Distance between two coordinates

Pitou:
Or can I just copy The C or C++ code , then include it to a arduino?
If yes, how could I do that?

Thanks.

No, you can't just copy it to the Arduino. You need to look at the code and adapt it.

For instance

static const double DEG_TO_RAD = 0.017453292519943295769236907684886;

Looks a little beyond what the average Arduino can cope with, but round it to less decimal places and you might have a chance.