Hi Carlos, not sure what to do with this. Seems your patch removes the files which are listed here: https://www.opentopodata.org/notes/invalid-srtm-zips/ My SRTM directory contains the listed files and they show a constant height of -29m as stated in the linked page. My understanding is that you don't have those files, but you should have. A non-existing file is treated like a file with height 0. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <carlos@alternativaslibres.org> Gesendet: Samstag, 3. April 2021 09:45 An: Development list for mkgmap Betreff: [mkgmap-dev] Deletion of unneeded hgt files Attached patch deletes some hgt files which correspond to ocean areas from known-hgt.txt file. They just lead to confusing warnings when running mkgmap to generate a map with DEM.