I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, chaiken, douglas...) ends after minutes of working in a programm crash (GRASS and Qgis using sextante).

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How can I smooth the edges of my polygons? Thanks!

  • 2
    How large are we talking?
    – underdark
    Nov 29, 2012 at 20:21
  • 10.000 polygons. the shapefile is 12MB.
    – MartinMap
    Nov 29, 2012 at 20:58
  • 2
    try convert your polygons to lines first then run the tool on lines - rebuild polygons afterwards.
    – Mapperz
    Nov 29, 2012 at 21:22
  • 1
    If you still have the raster, then the GRASS module r.to.vect has an option "-s" to smooth the corners when creating vector polygons from raster areas.
    – Micha
    Dec 1, 2012 at 15:14
  • the smooth corners fuction just replaces a vertical + horizontally line by one diagonal line so its not getting realy smooth.
    – MartinMap
    Dec 4, 2012 at 19:10

1 Answer 1


In GRASS 7 the processing of massive vector data has been implemented. While not yet officially released, you can download weekly binary snapshots (source code as well of course) from:


and tell Sextante in QGIS to use this installation instead of the existing one.

You can install GRASS 7 in parallel to GRASS 6, it will not interfere.

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