NAME
r.buffer - Creates a raster map layer showing buffer zones surrounding cells that contain non-NULL category values.
KEYWORDS
raster, buffer
SYNOPSIS
r.buffer
r.buffer help
r.buffer [-qz] input=name output=name distances=float[,float,...] [units=string] [--overwrite]
Flags:
- -q
- Run quietly
- -z
- Ignore zero (0) data cells instead of NULL cells
- --overwrite
- Force overwrite of output files
Parameters:
- input=name
- Name of input raster map
- output=name
- Name for output raster map
- distances=float[,float,...]
- Distance zone(s)
- units=string
- Units of distance
- Options: meters,kilometers,feet,miles,nautmiles
- Default: meters
DESCRIPTION
r.buffer creates a new raster map layer showing
buffer (a.k.a. "distance" or "proximity") zones around all
cells that contain non-NULL category values in an existing
raster map layer. The distances of buffer zones from cells
with non-zero category values are user-chosen. Suppose,
for example, that you want to place buffer zones around
roads. This program could create the raster map layer
shown below on the right based on road information
contained in the raster map layer shown on the left.
000000000000000000000000 222233333333333333444444
111000000000000000000000 111222222222223333333333
000111111111100000000000 222111111111122223333333
000000001000011100000000 332222221222211122222222
000000001000000011111111 333333321233222211111111
000000001000000000000000 433333321233333222222222
000000001000000000000000 444443321233333333333333
000000001000000000000000 444443321233443333333333
000000001000000000000000 444443321233444444444444
Category 0: No roads
Category 1: Road location
Category 2: Buffer Zone 1 around roads
Category 3: Buffer Zone 2 around roads
Category 4: Buffer Zone 3 around roads
NOTES
The user has the option of identifying up to 250 continuous zones.
The zones are identified by specifying the upper limit of each desired zone
(r.buffer assumes that 0 is the starting point).
("Continuous" is used in the sense that each category
zone's lower value is the previous zone's upper value. The
first buffer zone always has distance 0 as its lower
bound.) Distances can be entered in one of five units:
meters, kilometers, feet, miles, and nautmiles
(nautical miles).
Distances from cells containing the user-specified category values
are calculated using the "fromcell" method. This method goes to each
cell that contains a category value from which distances are to be
calculated, and draws the requested distance rings around
them. This method works very fast when there are few cells
containing the category values of interest, but works
slowly when there are numerous cells containing the
category values of interest spread throughout the area.
r.buffer measures distances from center of cell to
center of cell using Euclidean distance measure for
planimetric locations (like UTM) and using ellipsoidal
geodesic distance measure for latitude/longitude locations.
r.buffer calculates distance zones from all cells having non-NULL
category values in the input map. If the user wishes to calculate
distances from only selected input map layer
category values, the user should run (for example)
r.reclass prior to
r.buffer, to reclass all categories from which distance zones
are not desired to be calculated into category NULL.
EXAMPLE
In the following example, the buffer zones would be (in the default units
of meters): 0-100, 101-200, 201-300, 301-400 and 401-500.
r.buffer input=roads output=roads.buf distances=100,200,300,400,500
Result:
r.cats input=roads.buf
1 distances calculated from these locations
2 0-100 meters
3 100-200 meters
4 200-300 meters
5 300-400 meters
6 400-500 meters
SEE ALSO
g.region
r.cost
r.mapcalc
r.reclass
v.buffer
AUTHORS
Michael Shapiro, U.S. Army Construction Engineering
Research Laboratory
James Westervelt, U.S. Army Construction Engineering
Research Laboratory
Last changed: $Date: 2006/09/13 12:28:04 $
Main index - raster index - Full index