Hi, Frank, thanks for your work. Your analysis of DEM headers looks good to me, I have done similar task for gmaptool. Yours is of course more detailed. I haven't looked at your program yet, but I hope it can create usable data. Gerd, there are 2 flags in TDB. One is for DEM, other for using contours for calculating height profiles. See file tdbfmt/HeaderBlock.java, you already have both in code. I think the meaning of these flags in mkgmap is swapped, but I could be wrong. When adding DEM to a tile, area of DEM can probably be bigger than tile, I have seen some examples, when people were using DEM from Garmin maps that way. DEM subfile can't have more layers than TRE but I think less layers should work. When creating a map with DEM for PC, overview map should include DEM too. This could be a DEM with empty data, gmaptool can create that kind of DEM. -- Best regards, Andrzej