1X2SYS_CROSS(1) Generic Mapping Tools X2SYS_CROSS(1)
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6 x2sys_cross - Find and compute Cross-Over Errors
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9 x2sys_cross track(s) -TTAG [ -Cc|f|g|e ] [ -Fflags ] [ -Il|a|c ] [
10 -Jparameters ] [ -Kcombi.lis] [ -O ] [ -Nd|sunit ] [ -Qe|i ] [
11 -Sl|u|hspeed ] [ -V ][ -Wt|d|nsize ] [ -2 ] [
12 -bo[s|S|d|D[ncol]|c[var1/...]] ]
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15 x2sys_cross is used to determine all intersections between ("external
16 cross-overs") or within ("internal cross-overs") tracks, and report the
17 time, position, distance along track, heading and speed along each
18 tracksegment, and the crossover and mean values for all observables.
19 The names of the tracks are passed on the command line. By default,
20 x2sys_cross will look for both external and internal cross-overs. As
21 an option, you may choose to project all data using one of the map-pro‐
22 jections prior to calculating the crossovers.
23 tracks Can be one or more binary or ASCII data files. To give a list of
25 names, use `cat tracks.lis` or give the name of the track list
26 after a colon (e.g., :tracks.lis). If the names are missing the
27 suffix we will append the suffix that goes with this TAG. Track
28 files will be looked for first in the current directory and sec‐
29 ond in all directories listed in $X2SYS_HOME/TAG_paths.txt (if
30 it exists). [If $X2SYS_HOME is not set it will default to
31 $GMT_SHAREDIR/x2sys].
32 -T Sets the data set TAG which, among other things, sets the defi‐
34 nition file.
35
37 No space between the option flag and the associated arguments.
38 -C Select procedure for along-track distance calculation:
40 c Cartesian distances [Default].
41 f Flat Earth distances.
42 g Great circle distances.
43 e Geodesic distances on current GMT ellipsoid.
44 -F Sets which columns to use. Give a comma-separated list of col‐
46 umn names; this list must include x, y or lon, lat and ideally
47 time [Default selects all columns]. If time is not selected (or
48 selected but the cruises do not have time information), then we
49 output proxy times (e.g., floating point record numbers) instead
50 of time.
51 -I Sets the interpolation mode. Choose among:
53 l Linear interpolation [Default].
54 a Akima spline interpolation.
55 c Cubic spline interpolation.
56 -J Selects the map projection. Scale is UNIT/degree, 1:xxxxx, or
58 width in UNIT (upper case modifier). UNIT is cm, inch, or m,
59 depending on the MEASURE_UNIT setting in .gmtdefaults4, but this
60 can be overridden on the command line by appending c, i, or m to
61 the scale/width value. When central meridian is optional,
62 default is center of longitude range on -R option. Default
63 standard parallel is the equator. For map height, max dimen‐
64 sion, or min dimension, append h, +, or - to the width, respec‐
65 tively.
66 More details can be found in the psbasemap man pages.
67 CYLINDRICAL PROJECTIONS:
69 -Jclon0/lat0/scale (Cassini)
71 -Jcyl_stere/[lon0/[lat0/]]scale (Cylindrical Stereographic)
72 -Jj[lon0/]scale (Miller)
73 -Jm[lon0/[lat0/]]scale (Mercator)
74 -Jmlon0/lat0/scale (Mercator - Give meridian and standard paral‐
75 lel)
76 -Jo[a]lon0/lat0/azimuth/scale (Oblique Mercator - point and
77 azimuth)
78 -Jo[b]lon0/lat0/lon1/lat1/scale (Oblique Mercator - two points)
79 -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point and
80 pole)
81 -Jq[lon0/[lat0/]]scale (Cylindrical Equidistant)
82 -Jtlon0/[lat0/]scale (TM - Transverse Mercator)
83 -Juzone/scale (UTM - Universal Transverse Mercator)
84 -Jy[lon0/[lat0/]]scale (Cylindrical Equal-Area)
85 CONIC PROJECTIONS:
87 -Jblon0/lat0/lat1/lat2/scale (Albers)
89 -Jdlon0/lat0/lat1/lat2/scale (Conic Equidistant)
90 -Jllon0/lat0/lat1/lat2/scale (Lambert Conic Conformal)
91 AZIMUTHAL PROJECTIONS:
93 -Jalon0/lat0[/horizon]/scale (Lambert Azimuthal Equal-Area)
95 -Jelon0/lat0[/horizon]/scale (Azimuthal Equidistant)
96 -Jflon0/lat0[/horizon]/scale (Gnomonic)
97 -Jglon0/lat0[/horizon]/scale (Orthographic)
98 -Jglon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale
99 (General Perspective).
100 -Jslon0/lat0[/horizon][/slat]/scale (General Stereographic)
101 MISCELLANEOUS PROJECTIONS:
103 -Jh[lon0/]scale (Hammer)
105 -Ji[lon0/]scale (Sinusoidal)
106 -Jkf[lon0/]scale (Eckert IV)
107 -Jk[s][lon0/]scale (Eckert IV)
108 -Jn[lon0/]scale (Robinson)
109 -Jr[lon0/]scale (Winkel Tripel)
110 -Jv[lon0/]scale (Van der Grinten)
111 -Jw[lon0/]scale (Mollweide)
112 NON-GEOGRAPHICAL PROJECTIONS:
114 -Jp[a]scale[/origin][r|z] (Polar coordinates (theta,r))
116 -Jxx-scale[d|l|ppow|t|T][/y-scale[d|l|ppow|t|T]] (Linear, log,
117 and power scaling)
118 -K Only process the pair-combinations found in the file combi.lis
120 [Default process all possible combinations among the specified
121 files].
122 -L Output results using the old XOVER format [Default is X2SYS for‐
124 mat]. This option should only be used with *.gmt-formatted
125 MGD77 files.
126 -N Append d for distance or s for speed, then give the desired unit
128 as e (meter or m/s), k (km or km/hr), m (miles or miles/hr), or
129 n (nautical miles or knots). [Default is -Ndk -Nse (km and
130 m/s)].
131 -Q Append e for external crossovers only, and i for internal
133 crossovers only [Default is all crossovers].
134 -R west, east, south, and north specify the Region of interest, and
136 you may specify them in decimal degrees or in
137 [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left and
138 upper right map coordinates are given instead of w/e/s/n. The
139 two shorthands -Rg and -Rd stand for global domain (0/360 and
140 -180/+180 in longitude respectively, with -90/+90 in latitude).
141 -S Defines window of track speeds. If speeds are outside this win‐
143 dow we do not calculate a crossover. Specify
144 -Sl sets lower speed [Default is 0].
145 -Su sets upper speed [Default is Infinity].
146 -Sh does not limit the speed but sets a lower speed below
147 which headings will not be computed (i.e., set to NaN) [Default
148 calculates headings regardless of speed].
149 -V Selects verbose mode, which will send progress reports to stderr
151 [Default runs "silently"].
152 -W Give t, d, or n and append the corresponding maximum time gap
154 [Infinity], or distance gap [Infinity] (both in user units)
155 allowed between the two points immediately on either side of a
156 crossover. If the gap exceeds this maximum gap we skip the
157 crossover calculation. For -Wn, give the maximum number of
158 points on either side to use in the interpolation [3].
159 -2 Report the values of each track at the crossover [Default
161 reports the crossover value and the mean value].
162 -bo Selects binary output. Append s for single precision [Default
164 is d (double)]. Uppercase S or D will force byte-swapping.
165 Optionally, append ncol, the number of desired columns in your
166 binary output file.
167
169 The COEs found are printed out to standard output in ASCII format
170 (unless -bo is set). When ASCII is chosen, the output format depends
171 on whether or not old-style XOVER output (-L) has been selected. If
172 so, then the first record contains the file names and their start year,
173 whereas subsequent records have the data for each COE encountered. The
174 fields written out are lat, lon, time along track #1 and #2, x_gravity,
175 x_magnetics, x_bathymetry, average gravity, average magnetics, average
176 bathymetry, heading along track #1 and #2. If the default format is
177 chosen then the header record starts with "> ", and the output format
178 for crossovers are first 10 columns that contain x, y, time along track
179 #1 and #2, distance along track #1 and #2, heading along track #1 and
180 #2, velocity along track #1 and #2, and then pairs of (COE, average
181 value) for each data type (or track-values #1 and #2; see -2). It is
182 recommended that the Akima spline is used instead of the natural cubic
183 spline, since it is less sensitive to outliers that tend to introduce
184 wild oscillations in the interpolation.
185
187 If lega and legb are passed on the command line, then the COE value is
188 Value (lega) - Value (legb).
189
191 THe output format of individual columns are controlled by D_FORMAT
192 except for geographic coordinates (OUTPUT_DEGREE_FORMAT) and absolute
193 calendar time (OUTPUT_DATE_FORMAT, OUTPUT_CLOCK_FORMAT). Make sure
194 these are set to give you enough significant digits to achieve the
195 desired precision.
196
198 To compute all internal crossovers in the gmt-formatted file c2104.gmt,
199 and output in the old XOVER format, using the tag MGG, try
200 x2sys_cross c2104.gmt -L -TMGG > c2104.d
202 To find the crossover locations with bathymetry between the two MGD77
204 files A13232.mgd77 and A99938.mgd77, using the MGD77 tag, try
205 x2sys_cross A13232.mgd77 A99938.mgd77 -Qe -TNGD77 -Flon,lat,depth >
207 crossovers.d
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210 GMT(1), x2sys_init(1) x2sys_datalist(1) x2sys_get(1) x2sys_put(1)
211GMT 4.3.1 15 May 2008 X2SYS_CROSS(1)