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I am working on a project on islands in inland waters in Europe. In the first step I was sorting to large point layers which I got from a state office, trying to identify only points lying on such islands. I used a small Python-Script in QGIS to alter large OSM layers mapping inland waters for that, which worked quite good. But since OSM-data contain some errors, I would also like to try other approaches. Also, for comparison and some statistics I would like to identify all other islands, for which I did not get any points.

I thought, there might be a way to extract islands from the free EU-DEM dataset (see https://www.eea.europa.eu/data-and-maps/data/copernicus-land-monitoring-service-eu-dem), but I am not sure how to start on that.

So the question for me is: Is there a way to extract islands from DEMs like the EU-DEM?

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    Please ask only One question per Question. – Vince Dec 19 '19 at 22:35
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    If it's open data that you seek then I think the place to ask is the Open Data Stack Exchange. – PolyGeo Dec 19 '19 at 23:20
  • Thanks for the hint. Question has been straightened and I will add another on to Open Data SE. – C.-F. Vintar Dec 20 '19 at 9:39
  • naturalearthdata.com/downloads/10m-physical-vectors has islands. You probably want the "minor islands" dataset, and perhaps the "land" dataset if you want large islands as well. – csk Dec 20 '19 at 20:40
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    Anything above sea level in a DEM is going to be part of an island (even if that island is the size of a continent...). What do you want for your final output? – Spacedman Dec 20 '19 at 20:56
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I have looked into the problem a while now and found a solution that suits my needs quite well. If you run the GRASS tool r.geomorphon (https://grass.osgeo.org/grass76/manuals/addons/r.geomorphon) on a e.g. an ASTER DEM with water bodies and islands the islands are usually clearly visible as slopes and peaks within the water bodie, classified as flat. I tested that on a couple of test areas now and it has a very good success rate, although some of the very small and shallow islands are invisble in the ASTER DEM or EU-DEM. There are, however, better DEM's freely available for some of my regions of interest (e.g. the state office of Brandenburg in Germany offers free 1m DEM's now).

The interesting thing about this solution is that it also allows to identify possible former islands in dried up areas.

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