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

NAME

       r.grow.distance   - Generates a raster map containing distances to nearest raster features
       and/or the value of the nearest non-null cell.

KEYWORDS

       raster, distance, proximity

SYNOPSIS

       r.grow.distance
       r.grow.distance --help
       r.grow.distance  [-mn]  input=name    [distance=name]     [value=name]     [metric=string]
       [minimum_distance=float]   [maximum_distance=float]   [--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

       minimum_distance=float
           Minimum distance threshold

       maximum_distance=float
           Maximum distance threshold

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 coordinate reference system. It is recommended to use it along with the
-m flag in order to output distances in meters instead of map units.

If minimum_distance is given, all cells with a distance smaller than minimum_distance will
be set to NULL.

If maximum_distance is given, all cells with a distance larger than maximum_distance will
be set to NULL. The resultant output is equivalent to a buffer.

If both minimum_distance and maximum_distance are given, the result will be similar to a
doughnut, a restricted belt for a given distance range. All cells outside this distance
range will be set to NULL.

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 CRS
       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

AUTHOR

       Glynn Clements

SOURCE CODE

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

       Accessed: Thursday Aug 01 11:29:58 2024

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       © 2003-2024 GRASS Development Team, GRASS GIS 8.4.0 Reference Manual