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# r.grow.distance

## man page of r.grow.distance

### r.grow.distance: Generates a raster map layer of distance to features in input layer.

```NAME
r.grow.distance  - Generates a raster map layer of distance to features
in input layer.

KEYWORDS
raster

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
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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(C) 2003-2010 GRASS Development Team

R.GROW.DISTANCE(1)
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