DESCRIPTION
r3.neighbors looks at each voxel in a 3D raster input
map layer, and examines the values assigned to the
voxel in a user-defined "neighborhood" around it. It
outputs a new 3D raster map in which each voxel is
assigned a value that is a (user-specified)
function of the values in that voxel's neighborhood. For
example, each voxel in the output map might be assigned a
value equal to the average of the values
appearing in its 3 x 3 x 3 voxel "neighborhood" in the input
map layer.
OPTIONS
The user must specify the names of the 3D raster map layers to
be used for input and output, the
method used to analyze neighborhood
values (i.e., the neighborhood function or operation to be
performed), and the moving window of the neighborhood.
Neighborhood Operation Methods:
The neighborhood operators determine what new
value a center voxel in a neighborhood will have after examining
values inside its neighboring voxels.
Each voxel in a 3D raster map layer becomes the center voxel of a neighborhood
as the neighborhood window moves from voxel to voxel throughout the map layer.
r3.neighbors can perform the following operations:
- average
- The average value within the neighborhood.
- median
- The value found half-way through a list of the
neighborhood's values,
when these are ranged in numerical order.
- mode
- The most frequently occurring value in the neighborhood.
- minimum
- The minimum value within the neighborhood.
- maximum
- The maximum value within the neighborhood.
- range
- The range value within the neighborhood.
- stddev
- The statistical standard deviation of values
within the neighborhood.
- sum
- The sum of values within the neighborhood.
- variance
- The statistical variance of values
within the neighborhood.
- diversity
- The number of different values within the neighborhood.
- interspersion
- The percentage of voxels containing values which differ from the values
assigned to the center voxel in the neighborhood, plus 1.
Neighborhood Size:
The neighborhood moving window specifies which voxel surrounding any given
voxel fall into the neighborhood for that voxel.
The window must be three comma separated odd integers. The dimension order is: x,y,z.
For example: the parameter window=3,3,3 specifies a moving window (a cube) with 27 voxel.
NOTES
The r3.neighbors program works in the current geographic region.
It is recommended, but not required,
that the 3D resolution of the geographic region be the same as that
of the 3D raster map layer.
r3.neighbors doesn't propagate NULLs, but computes the
aggregation over the non-NULL voxels in the neighborhood.
SEE ALSO
g.region
r.neighbors
r3.mapcalc
r3.stats
r3.support
AUTHOR
Soeren Gebbert
Last changed: $Date$