[mkgmap-dev] Issues generating DEM

Wed Nov 1 10:10:07 GMT 2017

I have done some tests with BuildDEMFile (thanks Frank for providing 
it!), but with some problems. I have followed the procedure described by 
Gerd at [1]. What I have done is the following:
1-Try to generate a DEM for my Western-Sahara map with command
wine ../../../../DEM/BuildDEMFile.exe --usedummydata=true -d 
55132001/55132001.DEM --hgtpath=../../../../DEM/hgt/ 
--tre=55132001/55132001.TRE --dlon=0.00027761
Result:
Daten aus der TRE-Datei '55132001/55132001.TRE' gelesen
Höhen für -18° .. -17° / 20° .. 21° eingelesen
...
1 Zoomlevel
erzeuge 31594 x 25790 interpolierte Höhenwerte für den Abstand 
0,00027761° x 0,00027761°...
Out of memory
BuildDEMFile was using about 1 GB RAM when it stopped, while there was 
~2 GB free available on system. How can I allocate more memory for 
BuildDEMFile? Western Sahara is very low mapped, so that a large area 
fits in a single img, but it covers 80 hgt files. Is there a size limit 
for DEM files and thus large areas should be split for img generation?

2-Try to generate a DEM for my region (Extremadura, Spain) with command
wine ../../../../DEM/BuildDEMFile.exe --usedummydata=true -d 
55113002/55113002.DEM --hgtpath=../../../../DEM/hgt/ --lastcolstd 
--tre=55113002/55113002.TRE --dlon=0.00027761
Result:
Daten aus der TRE-Datei '55113002/55113002.TRE' gelesen
Höhen für -8° .. -7° / 37° .. 38° eingelesen
...
1 Zoomlevel
erzeuge 10560 x 9339 interpolierte Höhenwerte für den Abstand 
0,00027761° x 0,00027761°...
Daten 10560 x 9339, Min. 70, Max. 2577 für Zoomlevel 0
Value cannot be null.
Parameter name: destinationArray
What does it mean and how to fix it?

3-Try to generate a DEM for an small portion of my region (only 4 hgt 
files required) with the same command as previous
Result: DEM created.

[1] http://www.mkgmap.org.uk/pipermail/mkgmap-dev/2017q4/027176.html