Hi Andrzej, I looked at the three demo topo maps that I have which have more that one zoom level and I found this: All have the same levels 24,22,20,18. topo2 uses DEM point distances 1648, 6624, 26512, 106048 and was created 17 Dez 2007 Transalpin uses DEM point distances 3312, 13248, 26512, 53024 and was created 2 Sep 2009 topo-2010 uses DEM point distances 5520, 16560, 44178, 88368 and was created 28 Apr 2010
The distance between two DEM points is 360° / 2^32 or ~40000km / 2^32 ~ 0,00931 m (lat), so 3312 *0,00931 m is ~ 30 m. So, I see no obvious rule for the ratios, esp. there are not always exact multiples, so we probably need an option for this. I see no need to store the ratio in an extra field in the header. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-boun...@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <po...@poczta.onet.pl> Gesendet: Mittwoch, 20. Dezember 2017 00:28:59 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] r4006: 1st alpha version to write DEM data Hi Gerd, great news! > It will crash if any hgt file is missing I have them all, but there is no HGT for sea area, missing files is a standard case. > I did not check if the flags in the tdb file are set correctly now I didn't check either, but tdb created by mkgmap v3999 works correctly for maps with DEM. > My currennt understanding is that mkgmap should do the calculation of > the DEM resolution based on the levels used to create the rest of the > map. I think it should be like that and some Garmin maps follow this rule. I have tried to create DEM with pixel size ratio like 1:4:16:64 for levels 24,22,20,18. It didn't work correctly in Mapsource. What works for me is ratio 1:2:4:8. I think some of unknown fields in DEM header could contain this ratio. It is something to investigate further. -- Best regards, Andrzej _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
