## DESCRIPTION

Locates the closest points between "objects" in two raster maps. An "object" is defined as all the grid cells that have the same category number, and closest means having the shortest "straight-line" distance. The cell centers are considered for the distance calculation (two adjacent grid cells have the distance between their cell centers).

The output is an ascii list, one line per pair of objects

               cat1:cat2:distance:east1:north1:east2:north2

### Explanation:

cat1
  Category number from map1
cat2
  Category number from map2
distance
  The distance in meters between "cat1" and "cat2"
east1,north1
  The coordinates of the grid cell "cat1" which is closest to "cat2"
east2,north2
  The coordinates of the grid cell "cat2" which is closest to "cat1"

## NOTES

The output format lends itself to filtering. For example, to "see" lines connecting each of the category pairs in two maps, filter the output using awk and then into d.map graph:

r.distance maps=map1,map2 | \
awk -F: '{print "move",$4,$5,"\ndraw",$6,$7}' | d.graph -m

To create a site list of all the "map1" coordinates, filter the output into awk and then into s.in.ascii:

r.distance maps=map1,map2 | \
awk -F: '{print $4,$5}' | s.in.ascii sites=name

## SEE ALSO

r.buffer, r.cost, r.drain, v.distance

## AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory

Last changed: $Date: 2007/05/28 13:08:50 $