>George suggests to use
>
>I would recommend that you allow the calculations to process the data using miles. If you want the results in KM, simply multiply values by 1.609344. You could modify the CalculateDistance function to multiply by this value just prior to returning.
>
>but I don't see how did he arrive to the constants used in these formulas (I assume Michel used his scripts).

This goes back to last year from several threads created on the topic. At that time, it was R & D but only since a week I have put it all in a class Geography to do multiple related operations. So, those values probably come from one of those threads. I did adjust it to kilometer as this is our baseline. But, if a request to go in miles would apply, I also have a formula for that.