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


       raster, buffer


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

           Ignore zero (0) data cells instead of NULL cells

           Allow output files to overwrite existing files

           Print usage summary

           Verbose module output

           Quiet module output

           Force launching GUI dialog

       input=name [required]
           Name of input raster map

       output=name [required]
           Name for output raster map

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

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


       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


       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

       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.


       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
       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


        r.buffer.lowmem, r.grow, v.buffer

        g.region, r.cost, r.distance, r.grow.distance, r.mapcalc, r.reclass


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


       Available at: r.buffer source code (history)

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