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<H2><A NAME="SECTION001323000000000000000">
5.2.3 Equidistant Conic Projection (<B>-Jd</B> <B>-JD</B>)</A>
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<A NAME="6585"></A>
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<P>
The equidistant conic projection was described by the Greek
philosopher Claudius Ptolemy about A.D. 150. It is neither
conformal or equal-area, but serves as a compromise between them.
The scale is true along all meridians and the standard parallels.
To select this projection in <A NAME="tex2html309"
HREF="http://www.soest.hawaii.edu/gmt"><B>GMT</B></A> you must
provide the same information as for the other conic projection, i.e.
<P>
<DL>
<DT><STRONG><IMG
WIDTH="12" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"
SRC="img54.gif"
ALT="$\bullet$"></STRONG></DT>
<DD>Longitude and latitude of the projection center
</DD>
<DT><STRONG><IMG
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SRC="img54.gif"
ALT="$\bullet$"></STRONG></DT>
<DD>Two standard parallels
</DD>
<DT><STRONG><IMG
WIDTH="12" HEIGHT="13" ALIGN="BOTTOM" BORDER="0"
SRC="img54.gif"
ALT="$\bullet$"></STRONG></DT>
<DD>Map scale in inch/degree or 1:xxxxx notation
(<B>-Jd</B>), or map width (<B>-JD</B>)
</DD>
</DL>
<P>
The equidistant conic projection is often used for atlases with
maps of small countries. As an example, we generate a map of
Cuba:
<P>
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<PRE>
#!/bin/sh
# $Id: GMT_equidistant_conic.sh,v 1.1 2001/03/21 04:10:21 pwessel Exp $
#
gmtset DEGREE_FORMAT 3 GRID_CROSS_SIZE 0.05i
pscoast -R-88/-70/18/24 -JD-79/21/19/23/4.5i -B5g1 -Di -N1/1p -G200 \
-W0.25p -P > GMT_equidistant_conic.ps
gmtset GRID_CROSS_SIZE 0
</PRE>
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<DIV ALIGN="CENTER"><A NAME="fig:GMT_equidistant_conic"></A><A NAME="6713"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.8:</STRONG>
Equidistant conic map projection</CAPTION>
<TR><TD><IMG
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<ADDRESS>
Paul Wessel
2001-04-18
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