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.

GMT 4.5.11                                         5 Nov 2013                                       X_OVER(1gmt)