NAME
x_solve_dc_drift - Find Best-fitting D.C.-shift and Drift
Estimates
SYNOPSIS
x_solve_dc_drift [ -Xxbase ] [ -Llbase ] [ -Iignorefile ]
[ -S ] [ -Citeration ] [ -Mmin_nx ] [
-Rwest/east/south/north ] [ -Uuselegsfile ] [ -V ] [
-Bbinfile ] [ -AASCIIfile ]
DESCRIPTION
x_solve_dc_drift will read the database files and, by
iterating, find the best-fitting regression line to the
<time,COE> points for each leg that minimizes the overall
standard deviation of the data set in a least squares
sense. Finally, correction file(s) are created.
-X Indicate an alternate database to read. [Default is
xx_base.b].
-L Indicate an alternate legbase to read. [Default is
xx_legs.b].
-I Ignore information for certain legs (that might be
bad etc).
-S Reset the old d.c.-shift and drift estimates to
zero before iterating.
-C Specify how many iterations to do. Default is
interactive session.
-M Solve for drift only if the leg has more than
min_nx cross-overs.
-R Only take COEs inside this region into account.
[Default is world].
-U Solve for corrections involving COEs from legs in
the uselegsfile only.
-B Create a binary correction file (which can be read
by xlist and gmtlist).
-A Create an ASCII correction table. At least one of
-A and -B must be specified.
-V Operate in verbose mode.
The reason for the -M option is that if the COEs are few, then a
stable estimate of the slope may
not be obtained (e.g. when most of the COEs occur midway
between ports). However, in most cases the bulk of the
COEs do occur near the ports so that a drift estimate can
be computed. Conventional wisdom recommends plotting the
time-series and the computed regression line to see if it
makes sense.
SEE ALSO
gmt(l), x_system(l)
REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track
Data, Computers & Geosciences, 15, 333-346.
15 Oct 2001 x_solve_dc_drift(l)
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