## NAME

           x_over - Find and compute Cross-Over Errors

## SYNOPSIS

           x_over  leg_1  [  leg_2  ]  [  -A ] [ -C ] [ -L ] [ -V ] [
           -Wtimegap ] [ -Gfact ] [ -Mfact ] [ -Tfact ] [ -Nnp_int ]

## DESCRIPTION

           x_over is used to inspect  two  cruises  to  see  if  they
           intersect, and if so report the time, position, discrepan
           cies in  gravity/magnetics/bathymetry,  heading  for  each
           track  segment,  and the average values of the geophysical
           observables at the cross-over point. The names of the legs
           are  passed  on the command line. If they are identical or
           only one name is passed, then x_over  looks  for  internal
           cross-overs. The optional parameters are:

           -A     Use  Akima's  spline to interpolate the geophysical
                  field at the cross-over point.'

           -C     Use a Natural Cubic spline function instead.

           -L     Use a linear interpolant [Default].

           -W     Do not compute cross-overs if the 2 nearest  points
                  are more than timegap minutes apart.

           -G     Scale  gravity  by  fact [Default is 0.1 since gmt-
                  files store gravity in g.u.]

           -M     Scale magnetic anomaly by fact [1.0].

           -T     Scale bathymetry by fact [1.0].

           -N     Specify how many points to use in the interpolation
                  [Default is 6].

           -V     Verbose,  report the number of cross-overs for this
                  pair of legs.

## The COEs found are printed out to standard output in ASCII for

           mat. The first record contains the
           leg names and their start year, whereas subsequent records
           have the data for each COE encountered. The fields written
           out  are  lat,  lon, time along track #1, time along track
           #2, x_gravity, x_magnetics, x_bathymetry, average gravity,
           average magnetics, average bathymetry, heading along track
           #1, and heading along track #2. Sign convention:  If  lega
           and  legb  are  passed  on  the command line, then the COE
           value is Value (lega) - Value (legb).  It  is  recommended
           that  the  Akima's  spline  is used instead of the natural
           cubic spline, since it is less sensitive to' outliers that
           tend  to introduce wild oscillations in the interpolation.
           A version of x_over compiled for a SUN with FPA  board  is
           provided (x_over).

## SEE ALSO

           gmt(l), x_system(l)

## REFERENCES

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