Hi Ceppo, The above equation will calculate the distance between any two pooints on a perfect sphere, the earth is not a perfect sphere hence the 59.99985, use 60 if you want to. The ACOS means ARC COS, if you convert cos 30 deg to numerical value you get .87 to get it back to 30 deg push ACOS on the calculator. Most calculators will allow you to convert standard degrees into decimal degress far calculation purposes, use the HMMSS feature supplied for this.
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