Great Circle Sailing distance calculator - loxodrome (rhumb line)
Great-circle distance - Wikipedia
worksheet function - How to do a "great circle" calculation in MS Excel or LibreOffice? - Super User
python - Great Circle Distance between two "P = (x, y, z)" points on a unit sphere - Stack Overflow
Solved Lab 5 1. The great-circle distance between two points | Chegg.com
Smashwords – H. Rajpoot's formula to compute the minimum distance or great circle distance between any two arbitrary points on any sphere or globe for given values of latitude & longitude –