Hi David, I assume you don't like the empty rectangles in the NW? Those are probably caused by the trimming in splitter. Please try to split with the polygon that I provided with my sample in david2.zip. Sometimes the SRTM data shows heights > 0 where OSM data shows ocean. It would be quite complex to avoid that, also the shadowing in the Garmin software doesn't seem to care much about this. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von David <david.tlp@orange.fr> Gesendet: Mittwoch, 21. Februar 2018 23:34:39 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM test & artifacts Hello Gerd, I compiled my map without my custom dem-poly option and the result is as I tried to explained in my first message. You can see the result at : http://emerald-island.eu/wikka/ShadowArtifacts Artifacts are also still present along shorelines. But it seems to be normal : I checked SRTM1 tiles and the problem is in source data. In fact, mkgmap works nicely ! Thank you for your work and also many thanks to Andzej Popowski and Frank Stinner. David