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<H3><A NAME="SECTION001722200000000000000"></A>
<A NAME="13280"></A>
<BR>
B.2.2.2 Pixel registration
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<P>
Here, the nodes are centered in the grid cells, i.e., the areas
between grid lines, and the data points represent the average
values within each cell (Figure <A HREF="node117.html#fig:GMT_pixelreg">B.2</A>.
In the case of pixel 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} \\
ny & = & (y_{max} - y_{min}) / y_{inc}
\end{array}
\end{displaymath}
-->
<IMG
WIDTH="171" HEIGHT="45" BORDER="0"
SRC="img146.gif"
ALT="\begin{displaymath}\begin{array}{ccl}
nx & = & (x_{max} - x_{min}) / x_{inc} \\
ny & = & (y_{max} - y_{min}) / y_{inc}
\end{array} \end{displaymath}">
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Thus, given the same region (<B>-R</B>), the pixel registered grids have one less
column and one less row than the grid line registered grids; here we
find <IMG
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SRC="img147.gif"
ALT="$nx = ny = 3$">.
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<DIV ALIGN="CENTER"><A NAME="fig:GMT_pixelreg"></A><A NAME="13529"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure B.2:</STRONG>
Pixel registration of data nodes</CAPTION>
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SRC="img148.gif"
ALT="\begin{figure}\centering\epsfig{figure=eps/GMT_pixelreg.eps}\end{figure}"></TD></TR>
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<P>
<A NAME="13294"></A>
<A NAME="13295"></A>
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<BR><HR>
<ADDRESS>
Paul Wessel
2001-04-18
</ADDRESS>
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