X_OVER(1) Generic Mapping Tools X_OVER(1)NAMEx_over - Find and compute Cross-Over Errors
SYNOPSISx_over leg_1 [ leg_2 ] [ -A ] [ -C ] [ -L ] [ -V ] [ -Wtimegap ] [
-Gfact ] [ -Mfact ] [ -Tfact ] [ -Nnp_int ]
DESCRIPTIONx_over is used to inspect two cruises to see if they intersect, and if
so report the time, position, discrepancies in gravity/magnetics/ba‐
thymetry, 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 sub‐
sequent 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 magnet‐
ics, 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 recom‐
mended 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 ALSOGMT(1), x_system(1)REFERENCES
Wessel, P. XOVER: A Cross-over Error Detector for Track Data, Computers
& Geosciences, 15, 333-346.
GMT 4.5.14 1 Nov 2015 X_OVER(1)
