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

6       v.buffer  - Creates a buffer around vector features of given type.
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KEYWORDS

9       vector, buffer, area, circle, geometry, line, grow, shrink
10

SYNOPSIS

12       v.buffer
13       v.buffer --help
14       v.buffer     [-sct]     input=name     [layer=string]      [cats=range]
15       [where=sql_query]    [type=string[,string,...]]    output=name    [dis‐
16       tance=float]    [minordistance=float]    [angle=float]    [column=name]
17       [scale=float]   [tolerance=float]    [--overwrite]   [--help]   [--ver‐
18       bose]  [--quiet]  [--ui]
19
20   Flags:
21       -s
22           Make outside corners straight
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24       -c
25           Do not make caps at the ends of polylines
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27       -t
28           Transfer categories and attributes
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30       --overwrite
31           Allow output files to overwrite existing files
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33       --help
34           Print usage summary
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36       --verbose
37           Verbose module output
38
39       --quiet
40           Quiet module output
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42       --ui
43           Force launching GUI dialog
44
45   Parameters:
46       input=name [required]
47           Name of input vector map
48           Or data source for direct OGR access
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50       layer=string
51           Layer number or name (’-1’ for all layers)
52           A  single  vector map can be connected to multiple database tables.
53           This number determines which table to use. When  used  with  direct
54           OGR access this is the layer name.
55           Default: -1
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57       cats=range
58           Category values
59           Example: 1,3,7-9,13
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61       where=sql_query
62           WHERE conditions of SQL statement without ’where’ keyword
63           Example: income < 1000 and population >= 10000
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65       type=string[,string,...]
66           Input feature type
67           Options: point, line, boundary, centroid, area
68           Default: point,line,area
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70       output=name [required]
71           Name for output vector map
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73       distance=float
74           Buffer distance along major axis in map units
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76       minordistance=float
77           Buffer distance along minor axis in map units
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79       angle=float
80           Angle of major axis in degrees
81           Default: 0
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83       column=name
84           Name of column to use for buffer distances
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86       scale=float
87           Scaling factor for attribute column values
88           Default: 1.0
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90       tolerance=float
91           Maximum  distance  between  theoretical arc and polygon segments as
92           multiple of buffer (default 0.01)
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DESCRIPTION

95       v.buffer creates a buffer around features of given type, which  have  a
96       category  in the given layer. The tolerance controls the number of vec‐
97       tor segments being generated (the smaller the value,  the  more  vector
98       segments are generated).
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NOTES

101       Internal buffers for areas can be generated with negative distance val‐
102       ues ("inward buffer" or "negative buffer" or "shrinking").
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104       v.buffer fusions the geometries of buffers by default.  Categories  and
105       attribute  table  will not be transferred (this would not make sense as
106       one buffer geometry can be the result of many  different  input  geome‐
107       tries).  To transfer the categories and attributes the user can set the
108       t flag. This will result in buffers being cut up where buffers of indi‐
109       vidual input geometries overlap.  Each part that is the result of over‐
110       lapping buffers of multiple geometries will  have  multiple  categories
111       corresponding  to  those geometries, and multiple buffer areas can have
112       the same category. The buffer for the input feature with category X can
113       thus  be  retrieved  by selecting all buffer areas with category X (see
114       example below).
115
116       Buffers for lines and areas are generated using the algorithms from the
117       GEOS library.
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119       For advanced users: built-in buffer algorithm no longer desired, we use
120       GEOS: If GRASS is not compiled with GEOS support or environmental vari‐
121       able GRASS_VECTOR_BUFFER is defined, then GRASS generates buffers using
122       built-in buffering algorithm (which  is  still  buggy  for  some  input
123       data).
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125       The  options minordistance, angle, tolerance are kept for backward com‐
126       patibility and have no effect with GEOS buffering.
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128   Corner settings
129       The following vector line related corners (also called "cap") exist:
130
131           ·   no cap:      
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133           ·   rounded cap:
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135           ·   square cap:
136       By default v.buffer creates  rounded  buffers  (blue  color  on  figure
137       below): Straight corners with caps are created by -s flag (red color on
138       the figure below), while -c flag doesn’t make caps at the ends of poly‐
139       lines  (green  color on the figure below): Using -s with a point vector
140       map as input data, square buffers are created instead of round buffers.
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EXAMPLES

143       All examples are based on the North Carolina sample dataset.
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145   Buffer around input lines
146       v.buffer input=roadsmajor output=roadsmajor_buffer type=line distance=100
147       Buffer of 100m along the "roadsmajor" lines (map subset, original  cen‐
148       ter line shown in black)
149
150   Circles around input points
151       v.buffer input=hospitals output=hospitals_circled type=point distance=2000
152       Buffer  of  2000m  around  the "hospitals" points (map subset, original
153       points shown in black, new area centroids in red)
154
155   Circles around input points with attribute transfer
156       v.buffer input=hospitals output=hospitals_circled type=point distance=1000 -t
157       # display buffer around hospital with category 36,
158       # this buffer is composed of several areas:
159       d.vect map=hospitals_circled type=area layer=1 cats=36
160       # extract this buffer, dissolving boundaries
161       v.extract in=hospitals_circled output=hospital_36_circled layer=1 cats=36 -d
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163   Buffer around input areas
164       v.buffer input=lakes output=lakes_buffer type=area distance=100
165       Buffer of 100m around the "lakes" polygons (map subset, original  areas
166       shown in black)
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168   Buffer inside input areas
169       In  this example, an internal buffer ("inward buffer" or "negative buf‐
170       fer") is generated using a negative distance value:
171       v.buffer input=lakes output=lakes_buffer type=area distance=-50
172       Internal buffer of 50m inside the "lakes" polygons (map subset,  origi‐
173       nal areas shown in black)
174       Not  all  features  are buffered, only the polygons that allow creation
175       inside a topological cleaned polygon.
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REFERENCES

178           ·   GEOS Library
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SEE ALSO

181        r.buffer, v.parallel, v.extract, v.type, v.patch, v.db.connect
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AUTHORS

184       Radim Blazek
185       Rewritten by Rosen Matev (with support through  the  Google  Summer  of
186       Code program 2008)
187       Rewritten by Markus Metz (2011, 2012)
188

SOURCE CODE

190       Available at: v.buffer source code (history)
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192       Main  index  | Vector index | Topics index | Keywords index | Graphical
193       index | Full index
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195       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual
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199GRASS 7.8.2                                                        v.buffer(1)
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