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<h2>NAME</h2>
<em><b>i.pca</b></em> - Principal components analysis (pca) program for image processing.
<h2>KEYWORDS</h2>
imagery
<h2>SYNOPSIS</h2>
<b>i.pca</b><br>
<b>i.pca help</b><br>
<b>i.pca</b> <b>input</b>=<em>name</em>[,<i>name</i>,...] <b>output</b>=<em>name</em> [<b>rescale</b>=<em>min,max</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>--overwrite</b></DT>
<DD>Allow output files to overwrite existing files</DD>
<DT><b>--verbose</b></DT>
<DD>Verbose module output</DD>
<DT><b>--quiet</b></DT>
<DD>Quiet module output</DD>
</DL>
<h3>Parameters:</h3>
<DL>
<DT><b>input</b>=<em>name[,<i>name</i>,...]</em></DT>
<DD>Name of input raster map(s)</DD>
<DT><b>output</b>=<em>name</em></DT>
<DD>Name for output raster map</DD>
<DT><b>rescale</b>=<em>min,max</em></DT>
<DD>Rescaling range output (For no rescaling use 0,0)</DD>
<DD>Default: <em>0,255</em></DD>
</DL>
<H2>DESCRIPTION</H2>
<EM>i.pca</EM> is an image processing program based on the
algorithm provided by Vali (1990), that processes n (2
>= n) input raster map layers and produces n output
raster map layers containing the principal components of
the input data in decreasing order of variance
("contrast"). The output raster map layers are assigned
names with .1, .2, ... .n suffixes. The current geographic
region definition and mask settings are respected when
reading the input raster map layers. When the rescale
option is used, the output files are rescaled to fit the
min,max range.
<H2>OPTIONS</H2>
<H3>Parameters:</H3>
<DL>
<DT><B>input=</B><EM>name,name</EM>[<EM>,name,name</EM>,...]
<DD>Name of two or more input raster map layers.
<DT><B>output=</B><EM>name</EM>
<DD>The output raster map layer name to which suffixes are
added. Each output raster map layer is assigned this
user-specified <EM>name</EM> with a numerical (.1, .2, ...
.n) suffix.
<DT><B>rescale=</B><EM>min,max</EM>
<DD>The optional output category range. (Default: 0,255) If
rescale=0,0, no rescaling is performed on output files.
<DD>If output is rescaled, the output raster will be of type CELL. If
the output is not rescaled, the output raster will be of type DCELL.
</DL>
<H2>NOTES</H2>
Richards (1986) gives a good example of the application of principal
components analysis (pca) to a time series of LANDSAT images of a burned
region in Australia.
<H2>SEE ALSO</H2>
Richards, John A.,
<B>Remote Sensing Digital Image Analysis</B>,
Springer-Verlag, 1986.
<P>
Vali, Ali R.,
Personal communication,
Space Research Center,
University of Texas, Austin, 1990.
<P>
<EM><A HREF="i.cca.html">i.cca</A></EM><br>
<EM><A HREF="i.class.html">i.class</A></EM><br>
<EM><A HREF="i.fft.html">i.fft</A></EM><br>
<EM><A HREF="i.ifft.html">i.ifft</A></EM><br>
<EM><A HREF="m.eigensystem.html">m.eigensystem</A></EM><br>
<EM><A HREF="r.covar.html">r.covar</A></EM><br>
<EM><A HREF="r.mapcalc.html">r.mapcalc</A></EM>
<H2>AUTHOR</H2>
David Satnik, GIS Laboratory
<p>
Major modifications for GRASS 4.1 were made by <br>
Olga Waupotitsch and
Michael Shapiro,
U.S.Army Construction Engineering
Research Laboratory
<p>
Rewritten for GRASS 6.x and major modifications by <br>
Brad Douglas
<p><i>Last changed: $Date: 2007-02-19 23:55:56 +0100 (Mon, 19 Feb 2007) $</i>
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