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,  discrepancies  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 an Akima 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     Selects  verbose  mode,  which  will  send progress reports to stderr [Default runs
              "silently"].  Report the number of cross-overs for this pair of legs.

BEWARE

       The COEs found are printed out to standard  output  in  ASCII  format.  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 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.

SEE ALSO

       GMT(1), x_system(1)

REFERENCES

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