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[mkgmap-dev] a new DEM-File Option

From Gerd Petermann GPetermann_muenchen at hotmail.com on Sun Oct 22 05:36:30 BST 2017

Hi Frank,

sorry, I did not find much until now because I was distracted with some mapping work. My first simple approach is probably not enough.
I did not yet try your program because I don't have a c# dev system. I also did not find much information about the location of the DEM flag. If you know more, please let me know.
Do you plan to maintain the program or do you think the algo should be integrated in mkgmap?

My understanding is that you can calculate the DEM tiles once and keep them because SRTM data doesn't change often.
So, I assume a service like that on http://garmin.openstreetmap.nl would have to calc the DEM tiles for all continents once in a while
and  merge it with the tiles generated from OSM data.
Is that correct or do we have to calc DEM tiles with exactly the same bounds as the OSM tiles?


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Frank.Stinner <fstinner at gmx.de>
Gesendet: Mittwoch, 18. Oktober 2017 18:30:48
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] a new DEM-File Option


i have find with a lot of "trial and error" a algorithm to create
DEM-Files for a Height-Profil. You can find the description (in german)
at https://github.com/FSofTlpz/Garmin-DEM-Build/blob/master/DEM-Daten.pdf

With this data we can for example draw a track in mapsource or basemap
and we at once the Height-Profil of our track. At second, the map looks
like better.

I have create a experimental program called BuildDEMFile :) to build
this files. Experimental means, the encoder is for exploring the
algorithm but not for speed. You can find the programit at

It is possible, that there minor bugs, but i have it successfull testet
for 2 different germany-maps.

I have a wish:
Can you in mkgmap insert a new option, for example --dem with path to
DEM-files, and include these files in the join-process for the
IMG-files? So far only joined the LBL-, NET-, NOD-, RGN- and TRE-File.
Also should be set the dem-flag in TDB-File.
If so, i can build the DEM-Files with area-size from the splitter-file
areas.list. I hope thats the same like in the TRE-Files?

That would be a little bit easier then my fiddly way:
split the ready IMG-files, build the DEM-files and then join the files
to new IMG-files. And at last i must change the dem-flag in the TDB-File.

with best regards

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