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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