r.distancegrass - Online in the Cloud

PROGRAM:

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

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