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Multi-polygon drainage basin

Hello everyone,

According to the implementation rules, the geometry of a DrainageBasin should be of the type GM_Surface (single-polygon).  However a basin crossing the national border can be split in several polygons. In our dataset this is represented as a multi-polygon, not as multiple single-polygons.

Is it intended that one basin can be represented by several single-polygon spatial objects of the type DrainageBasin? 

Has anyone else encountered such (or similar) issue?


  • Lena Hallin-Pihlatie

    By Lena Hallin-Pihlatie

    Hi Koen,

    Yes indeed, we have encountered the same issue. We also have multi-polygon features in our national Drainage Basin dataset. They share the same well-established id, and we would not like to split them up into single polygon spatial objects due to INSPIRE. Therefore we have made a change proposal concerning this, which proposes that the geometry type GM_MultiSurface would also be allowed for the DranageBasin.  Do you support this solution?

    The change proposal in question will be discussed at the MIG meeting in December and it would be valuable to get support and feedback from other countries on this issue before that.


  • Thomas ROSMANN

    By Thomas ROSMANN


    we also encountered the same problem in Austria. We decided to publish the Drainage Basins with multi-polygon geometries for now, even though they are not INSPIRE-compliant. It would have been a lot of work to assign new IDs and calculate the whole network again with them, and does not represent the original national dataset.

    @ Lena: good to hear that you have made the proposal, we definitely support this!


  • Lena Hallin-Pihlatie

    By Lena Hallin-Pihlatie


    Thanks Tomas. We made the same decision.

    For clarity, here's the change proposal I'm referring to:

    Change Proposal related to the geometry of Drainage Basin

    Perhaps GM_MultiSurface would be enough, but our proposal here is to allow both: GM_Surface and GM_MultiSurface. As long as GM_MultiSurface is allowed (alone or together with GM_Surface), we'd be happy.


  • Koen DE BAETS

    Thanks for the replies.

    We also support the GM_MultiSurface solution. That way we don't have to create new features with new Id's and separate life-cycles.