If you're interested in math and algorithms more than simple (and perhaps correct) solutions, this might be of interest: https://en.wikipedia.org/wiki/Vincenty

If you're interested in math and algorithms more than simple (and perhaps correct) solutions, this might be of interest: https://en.wikipedia.org/wiki/Vincenty%27s_formulae https://en.wikipedia.org/wiki/Vincenty%27s_formulae