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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!

MartinMap
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    How large are we talking? – underdark Nov 29 '12 at 20:21
  • 10.000 polygons. the shapefile is 12MB. – MartinMap Nov 29 '12 at 20:58
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    try convert your polygons to lines first then run the tool on lines - rebuild polygons afterwards. – Mapperz Nov 29 '12 at 21:22
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    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 01 '12 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 04 '12 at 19:10
  • @mapperz: woking on that... but still have problems because adjacent lines are generalized differently so that they overlap – MartinMap Dec 04 '12 at 19:15
  • Which GRASS GIS version are you using? Recently many performance updates have been implemented (to be published in the next version but snapshots are available). Perhaps you can make the file available to me for testing? – markusN Dec 09 '12 at 22:32
  • Try to do it by land use class – Gago-Silva Jan 07 '13 at 17:21

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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:

http://grass.osgeo.org/download/

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.

markusN
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