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<H1><A NAME="SECTION001540000000000000000"></A>
<A NAME="23747"></A>
<BR>
7.4 A 3-D perspective mesh plot
</H1>
<P>
This example will illustrate how to make a fairly complicated
composite figure. We need a subset of the ETOPO5 bathymetry<A NAME="tex2html1323"
HREF="footnode.html#foot23748"><SUP>7.1</SUP></A>and Geosat geoid data sets which we will extract from the local
data bases using <A NAME="tex2html1325"
HREF="../man/grdraster.html"><I><B>grdraster</B></I></A><A NAME="24369"></A>. We would like to show a
2-layer perspective plot where layer one shows a contour map
of the marine geoid with the location of the Hawaiian islands
superposed, and a second layer showing the 3-D mesh plot of
the topography. We also add an arrow pointing north and some
text. This is how to do it:
<P>
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<PRE>#!/bin/sh
# GMT EXAMPLE 04
#
# Purpose: 3-D mesh plot of Hawaiian topography and geoid
# GMT progs: grdcontour, grdview, pscoast, pstext
# Unix progs: echo, rm
#
ps=example_04.ps
echo '-10 255 0 255' > zero.cpt
echo ' 0 100 10 100' >> zero.cpt
grdcontour HI_geoid4.nc -Jm0.45i -E60/30 -R195/210/18/25 -C1 -A5+o -Gd4i -K -P -X1.5i -Y1.5i \
-U/-1.25i/-1.25i/"Example 4 in Cookbook" > $ps
pscoast -J -E60/30 -R -B2/2NEsw -Gblack -O -K -T209/19.5/1i >> $ps
grdview HI_topo4.nc -J -Jz0.34i -Czero.cpt -E60/30 -R195/210/18/25/-6/4 -N-6/lightgray -Qsm -O -K \
-B2/2/2:"Topo (km)":neswZ -Y2.2i >> $ps
echo '3.25 5.75 60 0.0 33 BC H@#awaiian@# R@#idge' | pstext -R0/10/0/10 -Jx1i -O >> $ps
rm -f zero.cpt .gmt*
</PRE>
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<P>
The purpose of the color palette file <U>zero.cpt</U> is to have
the positive topography mesh painted light gray (the remainder
is white). The left side of Figure <A HREF="#fig:GMT_example_04">7.4</A> shows the complete illustration.
<P>
<DIV ALIGN="CENTER"><A NAME="fig:GMT_example_04"></A><A NAME="23756"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 7.4:</STRONG>
3-D perspective mesh plot (left) and colored version (right).</CAPTION>
<TR><TD><IMG
WIDTH="335" HEIGHT="418" ALIGN="BOTTOM" BORDER="0"
SRC="img158.png"
ALT="\includegraphics[scale=0.42]{scripts/example_04}">
<IMG
WIDTH="335" HEIGHT="418" ALIGN="BOTTOM" BORDER="0"
SRC="img159.png"
ALT="\includegraphics[scale=0.42]{scripts/example_04c}"></TD></TR>
</TABLE>
</DIV>
<P>
A color version of this figure was used in our first article in <I>EOS
Trans. AGU</I> (Oct. 8th, 1991). It was created along similar
lines, but instead of a mesh plot we chose a color-coded surface
with artificial illumination from a light-source due north.
We choose to use the <B>-Qi</B> option in <A NAME="tex2html1326"
HREF="../man/grdview.html"><I><B>grdview</B></I></A><A NAME="24377"></A> to
achieve a high degree of smoothness. Here, we select 100 dpi
since that will be the resolution of our final raster
(The EOS raster was 300 dpi). We used <A NAME="tex2html1327"
HREF="../man/grdgradient.html"><I><B>grdgradient</B></I></A><A NAME="24382"></A> to
provide the intensity files. The following script creates
the color <I>PostScript</I> file. Note that the size of the
resulting output file is directly dependent on the square of
the dpi chosen for the scanline conversion. A higher value
for dpi in <B>-Qi</B> would have resulted in a much larger
output file. The cpt files were taken from Section <A HREF="node122.html#sec:example_02">7.2</A>.
<P>
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<PRE>#!/bin/sh
# GMT EXAMPLE 04c
#
# 3-D perspective color plot of Hawaiian topography and geoid
# GMT progs: grdcontour, grdview, pscoast, pstext
# Unix progs: echo, rm
#
ps=example_04c.ps
grdgradient HI_geoid4.nc -A0 -Gg_intens.grd -Nt0.75 -M
grdgradient HI_topo4.nc -A0 -Gt_intens.grd -Nt0.75 -M
grdview HI_geoid4.nc -Ig_intens.grd -JM6.75i -E60/30 -R195/210/18/25 -Cgeoid.cpt -Qi100 -K \
-X1.5i -Y1.25i -P -U/-1.25i/-1i/"Example 04c in Cookbook" > $ps
pscoast -J -E60/30 -R -B2/2NEsw -Gblack -O -K >> $ps
psbasemap -R -J -E60/30 -O -K -T209/19.5/1i --COLOR_BACKGROUND=red --TICK_PEN=thinner,red >> $ps
grdview HI_topo4.nc -It_intens.grd -J -JZ3.4i -Ctopo.cpt -E60/30 -R195/210/18/25/-6/4 \
-N-6/lightgray -Qi100 -O -K -Y2.2i >> $ps
psbasemap -J -JZ3.4i -E60/30 -R -Z-6 -O -K -B2/2/2:"Topo (km)":neZ >> $ps
echo '3.25 5.75 60 0.0 33 BC H@#awaiian@# R@#idge' | pstext -R0/10/0/10 -Jx1i -O >> $ps
rm -f *_intens.grd .gmt*
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Paul Wessel
2010-01-14
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