[mkgmap-dev] DEM test & artifacts

Tue Feb 20 14:56:03 GMT 2018

Hi David,

just noticed that the extract from geofabrik contains a far too large bounds statement.
So, I've defined a rectangular polygon that is a bit closer to the coast. This is used for splitter
in the attached modified scripts. Maybe it helps?

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Dienstag, 20. Februar 2018 15:35:48
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] DEM test & artifacts

Hi David,

you did not tell us much about your options for splitter and mkgmap, so it is difficult to reproduce your results.
Did you use the polygon for splitter or for mkgmap (--dem-poly) or for both?
When you use --dem-poly you will see a different shading for those areas outside the polygon, so I would not use
that option.  No idea about the artifacts. I don't see them in a map created created with the attached script, using
splitter r590 and mkgmap r4125. Please post a screen shot or a link to your map and describe the position of the problem.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von David <david.tlp at orange.fr>
Gesendet: Dienstag, 20. Februar 2018 11:13:17
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: [mkgmap-dev] DEM test & artifacts

Hello,

I tested the new DEM option with my map. It works with Basecamp. I can display shadow mountain relief and at the same time my contour lines layer and my OSM layer. Both are transparent and without background polygon. I am also able to display the profile of a route as the option showprofile is activated in my mkgmap configuration (I think it works with my contour lines as it worked before I introduced DEM).

I discovered two problems with DEM rendering.
For areas not covered by a SRTM tile, mkgmap produces a uniform shadowed surface (pure ocean surface) whereas for SRTM tile with both ocean and ground, there is a totally blank surface for ocean. To avoid this effect, I had to define my own polygon for Ireland (the one from geofabrik is too large : it includes a large part of ocean surface). I also reduced the size of my map by  30Mb :-)
Along the coast, the DEM border is roughly cut in square shapes and it does not follow the shoreline. It is a minor problem but it look strange for coastal areas and isles.
Would it be possible to automatically use the shoreline to clip nicely the DEM data ?

David
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