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<title>X2SYS_CROSS</title>
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<body bgcolor="#ffffff">
<h1 align=center>X2SYS_CROSS</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#OPTIONS">OPTIONS</a><br>
<a href="#REMARKS">REMARKS</a><br>
<a href="#SIGN CONVENTION">SIGN CONVENTION</a><br>
<a href="#PRECISION AND FORMAT">PRECISION AND FORMAT</a><br>
<a href="#EXAMPLES">EXAMPLES</a><br>
<a href="#REFERENCES">REFERENCES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<hr>
<a name="NAME"></a>
<h2>NAME</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x2sys_cross</b>
− Find and compute crossover errors</p>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x2sys_cross</b>
<i>track(s)</i> <b>−T</b><i>TAG</i> [
<b>−Il</b>|<b>a</b>|<b>c</b> ] [
<b>−J</b><i>parameters</i> ] [
<b>−K</b><i>combi.lis</i> ] [ <b>−L</b> ] [
<b>−Qe</b>|<b>i</b> ] [
<b>−Sl</b>|<b>u</b>|<b>h</b><i>speed</i> ] [
<b>−V</b> ] [ <b>−W</b><i>size</i> ] [
<b>−2</b> ] [
<b>−bo</b>[<b>s</b>|<b>S</b>|<b>d</b>|<b>D</b>[<i>ncol</i>]|<b>c</b>[<i>var1</i><b>/</b><i>...</i>]]
]</p>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x2sys_cross</b>
is used to determine all intersections between
("external cross-overs") or within ("internal
cross-overs") tracks (Cartesian or geographic), and
report the time, position, distance along track, heading and
speed along each track segment, and the crossover error
(COE) and mean values for all observables. The names of the
tracks are passed on the command line. By default,
<b>x2sys_cross</b> will look for both external and internal
COEs. As an option, you may choose to project all data using
one of the map-projections prior to calculating the COE.</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p style="margin-top: 1em" valign="top"><i>tracks</i></p></td>
<td width="2%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Can be one or more
ASCII, native binary, or COARDS netCDF 1-D data files. To
supply the data files via a text file with a list of tracks
(one per record), specify the name of the track list after a
leading equal-sign (e.g., =tracks.lis). If the names are
missing their file extension we will append the suffix
specified for this <i>TAG</i>. Track files will be searched
for first in the current directory and second in all
directories listed in
<b>$X2SYS_HOME</b>/<i>TAG</i>/<i>TAG</i>_paths.txt (if it
exists). [If <b>$X2SYS_HOME</b> is not set it will default
to <b>$GMT_SHAREDIR</b>/x2sys]. (Note: MGD77 files will also
be looked for via <b>MGD77_HOME</b>/mgd77_paths.txt and
*.gmt files will be searched for via
<b>$GMT_SHAREDIR</b>/mgg/gmtfile_paths).</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="9%">
<p style="margin-top: 1em" valign="top"><b>−T</b></p> </td>
<td width="2%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specify the x2sys
<i>TAG</i> which tracks the attributes of this data
type.</p> </td>
</table>
<a name="OPTIONS"></a>
<h2>OPTIONS</h2>
<p style="margin-left:11%; margin-top: 1em">No space
between the option flag and the associated arguments.</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−I</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Sets the
interpolation mode for estimating values at the crossover.
Choose among:</p></td>
</table>
<p style="margin-left:22%;"><b>l</b> Linear interpolation
[Default]. <b><br>
a</b> Akima spline interpolation. <b><br>
c</b> Cubic spline interpolation.</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−J</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 <b><A HREF="gmtdefaults.html#MEASURE_UNIT">MEASURE_UNIT</A></b> setting in .gmtdefaults4, but this
can be overridden on the command line by appending <b>c</b>,
<b>i</b>, or <b>m</b> to the scale/width value. When central
meridian is optional, default is center of longitude range
on <b>−R</b> option. Default standard parallel is the
equator. For map height, max dimension, or min dimension,
append <b>h</b>, <b>+</b>, or <b>-</b> to the width,
respectively.</p> </td>
</table>
<p style="margin-left:22%;">More details can be found in
the <b><A HREF="psbasemap.html">psbasemap</A></b> man pages.</p>
<p style="margin-left:22%; margin-top: 1em"><b>CYLINDRICAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jc</b><i>lon0/lat0/scale</i>
(Cassini) <b><br>
−Jcyl_stere</b>/[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Stereographic) <b><br>
−Jj</b>[<i>lon0/</i>]<i>scale</i> (Miller) <b><br>
−Jm</b>[<i>lon0</i>/[<i>lat0/</i>]]<i>scale</i>
(Mercator) <b><br>
−Jm</b><i>lon0/lat0/scale</i> (Mercator - Give
meridian and standard parallel) <b><br>
−Jo</b>[<b>a</b>]<i>lon0/lat0/azimuth/scale</i>
(Oblique Mercator - point and azimuth) <b><br>
−Jo</b>[<b>b</b>]<i>lon0/lat0/lon1/lat1/scale</i>
(Oblique Mercator - two points) <b><br>
−Joc</b><i>lon0/lat0/lonp/latp/scale</i> (Oblique
Mercator - point and pole) <b><br>
−Jq</b>[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Equidistant) <b><br>
−Jt</b><i>lon0/</i>[<i>lat0/</i>]<i>scale</i> (TM -
Transverse Mercator) <b><br>
−Ju</b><i>zone/scale</i> (UTM - Universal Transverse
Mercator) <b><br>
−Jy</b>[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Equal-Area)</p>
<p style="margin-left:22%; margin-top: 1em"><b>CONIC
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jb</b><i>lon0/lat0/lat1/lat2/scale</i>
(Albers) <b><br>
−Jd</b><i>lon0/lat0/lat1/lat2/scale</i> (Conic
Equidistant) <b><br>
−Jl</b><i>lon0/lat0/lat1/lat2/scale</i> (Lambert Conic
Conformal) <b><br>
−Jpoly</b>/[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
((American) Polyconic)</p>
<p style="margin-left:22%; margin-top: 1em"><b>AZIMUTHAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Ja</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Lambert Azimuthal Equal-Area) <b><br>
−Je</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Azimuthal Equidistant) <b><br>
−Jf</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Gnomonic) <b><br>
−Jg</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Orthographic) <b><br>
−Jg</b><i>lon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale</i>
(General Perspective). <b><br>
−Js</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(General Stereographic)</p>
<p style="margin-left:22%; margin-top: 1em"><b>MISCELLANEOUS
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jh</b>[<i>lon0/</i>]<i>scale</i>
(Hammer) <b><br>
−Ji</b>[<i>lon0/</i>]<i>scale</i> (Sinusoidal) <b><br>
−Jkf</b>[<i>lon0/</i>]<i>scale</i> (Eckert IV) <b><br>
−Jk</b>[<b>s</b>][<i>lon0/</i>]<i>scale</i> (Eckert
VI) <b><br>
−Jn</b>[<i>lon0/</i>]<i>scale</i> (Robinson) <b><br>
−Jr</b>[<i>lon0/</i>]<i>scale</i> (Winkel Tripel)
<b><br>
−Jv</b>[<i>lon0/</i>]<i>scale</i> (Van der Grinten)
<b><br>
−Jw</b>[<i>lon0/</i>]<i>scale</i> (Mollweide)</p>
<p style="margin-left:22%; margin-top: 1em"><b>NON-GEOGRAPHICAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jp</b>[<b>a</b>]<i>scale</i>[<i>/origin</i>][<b>r</b>|<b>z</b>]
(Polar coordinates (theta,r)) <b><br>
−Jx</b><i>x-scale</i>[<b>d</b>|<b>l</b>|<b>p</b><i>pow</i>|<b>t</b>|<b>T</b>][<i>/y-scale</i>[<b>d</b>|<b>l</b>|<b>p</b><i>pow</i>|<b>t</b>|<b>T</b>]]
(Linear, log, and power scaling)</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−K</b></p> </td>
<td width="4%"></td>
<td width="82%">
<p style="margin-top: 1em" valign="top">Only process the
pair-combinations found in the file <i>combi.lis</i>
[Default process all possible combinations among the
specified files].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−L</b></p> </td>
<td width="4%"></td>
<td width="82%">
<p style="margin-top: 1em" valign="top">Output results
using the old XOVER format [Default is x2sys format]. This
option should only be used with *.gmt-formatted MGD77 files.
See the GMT mgg supplement for file description; see
<i>Wessel</i> [1989] for details on the XOVER format.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−Q</b></p> </td>
<td width="4%"></td>
<td width="82%">
<p style="margin-top: 1em" valign="top">Append <b>e</b> for
external COEs only, and <b>i</b> for internal COEs only
[Default is all COEs].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−R</b></p> </td>
<td width="4%"></td>
<td width="82%">
<p style="margin-top: 1em" valign="top"><i>west, east,
south,</i> and <i>north</i> specify the Region of interest,
and you may specify them in decimal degrees or in
[+-]dd:mm[:ss.xxx][W|E|S|N] format. Append <b>r</b> if lower
left and upper right map coordinates are given instead of
w/e/s/n. The two shorthands <b>−Rg</b> and
<b>−Rd</b> stand for global domain (0/360 and
-180/+180 in longitude respectively, with -90/+90 in
latitude). Alternatively, specify the name of an existing
grid file and the <b>−R</b> settings (and grid
spacing, if applicable) are copied from the grid. For
Cartesian data just give <i>xmin/xmax/ymin/ymax</i>. This
option limits the COEs to those that fall inside the
specified domain.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−S</b></p> </td>
<td width="4%"></td>
<td width="82%">
<p style="margin-top: 1em" valign="top">Defines window of
track speeds. If speeds are outside this window we do not
calculate a COE. Specify</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%"></td>
<td width="4%"></td>
<td width="82%">
<p valign="top"><b>−Sl</b> sets lower speed [Default
is 0].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%"></td>
<td width="4%"></td>
<td width="82%">
<p valign="top"><b>−Su</b> sets upper speed [Default
is Infinity].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%"></td>
<td width="4%"></td>
<td width="82%">
<p valign="top"><b>−Sh</b> does not limit the speed
but sets a lower speed below which headings will not be
computed (i.e., set to NaN) [Default calculates headings
regardless of speed].</p></td>
</table>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−V</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects verbose
mode, which will send progress reports to stderr [Default
runs "silently"].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−W</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Give the maximum
number of data points on either side of the crossover to use
in the spline interpolation [3].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−2</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Report the values
of each track at the crossover [Default reports the
crossover value and the mean value].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="4%">
<p style="margin-top: 1em" valign="top"><b>−bo</b></p> </td>
<td width="7%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects binary
output. Append <b>s</b> for single precision [Default is
<b>d</b> (double)]. Uppercase <b>S</b> or <b>D</b> will
force byte-swapping. Optionally, append <i>ncol</i>, the
number of desired columns in your binary output file.</p></td>
</table>
<a name="REMARKS"></a>
<h2>REMARKS</h2>
<p style="margin-left:11%; margin-top: 1em">The COEs found
are printed out to standard output in ASCII format (unless
<b>−bo</b> is set). When ASCII is chosen, the output
format depends on whether or not old-style XOVER output
(<b>−L</b>) has been selected [See the <b><A HREF="x_over.html">x_over</A></b>
man page for more details]. If ASCII, then the first record
contains the name of the tag used, the second records
specifies the exact command line used for this run, and the
third record contains the names of each column. For each
track pair, there will be a multisegment header record
containing the two file names and their start/stop/dist
information (start/stop is absolute time or NaN if
unavailable while dist is the total track length), whereas
subsequent records have the data for each COE encountered.
The fields written out are x, y, time along track #1 and #2,
distance along track #1 and #2, heading along track #1 and
#2, velocity along track #1 and #2, and then pairs of
columns for each selected observable. These are either pairs
of (COE, average value) for each data type (or track-values
#1 and #2; see <b>−2</b>). It is recommended 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.</p>
<a name="SIGN CONVENTION"></a>
<h2>SIGN CONVENTION</h2>
<p style="margin-left:11%; margin-top: 1em">If track_a and
track_b are passed on the command line, then the COE value
is Value (track_a) - Value (track_b).</p>
<a name="PRECISION AND FORMAT"></a>
<h2>PRECISION AND FORMAT</h2>
<p style="margin-left:11%; margin-top: 1em">The output
format of individual columns are controlled by
<b><A HREF="gmtdefaults.html#D_FORMAT">D_FORMAT</A></b> except for geographic coordinates
(<b><A HREF="gmtdefaults.html#OUTPUT_DEGREE_FORMAT">OUTPUT_DEGREE_FORMAT</A></b>) and absolute calendar time
(<b><A HREF="gmtdefaults.html#OUTPUT_DATE_FORMAT">OUTPUT_DATE_FORMAT</A></b>, <b><A HREF="gmtdefaults.html#OUTPUT_CLOCK_FORMAT">OUTPUT_CLOCK_FORMAT</A></b>).
Make sure these are set to give you enough significant
digits to achieve the desired precision.</p>
<a name="EXAMPLES"></a>
<h2>EXAMPLES</h2>
<p style="margin-left:11%; margin-top: 1em">To compute all
internal crossovers in the gmt-formatted file c2104.gmt, and
output in the old XOVER format, using the tag GMT, try</p>
<p style="margin-left:11%; margin-top: 1em"><b>x2sys_cross</b>
c2104.gmt <b>−L −T</b> GMT > c2104.d</p>
<p style="margin-left:11%; margin-top: 1em">To find the
crossover locations with bathymetry between the two MGD77
files A13232.mgd77 and A99938.mgd77, using the MGD77 tag,
try</p>
<p style="margin-left:11%; margin-top: 1em"><b>x2sys_cross</b>
A13232.mgd77 A99938.mgd77 <b>−Qe −T</b> MGD77
> crossovers.d</p>
<a name="REFERENCES"></a>
<h2>REFERENCES</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P.
(2010), Tools for analyzing intersecting tracks: the x2sys
package. IT(Computers and Geosciences), BD(36), 348-354.
<br>
Wessel, P. (1989), XOVER: A cross-over error detector for
track data, <i>Computers and Geosciences, 15</i>(3),
333-346.</p>
<a name="SEE ALSO"></a>
<h2>SEE ALSO</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="GMT.html">GMT</A></i>(1),
<i><A HREF="x2sys_binlist.html">x2sys_binlist</A></i>(1), <i><A HREF="x2sys_init.html">x2sys_init</A></i>(1),
<i><A HREF="x2sys_datalist.html">x2sys_datalist</A></i>(1), <i><A HREF="x2sys_get.html">x2sys_get</A></i>(1),
<i><A HREF="x2sys_list.html">x2sys_list</A></i>(1), <i><A HREF="x2sys_put.html">x2sys_put</A></i>(1),
<i><A HREF="x2sys_report.html">x2sys_report</A></i>(1), <i><A HREF="x2sys_solve.html">x2sys_solve</A></i>(1),
<i><A HREF="x_over.html">x_over</A></i>(1)</p>
<hr>
</body>
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