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

Provided by: grass-doc_7.0.3-1build1_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   [-m]   input=name    [distance=name]     [value=name]    [metric=string]
       [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

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

       --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 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
       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

       Geodesic distances to sea in meters

AUTHORS

       Glynn Clements

       Last changed: $Date: 2016-01-21 12:46:54 +0100 (Thu, 21 Jan 2016) $

       Main index | Raster index | Topics index | Keywords index | Full index

       © 2003-2016 GRASS Development Team, GRASS GIS 7.0.3 Reference Manual