VRECKON: Find the endpoint of a geodesic on the ellipsoidal earth

This function uses the Vincenty direct algorithm to solve the "forward geodesic problem," which is the problem of computing the endpoint of a geodesic (shortest-distance) path on the ellipsoidal earth, given the start point, a path length, and a starting azimuth. This process is also called "reckoning."

In 1975, Vincenty published a rapidly converging algorithm for this calculation. Since then, his algorithm has since seen significant implementation in geodesy and engineering. The algorithm is precise to within a few millimeters. Please see code comments for references.

Michael Kleder, Nov 2007