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<h2>NAME</h2>
<em><b>v.build.polylines</b></em> - Builds polylines from lines or boundaries.
<h2>KEYWORDS</h2>
vector, geometry, topology
<h2>SYNOPSIS</h2>
<b>v.build.polylines</b><br>
<b>v.build.polylines help</b><br>
<b>v.build.polylines</b> [-<b>q</b>] <b>input</b>=<em>name</em> <b>output</b>=<em>name</em> [<b>cats</b>=<em>string</em>] [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>]
<h3>Flags:</h3>
<DL>
<DT><b>-q</b></DT>
<DD>Do not print polyline info</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>
<DT><b>cats</b>=<em>string</em></DT>
<DD>Category number mode</DD>
<DD>Options: <em>no,first,multi</em></DD>
<DD>Default: <em>no</em></DD>
<DD><b>no</b>: Do not assign any category number to polyline</DD>
<DD><b>first</b>: Assign category number of first line to polyline</DD>
<DD><b>multi</b>: Assign multiple category numbers to polyline</DD>
</DL>
<h2>DESCRIPTION</h2>
<em>v.build.polylines</em> builds polylines from the lines or
boundaries in a vector map. <!-- ???? and copies the attribute
and category files from the original file. -->
<P>
A line is a single straight line segment defined by one start node, one end
node and no other nodes. A polyline is also defined by one start node, one end
node and no other nodes, but is made of two or more consecutive straight line
segments. The connections between the constituent line segments of a polyline
do not appear as nodes in the vector map.
<P>
Polylines provide the most appropriate representation of curved lines when it
is important that nodes serve to define topology rather than geometry. Curved
lines are usually digitized as polylines, but these are sometimes broken into
their constituent straight line segments during conversion from one data
format to another. <em>v.build.polylines</em> can be used to rebuild such broken
polylines.
<h2>NOTES</h2>
<p>
If the lines that make up a polyline are of different types, then
<i>v.build.polylines</i> will set the type from the first constituent line.
<!--
<i>v.build.polylines </i> will issue a warning unless the flag <b>-q</b> has
been set. It is possible to keep a list of all such warnings by redirecting
standard output to a file.
-->
<p>
Category number(s) are assigned to a polyline based on <b>cats</b> parameter.
<ul>
<li>cats=no - No category number is assigned to a polyline. Also
attributes tables linked to the input vector map are not copied to
the output vector map.</li>
<li>cats=first - Assign to a polyline category number of the first
line. All linked attributes tables are copied to the output vector map.</li>
<li>cats=multi - If the lines that make up a polyline have different category numbers
then <em>v.build.polylines</em> will set the multiple catetory numbers to a polyline.
Also all linked attributes tables are copied to the output vector map.</li>
</ul>
<p>
<em>v.build.polylines</em> correctly handles <b>input</b> vector maps
containing lines, boundaries, centroids and points. Lines and
boundaries will be converted to polylines of the desired type. Areas
are only guaranteed to be preserved if the constituent lines of the
polylines that define them are all boundaries in the input vector map.
<!-- Points will remain points provided that <b>type</b> has been set to `source'.
It is possible to convert lines and area edges to points or vice versa, but this
is rarely useful. [type no longer exists, other behaviour still true??] -->
<h2>ACKNOWLEDGEMENTS</h2>
This program was originally written during Mark Lake's tenure of a
Leverhulme Special Research Fellowship at University College London.
<h2>SEE ALSO</h2>
<em>
<a href=v.build.html>v.build</a>,
<a href=v.in.ascii.html>v.in.ascii</a>,
<a href="v.split.html">v.split</a>,
<a href="v.edit.html">v.edit</a>
</em>
<h2>AUTHORS</h2>
Mark Lake, Institute of Archaeology, University College London.<br>
Major rewrite by Radim Blazek, October 2002<br>
Category mode added by Martin Landa, FBK-irst, Trento, Italy, October 2007
<p><i>Last changed: $Date: 2007-10-10 13:49:16 +0200 (Wed, 10 Oct 2007) $</i>
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