Reference DEM for Back Geocoding

[loreabad6]

For Norway, the SRTM does not cover the northern areas, hence the use of the DEM should default to the Copernicus DEM "demName", "Copernicus 30m Global DEM".
For Austria, the SRTM 1 sec should work properly, as SRTM 1Sec HGT.

To do:

• Test external DEM use, so for example ArcticDEM could be used
• Check parameters to change when selecting each type of DEM

[loreabad6]

It is possible to use a external DEM file in theory. We should test it. We can pass the file to externalDEMFile and the demName parameter to External DEM.

Seems like using a too high resolution DEM will not be useful, so resampling would be needed. See here.