Algorithm to be defined for DEM tiles without the same resolution.
Done:
Test on anti-meridian added
Test with real data from SRTM (put in comment as needs GDAL)

Add light time correction in atmospheric refraction correction

See merge request !4

Algorithm to be defined for DEM tiles without the same resolution.
Some tests around anti-meridian need to be added.
Some tests with more real data to be added.

Change http to https

Custom margin for atmospheric refraction; made exception message clearer

See merge request !3

Fixes #391

Fixes #391