r.buffergrass - Online in the Cloud

PROGRAM:

NAME

r.buffer - Creates a raster map showing buffer zones surrounding cells that contain
non-NULL category values.

KEYWORDS

raster, buffer

SYNOPSIS

r.buffer
r.buffer --help
r.buffer [-z] input=name output=name distances=float[,float,...] [units=string]
[--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:
-z
Ignore zero (0) data cells instead of NULL 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

Parameters:
input=name [required]
Name of input raster map

output=name [required]
Name for output raster map

distances=float[,float,...] [required]
Distance zone(s)

units=string
Units of distance
Options: meters, kilometers, feet, miles, nautmiles
Default: meters

DESCRIPTION

r.buffer creates a new raster map showing buffer (a.k.a. "distance" or "proximity") zones
around all cells that contain non-NULL category values in an existing raster map. The
distances of buffer zones from cells with non-zero category values are user-chosen and
must be positive value(s). Suppose, for example, that you want to place buffer zones
around roads. This program could create the raster map shown below on the right based on
road information contained in the raster map 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. Buffer distances can be specified using one of five units with the units
parameter.

Distances from cells containing the user-specified category values are calculated using
the "fromcell" method. This method locates 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 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.

The -z flag can be used to ignore raster values of zero instead of NULL values in the
input raster map.

When working with massive raster regions consider the r.buffer.lowmem module if RAM use
becomes a problem. The lowmem version can be > 40x slower, but will work with minimal
memory requirements. The classic r.buffer should be able to deal with raster maps of
32000x32000 size on a system with 1 GB RAM, and rasters of 90000x90000 on a system with 8
GB RAM without going into swap.

EXAMPLE

In the following example (North Carolina sample dataset), the buffer zones would be (in
the default map units of meters): 0-100, 101-200, 201-300, 301-400 and 401-500.
g.region raster=roadsmajor -p
r.buffer input=roadsmajor output=roadsmajor_buf distances=100,200,300,400,500
Result:
r.category 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
Distances to road

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