<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <!--Converted with LaTeX2HTML 2002-2-1 (1.71) original version by: Nikos Drakos, CBLU, University of Leeds * revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan * with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --> <HTML> <HEAD> <TITLE>5. GMT Coordinate Transformations</TITLE> <META NAME="description" CONTENT="5. GMT Coordinate Transformations"> <META NAME="keywords" CONTENT="GMT_Docs"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <META NAME="Generator" CONTENT="LaTeX2HTML v2002-2-1"> <META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"> <LINK REL="STYLESHEET" HREF="GMT_Docs.css"> <LINK REL="next" HREF="node85.html"> <LINK REL="previous" HREF="node31.html"> <LINK REL="up" HREF="GMT_Docs.html"> <LINK REL="next" HREF="node77.html"> </HEAD> <BODY bgcolor="#ffffff"> <!--Navigation Panel--> <A NAME="tex2html3622" HREF="node77.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> <A NAME="tex2html3616" HREF="GMT_Docs.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> <A NAME="tex2html3610" HREF="node75.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> <A NAME="tex2html3618" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> <A NAME="tex2html3620" HREF="node256.html"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A> <BR> <B> Next:</B> <A NAME="tex2html3623" HREF="node77.html">5.1 Cartesian transformations</A> <B> Up:</B> <A NAME="tex2html3617" HREF="GMT_Docs.html">GMT - Technical Reference</A> <B> Previous:</B> <A NAME="tex2html3611" HREF="node75.html">4.20 GMT environment parameters</A> <B> <A NAME="tex2html3619" HREF="node1.html">Contents</A></B> <B> <A NAME="tex2html3621" HREF="node256.html">Index</A></B> <BR> <BR> <!--End of Navigation Panel--> <H1><A NAME="SECTION001300000000000000000"></A> <A NAME="ch:5"></A> <BR> 5. <A NAME="tex2html1241" HREF="http://gmt.soest.hawaii.edu"><B>GMT</B></A> Coordinate Transformations </H1> <P> <A NAME="tex2html1242" HREF="http://gmt.soest.hawaii.edu"><B>GMT</B></A> programs read real-world coordinates and convert them to positions on a plot. This is achieved by selecting one of several coordinate transformations or projections. We distinguish between three sets of such conversions: <P> <UL> <LI>Cartesian coordinate transformations </LI> <LI>Polar coordinate transformations </LI> <LI>Map coordinate transformations </LI> </UL> <P> The next chapter will be dedicated to <A NAME="tex2html1243" HREF="http://gmt.soest.hawaii.edu"><B>GMT</B></A> map projections in its entirety. Meanwhile, the present chapter will summarize the properties of the Cartesian and Polar coordinate transformations available in <A NAME="tex2html1244" HREF="http://gmt.soest.hawaii.edu"><B>GMT</B></A>, list which parameters define them, and demonstrate how they are used to create simple plot axes. We will mostly be using <A NAME="tex2html1245" HREF="../man/psbasemap.html"><I><B>psbasemap</B></I></A><A NAME="21129"></A> (and occasionally <A NAME="tex2html1246" HREF="../man/psxy.html"><I><B>psxy</B></I></A><A NAME="21134"></A>) to demonstrate the various transformations. Our illustrations may differ from those you reproduce with the same commands because of different settings in our <U>.gmtdefaults4</U> file.) Finally, note that while we will specify dimensions in inches (by appending <B>i</B>), you may want to use cm (<B>c</B>), meters (<B>m</B>), or points (<B>p</B>) as unit instead (see the <A NAME="tex2html1247" HREF="../man/gmtdefaults.html"><I><B>gmtdefaults</B></I></A><A NAME="21140"></A> man page). <P> <BR><HR> <!--Table of Child-Links--> <A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A> <UL> <LI><A NAME="tex2html3624" HREF="node77.html">5.1 Cartesian transformations</A> <UL> <LI><A NAME="tex2html3625" HREF="node78.html">5.1.1 Cartesian linear transformation (<B>-Jx</B> <B>-JX</B>)</A> <UL> <LI><A NAME="tex2html3626" HREF="node79.html">5.1.1.1 Regular floating point coordinates</A> <LI><A NAME="tex2html3627" HREF="node80.html">5.1.1.2 Geographic coordinates</A> <LI><A NAME="tex2html3628" HREF="node81.html">5.1.1.3 Calendar time coordinates</A> </UL> <LI><A NAME="tex2html3629" HREF="node82.html">5.1.2 Cartesian logarithmic projection</A> <LI><A NAME="tex2html3630" HREF="node83.html">5.1.3 Cartesian power projection</A> </UL> <BR> <LI><A NAME="tex2html3631" HREF="node84.html">5.2 Linear projection with polar (<IMG WIDTH="27" HEIGHT="29" ALIGN="MIDDLE" BORDER="0" SRC="img5.png" ALT="$\theta , r$">) coordinates (<B>-Jp </B> <B>-JP</B>)</A> </UL> <!--End of Table of Child-Links--> <HR> <!--Navigation Panel--> <A NAME="tex2html3622" HREF="node77.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> <A NAME="tex2html3616" HREF="GMT_Docs.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> <A NAME="tex2html3610" HREF="node75.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> <A NAME="tex2html3618" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> <A NAME="tex2html3620" HREF="node256.html"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A> <BR> <B> Next:</B> <A NAME="tex2html3623" HREF="node77.html">5.1 Cartesian transformations</A> <B> Up:</B> <A NAME="tex2html3617" HREF="GMT_Docs.html">GMT - Technical Reference</A> <B> Previous:</B> <A NAME="tex2html3611" HREF="node75.html">4.20 GMT environment parameters</A> <B> <A NAME="tex2html3619" HREF="node1.html">Contents</A></B> <B> <A NAME="tex2html3621" HREF="node256.html">Index</A></B> <!--End of Navigation Panel--> <ADDRESS> Paul Wessel 2010-07-14 </ADDRESS> </BODY> </HTML>
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