[mkgmap-dev] r4006: 1st alpha version to write DEM data

Tue Dec 19 18:12:57 GMT 2017

Congratulations Gerd! Brilliant.

I know its just the beginning.

Have just done Luxembourg - very fast - however there is an obvious dip 
perhaps where 2 hgt files join?

http://files.mkgmap.org.uk/download/375/luxstripe.jpg

r

Nick

On 19/12/2017 17:41, Gerd Petermann wrote:
> Hi all,
>
> FYI:
> r4006 in the dem-tdb branch implements a new option
> --x-dem=path_to_dir_with_hgt_files
>
> It will crash if any hgt file is missing, probably there are also other stupid problems, e.g. with negative lat/lon values.
>
> It cannot (yet) read zip files, so the directory must contain unzipped *.hgt files.
> The hgt files can be in 3'' or 1'' resolution, but for now DEM data is always stored with 3'' res.
> I plan to change that soon, so that 1'' is used if at least a part of the tile is covered by 1'' SRTM data.
>
> It doesn't yet create DEM for the overview map and it only creates DEM for level 0.
> So far I've only implemented a very basic hgt reader which doesn't do any interpolation,
> this might change soon.
> I did not check if the flags in the tdb file are set correctly now, I've only created some small
> maps for parts of the alps so far and they looked good in Basecamp /Mapsource.
>
> If you want to try this version, see
> http://www.mkgmap.org.uk/download/mkgmap-dem-tdb-r4006.zip
>
> @Frank:
> 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 have to find out how to calculate the values for lower resolutions.
> I assume it has to be the average of the values, so if at res 24 we have 4 points with 123, 124,128, and 122
> the value for res 23 would be Math.round((123+124+128+122)/4) = 124. For res 22 it would be the average of 4*4=16 values,
> and so on. Does that make sense?
>
> ciao,
> Gerd
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