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**- 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

**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

If **radius** is negative,*r.grow* shrinks areas by removing
cells around the perimeters of all areas.

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 *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))

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.

g.region raster=lakes -p # the lake raster map pixel resolution is 10m r.grow input=lakes output=lakes_grown_100m radius=10

g.region raster=lakes -p # the lake raster map pixel resolution is 10m r.grow input=lakes output=lakes_shrunk_100m radius=-10

*Wikipedia Entry: Euclidean Metric*

*Wikipedia Entry: Manhattan Metric*

Glynn Clements

Available at: r.grow source code (history)

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

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