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I'm trying to delete duplicate nodes from a shapefile with QGIS, but after running the tool to delete it, nothing happens and shows the same errors.

I thought that maybe importing to postgis could be easier. What I want to do is:

  1. Extract points from polygon (this is already done)

  2. Delete the duplicate points ¿with st_equals?

  3. To finish, reshape the points to polygons without the duplicate points.

Anyone know if this methodology would be ok? I can do the first and second steps, but don't know if number 3 is possible, or if there is a better alternative.

Any clue or suggestion?

  • 2
    It may be as easy as to simplify with zero tolerance. At least worth a try. – user30184 Aug 14 '14 at 14:55
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    be careful that there is a mandatory duplicate node at the start/end of the drawing. Removing one of those points could corrupt your data. I recommend that you use simplify with a diminutive tolerance, as suggested by @user30184 – radouxju Aug 14 '14 at 15:04
  • you are right. st_simplify(geom,0) is the best solution. Thanks – Pablo Pardo Aug 14 '14 at 17:44
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If you are running PostGIS 2.0+, you can use the ST_RemoveRepeatedPoints function, so no need to go thru all that trouble of extracting and reconstituting

http://postgis.net/docs/manual-2.1/ST_RemoveRepeatedPoints.html

UPDATE yourpolygontable SET geom = ST_RemoveRepeatedPoints(geom);

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