Provided by: grass-doc_6.4.3-3_all bug


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


       raster, buffer


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

           Ignore zero (0) data cells instead of NULL cells

           Run quietly

           Allow output files to overwrite existing files

           Verbose module output

           Quiet module output

           Name of input raster map

           Name for output raster map

           Distance zone(s)

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


       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


       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

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


       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
       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




       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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