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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!

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

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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