I have 4 vector shapefile that I would like to join/merge, without worrying about attributes.
Here are the shapefiles.
I would like to do an union and a spatial dissolve, but everytime I do a dissolve after "PUP" and "PRG" layers union, I got an error about wrong geometries and the output layer is empty.
I validated layers geometry with no errors (at least is what QGIS tells me).

Am I missing out something?

  • 1
    version of QGIS, GRASS? I would also check geometry with GRASS.
    – Vladimir
    Commented Nov 24, 2012 at 16:27
  • QGIS 1.8.0 GRASS 6.4 on a Mac Commented Nov 25, 2012 at 12:50

1 Answer 1


While doing spatial joins in QGIS you have to make sure that all your layers are in the same projection! Otherwise there is a high chance of wrong outputs.

In your example data the shapes PUP and PRG have no correct set CRS projection, while the other shapes are all in ETRS89/ETRS-TM32.

-> Reproject them by saving them with the correct CRS (right-click on layer -> save as with selected ETRS89/ETRS-TM32 projection). -> Then load in the reprojected layers and merge them via the mmqgis function merge layers or through the function in the QGIS vector menu.

As soon as you have one single shape, you'll find the dissolve function in the vector menu.

  • ok, I'm an idiot. I thought "they have the same projection, even if it's not specified, it should work..." It worked quite well. Thankyou so much! Commented Nov 25, 2012 at 13:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.