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[mkgmap-dev] a new DEM-File Option

From Gerd Petermann GPetermann_muenchen at hotmail.com on Tue Oct 24 08:52:45 BST 2017

Hi Frank,

okay, seems to be more work. Don't know if I am just getting old but I have no idea where to start.
We know a few demo maps which contain DEM data. Now we also have your doc and the demo program.
I am not familiar with c# and I don't have Microsoft Studio, but I think there are free versions for this as well.
I used to maintain some  c/c++ programs so I guess I should be able to dig into this again, but it will take a while.
My only advantage is that I am german and therefore able to read your doc and the comments in the source ;-)

I seem to remember that someone described how to extract DEM data from a gmapsupp and merge it into his own map,
that's why I assumed that it should be possible to calculdate this only once in a while.
I'd really prefer that solution, but this is a different problem.

I hope I get into this during the next weeks, but as of now I think it might take some months before we have this in mkgmap :-(

Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Frank Stinner <Frank.Stinner at kabelmail.de>
Gesendet: Sonntag, 22. Oktober 2017 18:56:04
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] a new DEM-File Option


at first:
yes i mean the DEM-flag in TDB-file like Andrzej Popowski wrote.

at second:
unfortunally it seems, that the corner left-top for TRE-file and
DEM-file should be the same. The height-data organized in subtiles with
64x64 points. The most right sub-tile is a problem, but my workaround
is, to use a normal tile with 64 points width. That's why, the DEM is at
most a little bit widend then the TRE.
The data in a sub-tile are organized as a bitstream. That's why, we can
not split a subtile in parts.
I belive, we must "compile" a DEM for anything TRE new.

at third:
Yes, the best way is, to build in the algorithm in mkgmap. But i'm not
familiar with java. It would be useful, if anybody translate my
description (my german is a little bit better than my english :).
For easy test:
builddemfile --dem=12345678.dem --hgtpath=path2zipped_hgt_files
--tre=12345678.tre --dlon=0.00027761
I build the program with the MS-Visual-Studio 2015.

at fourthly:
I build also a DEM-file for the overview-map, but with --dlon=0.005.

at fifthly:
Probably can a DEM-file several Zoomlevel. But for Mapsourec/Basecamp it
is not necessary. It seems, we need that for a GPS-Device. My Oregon
show DEM only for Zoom <= 800m.


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