NAME

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

KEYWORDS

       raster, distance

SYNOPSIS

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

   Flags:
       -l
           Include category labels in the output

       -o
           Report zero distance if rasters are overlapping

       -q
           Run quietly

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       maps=map1,map2[,map1,map2,...]
           Maps for computing inter-class distances

       fs=string
           Output field separator
           Default: :

DESCRIPTION

       r.distance  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, in the following form:
       cat1:cat2:distance:east1:north1:east2:north2

       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"

   Flags
       -l The -l flag outputs the category labels of the matched raster objects at the beginning of the line, if
       they exist.

       -o The -o flag reports zero distance if the input rasters are overlapping.

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.graph:

       awk -F: '{print "move",$4,$5,"\ndraw",$6,$7}' | d.graph -m

       To create a vector map of all  the  "map1"  coordinates,  filter  the  output  into  awk  and  then  into
       v.in.ascii:

       awk -F: '{print $4,$5}' | v.in.ascii format=point output=name fs=space

SEE ALSO

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

AUTHOR

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

       Last changed: $Date: 2011-11-08 03:29:50 -0800 (Tue, 08 Nov 2011) $

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       © 2003-2013 GRASS Development Team