<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>GRASS GIS: v.voronoi</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.voronoi</b></em> - Creates a Voronoi diagram from an input vector map containing points or centroids.
<h2>KEYWORDS</h2>
vector
<h2>SYNOPSIS</h2>
<b>v.voronoi</b><br>
<b>v.voronoi help</b><br>
<b>v.voronoi</b> [-<b>lt</b>] <b>input</b>=<em>name</em> <b>output</b>=<em>name</em> [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>-l</b></DT>
<DD>Output tessellation as a graph (lines), not areas</DD>
<DT><b>-t</b></DT>
<DD>Do not create attribute table</DD>
<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>
</DL>
<H2>DESCRIPTION</H2>
<EM>v.voronoi</EM> uses an existing vector points map (<B>input</B>) to create
a Voronoi diagram (Thiessen polygons) in a new vector map (<B>output</B>).
<P>
The bounds of the output map are limited by the current region.
(see <em>g.region</em>)
<P>
<BR>
Voronoi diagram and Delaunay triangulation example:
<center>
<img src=v_voronoi_delaunay.png border=1><BR>
<table border=0 width=590>
<tr><td><center>
<i>Delaunay Triangulation (left pane), Voronoi diagram (center pane),
and both (right pane)</i>
</center></td></tr>
</table>
</center>
<H2>NOTES</H2>
Voronoi diagrams may be used for nearest-neighbor flood filling.
Give the centroids attributes (start with
<em><A HREF="v.db.addcol.html">v.db.addcol</A></em>),
then optionally convert to a raster map with
<em><A HREF="v.to.rast.html">v.to.rast</A></em>.
<H2>EXAMPLE</H2>
Commands used with the Spearfish dataset to create the above figure.
<div class="code"><pre>
g.region n=4927250 s=4919400 w=588650 e=594850
d.frame -c fr=one at=0,100,0,33.3333
d.frame -c fr=two at=0,100,33.3333,66.6667
d.frame -c fr=three at=0,100,66.6667,100
v.delaunay -lr in=archsites out=arch_delaunay
d.frame -s one
d.vect arch_delaunay
d.vect archsites color=red fcolor=red size=5 icon=basic/circle
v.voronoi -l in=archsites out=arch_voronoi
d.frame -s two
d.vect arch_voronoi type=line
d.vect archsites color=red fcolor=red size=5 icon=basic/circle
d.frame -s three
d.vect arch_voronoi type=line
d.vect arch_delaunay color=blue
d.vect archsites color=red fcolor=red size=5 icon=basic/circle
</pre></div>
<H2>BUGS</H2>
Only attribute table of field 1 is copied.
<H2>REFERENCES</H2>
<EM>Steve J. Fortune, (1987). A Sweepline Algorithm for
Voronoi Diagrams, Algorithmica 2, 153-174.</EM>
<H2>SEE ALSO</H2>
<EM>
<A HREF="g.region.html">g.region</A>,
<A HREF="v.delaunay.html">v.delaunay</A>,
<A HREF="v.hull.html">v.hull</A>
</EM>
<H2>AUTHORS</H2>
James Darrell McCauley, Purdue University<br>
GRASS 5 update, improvements: <a href=mailto:aaime@libero.it>Andrea Aime</a>, Modena, Italy<br>
GRASS 5.7 update: Radim Blazek
<p>
<i>Last changed: $Date: 2007-11-15 02:55:18 +0100 (Thu, 15 Nov 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>
