NAME
X2SYS_CROSS - Find and compute Cross-Over Errors
SYNOPSIS
x2sys_cross file(s) OR -Lflist [ -Agap ] [ -Cc|f|g ] [ -Ddeffile ] [
-Fflags ] [ -Gd|g ] [ -Jparams ] [-Kcombi.lis] [ -Nwindow ] [ -O ] [
-Sl|uspeed ] [ -Tl|a|c ] [ -Wsize ] [ -V ] [ -Xe|i ] [ -bo[s] ]
DESCRIPTION
x2sys_cross is used to determine all intersections between or within
tracks, and report the time, position, discrepancies in all
observables, the mean values of the observables, heading along each
tracksegment, and the distance along track at the cross-over point.
The names of the files are passed on the command line, or as a list of
files with the -L option. If they are identical or only one name is
passed, then x2sys_cross will also look for internal cross-overs. The
optional parameters are:
-A Ignore crossovers on segments of length <= gap [no gap].
-C Select procedure for along-track distance calculation:
c Cartesian distances [Default].
f Flat earth distances.
g Great circle distances.
-D Give the definition file for this data format [x2sys].
-F Sets which columns to use. Give a comma-separated list of column
names [Default is all columns].
-G Selects geographical coordinates. Append d for discontinuity at
the Dateline (makes longitude go from -180 to + 180) or at
Greenwhich (makes longitude go from 0 to 360 [Default]).
-J Selects the map projection. Scale is inch/degree, 1:xxxxx, or
width in inch (upper case modifier).
CYLINDRICAL PROJECTIONS:
-Jclon0/lat0/scale (Cassini)
-Jjlon0/scale (Miller)
-Jmscale (Mercator - Greenwich and Equator as origin)
-Jmlon0/lat0/scale (Mercator - Give meridian and standard
parallel)
-Joalon0/lat0/azimuth/scale (Oblique Mercator - point and
azimuth)
-Joblon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
-Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and pole)
-Jqlon0/scale (Equidistant Cylindrical Projection (Plate Carree))
-Jtlon0/scale (TM - Transverse Mercator, with Equator as y = 0)
-Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-Jflon0/lat0/horizon/scale (Gnomonic).
-Jglon0/lat0/scale (Orthographic).
-Jslon0/lat0/scale (General Stereographic)
CONIC PROJECTIONS:
-Jblon0/lat0/lat1/lat2/scale (Albers)
-Jdlon0/lat0/lat1/lat2/scale (Equidistant)
-Jllon0/lat0/lat1/lat2/scale (Lambert)
MISCELLANEOUS PROJECTIONS:
-Jhlon0/scale (Hammer)
-Jilon0/scale (Sinusoidal)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jnlon0/scale (Robinson)
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jwlon0/scale (Mollweide)
NON-GEOGRAPHICAL PROJECTIONS:
-Jpscale (Linear projection for polar (theta,r) coordinates)
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power
scaling)
More details can be found in the psbasemap manpages.
-K Only process the pair-combinations found in the file combi.lis
[Default process all possible combinations among the specified
files]. Suitable option for passing old x_setup output.
-N Maximum number of points to use in the interpolation [6].
-O Output results using the old XOVER format [Default is X2SYS
format]. This options should only be used with *.gmt-formatted
MGD77 files.
-R west, east, south, and north specify the Region of interest. To
specify boundaries in degrees and minutes [and seconds], use the
dd:mm[:ss] format. Append r if lower left and upper right map
coordinates are given instead of wesn.
-S Defines window of track speed within which to calculate
crossovers.
-Sl sets lower speed [Default is 0].
-Su sets upper speed [Default is Infinity].
-T Sets the interpolation mode. Choose among:
l Linear interpolation [Default].
a Akima spline interpolation.
c Cubic spline interpolation.
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-W Sets maximum time gap (in user units) allowed between points on
either side of a crossover [Default is Infinity].
-X Append e for external crossovers only, and i for internal
crossovers only [Default is all crossovers].
-bo Selects binary output. Append s for single precision [Default is
double].
REMARKS
The COEs found are printed out to standard output in ASCII format
(unless -bo is set). When ASCII is chosen, the output format depends
on whether or not old-style XOVER output (-O) has been selected. If
so, then the first record contains the file 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. If the default format is chosen then
the header record starts with "> ", and the output format for
crossovers are first 8 columns that contain x, y, time along track #1,
time along track #2, distance along track #1, distance along track #2,
heading along track #1, and heading along track #2, and then pairs of
(COE, average value) for each data type. 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.
EXAMPLES
To compute all internal crossovers in the gmt-formatted file
c2104.gmt, and output in the old XOVER format, use
x2sys_cross c2104.gmt -O -Dgmt > c2104.d
To find the crossover locations with bathymetry between the two MGD77
files A13232.mgd77 and A99938.mgd77, try
x2sys_cross A13232.mgd77 A99938.mgd77 -Xe -Dmgd77 -Flon,lat,top >
crossovers.d
SEE ALSO
gmt, x2sys_datalist
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