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<title>GRDSPOTTER</title>
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<h1 align="center">GRDSPOTTER</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="#EXAMPLES">EXAMPLES</a><br>
<a href="#COORDINATES">COORDINATES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<a href="#REFERENCES">REFERENCES</a><br>
<hr>
<h2>NAME
<a name="NAME"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">grdspotter
− Create CVA image directly from gravity or bathymetry
grids</p>
<h2>SYNOPSIS
<a name="SYNOPSIS"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>grdspotter</b>
[<i>grdfile</i>] <b>−E</b><i>rotations_file</i>
<b>−G</b><i>CVAgrid</i>
<b>−I</b><i>xinc</i>[<i>unit</i>][<b>=</b>|<b>+</b>][/<i>yinc</i>[<i>unit</i>][<b>=</b>|<b>+</b>]]
<b>−R</b><i>west</i>/<i>east</i>/<i>south</i>/<i>north</i>[<b>r</b>]
[ <b>−A</b><i>agegrid</i> ] [
<b>−B</b><i>n_try</i> ] [ <b>−C</b> ] [
<b>−D</b><i>DIgrid</i> ] [ <b>−F</b> ] [
<b>−L</b> IT(IDgrid) ] [ <b>−M</b> ] [
<b>−N</b><i>upper_age</i> ] [
<b>−P</b><i>PAgrid</i> ] [
<b>−Q</b><i>IDinfo</i> ] [ <b>−S</b> ] [
<b>−T</b> ] [ <b>−U</b><i>fixed_val</i> ] [
<b>−V</b> ] [
<b>−Z</b><i>z_min</i>[/<i>z_max</i>[/<i>z_inc</i>]]
]</p>
<h2>DESCRIPTION
<a name="DESCRIPTION"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><b>grdspotter</b>
reads a grid file with residual bathymetry or gravity and
calculates flowlines from each node that exceeds a minimum
value using the specified rotations file. These flowlines
are then convolved with the volume of the prism represented
by each grid node and added up to give a Cumulative Volcano
Amplitude grid (CVA).</p>
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<td width="8%"></td>
<td width="7%"></td>
<td width="85%">
<p>No space between the option flag and the associated
arguments. Use upper case for the option flags and lower
case for modifiers.</p></td></tr>
</table>
<p style="margin-left:11%;"><i>grdfile</i></p>
<p style="margin-left:22%;">Data grid to be processed,
typically residual bathymetry or free-air anomalies.</p>
<table width="100%" border="0" rules="none" frame="void"
cellspacing="0" cellpadding="0">
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<td width="11%"></td>
<td width="3%">
<p><b>−E</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Give file with rotation parameters. This file must
contain one record for each rotation; each record must be of
the following format:</p></td></tr>
</table>
<p style="margin-left:22%; margin-top: 1em"><i>lon lat
tstart [tstop] angle</i> [ <i>khat a b c d e f g df</i>
]</p>
<p style="margin-left:22%; margin-top: 1em">where
<i>tstart</i> and <i>tstop</i> are in Myr and <i>lon lat
angle</i> are in degrees. <i>tstart</i> and <i>tstop</i> are
the ages of the old and young ends of a stage. If
<b>−C</b> is set then a total reconstruction rotation
is expected and <i>tstop</i> is implicitly set to 0 and
should not be specified in the file. If a covariance matrix
<b>C</b> for the rotation is available it must be specified
in a format using the nine optional terms listed in
brackets. Here, <b>C</b> = (<i>g</i>/<i>khat</i>)*[ <i>a b
d; b c e; d e f</i> ] which shows <b>C</b> made up of three
row vectors. If the degrees of freedom (<i>df</i>) in
fitting the rotation is 0 or not given it is set to 10000.
Blank lines and records whose first column contains # will
be ignored.</p>
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<p style="margin-top: 1em"><b>−G</b></p></td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em">Specify name for output CVA grid
file.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−I</b></p></td>
<td width="8%"></td>
<td width="78%">
<p><i>x_inc</i> [and optionally <i>y_inc</i>] is the grid
spacing. Optionally, append a suffix modifier.
<b>Geographical (degrees) coordinates</b>: Append <b>m</b>
to indicate arc minutes or <b>c</b> to indicate arc seconds.
If one of the units <b>e</b>, <b>k</b>, <b>i</b>, or
<b>n</b> is appended instead, the increment is assumed to be
given in meter, km, miles, or nautical miles, respectively,
and will be converted to the equivalent degrees longitude at
the middle latitude of the region (the conversion depends on
<b><A HREF="gmtdefaults.html#ELLIPSOID">ELLIPSOID</A></b>). If /<i>y_inc</i> is given but set to 0 it
will be reset equal to <i>x_inc</i>; otherwise it will be
converted to degrees latitude. <b>All coordinates</b>: If
<b>=</b> is appended then the corresponding max <i>x</i>
(<i>east</i>) or <i>y</i> (<i>north</i>) may be slightly
adjusted to fit exactly the given increment [by default the
increment may be adjusted slightly to fit the given domain].
Finally, instead of giving an increment you may specify the
<i>number of nodes</i> desired by appending <b>+</b> to the
supplied integer argument; the increment is then
recalculated from the number of nodes and the domain. The
resulting increment value depends on whether you have
selected a gridline-registered or pixel-registered grid; see
Appendix B for details. Note: if
<b>−R</b><i>grdfile</i> is used then grid spacing has
already been initialized; use <b>−I</b> to override
the values.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−R</b></p></td>
<td width="8%"></td>
<td width="78%">
<p><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.</p></td></tr>
</table>
<h2>OPTIONS
<a name="OPTIONS"></a>
</h2>
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cellspacing="0" cellpadding="0">
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<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em"><b>−A</b></p></td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em">Supply a crustal age grid that
is co-registered with the input data grid. These ages become
the upper ages to use when constructing flowlines [Default
extend flowlines back to oldest age found in the rotation
file; but see <b>−N</b>].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−B</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Get <i>n_try</i> bootstrap estimates of the maximum CVA
location; the longitude and latitude results are written to
stdout [Default is no bootstrapping]. Cannot be used with
<b>−M</b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−C</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Expect Total Reconstruction Rotations rather than
Forward Stage Rotations [Default]. File format is similar to
the stage pole format except that the <i>tstart</i> column
is not present (assumed to be 0 Ma).</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−D</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Use flowlines to determine the maximum CVA encountered
along each flowline and create a Data Importance (DI) grid
with these values at the originating nodes.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−F</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Force pixel registration [Default is grid
registration].</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−L</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Supply a co-registered grid with seamount chain IDs for
each node. This option requires that you also use
<b>−Q</b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−M</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Do not attempt to keep all flowlines in memory when
using <b>−D</b> and/or <b>−P</b>. Should you run
out of memory you can use this option to compute flowlines
on-the-fly. It will be slower as we no longer can reuse the
flowlines calculated for the CVA step. Cannot be used with
<b>−B</b> or the multi-slice mode in
<b>−Z</b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−N</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Set the upper age to assign to nodes whose crustal age
is unknown (i.e., NaN) [no upper age]. Also see
<b>−A</b>.</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−P</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Use flowlines to determine the flowline age at the CVA
maximum for each node and create a Predicted Age (PA) grid
with these values at the originating nodes.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−Q</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Either give (1) a single ID to use or (2) the name of a
file with a list of IDs to use [Default uses all IDs]. Each
line would be TAG ID [w e s n]. The <i>w/e/s/n</i> zoom box
is optional; if specified it means we only trace the
flowline if inside this region [Default uses region set by
<b>−R</b>]. Requires <b>−L</b>.</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−S</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Normalize the resulting CVA grid to percentages of the
CVA maximum. This also normalizes the DI grid (if
requested).</p> </td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−T</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Truncate crustal ages given via the <b>−A</b>
option that exceed the upper age set with <b>−N</b>
[no truncation].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−U</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>After a node passes the test implied by <b>−Z</b>,
use this <i>fixed_val</i> instead in the calculations.
[Default uses individual node values].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−V</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Selects verbose mode, which will send progress reports
to stderr [Default runs "silently"].</p></td></tr>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p><b>−Z</b></p></td>
<td width="8%"></td>
<td width="78%">
<p>Ignore nodes with z-values lower than <i>z_min</i> [0]
and optionally larger than <i>z_max</i> [Inf]. Give
<i>z_min/z_max/z_inc</i> to make separate CVA grids for each
<i>z</i>-slice [Default makes one CVA grid]. Multi-slicing
cannot be used with <b>−M</b>.</p></td></tr>
</table>
<h2>EXAMPLES
<a name="EXAMPLES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">To create a CVA
image from the Pacific topography grid Pac_res_topo.grd,
using the DC85.d Euler poles, and only output a grid for the
specified domain, run</p>
<p style="margin-left:11%; margin-top: 1em"><b>grdspotter</b>
Pac_res_topo.grd <b>−E</b> DC85.d <b>−G</b>
CVA.grd <b>−R</b> 190/220/15/25 <b>−I</b> 2<b>m
−N</b> 145 <b>−T −V</b></p>
<p style="margin-left:11%; margin-top: 1em">This file can
then be plotted with <b><A HREF="grdimage.html">grdimage</A></b>.</p>
<h2>COORDINATES
<a name="COORDINATES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Data
coordinates are assumed to be geodetic and will
automatically be converted to geocentric before spherical
rotations are performed. We convert back to geodetic
coordinates for output. Note: If your data already are
geocentric, you can avoid the conversion by using
--ELLIPSOID=sphere.</p>
<h2>SEE ALSO
<a name="SEE ALSO"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="GMT.html">GMT</A></i>(1),
<i><A HREF="grdimage.html">grdimage</A></i>(1), <i><A HREF="grdrotater.html">grdrotater</A></i>(1), <i><A HREF="project.html">project</A></i>(1),
<i><A HREF="mapproject.html">mapproject</A></i>(1), <i><A HREF="backtracker.html">backtracker</A></i>(1),
<i><A HREF="hotspotter.html">hotspotter</A></i>(1), <i><A HREF="originator.html">originator</A></i>(1)</p>
<h2>REFERENCES
<a name="REFERENCES"></a>
</h2>
<p style="margin-left:11%; margin-top: 1em">Wessel, P.,
1999, "Hotspotting" tools released, EOS Trans.
AGU, 80 (29), p. 319.</p>
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