OK, I read it quickly, the math seems to be quite heavy.
I also came across an interesting solution for a simpler spherical model:
https://www.movable-type.co.uk/scripts/latlong-vectors.html
It would be less accurate, I fear it will cause problems with geodesic data sets.
But it is worthy of a mention !
One possibility could be to scale the geodesic data sets of earth to a sphere, but then I worry the distances will be inaccurate, not sure if this can be solved...
And if it would be a problem at all, but I like to keep it real if possible ! ;)
Bye for now,
Skybuck.