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<H3><A NAME="SECTION001922100000000000000"></A>
<A NAME="28732"></A>
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B.2.2.1 Gridline registration
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In this registration, the nodes are centered on the grid line
intersections and the data points represent the average value
in a cell of dimensions (<!-- MATH
$x_{inc} \cdot y_{inc}$
-->
<IMG
WIDTH="58" HEIGHT="29" ALIGN="MIDDLE" BORDER="0"
SRC="img219.png"
ALT="$x_{inc} \cdot y_{inc}$">) centered on the
nodes (Figure <A HREF="#fig:GMT_App_B_1">B.1</A>).
In the case of grid line registration the number of nodes are
related to region and grid spacing by
<BR>
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<!-- MATH
\begin{displaymath}
\begin{array}{ccl}
nx & = & (x_{max} - x_{min}) / x_{inc} + 1 \\
ny & = & (y_{max} - y_{min}) / y_{inc} + 1
\end{array}
\end{displaymath}
-->
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SRC="img220.png"
ALT="\begin{displaymath}\begin{array}{ccl}
nx & = & (x_{max} - x_{min}) / x_{inc} + 1 \\
ny & = & (y_{max} - y_{min}) / y_{inc} + 1
\end{array} \end{displaymath}">
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<P>
which for the example in Figure <A HREF="#fig:GMT_App_B_1">B.1</A> yields <IMG
WIDTH="81" HEIGHT="29" ALIGN="MIDDLE" BORDER="0"
SRC="img221.png"
ALT="$nx = ny = 4$">.
<P>
<DIV ALIGN="CENTER"><A NAME="fig:GMT_App_B_1"></A><A NAME="29087"></A>
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<CAPTION ALIGN="BOTTOM"><STRONG>Figure B.1:</STRONG>
Gridline registration of data nodes.</CAPTION>
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<ADDRESS>
Paul Wessel
2010-01-14
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