Geografic-Information-System/vector/v.buffer/v.buffer.html

<h2>DESCRIPTION</h2>

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

<h2>NOTES</h2>

Internal buffers for areas can be generated with negative distance 
values ("inward buffer" or "negative buffer").
<p>
Categories and attributes can be transferred with the <b>t</b> flag. 
The resulting buffer areas can have multiple categories, 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).

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

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

<h2>EXAMPLES</h2>

All examples are based on the North Carolina sample dataset.

<h3>Buffer around input lines</h3>

<div class="code"><pre>
v.buffer input=roadsmajor output=roadsmajor_buffer type=line distance=100
</pre></div>

<center>
<img src="v_buffer_lines.png" border="1"><br>
Buffer of 100m along the "roadsmajor" lines (map subset, original center line
shown in black)
</center>

<h3>Circles around input points</h3>

<div class="code"><pre>
v.buffer input=hospitals output=hospitals_circled type=point distance=2000 
</pre></div>

<center>
<img src="v_buffer_points.png" border="1"><br>
Buffer of 2000m around the "hospitals" points (map subset, original points
shown in black, new area centroids in red)
</center>

<h3>Circles around input points with attribute transfer</h3>

<div class="code"><pre>
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
</pre></div>

<h3>Buffer around input areas</h3>

<div class="code"><pre>
v.buffer input=lakes output=lakes_buffer type=area distance=100
</pre></div>

<center>
<img src="v_buffer_areas.png" border="1"><br>
Buffer of 100m around the "lakes" polygons (map subset, original areas
shown in black)
</center>

<h2>REFERENCE</h2>

<ul>
<li><a href="http://trac.osgeo.org/geos">GEOS Library</a></li>
</ul>

<h2>SEE ALSO</h2>

<em>
<a href="r.buffer.html">r.buffer</a>,
<a href="v.parallel.html">v.parallel</a>,
<a href="v.extract.html">v.extract</a>,
<a href="v.type.html">v.type</a>,
<a href="v.patch.html">v.patch</a>,
<a href="v.db.connect.html">v.db.connect</a>
</em>

<h2>AUTHORS</h2>

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

<p>
<i>Last changed: $Date$</i>