GRASS GIS: v.buffer

NAME

v.buffer - Creates a buffer around features of given type (areas must contain centroid).

KEYWORDS

vector

SYNOPSIS

v.buffer
v.buffer help
v.buffer input=name output=name [type=string[,string,...]] [layer=integer] [buffer=float] [bufcol=string] [scale=float] [tolerance=float] [debug=string] [--overwrite] [--verbose] [--quiet]

Flags:

--overwrite: Allow output files to overwrite existing files
--verbose: Verbose module output
--quiet: Quiet module output

Parameters:

input=name: Name of input vector map
output=name: Name for output vector map
type=string[,string,...]: Type; Feature type(s); Options: point,line,boundary,centroid,area; Default: point,line,area
layer=integer: Layer number; A single vector map can be connected to multiple database tables. This number determines which table to use.; Default: 1
buffer=float: Buffer distance in map units
bufcol=string: Attribute 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
debug=string: Stop the process at a certain stage; Options: buffer,clean

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

Attributes are not transferred due to potential buffer overlap, which cannot be resolved automatically.

EXAMPLES

Buffer around input lines

v.buffer input=map output=buffer type=line buffer=100

Circles around input points

v.buffer input=pointsmap output=circles type=point buffer=1000

Non-overlapping circles around input points with attribute transfer

v.buffer input=archsites output=circles type=point buffer=200 
# change original points to centroids: 
v.type in=archsites out=archcentroids type=point,centroid 
# patch circles and centroids: 
v.patch in=archcentroids,circles out=circles_db 
# attach attributes, either use 
# db.copy ... 
# or link to the original table: 
v.db.connect map=circles_db table=archsites field=1 key=cat driver=dbf \
database='$GISDBASE/$LOCATION_NAME/$MAPSET/dbf'

BUGS

For some data v.buffer can produce strange results, especially if the buffer size is bigger than input features. Usually you can solve the problem if you run v.buffer more times with smaller buffer.

The bufcol dynamic buffer distance parameter has problems cleaning complex features (holes left filled, etc.). If you experience problems, try running v.buffer multiple times with a single buffer distance, patch the results with v.patch and remove any overlaps with v.extract -d.

AUTHOR

Radim Blazek

Last changed: $Date: 2008-03-16 08:29:33 -0700 (Sun, 16 Mar 2008) $

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