NAME

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

KEYWORDS

       raster, distance

SYNOPSIS

       r.distance
       r.distance --help
       r.distance [-lon] map=name1,name2[,name1,name2,...]  [separator=character]   [sort=string]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -l
           Include category labels in the output

       -o
           Report zero distance if rasters are overlapping

       -n
           Report null objects as *

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       map=name1,name2[,name1,name2,...] [required]
           Name of two input raster maps for computing inter-class distances

       separator=character
           Field separator
           Special characters: pipe, comma, space, tab, newline
           Default: :

       sort=string
           Sort output by distance
           Default: sorted by categories
           Options: asc, desc
           asc: Sort by distance in ascending order
           desc: Sort by distance in descending order

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:

       r.distance map=map1,map2 | \
         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:

       r.distance map=map1,map2 | \
         awk -F: ’{print $4,$5}’ | v.in.ascii format=point output=name separator=space

SEE ALSO

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

AUTHOR

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

SOURCE CODE

       Available at: r.distance source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual