On 02/06/2012 11:02, Matej Mailing wrote:
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.

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.
Here's an old thread that mentions the method:
http://www.mail-archive.com/[email protected]/msg01015.html

Two difficulties:
* 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
* and you loose the attribute table on the way...

What is the best way to achieve it?

Thanks,
Matej
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