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On 02/06/2012 11:02, Matej Mailing wrote:
<blockquote
cite="mid:CAF44DZcCKri0T7-t+uYearnEif5hR=pHhNyrDA8VhXhyyjNqAw@mail.gmail.com"
type="cite">
<pre wrap="">Hi,
I have a layer that contains roads in polygons and I need to get
central lines of the polygons. When I convert directly from polygons
to lines, I get two lines for each part of the road representing road
"boundaries" which isn't good.
</pre>
</blockquote>
<br>
There's a procedure using GRASS that you might choose. It involves
converting the polygons to a GRASS raster, then running the GRASS
module r.thin, and then converting back to a vector.<br>
Here's an old thread that mentions the method:<br>
<a
href="http://www.mail-archive.com/grass-user@lists.osgeo.org/msg01015.html">http://www.mail-archive.com/grass-user@lists.osgeo.org/msg01015.html</a><br>
<br>
Two difficulties: <br>
* you have to set the resolution fairly high in order to keep the
road's shapes, but then the raster might be too large to work with
on a large area<br>
* and you loose the attribute table on the way...<br>
<br>
<blockquote
cite="mid:CAF44DZcCKri0T7-t+uYearnEif5hR=pHhNyrDA8VhXhyyjNqAw@mail.gmail.com"
type="cite">
<pre wrap="">
What is the best way to achieve it?
Thanks,
Matej
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</pre>
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<br>
<pre class="moz-signature" cols="72">--
Micha Silver
052-3665918
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