## DESCRIPTION

This module creates a raster map containing concentric rings around a given point. The cell values are increasing linear from the center point to outer rings. Minimum and maximum radius can be selected. Optionally a "donut" ring can be created to use as (binary) filter for i.ifft inverse Fourier transform (apply filter with r.mask).

## EXAMPLES

Generate a circle at current map center with a radius of 300m:

          EASTCENTER=`g.region -c |  awk ' /region center easting:/ { print $4 }'`
          NORTHCENTER=`g.region -c | awk ' /region center northing:/ { print $4 }'`
          r.circle -b out=circle coordinate=$EASTCENTER,$NORTHCENTER max=300

## SEE ALSO

g.remove, g.rename, i.fft, i.ifft, r.mask

## AUTHOR

Bill Brown, U.S. Army Construction Engineering Research Laboratory
Additional flag/min/max parameter by Markus Neteler, University of Hannover

Last changed: $Date: 2003/05/06 12:50:53 $