Hi Gerd,
So far I understand you have implemented already cutting the DEM to the map area and just looking for another way to have some larger area for DEM data? I don't see a use case for that. Probably the reason why I first didn't realised the beginning of your svn comment.
Henning
On 28 Dec 2017, at 11:01, Gerd Petermann <GPetermann_muenchen@hotmail.com> wrote:
Hi all,

see the log message http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4022 
for details about the changes.

I've also experimented with code to read a *.poly file and use that to define an area for which mkgmap should 
not calculate DEM data but was not happy with the results so far. Maybe I'll try again.

Henning has pointed me to an error:
It seems that mkgmap (and probably also BuildDEMFile) somtimes create invalid DEM data 
for areas where the hgt files contain large holes, esp. when resolution is low (high dem-dist value).
See e.g. http://files.mkgmap.org.uk/download/377/holes.jpg
I try to find out more now.


Gerd

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