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<h2>NAME</h2>
<em><b>r.circle</b></em> - Creates a raster map containing concentric rings around a given point.
<h2>KEYWORDS</h2>
raster
<h2>SYNOPSIS</h2>
<b>r.circle</b><br>
<b>r.circle help</b><br>
<b>r.circle</b> [-<b>b</b>] <b>output</b>=<em>name</em> <b>coordinate</b>=<em>x,y</em> [<b>min</b>=<em>float</em>] [<b>max</b>=<em>float</em>] [<b>mult</b>=<em>float</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>-b</b></DT>
<DD>Generate binary raster map</DD>
<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>output</b>=<em>name</em></DT>
<DD>Name for output raster map</DD>
<DT><b>coordinate</b>=<em>x,y</em></DT>
<DD>The coordinate of the center (east,north)</DD>
<DT><b>min</b>=<em>float</em></DT>
<DD>Minimum radius for ring/circle map (in meters)</DD>
<DT><b>max</b>=<em>float</em></DT>
<DD>Maximum radius for ring/circle map (in meters)</DD>
<DT><b>mult</b>=<em>float</em></DT>
<DD>Multiplier</DD>
</DL>
<H2>DESCRIPTION</H2>
This module creates an output raster map centered on the <EM>x,y</EM> values specified
with the <EM>coordinate</EM> parameter, out to the edge of the current region.
The output cell values increase linearly from the specified center. The <EM>min</EM>
and <EM>max</EM> parameters control the inner and outer output raster map radii, respectively.
<p>
The <EM>mult</EM> parameter can be used to multiply the output raster cells by a common factor.
Note that this parameter does not affect the output raster position or size; only the z-values
are changed with this parameter.
<P>
Binary-output raster maps (solid circles of one value) can be created
with the <B>-b</B> flag. Raster maps so created can be used to create
binary filters for use in <EM>i.ifft</EM> (inverse Fourier transformations;
apply filter with <EM>r.mask</EM>).
<H2>EXAMPLES</H2>
Generate a raster circle at current map center with a radius of 300m and outwardly
increasing raster values:
<PRE>
EASTCENTER=`g.region -c | awk ' /center easting:/ { print $3 }'`
NORTHCENTER=`g.region -c | awk ' /center northing:/ { print $3 }'`
r.circle output=circle coordinate=${EASTCENTER},${NORTHCENTER} max=300
</PRE>
Generate a binary raster ring around current map center with an inner radius
of 500m and an outer radius of 1000m:
<PRE>
EASTCENTER=`g.region -c | awk ' /center easting:/ { print $3 }'`
NORTHCENTER=`g.region -c | awk ' /center northing:/ { print $3 }'`
r.circle -b output=circle coordinate=${EASTCENTER},${NORTHCENTER} min=500 max=1000
</PRE>
<H2>SEE ALSO</H2>
<EM>
<A HREF="g.region.html">g.region</A>,
<A HREF="g.remove.html">g.remove</A>,
<A HREF="g.rename.html">g.rename</A>,
<A HREF="i.fft.html">i.fft</A>,
<A HREF="i.ifft.html">i.ifft</A>,
<A HREF="r.mask">r.mask</A>
</EM>
<H2>AUTHOR</H2>
Bill Brown, U.S. Army Construction Engineering Research Laboratory<br>
Additional flag/min/max parameter by Markus Neteler, University of Hannover
<p>
<i>Last changed: $Date: 2008-01-22 15:21:36 +0100 (Tue, 22 Jan 2008) $</i>
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<P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p>
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