[mkgmap-dev] DEM test & artifacts

Tue Feb 20 10:13:17 GMT 2018

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