[PROLOG]

Give a predicate that calculates the distance between two geographic locations specified by latitude and longitude in radians.

?- distance( 45.421016, -75.690018, 45.4222, -75.6824, D). D = 0.6089563918931657. 

This distance can be found as follows (great circle interpolation): Input: lat1,lon, and lat2, lon2 in radians Output: distance in kilometers lat -latz dradians = 2 * asin sqrt sin + cos(lat1) * cos(lat2) lony - lon2 sin distance = 6371.0 * drad ians Note that the GPS location use angles in degree but the above formula expects angles in radians. The angles can be converted as usual: angledegrees pi* 180 angle,adians =