I want to intersect contours with polygon like in the image below. But I got this error:

GEOS geoprocessing error: One or more input features have invalid geometry.
Some output geometries may be missing or invalid.

I don't know what's wrong with my geometries. I even don't know, where to search. I tested it also with a simple single-line. Same thing happened. The result: a empty shapefile

enter image description here

What should I do now? Where can I expect an invalid geometry? Or is it because of the shapefile (OGR ESRI)? Please help!

  • 1
    Have you tested the validity of the contours and the polygon layer? (Vector - Geometry tools - Check geometry validity) It should show where the problem is located.
    – underdark
    May 25, 2012 at 8:35
  • 1
    No errors found! But I do it now with ogr2ogr: gis.stackexchange.com/questions/25996/…
    – MartinMap
    May 25, 2012 at 11:11

3 Answers 3


I have encountered the same problem elsewhere. Reset the CRS. Go to Settings>Project Properties> CRS and Set a Reference system again. This should do the job. If not, export it as an ESRI shapefile.


I just had this error, and re-projecting did not solve the problem. I also ran the Validity tool, and there were no errors. I ran previous intersections with one of the files, so I suspected the new file was causing the problem. I saved it as geojson, then it worked. Not sure why, but it worked.


The problem are cross nodes in the shapefile, it's need to edit the shape. Firstly, select the shapefile and go in toggle editing > node tool, then select the shape and a different point will arise, delete or undo the node.

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