x2sys_cross
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] ] [ -2 ]
DESCRIPTION
x2sys_cross is used to determine all intersections between
or within tracks, and report the time, position, discrep
ancies in all observables, the mean values of the observ
ables, 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 checking].
-C Select procedure for along-track distance calcula
tion:
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 dis
continuity at the Dateline (makes longitude go from
-180 to + 180) or g for discontinuity at Greenwhich
(makes longitude go from 0 to 360 [Default]).
-J Selects the map projection. Scale is UNIT/degree,
1:xxxxx, or width in UNIT (upper case modifier).
UNIT is cm, inch, or m, depending on the MEA
SURE_UNIT setting in .gmtdefaults, but this can be
overridden on the command line by appending the c,
i, or m to the scale/width value.
CYLINDRICAL PROJECTIONS:
-Jclon0/lat0/scale (Cassini)
-Jjlon0/scale (Miller)
-Jmscale (Mercator - Greenwich and Equator as ori
gin)
-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 Equa
tor 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/[slat/]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:
-Jp[a]scale[/origin] (polar (theta,r) coordinates,
optional a for azimuths and offset theta [0])
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log,
and power scaling)
More details can be found in the psbasemap man
pages.
-K Only process the pair-combinations found in the
file combi.lis [Default process all possible combi
nations among the specified files]. Suitable
option for passing old x_setup output.
tion [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 min
utes [and seconds], use the dd:mm[:ss] format.
Append r if lower left and upper right map coordi
nates are given instead of wesn.
-S Defines window of track speed within which to cal
culate 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].
-2 Report the values of each track at the crossover
[Default is the crossover value and the mean
value].
-bo Selects binary output. Append s for single preci
sion [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 out
put format depends on whether or not old-style XOVER out
put (-O) has been selected. If so, then the first record
contains the file 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 magnetics, average bathymetry,
heading along track #1, and heading along track #2. If the
default format is chosen then the header record starts
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 sen
sitive to outliers that tend to introduce wild oscilla
tions 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(l), x2sys_datalist(l)
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