r.distance

NAME

r.distance - Locates the closest points between objects in two raster maps. (GRASS Raster Program)

SYNOPSIS

r.distance
r.distance help
r.distance [-lq] maps=map1,map2 [fs=name]

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 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"

COMMAND LINE OPTIONS

Flags:

-l
Include category labels in the output
-q
Run quietly

Parameters:

maps
Maps for computing inter-class distances
fs
Output field separator
Default is a colon (:)

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;"draw",$6,$7}' | d.mapgraph

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

AUTHOR

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