<!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>5.1.1.1 Regular floating point coordinates</TITLE> <META NAME="description" CONTENT="5.1.1.1 Regular floating point coordinates"> <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="node82.html"> <LINK REL="previous" HREF="node80.html"> <LINK REL="up" HREF="node80.html"> <LINK REL="next" HREF="node82.html"> </HEAD> <BODY bgcolor="#ffffff"> <!--Navigation Panel--> <A NAME="tex2html3783" HREF="node82.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> <A NAME="tex2html3777" HREF="node80.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> <A NAME="tex2html3771" HREF="node80.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> <A NAME="tex2html3779" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> <A NAME="tex2html3781" HREF="node258.html"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A> <BR> <B> Next:</B> <A NAME="tex2html3784" HREF="node82.html">5.1.1.2 Geographic coordinates</A> <B> Up:</B> <A NAME="tex2html3778" HREF="node80.html">5.1.1 Cartesian linear transformation</A> <B> Previous:</B> <A NAME="tex2html3772" HREF="node80.html">5.1.1 Cartesian linear transformation</A> <B> <A NAME="tex2html3780" HREF="node1.html">Contents</A></B> <B> <A NAME="tex2html3782" HREF="node258.html">Index</A></B> <BR> <BR> <!--End of Navigation Panel--> <H3><A NAME="SECTION001311100000000000000"> 5.1.1.1 Regular floating point coordinates</A> </H3> <P> Selection of the Cartesian linear transformation with regular floating point coordinates will result in a simple linear scaling <IMG WIDTH="76" HEIGHT="32" ALIGN="MIDDLE" BORDER="0" SRC="img94.png" ALT="$u' = au + b$"> of the input coordinates. The projection is defined by stating <P> <UL> <LI>scale in inches/unit (<B>-Jx</B>) or axis length in inches (<B>-JX</B>) </LI> </UL> <P> If the <I>y</I>-scale or <I>y</I>-axis length is different from that of the <I>x</I>-axis (which is most often the case), separate the two scales (or lengths) by a slash, e.g., <B>-Jx</B>0.1i/0.5i or <B>-JX</B>8i/5i. Thus, our <IMG WIDTH="51" HEIGHT="33" ALIGN="MIDDLE" BORDER="0" SRC="img95.png" ALT="$y = \sqrt{x}$"> data sets will plot as shown in Figure <A HREF="#fig:GMT_linear">5.1</A>. <P> <DIV ALIGN="CENTER"><A NAME="fig:GMT_linear"></A><A NAME="21663"></A> <TABLE> <CAPTION ALIGN="BOTTOM"><STRONG>Figure 5.1:</STRONG> Linear transformation of Cartesian coordinates.</CAPTION> <TR><TD> <DIV ALIGN="CENTER"><IMG WIDTH="391" HEIGHT="209" ALIGN="BOTTOM" BORDER="0" SRC="img96.png" ALT="\includegraphics{scripts/GMT_linear}"></DIV></TD></TR> </TABLE> </DIV> <P> The complete commands given to produce this plot were <P> <BR CLEAR="ALL"> <HR> <BR> <PRE>psxy -R0/100/0/10 -JX3i/1.5i -Ba20f10g10/a2f1g2WSne -Wthick,- -P -K sqrt.d > GMT_linear.ps psxy -R -J -St0.075i -Glightgray -W -O sqrt.d10 >> GMT_linear.ps </PRE> <BR CLEAR="ALL"> <HR><A NAME="21457"></A> <A NAME="21458"></A> <P> Normally, the user's <I>x</I>-values will increase to the right and the <I>y</I>-values will increase upwards. It should be noted that in many situations it is desirable to have the direction of positive coordinates be reversed. For example, when plotting depth on the <I>y</I>-axis it makes more sense to have the positive direction downwards. All that is required to reverse the sense of positive direction is to supply a negative scale (or axis length). Finally, sometimes it is convenient to specify the width (or height) of a map and let the other dimension be computed based on the implied scale and the range of the other axis. To do this, simply specify the length to be recomputed as 0. <P> <HR> <!--Navigation Panel--> <A NAME="tex2html3783" HREF="node82.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.png"></A> <A NAME="tex2html3777" HREF="node80.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.png"></A> <A NAME="tex2html3771" HREF="node80.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="prev.png"></A> <A NAME="tex2html3779" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents.png"></A> <A NAME="tex2html3781" HREF="node258.html"> <IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index.png"></A> <BR> <B> Next:</B> <A NAME="tex2html3784" HREF="node82.html">5.1.1.2 Geographic coordinates</A> <B> Up:</B> <A NAME="tex2html3778" HREF="node80.html">5.1.1 Cartesian linear transformation</A> <B> Previous:</B> <A NAME="tex2html3772" HREF="node80.html">5.1.1 Cartesian linear transformation</A> <B> <A NAME="tex2html3780" HREF="node1.html">Contents</A></B> <B> <A NAME="tex2html3782" HREF="node258.html">Index</A></B> <!--End of Navigation Panel--> <ADDRESS> Paul Wessel 2011-02-27 </ADDRESS> </BODY> </HTML>