r.buffer(1)

1r.buffer(1)                   Grass User's Manual                  r.buffer(1)
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NAME

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

10       raster, buffer
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SYNOPSIS

13       r.buffer
14       r.buffer help
15       r.buffer  [-qz]  input=name   output=name   distances=float[,float,...]
16       [units=string]   [--overwrite]
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18   Flags:
19       -q  Run quietly
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21       -z  Ignore zero (0) data cells instead of NULL cells
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23       --overwrite
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25   Parameters:
26       input=name
27           Name of input raster map
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29       output=name
30           Name for output raster map
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32       distances=float[,float,...]
33           Distance zone(s)
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35       units=string
36           Units  of  distance Options: meters,kilometers,feet,miles,nautmiles
37           Default: meters
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DESCRIPTION

40       r.buffer creates a new raster map layer showing  buffer  (a.k.a.  "dis‐
41       tance"  or  "proximity")  zones  around all cells that contain non-NULL
42       category values in an existing raster map layer.  The distances of buf‐
43       fer  zones  from  cells  with non-zero category values are user-chosen.
44       Suppose, for example, that you want to place buffer zones around roads.
45       This program could create the raster map layer shown below on the right
46       based on road information contained in the raster map  layer  shown  on
47       the left.
48             000000000000000000000000 222233333333333333444444
49             111000000000000000000000 111222222222223333333333
50             000111111111100000000000 222111111111122223333333
51             000000001000011100000000 332222221222211122222222
52             000000001000000011111111 333333321233222211111111
53             000000001000000000000000 433333321233333222222222
54             000000001000000000000000 444443321233333333333333
55             000000001000000000000000 444443321233443333333333
56             000000001000000000000000 444443321233444444444444
57             Category 0: No roads
58             Category 1: Road location
59             Category 2: Buffer Zone 1 around roads
60             Category 3: Buffer Zone 2 around roads
61             Category 4: Buffer Zone 3 around roads
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NOTES

65       The user has the option of identifying up to 250 continuous zones.  The
66       zones are identified by specifying the upper limit of each desired zone
67       (r.buffer assumes that 0 is the starting point).  ("Continuous" is used
68       in the sense that each category zone's  lower  value  is  the  previous
69       zone's  upper value. The first buffer zone always has distance 0 as its
70       lower bound.) Distances can be entered in one of  five  units:  meters,
71       kilometers, feet, miles, and nautmiles (nautical miles).
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73       Distances  from cells containing the user-specified category values are
74       calculated using the "fromcell" method. This method goes to  each  cell
75       that  contains  a  category value from which distances are to be calcu‐
76       lated, and draws the requested distance rings around them. This  method
77       works very fast when there are few cells containing the category values
78       of interest, but works slowly when there are numerous cells  containing
79       the category values of interest spread throughout the area.
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81       r.buffer measures distances from center of cell to center of cell using
82       Euclidean distance measure for planimetric  locations  (like  UTM)  and
83       using  ellipsoidal  geodesic  distance  measure  for latitude/longitude
84       locations.
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86       r.buffer calculates distance zones from all cells having non-NULL cate‐
87       gory values in the input map. If the user wishes to calculate distances
88       from only selected input map layer category values, the user should run
89       (for  example)  r.reclass  prior to r.buffer, to reclass all categories
90       from which distance zones are not desired to be calculated  into  cate‐
91       gory NULL.
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EXAMPLE

94       In  the  following  example,  the buffer zones would be (in the default
95       units of meters):  0-100, 101-200, 201-300, 301-400 and 401-500.
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97       r.buffer input=roads output=roads.buf distances=100,200,300,400,500
98        Result:
99       r.cats input=roads.buf
100             1       distances calculated from these locations
101             2       0-100 meters
102             3       100-200 meters
103             4       200-300 meters
104             5       300-400 meters
105             6       400-500 meters
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AUTHORS

116       Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
117       James Westervelt, U.S. Army Construction Engineering  Research  Labora‐
118       tory
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120       Last changed: $Date: 2006/09/13 12:28:04 $
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122       Full index
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126GRASS 6.2.2                                                        r.buffer(1)