r.distance(1)

NAME
r.distance - Locates the closest points between objects in two raster maps.

KEYWORDS
raster

SYNOPSIS
r.distance
r.distance help
r.distance [-loq] maps=map1,map2 [fs=string]

  Flags:

-l  Include category labels in the output

-o  Report zero distance if rasters are overlapping

-q  Run quietly

  Parameters:

maps=map1,map2
    Maps for computing inter-class distances

fs=string
    Output field separator Default: :

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 $

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