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  ses-
              sion.

       -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 uselegs-
              file 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.

BEWARE

       The reason for the -M  option is that if the COEs are few, then a  sta-
       ble  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 com-
       puted.  Conventional wisdom recommends plotting the time-series and the
       computed regression line to see if it makes sense.

SEE ALSO

       gmt(GMTMANSECTION), x_system(GMTMANSECTION)

REFERENCES