The surface of the Earth is curved, and the distance between degrees of longitude varies with latitude. As a result, finding the distance between two points on the surface of the Earth is more...

The surface of the Earth is curved, and the distance between degrees of longitude varies with latitude. As a result, finding the distance between two points on the surface of the Earth is more complicated than simply using the Pythagorean theorem. Let (,
) and (,
) be the latitude and longitude of two points on the Earth’s surface. The distance between these points, following the surface of the Earth, in kilometers is:

Distance = 6371.01 × arc cos(sin() × sin() + cos() × cos() × cos( −))