WANTED!

Formula for Distance Calculation

Let me know your formula for distance calculation
or any organization opening its formula for public.

We use an approximation method in Japan.
The formula is as follows:

D = square root ( AaAa + BbBb - AaBbBbc )

 starting point: n1, e1
 loft location:  n2, e2
 A: n1-n2   a: 111.323
 B: e1-e2   b: 111.323 * cos(n2)
          c: tan(n2)/6378.388
 
 Thank you for your cooperation.