r.grow(1grass) GRASS GIS User's Manual r.grow(1grass)
NAME
r.grow - Generates a raster map layer with contiguous areas grown by
one cell.
KEYWORDS
raster, distance, proximity
SYNOPSIS
r.grow
r.grow --help
r.grow [-m] input=name output=name [radius=float] [metric=string]
[old=integer] [new=integer] [--overwrite] [--help] [--verbose]
[--quiet] [--ui]
Flags:
-m
Radius is in map units rather than cells
--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
output=name [required]
Name for output raster map
radius=float
Radius of buffer in raster cells
Default: 1.01
metric=string
Metric
Options: euclidean, maximum, manhattan
Default: euclidean
old=integer
Value to write for input cells which are non-NULL (-1 => NULL)
new=integer
Value to write for "grown" cells
DESCRIPTION
r.grow adds cells around the perimeters of all areas in a user-speci-
fied raster map layer and stores the output in a new raster map layer.
The user can use it to grow by one or more than one cell (by varying
the size of the radius parameter), or like r.buffer, but with the op-
tion of preserving the original cells (similar to combining r.buffer
and r.patch).
If radius is negative,r.grow shrinks areas by removing cells around the
perimeters of all areas.
NOTES
The user has the option of specifying three different metrics which
control the geometry in which grown cells are created, (controlled by
the metric parameter): Euclidean, Manhattan, and Maximum.
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 Manhattan metric, or Taxicab geometry, is a form of geometry in
which the usual metric of Euclidean geometry is replaced by a new met-
ric in which the distance between two points is the sum of the (abso-
lute) 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.
If there are two cells which are equal candidates to grow into an empty
space, r.grow will choose the northernmost candidate; if there are mul-
tiple candidates with the same northing, the westernmost is chosen.
EXAMPLE
In this example, the lakes map in the North Carolina sample dataset lo-
cation is buffered:
g.region raster=lakes -p
# the lake raster map pixel resolution is 10m
r.grow input=lakes output=lakes_grown_100m radius=10
Shrinking instead of growing:
g.region raster=lakes -p
# the lake raster map pixel resolution is 10m
r.grow input=lakes output=lakes_shrunk_100m radius=-10
SEE ALSO
r.buffer, r.grow.distance, r.patch
Wikipedia Entry: Euclidean Metric
Wikipedia Entry: Manhattan Metric
AUTHORS
Marjorie Larson, U.S. Army Construction Engineering Research Laboratory
Glynn Clements
SOURCE CODE
Available at: r.grow source code (history)
Accessed: unknown
Main index | Raster index | Topics index | Keywords index | Graphical
index | Full index
© 2003-2022 GRASS Development Team, GRASS GIS 7.8.7 Reference Manual
GRASS 7.8.7 r.grow(1grass)
Generated by dwww version 1.14 on Sun Dec 29 18:56:39 CET 2024.