Re: [mkgmap-dev] HGT - getElevation()

Hi Gerd, I have looked a bit at Garmin's DEM and I have some guesses. * Coordinate resolution for DEM is 28 bits. Since it is shifted to the left, 4 lower bits are always 0. * The same goes for pixel distance, lower 4 bits should be 0. This is the reason, why Garmin uses 3312 (CF0) instead of 3314 (CF2). * Coordinates of left top corner for each DEM layer are always exact multiple of pixel distance. Since layers get different distances, each layer get a bit different coordinates too. I would expect, that aligning of HGT in mkgmap should at least support 3-rd requirement, but it is not the case. I don't know why. Differences looks too big to be explained by rounding errors. -- Best regards, Andrzej