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