Ubuntu Manpage: r.grow.distance - Generates a raster map containing distances to nearest raster features.

Provided by: grass-doc_7.8.2-1build3_all

NAME

       r.grow.distance  - Generates a raster map containing distances to nearest raster features.

KEYWORDS

       raster, distance, proximity

SYNOPSIS

       r.grow.distance
       r.grow.distance --help
       r.grow.distance   [-mn]  input=name   [distance=name]    [value=name]    [metric=string]    [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -m
           Output distances in meters instead of map units

       -n
           Calculate distance to nearest NULL cell

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input raster map

       distance=name
           Name for distance output raster map

       value=name
           Name for value output raster map

       metric=string
           Metric
           Options: euclidean, squared, maximum, manhattan, geodesic
           Default: euclidean

DESCRIPTION

       r.grow.distance generates raster maps representing the distance to the nearest non-null cell in the input
       map and/or the value of the nearest non-null cell.

NOTES

The flag -n calculates the respective pixel distances to the nearest NULL cell.

The user has the option of specifying five different metrics which control the geometry in which grown
cells are created, (controlled by the metric parameter): Euclidean, Squared, Manhattan, Maximum, and
Geodesic.

The Euclidean distance or Euclidean metric is the "ordinary" distance between two points that one would
measure with a ruler, which can be proven by repeated application of the Pythagorean theorem. The
formula is given by:
d(dx,dy) = sqrt(dx^2 + dy^2)
Cells grown using this metric would form isolines of distance that are circular from a given point, with
the distance given by the radius.

The Squared metric is the Euclidean distance squared, i.e. it simply omits the square-root calculation.
This may be faster, and is sufficient if only relative values are required.

The Manhattan metric, or Taxicab geometry, is a form of geometry in which the usual metric of Euclidean
geometry is replaced by a new metric in which the distance between two points is the sum of the
(absolute) differences of their coordinates. The name alludes to the grid layout of most streets on the
island of Manhattan, which causes the shortest path a car could take between two points in the city to
have length equal to the points’ distance in taxicab geometry. The formula is given by:
d(dx,dy) = abs(dx) + abs(dy)
where cells grown using this metric would form isolines of distance that are rhombus-shaped from a given
point.

The Maximum metric is given by the formula
d(dx,dy) = max(abs(dx),abs(dy))
where the isolines of distance from a point are squares.

The Geodesic metric is calculated as geodesic distance, to be used only in latitude-longitude locations.
It is recommended to use it along with the -m flag in order to output distances in meters instead of map
units.

EXAMPLES

   Distance from the streams network
       North Carolina sample dataset:
       g.region raster=streams_derived -p
       r.grow.distance input=streams_derived distance=dist_from_streams
       r.colors map=dist_from_streams color=rainbow
       Euclidean distance from the streams network in meters (map subset)
       Euclidean distance from the streams network in meters (detail, numbers shown with d.rast.num)

   Distance from sea in meters in latitude-longitude location
       g.region raster=sea -p
       r.grow.distance -m input=sea distance=dist_from_sea_geodetic metric=geodesic
       r.colors map=dist_from_sea_geodetic color=rainbow

       Geodesic distances to sea in meters

AUTHORS

       Glynn Clements

SOURCE CODE

       Available at: r.grow.distance source code (history)

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