input geometry using the K-means algorithm.
- ST_GeneratePoints - Availability: 2.3.0 Generates a multipoint of random points contained in a Polygon or MultiPolygon.
- ST_MakeLine - Availability: 2.3.0 - Support for MultiPoint input elements was introduced Creates a LineString from Point, MultiPoint, or LineString geometries.
- ST_MinimumBoundingRadius - Availability - 2.3.0 Returns the center point and radius of the smallest circle that contains a geometry.
- ST_MinimumClearance - Availability: 2.3.0 Returns the minimum clearance of a geometry, a measure of a geometry's robustness.
- ST_MinimumClearanceLine - Availability: 2.3.0 - requires GEOS >= 3.6.0 Returns the two-point LineString spanning a geometry's minimum clearance.
- ST_Normalize - Availability: 2.3.0 Return the geometry in its canonical form.
- ST_Points - Availability: 2.3.0 Returns a MultiPoint containing the coordinates of a geometry.
- ST_VoronoiLines - Availability: 2.3.0 Returns the boundaries of the Voronoi diagram of the vertices of a geometry.
- ST_VoronoiPolygons - Availability: 2.3.0 Returns the cells of the Voronoi diagram of the vertices of a geometry.
- ST_WrapX - Availability: 2.3.0 requires GEOS Wrap a geometry around an X value.
- TopoGeom_addElement - Availability: 2.3 Adds an element to the definition of a TopoGeometry.
- TopoGeom_remElement - Availability: 2.3 Removes an element from the definition of a TopoGeometry.
- ~(box2df,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a 2D float precision bounding box (BOX2DF) contains another 2D float precision bounding box (BOX2DF).
- ~(box2df,geometry) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a 2D float precision bounding box (BOX2DF) contains a geometry's 2D bonding box.
- ~(geometry,box2df) - Availability: 2.3.0 support for Block Range INdexes (BRIN) was introduced. Requires PostgreSQL 9.5+. Returns TRUE if a geometry's 2D bonding box contains a 2D float precision bounding box (GIDX).

Functions enhanced in PostGIS 2.3

- ST_Contains - Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon. Tests if every point of B lies in A, and their interiors have a point in common
- ST_Covers - Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon. Tests if every point of B lies in A
- ST_Expand - Enhanced: 2.3.0 support was added to expand a box by different amounts in different dimensions. Returns a bounding box expanded from another bounding box or a geometry.
- ST_Intersects - Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon. Tests if two geometries intersect (they have at least one point in common)
- ST_Segmentize - Enhanced: 2.3.0 Segmentize geography now produces equal-length subsegments Returns a modified geometry/geography having no segment longer than a given distance.
- ST_Transform - Enhanced: 2.3.0 support for direct PROJ.4 text was introduced. Return a new geometry with coordinates transformed to a different spatial reference system.
- ST_Within - Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon. Tests if every point of A lies in B, and their interiors have a point in common

Functions changed in PostGIS 2.3

- ST_PointN - Changed: 2.3.0 : negative indexing available (-1 is last point) Returns the Nth point in the first LineString or circular LineString in a geometry.

### 13.12.10. PostGIS Functions new or enhanced in 2.2

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.2

- <<->> - Availability: 2.2.0 -- KNN only available for PostgreSQL 9.1+ Returns the n-D distance between the A and B geometries or bounding boxes
- ST_3DDifference - Availability: 2.2.0 Perform 3D difference
- ST_3DUnion - Availability: 2.2.0 Perform 3D union.
- ST_ApproximateMedialAxis - Availability: 2.2.0 Compute the approximate medial axis of an areal geometry.
- ST_AsEncodedPolyline - Availability: 2.2.0 Returns an Encoded Polyline from a LineString geometry.
- ST_AsTWKB - Availability: 2.2.0 Returns the geometry as TWKB, aka "Tiny Well-Known Binary"
- ST_BoundingDiagonal - Availability: 2.2.0 Returns the diagonal of a geometry's bounding box.
- ST_CPAWithin - Availability: 2.2.0 Tests if the closest point of approach of two trajectoriesis within the specified distance.
- ST_ClipByBox2D - Availability: 2.2.0 Computes the portion of a geometry falling within a rectangle.
- ST_ClosestPointOfApproach - Availability: 2.2.0 Returns a measure at the closest point of approach of two trajectories.
- ST_ClusterIntersecting - Availability: 2.2.0 Aggregate function that clusters input geometries into connected sets.
- ST_ClusterWithin - Availability: 2.2.0 Aggregate function that clusters geometries by separation distance.
- ST_CountAgg - Availability: 2.2.0 Aggregate. Returns the number of pixels in a given band of a set of rasters. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the NODATA value.
- ST_CreateOverview - Availability: 2.2.0 Create an reduced resolution version of a given raster coverage.
- ST_DistanceCPA - Availability: 2.2.0 Returns the distance between the closest point of approach of two trajectories.
- ST_ForceCurve - Availability: 2.2.0 Upcast a geometry into its curved type, if applicable.
- ST_IsPlanar - Availability: 2.2.0: This was documented in 2.1.0 but got accidentally left out in 2.1 release. Check if a surface is or not planar
- ST_IsSolid - Availability: 2.2.0 Test if the geometry is a solid. No validity check is performed.
- ST_IsValidTrajectory - Availability: 2.2.0 Tests if the geometry is a valid trajectory.
- ST_LineFromEncodedPolyline - Availability: 2.2.0 Creates a LineString from an Encoded Polyline.
- ST_MakeSolid - Availability: 2.2.0 Cast the geometry into a solid. No check is performed. To obtain a valid solid, the input geometry must be a closed Polyhedral Surface or a closed TIN.
- ST_MapAlgebra (callback function version) - Availability: 2.2.0: Ability to add a mask Callback function version - Returns a one-band raster given one or more input rasters, band indexes and one user-specified callback function.
- ST_MemSize - Availability: 2.2.0 Returns the amount of space (in bytes) the raster takes.
- ST_RemoveRepeatedPoints - Availability: 2.2.0 Returns a version of a geometry with duplicate points removed.
- ST_Retile - Availability: 2.2.0 Return a set of configured tiles from an arbitrarily tiled raster coverage.
- ST_SetEffectiveArea - Availability: 2.2.0 Sets the effective area for each vertex, using the Visvalingam-Whyatt algorithm.
- ST_SimplifyVW - Availability: 2.2.0 Returns a simplified representation of a geometry, using the Visvalingam-Whyatt algorithm
- ST_Subdivide - Availability: 2.2.0 Computes a rectilinear subdivision of a geometry.
- ST_SummaryStatsAgg - Availability: 2.2.0 Aggregate. Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a set of raster. Band 1 is assumed is no band is specified.
- ST_SwapOrdinates - Availability: 2.2.0 Returns a version of the given geometry with given ordinate values swapped.
- ST_Volume - Availability: 2.2.0 Computes the volume of a 3D solid. If applied to surface (even closed) geometries will return 0.
- parse_address - Availability: 2.2.0 Takes a 1 line address and breaks into parts
- postgis.enable_outdb_rasters - Availability: 2.2.0 A boolean configuration option to enable access to out-db raster bands.
- postgis.gdal_datapath - Availability: 2.2.0 A configuration option to assign the value of GDAL's GDAL_DATA option. If not set, the environmentally set GDAL_DATA variable is used.
- postgis.gdal_enabled_drivers - Availability: 2.2.0 A configuration option to set the enabled GDAL drivers in the PostGIS environment. Affects the GDAL configuration variable GDAL_SKIP.
- standardize_address - Availability: 2.2.0 Returns an stdaddr form of an input address utilizing lex, gaz, and rule tables.
- |=| - Availability: 2.2.0. Index-supported only available for PostgreSQL 9.5+ Returns the distance between A and B trajectories at their closest point of approach.

Functions enhanced in PostGIS 2.2

- <-> - Enhanced: 2.2.0 -- True KNN ("K nearest neighbor") behavior for geometry and geography for PostgreSQL 9.5+. Note for geography KNN is based on sphere rather than spheroid. For PostgreSQL 9.4 and below, geography support is new but only supports centroid box. Returns the 2D distance between A and B.
- AsTopoJSON - Enhanced: 2.2.1 added support for puntal inputs Returns the TopoJSON representation of a topogeometry.
- ST_Area - Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature. Returns the area of a polygonal geometry.
- ST_AsX3D - Enhanced: 2.2.0: Support for GeoCoordinates and axis (x/y, long/lat) flipping. Look at options for details. Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_Azimuth - Enhanced: 2.2.0 measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature. Returns the north-based azimuth of a line between two points.
- ST_Distance - Enhanced: 2.2.0 - measurement on spheroid performed with GeographicLib for improved accuracy and robustness. Requires PROJ >= 4.9.0 to take advantage of the new feature. Returns the distance between two geometry or geography values.
- ST_Scale - Enhanced: 2.2.0 support for scaling all dimension (factor parameter) was introduced. Scales a geometry by given factors.
- ST_Split - Enhanced: 2.2.0 support for splitting a line by a multiline, a multipoint or (multi)polygon boundary was introduced. Returns a collection of geometries created by splitting a geometry by another geometry.
- ST_Summary - Enhanced: 2.2.0 Added support for TIN and Curves Returns a text summary of the contents of a geometry.

Functions changed in PostGIS 2.2

- <-> - Changed: 2.2.0 -- For PostgreSQL 9.5 users, old Hybrid syntax may be slower, so you'll want to get rid of that hack if you are running your code only on PostGIS 2.2+ 9.5+. See examples below. Returns the 2D distance between A and B.
- Get_Geocode_Setting - Changed: 2.2.0 : default settings are now kept in a table called geocode_settings_default. Use customized settingsa are in geocode_settings and only contain those that have been set by user. Returns value of specific setting stored in tiger.geocode_settings table.
- ST_3DClosestPoint - Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z. Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DDistance - Changed: 2.2.0 - In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z. Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DLongestLine - Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z. Returns the 3D longest line between two geometries
- ST_3DMaxDistance - Changed: 2.2.0 - In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z. Returns the 3D cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DShortestLine - Changed: 2.2.0 - if 2 2D geometries are input, a 2D point is returned (instead of old behavior assuming 0 for missing Z). In case of 2D and 3D, Z is no longer assumed to be 0 for missing Z. Returns the 3D shortest line between two geometries
- ST_DistanceSphere - Changed: 2.2.0 In prior versions this used to be called ST_Distance_Sphere Returns minimum distance in meters between two lon/lat geometries using a spherical earth model.
- ST_DistanceSpheroid - Changed: 2.2.0 In prior versions this was called ST_Distance_Spheroid Returns the minimum distance between two lon/lat geometries using a spheroidal earth model.
- ST_Equals - Changed: 2.2.0 Returns true even for invalid geometries if they are binary equal Tests if two geometries include the same set of points
- ST_LengthSpheroid - Changed: 2.2.0 In prior versions this was called ST_Length_Spheroid and had the alias ST_3DLength_Spheroid Returns the 2D or 3D length/perimeter of a lon/lat geometry on a spheroid.
- ST_MemSize - Changed: 2.2.0 name changed to ST_MemSize to follow naming convention. Returns the amount of memory space a geometry takes.
- ST_PointInsideCircle - Changed: 2.2.0 In prior versions this was called ST_Point_Inside_Circle Tests if a point geometry is inside a circle defined by a center and radius
- ValidateTopology - Changed: 2.2.0 values for id1 and id2 were swapped for 'edge crosses node' to be consistent with error description. Returns a set of validatetopology_returntype objects detailing issues with topology.

### 13.12.11. PostGIS Functions new or enhanced in 2.1

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.1

- = - Availability: 2.1.0 Returns TRUE if A's bounding box is the same as B's. Uses double precision bounding box.
- AsTopoJSON - Availability: 2.1.0 Returns the TopoJSON representation of a topogeometry.
- Drop_Nation_Tables_Generate_Script - Availability: 2.1.0 Generates a script that drops all tables in the specified schema that start with county_all, state_all or state code followed by county or state.
- Get_Geocode_Setting - Availability: 2.1.0 Returns value of specific setting stored in tiger.geocode_settings table.
- Loader_Generate_Nation_Script - Availability: 2.1.0 Generates a shell script for the specified platform that loads in the county and state lookup tables.
- Pagc_Normalize_Address - Availability: 2.1.0 Given a textual street address, returns a composite norm_addy type that has road suffix, prefix and type standardized, street, streetname etc. broken into separate fields. This function will work with just the lookup data packaged with the tiger_geocoder (no need for tiger census data). Requires address_standardizer extension.
- ST_3DArea - Availability: 2.1.0 Computes area of 3D surface geometries. Will return 0 for solids.
- ST_3DIntersection - Availability: 2.1.0 Perform 3D intersection
- ST_Box2dFromGeoHash - Availability: 2.1.0 Return a BOX2D from a GeoHash string.
- ST_ColorMap - Availability: 2.1.0 Creates a new raster of up to four 8BUI bands (grayscale, RGB, RGBA) from the source raster and a specified band. Band 1 is assumed if not specified.
- ST_Contains - Availability: 2.1.0 Return true if no points of raster rastB lie in the exterior of raster rastA and at least one point of the interior of rastB lies in the interior of rastA.
- ST_ContainsProperly - Availability: 2.1.0 Return true if rastB intersects the interior of rastA but not the boundary or exterior of rastA.
- ST_CoveredBy - Availability: 2.1.0 Return true if no points of raster rastA lie outside raster rastB.
- ST_Covers - Availability: 2.1.0 Return true if no points of raster rastB lie outside raster rastA.
- ST_DFullyWithin - Availability: 2.1.0 Return true if rasters rastA and rastB are fully within the specified distance of each other.
- ST_DWithin - Availability: 2.1.0 Return true if rasters rastA and rastB are within the specified distance of each other.
- ST_DelaunayTriangles - Availability: 2.1.0 Returns the Delaunay triangulation of the vertices of a geometry.
- ST_Disjoint - Availability: 2.1.0 Return true if raster rastA does not spatially intersect rastB.
- ST_DumpValues - Availability: 2.1.0 Get the values of the specified band as a 2-dimension array.
- ST_Extrude - Availability: 2.1.0 Extrude a surface to a related volume
- ST_ForceLHR - Availability: 2.1.0 Force LHR orientation
- ST_FromGDALRaster - Availability: 2.1.0 Returns a raster from a supported GDAL raster file.
- ST_GeomFromGeoHash - Availability: 2.1.0 Return a geometry from a GeoHash string.
- ST_InvDistWeight4ma - Availability: 2.1.0 Raster processing function that interpolates a pixel's value from the pixel's neighborhood.
- ST_MapAlgebra (callback function version) - Availability: 2.1.0 Callback function version - Returns a one-band raster given one or more input rasters, band indexes and one user-specified callback function.
- ST_MapAlgebra (expression version) - Availability: 2.1.0 Expression version - Returns a one-band raster given one or two input rasters, band indexes and one or more user-specified SQL expressions.
- ST_MinConvexHull - Availability: 2.1.0 Return the convex hull geometry of the raster excluding NODATA pixels.
- ST_MinDist4ma - Availability: 2.1.0 Raster processing function that returns the minimum distance (in number of pixels) between the pixel of interest and a neighboring pixel with value.
- ST_MinkowskiSum - Availability: 2.1.0 Performs Minkowski sum
- ST_NearestValue - Availability: 2.1.0 Returns the nearest non-NODATA value of a given band's pixel specified by a columnx and rowy or a geometric point expressed in the same spatial reference coordinate system as the raster.
- ST_Neighborhood - Availability: 2.1.0 Returns a 2-D double precision array of the non-NODATA values around a given band's pixel specified by either a columnX and rowY or a geometric point expressed in the same spatial reference coordinate system as the raster.
- ST_NotSameAlignmentReason - Availability: 2.1.0 Returns text stating if rasters are aligned and if not aligned, a reason why.
- ST_Orientation - Availability: 2.1.0 Determine surface orientation
- ST_Overlaps - Availability: 2.1.0 Return true if raster rastA and rastB intersect but one does not completely contain the other.
- ST_PixelAsCentroid - Availability: 2.1.0 Returns the centroid (point geometry) of the area represented by a pixel.
- ST_PixelAsCentroids - Availability: 2.1.0 Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.
- ST_PixelAsPoint - Availability: 2.1.0 Returns a point geometry of the pixel's upper-left corner.
- ST_PixelAsPoints - Availability: 2.1.0 Returns a point geometry for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The coordinates of the point geometry are of the pixel's upper-left corner.
- ST_PixelOfValue - Availability: 2.1.0 Get the columnx, rowy coordinates of the pixel whose value equals the search value.
- ST_PointFromGeoHash - Availability: 2.1.0 Return a point from a GeoHash string.
- ST_RasterToWorldCoord - Availability: 2.1.0 Returns the raster's upper left corner as geometric X and Y (longitude and latitude) given a column and row. Column and row starts at 1.
- ST_Resize - Availability: 2.1.0 Requires GDAL 1.6.1+ Resize a raster to a new width/height
- ST_Roughness - Availability: 2.1.0 Returns a raster with the calculated "roughness" of a DEM.
- ST_SetValues - Availability: 2.1.0 Returns modified raster resulting from setting the values of a given band.
- ST_Simplify - Availability: 2.1.0 Returns a "simplified" geometry version of the given TopoGeometry using the Douglas-Peucker algorithm.
- ST_StraightSkeleton - Availability: 2.1.0 Compute a straight skeleton from a geometry
- ST_Summary - Availability: 2.1.0 Returns a text summary of the contents of the raster.
- ST_TPI - Availability: 2.1.0 Returns a raster with the calculated Topographic Position Index.
- ST_TRI - Availability: 2.1.0 Returns a raster with the calculated Terrain Ruggedness Index.
- ST_Tesselate - Availability: 2.1.0 Perform surface Tessellation of a polygon or polyhedralsurface and returns as a TIN or collection of TINS
- ST_Tile - Availability: 2.1.0 Returns a set of rasters resulting from the split of the input raster based upon the desired dimensions of the output rasters.
- ST_Touches - Availability: 2.1.0 Return true if raster rastA and rastB have at least one point in common but their interiors do not intersect.
- ST_Union - Availability: 2.1.0 ST_Union(rast, unionarg) variant was introduced. Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- ST_Within - Availability: 2.1.0 Return true if no points of raster rastA lie in the exterior of raster rastB and at least one point of the interior of rastA lies in the interior of rastB.
- ST_WorldToRasterCoord - Availability: 2.1.0 Returns the upper left corner as column and row given geometric X and Y (longitude and latitude) or a point geometry expressed in the spatial reference coordinate system of the raster.
- Set_Geocode_Setting - Availability: 2.1.0 Sets a setting that affects behavior of geocoder functions.
- UpdateRasterSRID - Availability: 2.1.0 Change the SRID of all rasters in the user-specified column and table.
- clearTopoGeom - Availability: 2.1 Clears the content of a topo geometry.
- postgis.backend - Availability: 2.1.0 The backend to service a function where GEOS and SFCGAL overlap. Options: geos or sfcgal. Defaults to geos.
- postgis_sfcgal_version - Availability: 2.1.0 Returns the version of SFCGAL in use

Functions enhanced in PostGIS 2.1

- ST_AddBand - Enhanced: 2.1.0 support for addbandarg added. Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.
- ST_AddBand - Enhanced: 2.1.0 support for new out-db bands added. Returns a raster with the new band(s) of given type added with given initial value in the given index location. If no index is specified, the band is added to the end.
- ST_AsBinary/ST_AsWKB - Enhanced: 2.1.0 Addition of outasin Return the Well-Known Binary (WKB) representation of the raster.
- ST_AsGML - Enhanced: 2.1.0 id support was introduced, for GML 3. Return the geometry as a GML version 2 or 3 element.
- ST_Aspect - Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional interpolate_nodata function parameter Returns the aspect (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_Boundary - Enhanced: 2.1.0 support for Triangle was introduced Returns the boundary of a geometry.
- ST_Clip - Enhanced: 2.1.0 Rewritten in C Returns the raster clipped by the input geometry. If band number is not specified, all bands are processed. If crop is not specified or TRUE, the output raster is cropped. If touched is set to TRUE, then touched pixels are included, otherwise only if the center of the pixel is in the geometry it is included.
- ST_DWithin - Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details. Tests if two geometries are within a given distance
- ST_DWithin - Enhanced: 2.1.0 support for curved geometries was introduced. Tests if two geometries are within a given distance
- ST_Distance - Enhanced: 2.1.0 improved speed for geography. See Making Geography faster for details. Returns the distance between two geometry or geography values.
- ST_Distance - Enhanced: 2.1.0 - support for curved geometries was introduced. Returns the distance between two geometry or geography values.
- ST_Distinct4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the number of unique pixel values in a neighborhood.
- ST_DumpPoints - Enhanced: 2.1.0 Faster speed. Reimplemented as native-C. Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_HillShade - Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional interpolate_nodata function parameter Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.
- ST_MakeValid - Enhanced: 2.1.0, added support for GEOMETRYCOLLECTION and MULTIPOINT. Attempts to make an invalid geometry valid without losing vertices.
- ST_Max4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the maximum pixel value in a neighborhood.
- ST_Mean4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the mean pixel value in a neighborhood.
- ST_Min4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the minimum pixel value in a neighborhood.
- ST_PixelAsPolygons - Enhanced: 2.1.0 exclude_nodata_value optional argument was added. Returns the polygon geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.
- ST_Polygon - Enhanced: 2.1.0 Improved Speed (fully C-Based) and the returning multipolygon is ensured to be valid. Returns a multipolygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.
- ST_Range4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the range of pixel values in a neighborhood.
- ST_SameAlignment - Enhanced: 2.1.0 addition of Aggegrate variant Returns true if rasters have same skew, scale, spatial ref, and offset (pixels can be put on same grid without cutting into pixels) and false if they don't with notice detailing issue.
- ST_Segmentize - Enhanced: 2.1.0 support for geography was introduced. Returns a modified geometry/geography having no segment longer than a given distance.
- ST_SetGeoReference - Enhanced: 2.1.0 Addition of ST_SetGeoReference(raster, double precision, ...) variant Set Georeference 6 georeference parameters in a single call. Numbers should be separated by white space. Accepts inputs in GDAL or ESRI format. Default is GDAL.
- ST_SetValue - Enhanced: 2.1.0 Geometry variant of ST_SetValue() now supports any geometry type, not just point. The geometry variant is a wrapper around the geomval[] variant of ST_SetValues() Returns modified raster resulting from setting the value of a given band in a given columnx, rowy pixel or the pixels that intersect a particular geometry. Band numbers start at 1 and assumed to be 1 if not specified.
- ST_Slope - Enhanced: 2.1.0 Uses ST_MapAlgebra() and added optional units, scale, interpolate_nodata function parameters Returns the slope (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_StdDev4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the standard deviation of pixel values in a neighborhood.
- ST_Sum4ma - Enhanced: 2.1.0 Addition of Variant 2 Raster processing function that calculates the sum of all pixel values in a neighborhood.
- ST_Summary - Enhanced: 2.1.0 S flag to denote if has a known spatial reference system Returns a text summary of the contents of a geometry.
- ST_Transform - Enhanced: 2.1.0 Addition of ST_Transform(rast, alignto) variant Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.
- ST_Union - Enhanced: 2.1.0 Improved Speed (fully C-Based). Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- ST_Union - Enhanced: 2.1.0 ST_Union(rast) (variant 1) unions all bands of all input rasters. Prior versions of PostGIS assumed the first band. Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- ST_Union - Enhanced: 2.1.0 ST_Union(rast, uniontype) (variant 4) unions all bands of all input rasters. Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- toTopoGeom - Enhanced: 2.1.0 adds the version taking an existing TopoGeometry. Converts a simple Geometry into a topo geometry.

Functions changed in PostGIS 2.1

- ST_Aspect - Changed: 2.1.0 In prior versions, return values were in radians. Now, return values default to degrees Returns the aspect (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_EstimatedExtent - Changed: 2.1.0. Up to 2.0.x this was called ST_Estimated_Extent. Returns the estimated extent of a spatial table.
- ST_Force2D - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_2D. Force the geometries into a "2-dimensional mode".
- ST_Force3D - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3D. Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DM - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DM. Force the geometries into XYM mode.
- ST_Force3DZ - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_3DZ. Force the geometries into XYZ mode.
- ST_Force4D - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_4D. Force the geometries into XYZM mode.
- ST_ForceCollection - Changed: 2.1.0. Up to 2.0.x this was called ST_Force_Collection. Convert the geometry into a GEOMETRYCOLLECTION.
- ST_HillShade - Changed: 2.1.0 In prior versions, azimuth and altitude were expressed in radians. Now, azimuth and altitude are expressed in degrees Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.
- ST_LineInterpolatePoint - Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Interpolate_Point. Returns a point interpolated along a line at a fractional location.
- ST_LineLocatePoint - Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Locate_Point. Returns the fractional location of the closest point on a line to a point.
- ST_LineSubstring - Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Substring. Returns the part of a line between two fractional locations.
- ST_PixelAsCentroids - Changed: 2.1.1 Changed behavior of exclude_nodata_value. Returns the centroid (point geometry) for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The point geometry is the centroid of the area represented by a pixel.
- ST_PixelAsPoints - Changed: 2.1.1 Changed behavior of exclude_nodata_value. Returns a point geometry for each pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel. The coordinates of the point geometry are of the pixel's upper-left corner.
- ST_PixelAsPolygons - Changed: 2.1.1 Changed behavior of exclude_nodata_value. Returns the polygon geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.
- ST_Polygon - Changed: 2.1.0 In prior versions would sometimes return a polygon, changed to always return multipolygon. Returns a multipolygon geometry formed by the union of pixels that have a pixel value that is not no data value. If no band number is specified, band num defaults to 1.
- ST_RasterToWorldCoordX - Changed: 2.1.0 In prior versions, this was called ST_Raster2WorldCoordX Returns the geometric X coordinate upper left of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_RasterToWorldCoordY - Changed: 2.1.0 In prior versions, this was called ST_Raster2WorldCoordY Returns the geometric Y coordinate upper left corner of a raster, column and row. Numbering of columns and rows starts at 1.
- ST_Rescale - Changed: 2.1.0 Works on rasters with no SRID Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline, Lanczos, Max or Min resampling algorithm. Default is NearestNeighbor.
- ST_Reskew - Changed: 2.1.0 Works on rasters with no SRID Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Segmentize - Changed: 2.1.0 As a result of the introduction of geography support, the usage ST_Segmentize('LINESTRING(1 2, 3 4)', 0.5) causes an ambiguous function error. The input needs to be properly typed as a geometry or geography. Use ST_GeomFromText, ST_GeogFromText or a cast to the required type (e.g. ST_Segmentize('LINESTRING(1 2, 3 4)'::geometry, 0.5) ) Returns a modified geometry/geography having no segment longer than a given distance.
- ST_Slope - Changed: 2.1.0 In prior versions, return values were in radians. Now, return values default to degrees Returns the slope (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_SnapToGrid - Changed: 2.1.0 Works on rasters with no SRID Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_WorldToRasterCoordX - Changed: 2.1.0 In prior versions, this was called ST_World2RasterCoordX Returns the column in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.
- ST_WorldToRasterCoordY - Changed: 2.1.0 In prior versions, this was called ST_World2RasterCoordY Returns the row in the raster of the point geometry (pt) or a X and Y world coordinate (xw, yw) represented in world spatial reference system of raster.

### 13.12.12. PostGIS Functions new or enhanced in 2.0

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 2.0

- && - Availability: 2.0.0 Returns TRUE if A's bounding box intersects B's bounding box.
- &&& - Availability: 2.0.0 Returns TRUE if A's n-D bounding box intersects B's n-D bounding box.
- <#> - Availability: 2.0.0 -- KNN only available for PostgreSQL 9.1+ Returns the 2D distance between A and B bounding boxes.
- <-> - Availability: 2.0.0 -- Weak KNN provides nearest neighbors based on geometry centroid distances instead of true distances. Exact results for points, inexact for all other types. Available for PostgreSQL 9.1+ Returns the 2D distance between A and B.
- @ - Availability: 2.0.0 raster @ raster, raster @ geometry introduced Returns TRUE if A's bounding box is contained by B's. Uses double precision bounding box.
- @ - Availability: 2.0.5 geometry @ raster introduced Returns TRUE if A's bounding box is contained by B's. Uses double precision bounding box.
- AddEdge - Availability: 2.0.0 Adds a linestring edge to the edge table and associated start and end points to the point nodes table of the specified topology schema using the specified linestring geometry and returns the edgeid of the new (or existing) edge.
- AddFace - Availability: 2.0.0 Registers a face primitive to a topology and gets its identifier.
- AddNode - Availability: 2.0.0 Adds a point node to the node table in the specified topology schema and returns the nodeid of new node. If point already exists as node, the existing nodeid is returned.
- AddOverviewConstraints - Availability: 2.0.0 Tag a raster column as being an overview of another.
- AddRasterConstraints - Availability: 2.0.0 Adds raster constraints to a loaded raster table for a specific column that constrains spatial ref, scaling, blocksize, alignment, bands, band type and a flag to denote if raster column is regularly blocked. The table must be loaded with data for the constraints to be inferred. Returns true if the constraint setting was accomplished and issues a notice otherwise.
- AsGML - Availability: 2.0.0 Returns the GML representation of a topogeometry.
- CopyTopology - Availability: 2.0.0 Makes a copy of a topology (nodes, edges, faces, layers and TopoGeometries) into a new schema
- DropOverviewConstraints - Availability: 2.0.0 Untag a raster column from being an overview of another.
- DropRasterConstraints - Availability: 2.0.0 Drops PostGIS raster constraints that refer to a raster table column. Useful if you need to reload data or update your raster column data.
- Drop_Indexes_Generate_Script - Availability: 2.0.0 Generates a script that drops all non-primary key and non-unique indexes on tiger schema and user specified schema. Defaults schema to tiger_data if no schema is specified.
- Drop_State_Tables_Generate_Script - Availability: 2.0.0 Generates a script that drops all tables in the specified schema that are prefixed with the state abbreviation. Defaults schema to tiger_data if no schema is specified.
- Geocode_Intersection - Availability: 2.0.0 Takes in 2 streets that intersect and a state, city, zip, and outputs a set of possible locations on the first cross street that is at the intersection, also includes a geomout as the point location in NAD 83 long lat, a normalized_address (addy) for each location, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10. Uses Tiger data (edges, faces, addr), PostgreSQL fuzzy string matching (soundex, levenshtein).
- GetEdgeByPoint - Availability: 2.0.0 Finds the edge-id of an edge that intersects a given point.
- GetFaceByPoint - Availability: 2.0.0 Finds face intersecting a given point.
- GetNodeByPoint - Availability: 2.0.0 Finds the node-id of a node at a point location.
- GetNodeEdges - Availability: 2.0 Returns an ordered set of edges incident to the given node.
- GetRingEdges - Availability: 2.0.0 Returns the ordered set of signed edge identifiers met by walking on ana given edge side.
- GetTopoGeomElements - Availability: 2.0.0 Returns a set of topoelement objects containing the topological element_id,element_type of the given TopoGeometry (primitive elements).
- GetTopologySRID - Availability: 2.0.0 Returns the SRID of a topology in the topology.topology table given the name of the topology.
- Get_Tract - Availability: 2.0.0 Returns census tract or field from tract table of where the geometry is located. Default to returning short name of tract.
- Install_Missing_Indexes - Availability: 2.0.0 Finds all tables with key columns used in geocoder joins and filter conditions that are missing used indexes on those columns and will add them.
- Loader_Generate_Census_Script - Availability: 2.0.0 Generates a shell script for the specified platform for the specified states that will download Tiger census state tract, bg, and tabblocks data tables, stage and load into tiger_data schema. Each state script is returned as a separate record.
- Loader_Generate_Script - Availability: 2.0.0 to support Tiger 2010 structured data and load census tract (tract), block groups (bg), and blocks (tabblocks) tables . Generates a shell script for the specified platform for the specified states that will download Tiger data, stage and load into tiger_data schema. Each state script is returned as a separate record. Latest version supports Tiger 2010 structural changes and also loads census tract, block groups, and blocks tables.
- Missing_Indexes_Generate_Script - Availability: 2.0.0 Finds all tables with key columns used in geocoder joins that are missing indexes on those columns and will output the SQL DDL to define the index for those tables.
- Polygonize - Availability: 2.0.0 Finds and registers all faces defined by topology edges.
- Reverse_Geocode - Availability: 2.0.0 Takes a geometry point in a known spatial ref sys and returns a record containing an array of theoretically possible addresses and an array of cross streets. If include_strnum_range = true, includes the street range in the cross streets.
- ST_3DClosestPoint - Availability: 2.0.0 Returns the 3D point on g1 that is closest to g2. This is the first point of the 3D shortest line.
- ST_3DDFullyWithin - Availability: 2.0.0 Tests if two 3D geometries are entirely within a given 3D distance
- ST_3DDWithin - Availability: 2.0.0 Tests if two 3D geometries are within a given 3D distance
- ST_3DDistance - Availability: 2.0.0 Returns the 3D cartesian minimum distance (based on spatial ref) between two geometries in projected units.
- ST_3DIntersects - Availability: 2.0.0 Tests if two geometries spatially intersect in 3D - only for points, linestrings, polygons, polyhedral surface (area)
- ST_3DLongestLine - Availability: 2.0.0 Returns the 3D longest line between two geometries
- ST_3DMaxDistance - Availability: 2.0.0 Returns the 3D cartesian maximum distance (based on spatial ref) between two geometries in projected units.
- ST_3DShortestLine - Availability: 2.0.0 Returns the 3D shortest line between two geometries
- ST_AddEdgeModFace - Availability: 2.0 Add a new edge and, if in doing so it splits a face, modify the original face and add a new face.
- ST_AddEdgeNewFaces - Availability: 2.0 Add a new edge and, if in doing so it splits a face, delete the original face and replace it with two new faces.
- ST_AsGDALRaster - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile in the designated GDAL Raster format. Raster formats are one of those supported by your compiled library. Use ST_GDALDrivers() to get a list of formats supported by your library.
- ST_AsJPEG - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile selected bands as a single Joint Photographic Exports Group (JPEG) image (byte array). If no band is specified and 1 or more than 3 bands, then only the first band is used. If only 3 bands then all 3 bands are used and mapped to RGB.
- ST_AsLatLonText - Availability: 2.0 Return the Degrees, Minutes, Seconds representation of the given point.
- ST_AsPNG - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster tile selected bands as a single portable network graphics (PNG) image (byte array). If 1, 3, or 4 bands in raster and no bands are specified, then all bands are used. If more 2 or more than 4 bands and no bands specified, then only band 1 is used. Bands are mapped to RGB or RGBA space.
- ST_AsRaster - Availability: 2.0.0 - requires GDAL >= 1.6.0. Converts a PostGIS geometry to a PostGIS raster.
- ST_AsTIFF - Availability: 2.0.0 - requires GDAL >= 1.6.0. Return the raster selected bands as a single TIFF image (byte array). If no band is specified or any of specified bands does not exist in the raster, then will try to use all bands.
- ST_AsX3D - Availability: 2.0.0: ISO-IEC-19776-1.2-X3DEncodings-XML Returns a Geometry in X3D xml node element format: ISO-IEC-19776-1.2-X3DEncodings-XML
- ST_Aspect - Availability: 2.0.0 Returns the aspect (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_Band - Availability: 2.0.0 Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters.
- ST_BandIsNoData - Availability: 2.0.0 Returns true if the band is filled with only nodata values.
- ST_Clip - Availability: 2.0.0 Returns the raster clipped by the input geometry. If band number is not specified, all bands are processed. If crop is not specified or TRUE, the output raster is cropped. If touched is set to TRUE, then touched pixels are included, otherwise only if the center of the pixel is in the geometry it is included.
- ST_CollectionHomogenize - Availability: 2.0.0 Returns the simplest representation of a geometry collection.
- ST_ConcaveHull - Availability: 2.0.0 Computes a possibly concave geometry that contains all input geometry vertices
- ST_Count - Availability: 2.0.0 Returns the number of pixels in a given band of a raster or raster coverage. If no band is specified defaults to band 1. If exclude_nodata_value is set to true, will only count pixels that are not equal to the nodata value.
- ST_CreateTopoGeo - Availability: 2.0 Adds a collection of geometries to a given empty topology and returns a message detailing success.
- ST_Distinct4ma - Availability: 2.0.0 Raster processing function that calculates the number of unique pixel values in a neighborhood.
- ST_FlipCoordinates - Availability: 2.0.0 Returns a version of a geometry with X and Y axis flipped.
- ST_GDALDrivers - Availability: 2.0.0 - requires GDAL >= 1.6.0. Returns a list of raster formats supported by PostGIS through GDAL. Only those formats with can_write=True can be used by ST_AsGDALRaster
- ST_GeomFromGeoJSON - Availability: 2.0.0 requires - JSON-C >= 0.9 Takes as input a geojson representation of a geometry and outputs a PostGIS geometry object
- ST_GetFaceEdges - Availability: 2.0 Returns a set of ordered edges that bound aface.
- ST_HasNoBand - Availability: 2.0.0 Returns true if there is no band with given band number. If no band number is specified, then band number 1 is assumed.
- ST_HillShade - Availability: 2.0.0 Returns the hypothetical illumination of an elevation raster band using provided azimuth, altitude, brightness and scale inputs.
- ST_Histogram - Availability: 2.0.0 Returns a set of record summarizing a raster or raster coverage data distribution separate bin ranges. Number of bins are autocomputed if not specified.
- ST_InterpolatePoint - Availability: 2.0.0 Returns the interpolated measure of a geometry closest to a point.
- ST_IsEmpty - Availability: 2.0.0 Returns true if the raster is empty (width = 0 and height = 0). Otherwise, returns false.
- ST_IsValidDetail - Availability: 2.0.0 Returns a valid_detail row stating if a geometry is valid or if not a reason and a location.
- ST_IsValidReason - Availability: 2.0 version taking flags. Returns text stating if a geometry is valid, or a reason for invalidity.
- ST_MakeLine - Availability: 2.0.0 - Support for LineString input elements was introduced Creates a LineString from Point, MultiPoint, or LineString geometries.
- ST_MakeValid - Availability: 2.0.0 Attempts to make an invalid geometry valid without losing vertices.
- ST_MapAlgebraExpr - Availability: 2.0.0 1 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the input raster band and of pixeltype provided. Band 1 is assumed if no band is specified.
- ST_MapAlgebraExpr - Availability: 2.0.0 2 raster band version: Creates a new one band raster formed by applying a valid PostgreSQL algebraic operation on the two input raster bands and of pixeltype provided. band 1 of each raster is assumed if no band numbers are specified. The resulting raster will be aligned (scale, skew and pixel corners) on the grid defined by the first raster and have its extent defined by the "extenttype" parameter. Values for "extenttype" can be: INTERSECTION, UNION, FIRST, SECOND.
- ST_MapAlgebraFct - Availability: 2.0.0 1 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the input raster band and of pixeltype prodived. Band 1 is assumed if no band is specified.
- ST_MapAlgebraFct - Availability: 2.0.0 2 band version - Creates a new one band raster formed by applying a valid PostgreSQL function on the 2 input raster bands and of pixeltype prodived. Band 1 is assumed if no band is specified. Extent type defaults to INTERSECTION if not specified.
- ST_MapAlgebraFctNgb - Availability: 2.0.0 1-band version: Map Algebra Nearest Neighbor using user-defined PostgreSQL function. Return a raster which values are the result of a PLPGSQL user function involving a neighborhood of values from the input raster band.
- ST_Max4ma - Availability: 2.0.0 Raster processing function that calculates the maximum pixel value in a neighborhood.
- ST_Mean4ma - Availability: 2.0.0 Raster processing function that calculates the mean pixel value in a neighborhood.
- ST_Min4ma - Availability: 2.0.0 Raster processing function that calculates the minimum pixel value in a neighborhood.
- ST_ModEdgeHeal - Availability: 2.0 Heals two edges by deleting the node connecting them, modifying the first edgeand deleting the second edge. Returns the id of the deleted node.
- ST_MoveIsoNode - Availability: 2.0.0 Moves an isolated node in a topology from one point to another. If new apoint geometry exists as a node an error is thrown. Returns description of move.
- ST_NewEdgeHeal - Availability: 2.0 Heals two edges by deleting the node connecting them, deleting both edges,and replacing them with an edge whose direction is the same as the firstedge provided.
- ST_Node - Availability: 2.0.0 Nodes a collection of lines.
- ST_NumPatches - Availability: 2.0.0 Return the number of faces on a Polyhedral Surface. Will return null for non-polyhedral geometries.
- ST_OffsetCurve - Availability: 2.0 Returns an offset line at a given distance and side from an input line.
- ST_PatchN - Availability: 2.0.0 Returns the Nth geometry (face) of a PolyhedralSurface.
- ST_Perimeter - Availability 2.0.0: Support for geography was introduced Returns the length of the boundary of a polygonal geometry or geography.
- ST_PixelAsPolygon - Availability: 2.0.0 Returns the polygon geometry that bounds the pixel for a particular row and column.
- ST_PixelAsPolygons - Availability: 2.0.0 Returns the polygon geometry that bounds every pixel of a raster band along with the value, the X and the Y raster coordinates of each pixel.
- ST_Project - Availability: 2.0.0 Returns a point projected from a start point by a distance and bearing (azimuth).
- ST_Quantile - Availability: 2.0.0 Compute quantiles for a raster or raster table coverage in the context of the sample or population. Thus, a value could be examined to be at the raster's 25%, 50%, 75% percentile.
- ST_Range4ma - Availability: 2.0.0 Raster processing function that calculates the range of pixel values in a neighborhood.
- ST_Reclass - Availability: 2.0.0 Creates a new raster composed of band types reclassified from original. The nband is the band to be changed. If nband is not specified assumed to be 1. All other bands are returned unchanged. Use case: convert a 16BUI band to a 8BUI and so forth for simpler rendering as viewable formats.
- ST_RelateMatch - Availability: 2.0.0 Tests if a DE-9IM Intersection Matrix matches an Intersection Matrix pattern
- ST_RemEdgeModFace - Availability: 2.0 Removes an edge, and if the edge separates two facesdeletes one face and modifies the other face to cover the space of both.
- ST_RemEdgeNewFace - Availability: 2.0 Removes an edge and, if the removed edge separated two faces,delete the original faces and replace them with a new face.
- ST_Resample - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster using a specified resampling algorithm, new dimensions, an arbitrary grid corner and a set of raster georeferencing attributes defined or borrowed from another raster.
- ST_Rescale - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by adjusting only its scale (or pixel size). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline, Lanczos, Max or Min resampling algorithm. Default is NearestNeighbor.
- ST_Reskew - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by adjusting only its skew (or rotation parameters). New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_SameAlignment - Availability: 2.0.0 Returns true if rasters have same skew, scale, spatial ref, and offset (pixels can be put on same grid without cutting into pixels) and false if they don't with notice detailing issue.
- ST_SetBandIsNoData - Availability: 2.0.0 Sets the isnodata flag of the band to TRUE.
- ST_SharedPaths - Availability: 2.0.0 Returns a collection containing paths shared by the two input linestrings/multilinestrings.
- ST_Slope - Availability: 2.0.0 Returns the slope (in degrees by default) of an elevation raster band. Useful for analyzing terrain.
- ST_Snap - Availability: 2.0.0 Snap segments and vertices of input geometry to vertices of a reference geometry.
- ST_SnapToGrid - Availability: 2.0.0 Requires GDAL 1.6.1+ Resample a raster by snapping it to a grid. New pixel values are computed using the NearestNeighbor (english or american spelling), Bilinear, Cubic, CubicSpline or Lanczos resampling algorithm. Default is NearestNeighbor.
- ST_Split - Availability: 2.0.0 requires GEOS Returns a collection of geometries created by splitting a geometry by another geometry.
- ST_StdDev4ma - Availability: 2.0.0 Raster processing function that calculates the standard deviation of pixel values in a neighborhood.
- ST_Sum4ma - Availability: 2.0.0 Raster processing function that calculates the sum of all pixel values in a neighborhood.
- ST_SummaryStats - Availability: 2.0.0 Returns summarystats consisting of count, sum, mean, stddev, min, max for a given raster band of a raster or raster coverage. Band 1 is assumed is no band is specified.
- ST_Transform - Availability: 2.0.0 Requires GDAL 1.6.1+ Reprojects a raster in a known spatial reference system to another known spatial reference system using specified resampling algorithm. Options are NearestNeighbor, Bilinear, Cubic, CubicSpline, Lanczos defaulting to NearestNeighbor.
- ST_UnaryUnion - Availability: 2.0.0 Computes the union of the components of a single geometry.
- ST_Union - Availability: 2.0.0 Returns the union of a set of raster tiles into a single raster composed of 1 or more bands.
- ST_ValueCount - Availability: 2.0.0 Returns a set of records containing a pixel band value and count of the number of pixels in a given band of a raster (or a raster coverage) that have a given set of values. If no band is specified defaults to band 1. By default nodata value pixels are not counted. and all other values in the pixel are output and pixel band values are rounded to the nearest integer.
- TopoElementArray_Agg - Availability: 2.0.0 Returns a topoelementarray for a set of element_id, type arrays (topoelements).
- TopoGeo_AddLineString - Availability: 2.0.0 Adds a linestring to an existing topology using a tolerance and possibly splitting existing edges/faces.
- TopoGeo_AddPoint - Availability: 2.0.0 Adds a point to an existing topology using a tolerance and possibly splitting an existing edge.
- TopoGeo_AddPolygon - Availability: 2.0.0 Adds a polygon to an existing topology using a tolerance and possibly splitting existing edges/faces. Returns face identifiers.
- TopologySummary - Availability: 2.0.0 Takes a topology name and provides summary totals of types of objects in topology.
- Topology_Load_Tiger - Availability: 2.0.0 Loads a defined region of tiger data into a PostGIS Topology and transforming the tiger data to spatial reference of the topology and snapping to the precision tolerance of the topology.
- toTopoGeom - Availability: 2.0 Converts a simple Geometry into a topo geometry.
- ~ - Availability: 2.0.0 Returns TRUE if A's bounding box is contains B's. Uses double precision bounding box.
- ~= - Availability: 2.0.0 Returns TRUE if A's bounding box is the same as B's.

Functions enhanced in PostGIS 2.0

- && - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- AddGeometryColumn - Enhanced: 2.0.0 use_typmod argument introduced. Defaults to creating typmod geometry column instead of constraint-based. Adds a geometry column to an existing table.
- Box2D - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns a BOX2D representing the 2D extent of a geometry.
- Box3D - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns a BOX3D representing the 3D extent of a geometry.
- CreateTopology - Enhanced: 2.0 added the signature accepting hasZ Creates a new topology schema and registers it in the topology.topology table.
- Geocode - Enhanced: 2.0.0 to support Tiger 2010 structured data and revised some logic to improve speed, accuracy of geocoding, and to offset point from centerline to side of street address is located on. The new parameter max_results useful for specifying number of best results or just returning the best result. Takes in an address as a string (or other normalized address) and outputs a set of possible locations which include a point geometry in NAD 83 long lat, a normalized address for each, and the rating. The lower the rating the more likely the match. Results are sorted by lowest rating first. Can optionally pass in maximum results, defaults to 10, and restrict_region (defaults to NULL)
- GeometryType - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns the type of a geometry as text.
- Populate_Geometry_Columns - Enhanced: 2.0.0 use_typmod optional argument was introduced that allows controlling if columns are created with typmodifiers or with check constraints. Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.
- ST_3DExtent - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Aggregate function that returns the 3D bounding box of geometries.
- ST_Affine - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Apply a 3D affine transformation to a geometry.
- ST_Area - Enhanced: 2.0.0 - support for 2D polyhedral surfaces was introduced. Returns the area of a polygonal geometry.
- ST_AsBinary - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsBinary - Enhanced: 2.0.0 support for higher coordinate dimensions was introduced. Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsBinary - Enhanced: 2.0.0 support for specifying endian with geography was introduced. Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsEWKB - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Return the Extended Well-Known Binary (EWKB) representation of the geometry with SRID meta data.
- ST_AsEWKT - Enhanced: 2.0.0 support for Geography, Polyhedral surfaces, Triangles and TIN was introduced. Return the Well-Known Text (WKT) representation of the geometry with SRID meta data.
- ST_AsGML - Enhanced: 2.0.0 prefix support was introduced. Option 4 for GML3 was introduced to allow using LineString instead of Curve tag for lines. GML3 Support for Polyhedral surfaces and TINS was introduced. Option 32 was introduced to output the box. Return the geometry as a GML version 2 or 3 element.
- ST_AsKML - Enhanced: 2.0.0 - Add prefix namespace, use default and named args Return the geometry as a KML element.
- ST_Azimuth - Enhanced: 2.0.0 support for geography was introduced. Returns the north-based azimuth of a line between two points.
- ST_Dimension - Enhanced: 2.0.0 support for Polyhedral surfaces and TINs was introduced. No longer throws an exception if given empty geometry. Returns the topological dimension of a geometry.
- ST_Dump - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns a set of geometry_dump rows for the components of a geometry.
- ST_DumpPoints - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_Expand - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns a bounding box expanded from another bounding box or a geometry.
- ST_Extent - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Aggregate function that returns the bounding box of geometries.
- ST_Force2D - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Force the geometries into a "2-dimensional mode".
- ST_Force3D - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Force the geometries into XYZ mode. This is an alias for ST_Force3DZ.
- ST_Force3DZ - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Force the geometries into XYZ mode.
- ST_ForceCollection - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Convert the geometry into a GEOMETRYCOLLECTION.
- ST_ForceRHR - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Force the orientation of the vertices in a polygon to follow the Right-Hand-Rule.
- ST_GMLToSQL - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced. Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
- ST_GMLToSQL - Enhanced: 2.0.0 default srid optional parameter added. Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
- ST_GeomFromEWKB - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced. Return a specified ST_Geometry value from Extended Well-Known Binary representation (EWKB).
- ST_GeomFromEWKT - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced. Return a specified ST_Geometry value from Extended Well-Known Text representation (EWKT).
- ST_GeomFromGML - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced. Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeomFromGML - Enhanced: 2.0.0 default srid optional parameter added. Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeometryN - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Return an element of a geometry collection.
- ST_GeometryType - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Returns the SQL-MM type of a geometry as text.
- ST_IsClosed - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Tests if a LineStrings's start and end points are coincident. For a PolyhedralSurface tests if it is closed (volumetric).
- ST_MakeEnvelope - Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced. Creates a rectangular Polygon from minimum and maximum coordinates.
- ST_MakeValid - Enhanced: 2.0.1, speed improvements Attempts to make an invalid geometry valid without losing vertices.
- ST_NPoints - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Returns the number of points (vertices) in a geometry.
- ST_NumGeometries - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Returns the number of elements in a geometry collection.
- ST_Relate - Enhanced: 2.0.0 - added support for specifying boundary node rule. Tests if two geometries have a topological relationship matching an Intersection Matrix pattern, or computes their Intersection Matrix
- ST_Rotate - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Rotates a geometry about an origin point.
- ST_Rotate - Enhanced: 2.0.0 additional parameters for specifying the origin of rotation were added. Rotates a geometry about an origin point.
- ST_RotateX - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Rotates a geometry about the X axis.
- ST_RotateY - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Rotates a geometry about the Y axis.
- ST_RotateZ - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Rotates a geometry about the Z axis.
- ST_Scale - Enhanced: 2.0.0 support for Polyhedral surfaces, Triangles and TIN was introduced. Scales a geometry by given factors.
- ST_ShiftLongitude - Enhanced: 2.0.0 support for Polyhedral surfaces and TIN was introduced. Shifts the longitude coordinates of a geometry between -180..180 and 0..360.
- ST_Summary - Enhanced: 2.0.0 added support for geography Returns a text summary of the contents of a geometry.
- ST_Transform - Enhanced: 2.0.0 support for Polyhedral surfaces was introduced. Return a new geometry with coordinates transformed to a different spatial reference system.
- ST_Value - Enhanced: 2.0.0 exclude_nodata_value optional argument was added. Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified. If exclude_nodata_value is set to false, then all pixels include nodata pixels are considered to intersect and return value. If exclude_nodata_value is not passed in then reads it from metadata of raster.
- ValidateTopology - Enhanced: 2.0.0 more efficient edge crossing detection and fixes for false positives that were existent in prior versions. Returns a set of validatetopology_returntype objects detailing issues with topology.

Functions changed in PostGIS 2.0

- AddGeometryColumn - Changed: 2.0.0 This function no longer updates geometry_columns since geometry_columns is a view that reads from system catalogs. It by default also does not create constraints, but instead uses the built in type modifier behavior of PostgreSQL. So for example building a wgs84 POINT column with this function is now equivalent to: ALTER TABLE some_table ADD COLUMN geom geometry(Point,4326); Adds a geometry column to an existing table.
- AddGeometryColumn - Changed: 2.0.0 If you require the old behavior of constraints use the default use_typmod, but set it to false. Adds a geometry column to an existing table.
- AddGeometryColumn - Changed: 2.0.0 Views can no longer be manually registered in geometry_columns, however views built against geometry typmod tables geometries and used without wrapper functions will register themselves correctly because they inherit the typmod behavior of their parent table column. Views that use geometry functions that output other geometries will need to be cast to typmod geometries for these view geometry columns to be registered correctly in geometry_columns. Refer to . Adds a geometry column to an existing table.
- Box3D - Changed: 2.0.0 In pre-2.0 versions, there used to be a box2d instead of box3d. Since box2d is a deprecated type, this was changed to box3d. Returns the box 3d representation of the enclosing box of the raster.
- DropGeometryColumn - Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a geometry column like any other table column using ALTER TABLE Removes a geometry column from a spatial table.
- DropGeometryTable - Changed: 2.0.0 This function is provided for backward compatibility. Now that since geometry_columns is now a view against the system catalogs, you can drop a table with geometry columns like any other table using DROP TABLE Drops a table and all its references in geometry_columns.
- Populate_Geometry_Columns - Changed: 2.0.0 By default, now uses type modifiers instead of check constraints to constrain geometry types. You can still use check constraint behavior instead by using the new use_typmod and setting it to false. Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.
- ST_3DExtent - Changed: 2.0.0 In prior versions this used to be called ST_Extent3D Aggregate function that returns the 3D bounding box of geometries.
- ST_3DLength - Changed: 2.0.0 In prior versions this used to be called ST_Length3D Returns the 3D length of a linear geometry.
- ST_3DMakeBox - Changed: 2.0.0 In prior versions this used to be called ST_MakeBox3D Creates a BOX3D defined by two 3D point geometries.
- ST_3DPerimeter - Changed: 2.0.0 In prior versions this used to be called ST_Perimeter3D Returns the 3D perimeter of a polygonal geometry.
- ST_AsBinary - Changed: 2.0.0 Inputs to this function can not be unknown -- must be geometry. Constructs such as ST_AsBinary('POINT(1 2)') are no longer valid and you will get an n st_asbinary(unknown) is not unique error. Code like that needs to be changed to ST_AsBinary('POINT(1 2)'::geometry);. If that is not possible, then install legacy.sql. Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsGML - Changed: 2.0.0 use default named args Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Changed: 2.0.0 support default args and named args. Return a geometry or feature in GeoJSON format.
- ST_AsSVG - Changed: 2.0.0 to use default args and support named args Returns SVG path data for a geometry.
- ST_EndPoint - Changed: 2.0.0 no longer works with single geometry MultiLineStrings. In older versions of PostGIS a single-line MultiLineString would work with this function and return the end point. In 2.0.0 it returns NULL like any other MultiLineString. The old behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0.0. Returns the last point of a LineString or CircularLineString.
- ST_GDALDrivers - Changed: 2.0.6, 2.1.3 - by default no drivers are enabled, unless GUC or Environment variable gdal_enabled_drivers is set. Returns a list of raster formats supported by PostGIS through GDAL. Only those formats with can_write=True can be used by ST_AsGDALRaster
- ST_GeomFromText - Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards. This should now be written as ST_GeomFromText('GEOMETRYCOLLECTION EMPTY') Return a specified ST_Geometry value from Well-Known Text representation (WKT).
- ST_GeometryN - Changed: 2.0.0 Prior versions would return NULL for singular geometries. This was changed to return the geometry for ST_GeometryN(..,1) case. Return an element of a geometry collection.
- ST_IsEmpty - Changed: 2.0.0 In prior versions of PostGIS ST_GeomFromText('GEOMETRYCOLLECTION(EMPTY)') was allowed. This is now illegal in PostGIS 2.0.0 to better conform with SQL/MM standards Tests if a geometry is empty.
- ST_Length - Changed: 2.0.0 Breaking change -- in prior versions applying this to a MULTI/POLYGON of type geography would give you the perimeter of the POLYGON/MULTIPOLYGON. In 2.0.0 this was changed to return 0 to be in line with geometry behavior. Please use ST_Perimeter if you want the perimeter of a polygon Returns the 2D length of a linear geometry.
- ST_LocateAlong - Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure. Returns the point(s) on a geometry that match a measure value.
- ST_LocateBetween - Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures. Returns the portions of a geometry that match a measure range.
- ST_ModEdgeSplit - Changed: 2.0 - In prior versions, this was misnamed ST_ModEdgesSplit Split an edge by creating a new node along an existing edge, modifying the original edge and adding a new edge.
- ST_NumGeometries - Changed: 2.0.0 In prior versions this would return NULL if the geometry was not a collection/MULTI type. 2.0.0+ now returns 1 for single geometries e.g POLYGON, LINESTRING, POINT. Returns the number of elements in a geometry collection.
- ST_NumInteriorRings - Changed: 2.0.0 - in prior versions it would allow passing a MULTIPOLYGON, returning the number of interior rings of first POLYGON. Returns the number of interior rings (holes) of a Polygon.
- ST_PointN - Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. Returns the Nth point in the first LineString or circular LineString in a geometry.
- ST_ScaleX - Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeX. Returns the X component of the pixel width in units of coordinate reference system.
- ST_ScaleY - Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeY. Returns the Y component of the pixel height in units of coordinate reference system.
- ST_SetScale - Changed: 2.0.0 In WKTRaster versions this was called ST_SetPixelSize. This was changed in 2.0.0. Sets the X and Y size of pixels in units of coordinate reference system. Number units/pixel width/height.
- ST_StartPoint - Changed: 2.0.0 no longer works with single geometry MultiLineStrings. In older versions of PostGIS a single-line MultiLineString would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other MultiLineString. The old behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0.0. Returns the first point of a LineString.

### 13.12.13. PostGIS Functions new or enhanced in 1.5

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 1.5

- && - Availability: 1.5.0 support for geography was introduced. Returns TRUE if A's 2D bounding box intersects B's 2D bounding box.
- PostGIS_LibXML_Version - Availability: 1.5 Returns the version number of the libxml2 library.
- ST_AddMeasure - Availability: 1.5.0 Interpolates measures along a linear geometry.
- ST_AsBinary - Availability: 1.5.0 geography support was introduced. Return the OGC/ISO Well-Known Binary (WKB) representation of the geometry/geography without SRID meta data.
- ST_AsGML - Availability: 1.5.0 geography support was introduced. Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Availability: 1.5.0 geography support was introduced. Return a geometry or feature in GeoJSON format.
- ST_AsText - Availability: 1.5 - support for geography was introduced. Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.
- ST_Buffer - Availability: 1.5 - ST_Buffer was enhanced to support different endcaps and join types. These are useful for example to convert road linestrings into polygon roads with flat or square edges instead of rounded edges. Thin wrapper for geography was added. Computes a geometry covering all points within a given distance from a geometry.
- ST_ClosestPoint - Availability: 1.5.0 Returns the 2D point on g1 that is closest to g2. This is the first point of the shortest line from one geometry to the other.
- ST_CollectionExtract - Availability: 1.5.0 Given a geometry collection, returns a multi-geometry containing only elements of a specified type.
- ST_Covers - Availability: 1.5 - support for geography was introduced. Tests if every point of B lies in A
- ST_DFullyWithin - Availability: 1.5.0 Tests if a geometry is entirely inside a distance of another
- ST_DWithin - Availability: 1.5.0 support for geography was introduced Tests if two geometries are within a given distance
- ST_Distance - Availability: 1.5.0 geography support was introduced in 1.5. Speed improvements for planar to better handle large or many vertex geometries Returns the distance between two geometry or geography values.
- ST_DistanceSphere - Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points. Returns minimum distance in meters between two lon/lat geometries using a spherical earth model.
- ST_DistanceSpheroid - Availability: 1.5 - support for other geometry types besides points was introduced. Prior versions only work with points. Returns the minimum distance between two lon/lat geometries using a spheroidal earth model.
- ST_DumpPoints - Availability: 1.5.0 Returns a set of geometry_dump rows for the coordinates in a geometry.
- ST_Envelope - Availability: 1.5.0 behavior changed to output double precision instead of float4 Returns a geometry representing the bounding box of a geometry.
- ST_Expand - Availability: 1.5.0 behavior changed to output double precision instead of float4 coordinates. Returns a bounding box expanded from another bounding box or a geometry.
- ST_GMLToSQL - Availability: 1.5, requires libxml2 1.6+ Return a specified ST_Geometry value from GML representation. This is an alias name for ST_GeomFromGML
- ST_GeomFromGML - Availability: 1.5, requires libxml2 1.6+ Takes as input GML representation of geometry and outputs a PostGIS geometry object
- ST_GeomFromKML - Availability: 1.5, requires libxml2 2.6+ Takes as input KML representation of geometry and outputs a PostGIS geometry object
- ST_HausdorffDistance - Availability: 1.5.0 Returns the Hausdorff distance between two geometries.
- ST_Intersection - Availability: 1.5 support for geography data type was introduced. Computes a geometry representing the shared portion of geometries A and B.
- ST_Intersects - Availability: 1.5 support for geography was introduced. Tests if two geometries intersect (they have at least one point in common)
- ST_Length - Availability: 1.5.0 geography support was introduced in 1.5. Returns the 2D length of a linear geometry.
- ST_LongestLine - Availability: 1.5.0 Returns the 2D longest line between two geometries.
- ST_MakeEnvelope - Availability: 1.5 Creates a rectangular Polygon from minimum and maximum coordinates.
- ST_MaxDistance - Availability: 1.5.0 Returns the 2D largest distance between two geometries in projected units.
- ST_ShortestLine - Availability: 1.5.0 Returns the 2D shortest line between two geometries
- ~= - Availability: 1.5.0 changed behavior Returns TRUE if A's bounding box is the same as B's.

### 13.12.14. PostGIS Functions new or enhanced in 1.4

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 1.4

- Populate_Geometry_Columns - Availability: 1.4.0 Ensures geometry columns are defined with type modifiers or have appropriate spatial constraints.
- ST_Collect - Availability: 1.4.0 - ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster. Creates a GeometryCollection or Multi* geometry from a set of geometries.
- ST_ContainsProperly - Availability: 1.4.0 Tests if every point of B lies in the interior of A
- ST_GeoHash - Availability: 1.4.0 Return a GeoHash representation of the geometry.
- ST_IsValidReason - Availability: 1.4 Returns text stating if a geometry is valid, or a reason for invalidity.
- ST_LineCrossingDirection - Availability: 1.4 Returns a number indicating the crossing behavior of two LineStrings
- ST_LocateBetweenElevations - Availability: 1.4.0 Returns the portions of a geometry that lie in an elevation (Z) range.
- ST_MakeLine - Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster. Creates a LineString from Point, MultiPoint, or LineString geometries.
- ST_MinimumBoundingCircle - Availability: 1.4.0 Returns the smallest circle polygon that contains a geometry.
- ST_Union - Availability: 1.4.0 - ST_Union was enhanced. ST_Union(geomarray) was introduced and also faster aggregate collection in PostgreSQL. Computes a geometry representing the point-set union of the input geometries.

### 13.12.15. PostGIS Functions new or enhanced in 1.3

The functions given below are PostGIS functions that were added or enhanced.

Functions new in PostGIS 1.3

- ST_AsGML - Availability: 1.3.2 Return the geometry as a GML version 2 or 3 element.
- ST_AsGeoJSON - Availability: 1.3.4 Return a geometry or feature in GeoJSON format.
- ST_CurveToLine - Availability: 1.3.0 Converts a geometry containing curves to a linear geometry.
- ST_LineToCurve - Availability: 1.3.0 Converts a linear geometry to a curved geometry.
- ST_SimplifyPreserveTopology - Availability: 1.3.3 Returns a simplified and valid representation of a geometry, using the Douglas-Peucker algorithm.

# Chapter 14. Reporting Problems

## 14.1. Reporting Software Bugs

Reporting bugs effectively is a fundamental way to help PostGIS development. The most effective bug report is that enabling PostGIS developers to reproduce it, so it would ideally contain a script triggering it and every information regarding the environment in which it was detected. Good enough info can be extracted running `SELECT postgis_full_version()` [for PostGIS] and `SELECT version()` [for postgresql].

If you aren't using the latest release, it's worth taking a look at its release changelog first, to find out if your bug has already been fixed.

Using the PostGIS bug tracker will ensure your reports are not discarded, and will keep you informed on its handling process. Before reporting a new bug please query the database to see if it is a known one, and if it is please add any new information you have about it.

You might want to read Simon Tatham's paper about How to Report Bugs Effectively before filing a new report.

## 14.2. Reporting Documentation Issues

The documentation should accurately reflect the features and behavior of the software. If it doesn't, it could be because of a software bug or because the documentation is in error or deficient.

Documentation issues can also be reported to the PostGIS bug tracker.

If your revision is trivial, just describe it in a new bug tracker issue, being specific about its location in the documentation.

If your changes are more extensive, a patch is definitely preferred. This is a four step process on Unix (assuming you already have git installed):

1. Clone the PostGIS' git repository. On Unix, type:

   git clone https://git.osgeo.org/gitea/postgis/postgis.git

   This will be stored in the directory postgis

2. Make your changes to the documentation with your favorite text editor. On Unix, type (for example):

   vim doc/postgis.xml

   Note that the documentation is written in DocBook XML rather than HTML, so if you are not familiar with it please follow the example of the rest of the documentation.

3. Make a patch file containing the differences from the master copy of the documentation. On Unix, type:

   git diff doc/postgis.xml > doc.patch

4. Attach the patch to a new issue in bug tracker.

# Appendix A. Appendix

### Release Notes

## A.1. PostGIS 3.5.1

2024/09/25

This version requires PostgreSQL 12-17, GEOS 3.8 or higher, and Proj 6.1+. To take advantage of all features, GEOS 3.12+ is needed. To take advantage of all SFCGAL features, SFCGAL 1.5.0+ is needed.

### Breaking Changes

#5677, Retain SRID during unary union (Paul Ramsey)

#5792, [topology] Prevent topology corruption with TopoGeo_addPoint near almost collinear edges (Sandro Santilli)

#5795, [topology] Fix ST_NewEdgesSplit can cause invalid topology (Björn Harrtell)

#5794, [topology] Fix crash in TopoGeo_addPoint (Sandro Santilli)

#5785, [raster] ST_MapAlgebra segfaults when expression references a supernumerary rast argument (Dian M Fay)

#5787, Check that ST_ChangeEdgeGeom doesn't change winding of rings (Sandro Santilli)

#5791, Add legacy stubs for old transaction functions to allow pg_upgrade (Regina Obe)

#5800, PROJ compiled version reading the wrong minor and micro (Regina Obe)

#5790, Non-schema qualified calls causing issue with materialized views (Regina Obe)

#5812, Performance regression in ST_Within (Paul Ramsey)

#5815, Remove hash/merge promise from <> operator (Paul Ramsey)

#5823, Build support for Pg18 (Paul Ramsey)

### Enhancements

#5782, Improve robustness of min distance calculation (Sandro Santilli)

[topology] Speedup topology building when closing large rings with many holes (Björn Harrtell)

#5810, Update tiger geocoder to handle TIGER 2024 data (Regina Obe)

### Breaking Changes

#5799, make ST_TileEnvelope clip envelopes to tile plane extent (Paul Ramsey)

## A.2. PostGIS 3.5.0

2024/09/25

This version requires PostgreSQL 12-17, GEOS 3.8 or higher, and Proj 6.1+. To take advantage of all features, GEOS 3.12+ is needed. To take advantage of all SFCGAL features, SFCGAL 1.5.0+ is needed.

Many thanks to our translation teams, in particular:

Dapeng Wang, Zuo Chenwei from HighGo (Chinese Team)

Teramoto Ikuhiro (Japanese Team)

Vincent Bre (French Team)

### Breaking Changes

#5546, TopoGeometry <> TopoGeometry is now ambiguous, to get the old behaviour, assuming your TopoGeometry objects are named tg1 and tg2, use: ( id(tg1) <> id(tg2) OR topology_id(tg1) <> topology_id(tg2) OR layer_id(tg1) <> layer_id(tg2) OR type(tg1) <> type(tg2) ) (Sandro Santilli)

#5536, comments are not anymore included in PostGIS extensions (Sandro Santilli)

xmllint is now required to build comments (Sandro Santilli)

DocBook5 XSL is now required to build html (Sandro Santilli)

#5602, Drop support for GEOS 3.6 and 3.7 (Regina Obe)

#5571, Improve ST_GeneratePoints performance, but old seeded pseudo random points will need to be regenerated.

#5596, GH-749, Allow promoting column as an id in ST_AsGeoJson(record,..). Views and materialized views that use the ST_AsGeoJSON(record ..) will need rebuilding to upgrade to new signature (Jan Tojnar)

#5496, ST_Clip all variants replaced, will require rebuilding of materialized views that use them (funding from The National Institute for Agricultural and Food Research and Technology (INIA-CSIC)), Regina Obe

#5659, ST_DFullyWithin behaviour has changed to be ST_Contains(ST_Buffer(A, R), B) (Paul Ramsey)

Remove the WFS_locks extra package. (Paul Ramsey)

5747, GH-776, ST_Length: Return 0 for CurvePolygon (Dan Baston)

5770, support for GEOS 3.13 and RelateNG. Most functionality remains the same, but new GEOS predicate implementation has a few small changes.

Boundary Node Rule relate matrices might be different when using the "multi-valent end point" rule.

Relate matrices for situations with invalid MultiPolygons with shared boundaries might be different. Run ST_MakeValid to get valid inputs to feed to the calculation.

Zero length LineStrings are treated as if they are the equivalent Point object.

### Deprecated signatures

GH-761, ST_StraightSkeleton => CG_StraightSkeleton (Loïc Bartoletti)

GH-189, All SFCGAL functions now use the prefix CG_, with the old ones using ST_ being deprecated. (Loïc Bartoletti)

### New features

Improvements in the 'postgis' script:

- new command list-enabled

- new command list-all

- command upgrade upgrades all databases that need to be

- command status reports status of all databases

(Sandro Santilli)

#5742, expose version of PROJ at compile time (Sandro Santilli)

#5721, postgis_topology: Allow sharing sequences between different topologies (Lars Opsahl)

#5667, postgis_topology: TopoGeo_LoadGeometry (Sandro Santilli)

#5055, add explicit <> geometry operator to prevent non-unique error with <> and != (Paul Ramsey)

Add ST_HasZ/ST_HasM (Loïc Bartoletti)

GT-123, postgis_sfcgal: CG_YMonotonePartition, CG_ApproxConvexPartition, CG_GreeneApproxConvexPartition and CG_OptimalConvexPartition (Loïc Bartoletti)

GT-156, postgis_sfcgal: CG_Visibility (Loïc Bartoletti)

GT-157, postgis_sfcgal: Add ST_ExtrudeStraightSkeleton (Loïc Bartoletti)

#5496, postgis_raster: ST_Clip support for touched (Regina Obe)

GH-760, postgis_sfcgal: CG_Intersection, CG_3DIntersects, CG_Intersects, CG_Difference, CG_Union (and aggregate), CG_Triangulate, CG_Area, CG_3DDistance, CG_Distance (Loïc Bartoletti)

#5687, Don't rely on search_path to determine postgis schema Fix for PG17 security change (Regina Obe)

#5705, GH-767, ST_RemoveIrrelevantPointsForView (Sam Peters)

#5706, GH-768, ST_RemoveSmallParts (Sam Peters)

### Enhancements

5550, Fix upgrades from 2.x in sandboxed systems (Sandro Santilli)

#3587, postgis_topology: faster load of big lines in topologies (Sandro Santilli)

#5670, postgis_topology: faster ST_CreateTopoGeo (Sandro Santilli)

#5531, documentation format upgraded to DocBook 5 (Sandro Santilli)

#5543, allow building without documentation (Sandro Santilli)

#5596, GH-749, Allow promoting column as an id in ST_AsGeoJson(record,..). (Jan Tojnar)

GH-744, Don't create docbook.css for the HTML manual, use style.css instead (Chris Mayo)

Faster implementation of point-in-poly cached index (Paul Ramsey)

Improve performance of ST_GeneratePoints (Paul Ramsey)

#5361, ST_CurveN, ST_NumCurves and consistency in accessors on curved geometry (Paul Ramsey)

GH-761, postgis_sfcgal: Add an optional parameter to CG_StraightSkeleton (was ST_StraightSkeleton) to use m as a distance in result (Hannes Janetzek, Loïc Bartoletti)