r.growgrass - Online in the Cloud

PROGRAM:

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-specified 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 option of preserving the original cells (similar to combining r.buffer and
r.patch).

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 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.

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 multiple candidates with the same
northing, the westernmost is chosen.

EXAMPLE

In this example, the lakes map in the North Carolina sample dataset location is buffered:
g.region raster=lakes -p
r.grow input=lakes output=lakes_grown_50m radius=10

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