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.