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r.distance(1grass) GRASS User's Manual r.distance(1grass)

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] format=name [--help] [--verbose] [--quiet] [--ui]

Flags:


Include category labels in the output

Report zero distance if rasters are overlapping

Report null objects as *

Print usage summary

Verbose module output

Quiet module output

Force launching GUI dialog

Parameters:


Name of two input raster maps for computing inter-class distances

Field separator
Special characters: pipe, comma, space, tab, newline

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

Output format
Options: plain, csv, json
Default: plain
plain: Human readable text output
csv: CSV (Comma Separated Values)
json: JSON (JavaScript Object Notation)

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

Category number from map1

Category number from map2

The distance in meters between "cat1" and "cat2"

The coordinates of the grid cell "cat1" which is closest to "cat2"

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)

Latest change: Saturday Oct 11 04:38:40 2025 in commit: 3dd71f5fab83b72a2db2da959fe075c5b3b52200

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© 2003-2026 GRASS Development Team, GRASS 8.5.0RC1 Reference Manual

GRASS 8.5.0RC1