NAME¶
r.grow.distance - Generates a raster map layer of distance to
features in input layer.
KEYWORDS¶
raster, geometry
SYNOPSIS¶
r.grow.distance
r.grow.distance help
r.grow.distance input=
name [
distance=
name]
[
value=
name] [
metric=
string] [--
overwrite]
[--
verbose] [--
quiet]
Flags:¶
- --overwrite
-
Allow output files to overwrite existing files
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- input=name
-
Name of input raster map
- distance=name
-
Name for distance output map
- value=name
-
Name for value output map
- metric=string
-
Metric
Options: euclidean,squared,maximum,manhattan
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 four different metrics which control the
geometry in which grown cells are created, (controlled by the
metric
parameter):
Euclidean,
Squared,
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: </div>
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:
</div>
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
</div>
where the isolines of distance from a point are squares.
EXAMPLE¶
Spearfish sample dataset
r.grow.distance input=roads distance=dist_from_roads
SEE ALSO¶
r.grow
r.buffer
r.cost
r.patch
Wikipedia Entry: Euclidean Metric
Wikipedia Entry: Manhattan Metric
AUTHORS¶
Glynn Clements
Last changed: $Date: 2008-11-20 11:59:22 +0100 (Thu, 20 Nov 2008) $
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