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X_SOLVE_DC_DRIFT(1)          Generic Mapping Tools         X_SOLVE_DC_DRIFT(1)

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 x_list and
              gmtlist).

       -A     Create an ASCII correction table. At least one of -A and -B must
              be specified.

       -V     Selects verbose mode, which will send progress reports to stderr
              [Default runs "silently"].

BEWARE
       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(1), x_system(1)

REFERENCES
       Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers
       & Geosciences, 15, 333-346.

GMT 4.5.14                        1 Nov 2015               X_SOLVE_DC_DRIFT(1)