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<h2>DESCRIPTION</h2>
In GRASS GIS, a centroid is a point within a closed ring of boundaries.
A vector area is defined as composite entity consisting of a set of
closed boundaries and a centroid. The attribute information associated
with this area is linked to the centroid.
The <em>v.centroids</em> module adds centroids to closed boundaries in
the <b>input</b> file and assigns a category number to them. The starting
value as well as the increment size may be set using optional parameters.
<p>Multiple attributes may be linked to a single vector entity through
numbered fields referred to as layers. Refer to <em>v.category</em>
for more details, as <em>v.centroids</em> is simply a frontend to that
module.
<p>The boundary itself is often stored without any category reference as it
can mark the border between two adjacent areas. Thus it would be ambiguous
as to which feature the attribute would belong. In some cases it may, for
example, represent a road between two parcels of land. In this case it
is entirely appropriate for the boundary to contain category information.
<h2>EXAMPLES</h2>
Create an area from a closed line using North Carolina sample dataset:
<div class="code"><pre>
v.type input=busroute11 output=busroute11_boundary from_type=line to_type=boundary
v.centroids input=busroute11_boundary output=busroute11_area
</pre></div>
<div align="center" style="margin: 10px">
<a href="v_centroids.png">
<img src="v_centroids.png" width="600" height="300" alt="v.centroids example" border="0">
</a><br>
<i>Figure: Creating area from closed line</i>
</div>
<h2>SEE ALSO</h2>
<em>
<a href="v.category.html">v.category</a>
</em>
<h2>AUTHORS</h2>
module: M. Hamish Bowman, Dept. Marine Science, Otago University, New Zealand
<br>
help page: Trevor Wiens
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