Sticked to 'err' as error identifier.
This factors in distorted latitudes when calculating distances.

I noticed that some of the simplifications still made no sense and this was the
reason for it: at a longitude of 50 degrees, one degree of latitude attributes
to 64% Euclidean distance (whereas 1 degree of longitude always yields 100%).
I used Math.cos only once at the middle of the geometry, so results will be bad
at the north and south pole!!!! AND FOR CONTINENTS!!!