Geografic-Information-System/raster/r.rescale/r.rescale.html

<h2>DESCRIPTION</h2>

The <em>r.rescale</em> program rescales the range of
category values appearing in a raster map layer.  A new
raster map layer, and an appropriate category file and
color table based upon the original raster map layer, are
generated with category labels that reflect the original
category values that produced each category.  This command
is useful for producing representations with a reduced
number of categories from a raster map layer with a large
range of category values (e.g., elevation).
<em>Rescaled</em> map layers are appropriate for use in
such GRASS programs as

<em><a href="r.stats.html">r.stats</a></em>,
<em><a href="r.report.html">r.report</a></em>, and 
<em><a href="r.coin.html">r.coin</a></em>.

<h2>EXAMPLE</h2>

To rescale an elevation raster map layer with category
values ranging from 1090 meters to 1800 meters into the
range 0-255, the following command line could be used
(without the <em>from</em> parameter, the full value range will 
be used):

<div class="code"><pre>
r.rescale input=elevation from=1090,1800 output=elevation.255 to=0,255
</pre></div>

<h2>NOTES</h2>

Category values that fall beyond the input range will
become NULL.  This allows the user to select a subset of
the full category value range for rescaling if desired.
This also means that the user should know the category
value range for the input raster map layer.  The user can
request the <em>r.rescale</em> program to determine
this range, or can obtain it using the
<em><a href="r.describe.html">r.describe</a></em> or <em><a href="r.info.html">r.info</a></em> 
command.  If the category value range is determined using
<em>r.rescale</em>, the input raster map layer is examined,
and the minimum and maximum non-NULL category values are
selected as the input range.

<h2>SEE ALSO</h2>

<em><a href="r.coin.html">r.coin</a></em>,
<em><a href="r.describe.html">r.describe</a></em>,
<em><a href="r.info.html">r.info</a></em>,
<em><a href="r.mapcalc.html">r.mapcalc</a></em>,
<em><a href="r.reclass.html">r.reclass</a></em>,
<em><a href="r.rescale.eq.html">r.rescale.eq</a></em>,
<em><a href="r.report.html">r.report</a></em>,
<em><a href="r.resample.html">r.resample</a></em>,
<em><a href="r.stats.html">r.stats</a></em>

<h2>AUTHOR</h2>
Michael Shapiro,
U.S.Army Construction Engineering Research Laboratory

<p><i>Last changed: $Date$</i>