I downloaded some road network data derived from OSM by GeoFabrik, see the initial state: Near Székesfehérvár (Hungary) Near Székesfehérvár (Hungary), parallel lines are probably trunk or motorway roads.

I would like to simplify it like this (drawn in Paint): enter image description here

I would like to use open source stuff for that (QGIS, GRASS), so I tried v.clean and v.simplify, v.generalize in some combination. Unfortunately, I cannot reach the desired result.

With v.clean 'snap' method, tolerance=50 I reached this:

After v.clean snap.

But I don't need duplicated geometries, or identical zig-zag lines. Probably the v.generalize.network (Closeness, Betweeness threshold) would solve the problem, if it worked.

You can download the clipped geodata here: https://github.com/ewirth/gistemp


Buffering the road may be a solution to this problem.

  • create a dissolved buffer of the road using around 20 unit map distance. enter image description here

  • import the layer into a postgis database and create the middle line using ST_ApproximateMedialAxis() function:

SELECT ST_ApproximateMedialAxis(geom) AS geom INTO road_centre_line FROM road_buffer;

  • in order to access this function you have to enable the postgis_sfcgal extension
  • with this you will get an output like this enter image description here

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