In QGIS add vector layer creates a layer with 3D geometry. All my postGIS tables have been created with 2D so I can not save them to PostGIS.

Are there any problems with converting my existing 2D tables to 3D to get around this?

I am aware that QGIS 3 will allow one to drop the z dimension but this question is explicitly about converting tables to 3D.

  • 1
    Your question is about creating new layers in postgis but using existing ones from postgis. There seems to be a mismatch here. Do you mean using and editing existing postgis layer from QGIS?
    – tilt
    Commented Jun 26, 2017 at 8:23
  • Furthermore I don't see problems with converting existing 2D tables to 3D, but I'm a little surprised this is needed with QGIS.
    – tilt
    Commented Jun 26, 2017 at 8:24
  • I am importing data from a GPS into QGIS and then adding it a master layer that is backed by PostGIS. When I try and save the updated master I get errors about the 3D data. Commented Jun 27, 2017 at 23:22
  • What do you mean with 'a master layer that is backed by PostGIS'. Is it a postgis layer or is it something else? Do you create that master layer yourself or is it already there? Please describe step-by-step what you are doing.
    – tilt
    Commented Jun 28, 2017 at 12:01
  • it is a vector layer which is defined by an sql query on a PostGIS db. It contains all my waypoints -- I have another that contains all lines. The problem comes when I try to save the updated vector layer to PostGIS. QGIS 3 will deal with this but in the mean time it is painful. Commented Jun 29, 2017 at 20:41

1 Answer 1


There is no problem with converting your existing 2D tables to 3D, apart from your data becoming slightly larger with an extra z-coordinate (with value 0) attached to it.

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