DESCRIPTION

This module creates an output raster map centered on the x,y values specified with the coordinate parameter, out to the edge of the current region. The output cell values increase linearly from the specified center. The min and max parameters control the inner and outer output raster map radii, respectively.

Binary output raster values can be created with the -b flag. Raster maps so created can be used to create binary filters for use in i.ifft (inverse Fourier transformations; apply filter with r.mask).

EXAMPLES

Generate a raster circle at current map center with a radius of 300m and outwardly increasing raster values: 
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
Generate a binary raster ring around current map center with an inner radius of 500m and an outer radius of 1000m: 
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

SEE ALSO

g.region, 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: $Date$