> For spherical earth, this is easy, just treat the 2 locations as > vectors whose origin is at the center of the earth and whose length is > the radius of the earth. Convert the lat-long to 3-D rectangular > coordinates and now the angle between the vectors is > arccos(x dotproduct y). The over-ground distance is then just R*theta > where theta is the angle.
It's a bit more complicated in the real world - usually one takes a spheroid as defined by the wgs84 standard: http://www.codeguru.com/Cpp/Cpp/algorithms/article.php/c5115/ Maybe for python, this is enteresting (haven't used it myself though): http://pyogclib.sourceforge.net/ Diez -- http://mail.python.org/mailman/listinfo/python-list
