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<title>X_OVER</title>
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<h1 align=center>X_OVER</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#BEWARE">BEWARE</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<a href="#REFERENCES">REFERENCES</a><br>
<hr>
<a name="NAME"></a>
<h2>NAME</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x_over</b>
− Find and compute Cross-Over Errors</p>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x_over</b>
<i>leg_1</i> [ <i>leg_2</i> ] [ <b>−A</b> ] [
<b>−C</b> ] [ <b>−L</b> ] [ <b>−V</b> ] [
<b>−W</b><i>timegap</i> ] [ <b>−G</b><i>fact</i>
] [ <b>−M</b><i>fact</i> ] [
<b>−T</b><i>fact</i> ] [ <b>−N</b><i>np_int</i>
]</p>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</h2>
<p style="margin-left:11%; margin-top: 1em"><b>x_over</b>
is used to inspect two cruises to see if they intersect, and
if so report the time, position, discrepancies in
gravity/magnetics/bathymetry, heading for each track
segment, and the average values of the geophysical
observables at the cross-over point. The names of the legs
are passed on the command line. If they are identical or
only one name is passed, then <b>x_over</b> looks for
internal cross-overs. The optional parameters are:</p>
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<p style="margin-top: 1em" valign="top"><b>−A</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Use an Akima spline
to interpolate the geophysical field at the cross-over
point.</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−C</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Use a Natural Cubic
spline function instead.</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="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Use a linear
interpolant [Default].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−W</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Do not compute
cross-overs if the 2 nearest points are more than
<i>timegap</i> minutes apart.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−G</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Scale gravity by
<i>fact</i> [Default is 0.1 since gmt-files store gravity in
g.u.]</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−M</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Scale magnetic
anomaly by <i>fact</i> [1.0].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−T</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Scale bathymetry by
<i>fact</i> [1.0].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−N</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specify how many
points to use in the interpolation [Default is 6].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−V</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects verbose
mode, which will send progress reports to stderr [Default
runs "silently"]. Report the number of cross-overs
for this pair of legs.</p></td>
</table>
<a name="BEWARE"></a>
<h2>BEWARE</h2>
<p style="margin-left:11%; margin-top: 1em">The COEs found
are printed out to standard output in ASCII format. The
first record contains the leg 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. 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 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="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="x_system.html">x_system</A></i>(1)</p>
<a name="REFERENCES"></a>
<h2>REFERENCES</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P.
XOVER: A Cross-over Error Detector for Track Data,
<i>Computers & Geosciences, 15</i>, 333-346.</p>
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