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<H2><A NAME="SECTION001314000000000000000"></A>
<A NAME="sec:linear"></A><A NAME="6074"></A>
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5.1.4 Geographical linear projection
</H2>
<P>
<P></P>
<DIV ALIGN="CENTER"><A NAME="fig:GMT_linear_d"></A><A NAME="6085"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.4:</STRONG>
Linear transformation of map coordinates</CAPTION>
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ALT="\begin{figure}\centering\epsfig{figure=eps/GMT_linear_d.eps}\end{figure}"></TD></TR>
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While these linear projections are primarily designed for generic
<I>x</I>,<I>y</I> data, it is sometimes necessary to plot geographical
data in a linear projection. This poses a problem since longitudes
have a 360<IMG
WIDTH="11" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
SRC="img61.gif"
ALT="$^{o}$"> periodicity. <A NAME="tex2html300"
HREF="http://www.soest.hawaii.edu/gmt"><B>GMT</B></A> therefore needs to be informed
that it has been given geographical data although a linear projection
has been chosen. We do so by appending a <B>d</B> (for degrees) to
the end of the <B>-Jx</B> (or <B>-JX</B>) option. As an example, we
want to plot a crude world map centered on 125<IMG
WIDTH="11" HEIGHT="15" ALIGN="BOTTOM" BORDER="0"
SRC="img61.gif"
ALT="$^{o}$">E. Our command will be
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#!/bin/sh
# $Id: GMT_linear_d.sh,v 1.1 2001/03/21 04:10:21 pwessel Exp $
#
gmtset GRID_CROSS_SIZE 0.1i BASEMAP_TYPE FANCY DEGREE_FORMAT 3
pscoast -R-55/305/-90/90 -Jx0.014id -B60g30f15/30g30f15WSen -Dc -A1000 -G200 -W0.25p -P \
> GMT_linear_d.ps
gmtset GRID_CROSS_SIZE 0
</PRE>
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with the result reproduced in Figure <A HREF="node39.html#fig:GMT_linear_d">5.4</A>.
<P>
<A NAME="6142"></A>
<A NAME="6143"></A>
<A NAME="6168"></A>
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<ADDRESS>
Paul Wessel
2001-04-18
</ADDRESS>
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