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NAME

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

KEYWORDS

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

SYNOPSIS

       v.buffer
       v.buffer --help
       v.buffer    [-sct]    input=name     [layer=string]     [cats=range]     [where=sql_query]
       [type=string[,string,...]]     output=name     [distance=float]      [minordistance=float]
       [angle=float]      [column=name]     [scale=float]     [tolerance=float]     [--overwrite]
       [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -s
           Make outside corners straight

       -c
           Do not make caps at the ends of polylines

       -t
           Transfer categories and attributes

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=name [required]
           Name of input vector map
           Or data source for direct OGR access

       layer=string
           Layer number or name (’-1’ for all layers)
           A single vector map  can  be  connected  to  multiple  database  tables.  This  number
           determines  which  table  to  use.  When used with direct OGR access this is the layer
           name.
           Default: -1

       cats=range
           Category values
           Example: 1,3,7-9,13

       where=sql_query
           WHERE conditions of SQL statement without ’where’ keyword
           Example: income < 1000 and population >= 10000

       type=string[,string,...]
           Input feature type
           Options: point, line, boundary, centroid, area
           Default: point,line,area

       output=name [required]
           Name for output vector map

       distance=float
           Buffer distance along major axis in map units

       minordistance=float
           Buffer distance along minor axis in map units

       angle=float
           Angle of major axis in degrees
           Default: 0

       column=name
           Name of column to use for buffer distances

       scale=float
           Scaling factor for attribute column values
           Default: 1.0

       tolerance=float
           Maximum distance between theoretical arc and polygon segments as  multiple  of  buffer
           (default 0.01)

DESCRIPTION

       v.buffer  creates  a  buffer  around  features of given type, which have a category in the
       given layer. The tolerance controls the number of vector  segments  being  generated  (the
       smaller the value, the more vector segments are generated).

NOTES

       Internal buffers for areas can be generated with negative distance values ("inward buffer"
       or "negative buffer" or "shrinking").

       v.buffer fusions the geometries of buffers by default.   Categories  and  attribute  table
       will  not  be  transferred  (this  would  not make sense as one buffer geometry can be the
       result of many different input geometries). To transfer the categories and attributes  the
       user  can  set  the  t  flag.  This  will  result in buffers being cut up where buffers of
       individual input geometries overlap.  Each part that is the result of overlapping  buffers
       of  multiple  geometries  will have multiple categories corresponding to those geometries,
       and multiple buffer areas can have the same category. The buffer  for  the  input  feature
       with  category  X can thus be retrieved by selecting all buffer areas with category X (see
       example below).

       Buffers for lines and areas are generated using the algorithms from the GEOS library.

       For advanced users: built-in buffer algorithm no longer desired, we use GEOS: If GRASS  is
       not  compiled  with GEOS support or environmental variable GRASS_VECTOR_BUFFER is defined,
       then GRASS generates buffers using built-in buffering algorithm (which is still buggy  for
       some input data).

       The  options  minordistance, angle, tolerance are kept for backward compatibility and have
       no effect with GEOS buffering.

   Corner settings
       The following vector line related corners (also called "cap") exist:

           ·   no cap:

           ·   rounded cap:

           ·   square cap:
       By default v.buffer creates rounded buffers (blue color on figure below): Straight corners
       with  caps  are  created by -s flag (red color on the figure below), while -c flag doesn’t
       make caps at the ends of polylines (green color on the figure below):

EXAMPLES

       All examples are based on the North Carolina sample dataset.

   Buffer around input lines
       v.buffer input=roadsmajor output=roadsmajor_buffer type=line distance=100
       Buffer of 100m along the "roadsmajor" lines (map subset, original  center  line  shown  in
       black)

   Circles around input points
       v.buffer input=hospitals output=hospitals_circled type=point distance=2000
       Buffer of 2000m around the "hospitals" points (map subset, original points shown in black,
       new area centroids in red)

   Circles around input points with attribute transfer
       v.buffer input=hospitals output=hospitals_circled type=point distance=1000 -t
       # display buffer around hospital with category 36,
       # this buffer is composed of several areas:
       d.vect map=hospitals_circled type=area layer=1 cats=36
       # extract this buffer, dissolving boundaries
       v.extract in=hospitals_circled output=hospital_36_circled layer=1 cats=36 -d

   Buffer around input areas
       v.buffer input=lakes output=lakes_buffer type=area distance=100
       Buffer of 100m around the "lakes" polygons (map subset, original areas shown in black)

   Buffer inside input areas
       In this example, an internal buffer ("inward buffer" or "negative  buffer")  is  generated
       using a negative distance value:
       v.buffer input=lakes output=lakes_buffer type=area distance=-50
       Internal  buffer  of  50m inside the "lakes" polygons (map subset, original areas shown in
       black)
       Not all features are buffered, only the polygons that allow creation inside a  topological
       cleaned polygon.

REFERENCES

           ·   GEOS Library

SEE ALSO

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

AUTHORS

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

       Last changed: $Date: 2017-11-12 23:40:40 +0100 (Sun, 12 Nov 2017) $

SOURCE CODE

       Available at: v.buffer source code (history)

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       © 2003-2018 GRASS Development Team, GRASS GIS 7.4.0 Reference Manual