<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: v.buffer</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" href="grassdocs.css" type="text/css"> </head> <body bgcolor="white"> <img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade> <h2>NAME</h2> <em><b>v.buffer</b></em> - Creates a buffer around features of given type (areas must contain centroid). <h2>KEYWORDS</h2> vector <h2>SYNOPSIS</h2> <b>v.buffer</b><br> <b>v.buffer help</b><br> <b>v.buffer</b> <b>input</b>=<em>name</em> <b>output</b>=<em>name</em> [<b>type</b>=<em>string</em>[,<i>string</i>,...]] [<b>layer</b>=<em>integer</em>] [<b>buffer</b>=<em>float</em>] [<b>bufcol</b>=<em>string</em>] [<b>scale</b>=<em>float</em>] [<b>tolerance</b>=<em>float</em>] [<b>debug</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>--overwrite</b></DT> <DD>Allow output files to overwrite existing files</DD> <DT><b>--verbose</b></DT> <DD>Verbose module output</DD> <DT><b>--quiet</b></DT> <DD>Quiet module output</DD> </DL> <h3>Parameters:</h3> <DL> <DT><b>input</b>=<em>name</em></DT> <DD>Name of input vector map</DD> <DT><b>output</b>=<em>name</em></DT> <DD>Name for output vector map</DD> <DT><b>type</b>=<em>string[,<i>string</i>,...]</em></DT> <DD>Type</DD> <DD>Feature type(s)</DD> <DD>Options: <em>point,line,boundary,centroid,area</em></DD> <DD>Default: <em>point,line,area</em></DD> <DT><b>layer</b>=<em>integer</em></DT> <DD>Layer number</DD> <DD>A single vector map can be connected to multiple database tables. This number determines which table to use.</DD> <DD>Default: <em>1</em></DD> <DT><b>buffer</b>=<em>float</em></DT> <DD>Buffer distance in map units</DD> <DT><b>bufcol</b>=<em>string</em></DT> <DD>Attribute column to use for buffer distances</DD> <DT><b>scale</b>=<em>float</em></DT> <DD>Scaling factor for attribute column values</DD> <DD>Default: <em>1.0</em></DD> <DT><b>tolerance</b>=<em>float</em></DT> <DD>Maximum distance between theoretical arc and polygon segments as multiple of buffer</DD> <DD>Default: <em>0.01</em></DD> <DT><b>debug</b>=<em>string</em></DT> <DD>Stop the process at a certain stage</DD> <DD>Options: <em>buffer,clean</em></DD> </DL> <h2>DESCRIPTION</h2> <em>v.buffer</em> creates a buffer around features of given <em>type</em>, which have a category in the given <em>layer</em>. The <em>tolerance</em> controls the number of vector segments being generated (the smaller the value, the more vector segments are generated). <h2>NOTES</h2> Attributes are not transferred due to potential buffer overlap, which cannot be resolved automatically. <h2>EXAMPLES</h2> <h4>Buffer around input lines</h4> <div class="code"><pre> v.buffer input=map output=buffer type=line buffer=100 </pre></div> <BR> <h4>Circles around input points</h4> <div class="code"><pre> v.buffer input=pointsmap output=circles type=point buffer=1000 </pre></div> <BR> <h4>Non-overlapping circles around input points with attribute transfer</h4> <div class="code"><pre> 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' </pre></div> <BR> <h2>BUGS</h2> For some data <em>v.buffer</em> can produce strange results, especially if the buffer size is bigger than input features. Usually you can solve the problem if you run <em>v.buffer</em> more times with smaller buffer. <P> The <b>bufcol</b> dynamic buffer distance parameter has problems cleaning complex features. (holes left filled, etc.) If you experience problems, try running <em>v.buffer</em> multiple times with a single buffer distance, patch the results with <em>v.patch</em> and remove any overlaps with <em>v.extract -d</em>. <h2>SEE ALSO</h2> <em><a HREF="r.buffer.html">r.buffer</a></em>, <em><a HREF="v.extract.html">v.extract</a></em>, <em><a HREF="v.type.html">v.type</a></em>, <em><a HREF="v.patch.html">v.patch</a></em>, <em><a HREF="v.db.connect.html">v.db.connect</a></em> <h2>AUTHOR</h2> Radim Blazek <p><i>Last changed: $Date: 2007-06-04 11:26:16 +0200 (Mon, 04 Jun 2007) $</i></p> <HR> <P><a href="index.html">Main index</a> - <a href="vector.html">vector index</a> - <a href="full_index.html">Full index</a></P> <P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p> </body> </html>
