Note: This document is for an older version of GRASS GIS that will be discontinued soon. You should upgrade, and read the current manual page.

**-m**- Output distances in meters instead of map units
**-n**- Calculate distance to nearest NULL cell
**--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

**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* **minimum_distance**=*float*- Minimum distance threshold
**maximum_distance**=*float*- Maximum distance threshold

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)

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)

The *Maximum metric* is given by the formula

d(dx,dy) = max(abs(dx),abs(dy))

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.

If **minimum_distance** is given, all cells with a distance smaller
than **minimum_distance** will be set to NULL.

If **maximum_distance** is given, all cells with a distance larger
than **maximum_distance** will be set to NULL. The resultant output
is equivalent to a buffer.

If both **minimum_distance** and **maximum_distance** are given,
the result will be similar to a doughnut, a restricted belt for a
given distance range. All cells outside this distance range will be set
to NULL.

g.region raster=streams_derived -p r.grow.distance input=streams_derived distance=dist_from_streams r.colors map=dist_from_streams color=rainbow

g.region raster=sea -p r.grow.distance -m input=sea distance=dist_from_sea_geodetic metric=geodesic r.colors map=dist_from_sea_geodetic color=rainbow

*
Wikipedia Entry:
Euclidean Metric
Wikipedia Entry:
Manhattan Metric
*

Available at: r.grow.distance source code (history)

Latest change: Thursday Jan 26 14:10:26 2023 in commit: cdd84c130cea04b204479e2efdc75c742efc4843

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