Calculating distances on a sphere

This small routine calculates the minimum distance of two points on the earth's surface, i.e. on a great circle.
Assumption: The earth is a perfect sphere with a radius of 6371 km.

Point 1 - Geographical latitude: degrees (0 - 90)     minutes (0 - 59) North South
Point 1 - Geographical longitude: degrees (0 - 180)     minutes (0 - 59) East West
Point 2 - Geographical latitude: degrees (0 - 90)     minutes (0 - 59) North South
Point 2 - Geographical longitude: degrees (0 - 180) minutes (0 - 59) East West

September 5th, 2002, Andreas Manschke