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<H1><A NAME="SECTION0014170000000000000000"></A>
<A NAME="11801"></A>
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6.17 Images clipped by coastlines
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<P>
This example demonstrates how <A NAME="tex2html458"
HREF="../pscoast.html"><I><B>pscoast</B></I></A><A NAME="11816"></A> can be used
to set up clippaths based on coastlines. This approach
is well suited when different gridded data sets are to be
merged on a plot using different color palette files.
Merging the files themselves may not be doable since they
may represent different data sets, as we show in this example.
Here, we lay down a color map of the geoid field near India
with <A NAME="tex2html459"
HREF="../grdimage.html"><I><B>grdimage</B></I></A><A NAME="11825"></A>, use <A NAME="tex2html460"
HREF="../pscoast.html"><I><B>pscoast</B></I></A><A NAME="11834"></A> to set up land
clippaths, and then overlay topography from the ETOPO5 data
set with another call to <A NAME="tex2html461"
HREF="../grdimage.html"><I><B>grdimage</B></I></A><A NAME="11843"></A>. We finally undo
the clippath with a second call to <A NAME="tex2html462"
HREF="../pscoast.html"><I><B>pscoast</B></I></A><A NAME="11852"></A> with the
option <B>-Q</B> (Figure <A HREF="node90.html#fig:GMT_example_17">6.17</A>):
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grd2cpt india_geoid.grd -Crainbow >! geoid.cpt
grdgradient india_geoid.grd -Nt1 -A45 -Gindia_geoid_i.grd
grdimage india_geoid.grd -Iindia_geoid_i.grd -JM6.5i -Cgeoid.cpt -P -K -U"Example 17 in Cookbook" \
>! example_17.ps
pscoast -R60/90/-10/25 -JM -O -K -Dl -Gc >> example_17.ps
echo "-10000 150 10000 150" >! gray.cpt
grdgradient india_topo.grd -Nt1 -A45 -Gindia_topo_i.grd
grdimage india_topo.grd -Iindia_topo_i.grd -JM -Cgray.cpt -O -K >> example_17.ps
pscoast -R -JM -O -K -Q -B10f5:."Clipping of Images": >> example_17.ps
pstext -R -JM -O -M -W255O0.5p -D-0.1i/0.1i << EOF >> example_17.ps
> 90 -10 12 0 4 RB 12p 3i j
@_@%5%Example 17.@%%@_ We first plot the color geoid image
for the entire region, followed by a gray-shaded @#etopo5@#
image that is clipped so it is only visible inside the coastlines.
EOF
\rm -f geoid.cpt gray.cpt *_i.grd .gmt*
</PRE>
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<DIV ALIGN="CENTER"><A NAME="fig:GMT_example_17"></A><A NAME="11908"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 6.17:</STRONG>
Clipping of images using coastlines</CAPTION>
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WIDTH="430" HEIGHT="538" BORDER="0"
SRC="img123.gif"
ALT="\begin{figure}\centering\epsfig{figure=eps/GMT_example_17.eps}\end{figure}"></TD></TR>
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2001-04-18
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