Ubuntu Manpage: r.buffer - Creates a raster map layer showing buffer zones surrounding cells that contain

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  [-zq]   input=name   output=name   distances=float[,float,...]    [units=string]
       [--overwrite]  [--verbose]  [--quiet]

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

       -q
           Run quietly

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   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.) Buffer distances can be specified using one of five units with the units
parameter: 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 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 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.

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

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.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

AUTHORS

       Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
       James Westervelt, U.S. Army Construction Engineering Research Laboratory

       Last changed: $Date: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $

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