1v.buffer(1) Grass User's Manual v.buffer(1)
2
6 v.buffer - Creates a buffer around vector features of given type.
7
9 vector, buffer, area, circle, geometry, line, grow, shrink
10
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 Flags:
21 -s
22 Make outside corners straight
23 -c
25 Do not make caps at the ends of polylines
26 -t
28 Transfer categories and attributes
29 --overwrite
31 Allow output files to overwrite existing files
32 --help
34 Print usage summary
35 --verbose
37 Verbose module output
38 --quiet
40 Quiet module output
41 --ui
43 Force launching GUI dialog
44 Parameters:
46 input=name [required]
47 Name of input vector map
48 Or data source for direct OGR access
49 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
56 cats=range
58 Category values
59 Example: 1,3,7-9,13
60 where=sql_query
62 WHERE conditions of SQL statement without ’where’ keyword
63 Example: income < 1000 and population >= 10000
64 type=string[,string,...]
66 Input feature type
67 Options: point, line, boundary, centroid, area
68 Default: point,line,area
69 output=name [required]
71 Name for output vector map
72 distance=float
74 Buffer distance along major axis in map units
75 minordistance=float
77 Buffer distance along minor axis in map units
78 angle=float
80 Angle of major axis in degrees
81 Default: 0
82 column=name
84 Name of column to use for buffer distances
85 scale=float
87 Scaling factor for attribute column values
88 Default: 1.0
89 tolerance=float
91 Maximum distance between theoretical arc and polygon segments as
92 multiple of buffer (default 0.01)
93
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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101 Internal buffers for areas can be generated with negative distance val‐
102 ues ("inward buffer" or "negative buffer" or "shrinking").
103 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 Buffers for lines and areas are generated using the algorithms from the
117 GEOS library.
118 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).
124 The options minordistance, angle, tolerance are kept for backward com‐
126 patibility and have no effect with GEOS buffering.
127 Corner settings
129 The following vector line related corners (also called "cap") exist:
130 · no cap:
132 · rounded cap:
134 · 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):
140
142 All examples are based on the North Carolina sample dataset.
143 Buffer around input lines
145 v.buffer input=roadsmajor output=roadsmajor_buffer type=line distance=100
146 Buffer of 100m along the "roadsmajor" lines (map subset, original cen‐
147 ter line shown in black)
148 Circles around input points
150 v.buffer input=hospitals output=hospitals_circled type=point distance=2000
151 Buffer of 2000m around the "hospitals" points (map subset, original
152 points shown in black, new area centroids in red)
153 Circles around input points with attribute transfer
155 v.buffer input=hospitals output=hospitals_circled type=point distance=1000 -t
156 # display buffer around hospital with category 36,
157 # this buffer is composed of several areas:
158 d.vect map=hospitals_circled type=area layer=1 cats=36
159 # extract this buffer, dissolving boundaries
160 v.extract in=hospitals_circled output=hospital_36_circled layer=1 cats=36 -d
161 Buffer around input areas
163 v.buffer input=lakes output=lakes_buffer type=area distance=100
164 Buffer of 100m around the "lakes" polygons (map subset, original areas
165 shown in black)
166 Buffer inside input areas
168 In this example, an internal buffer ("inward buffer" or "negative buf‐
169 fer") is generated using a negative distance value:
170 v.buffer input=lakes output=lakes_buffer type=area distance=-50
171 Internal buffer of 50m inside the "lakes" polygons (map subset, origi‐
172 nal areas shown in black)
173 Not all features are buffered, only the polygons that allow creation
174 inside a topological cleaned polygon.
175
177 · GEOS Library
178
180 r.buffer, v.parallel, v.extract, v.type, v.patch, v.db.connect
181
183 Radim Blazek
184 Rewritten by Rosen Matev (with support through the Google Summer of
185 Code program 2008)
186 Rewritten by Markus Metz (2011, 2012)
187 Last changed: $Date: 2017-11-12 23:40:40 +0100 (Sun, 12 Nov 2017) $
189
191 Available at: v.buffer source code (history)
192 Main index | Vector index | Topics index | Keywords index | Graphical
194 index | Full index
195 © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
197GRASS 7.4.4 v.buffer(1)