Nearly antipodal points distance accuracy improvement

Nearly antipodal points refer to the most geographically distant points on a sphere i.e. the points are diametrically opposite to each other. Computing the great circle distance between these points is often a corner case for most geodesic computations, and the distance is either overestimated or underestimated.

This project aims to provide an accurate implementation of geodesic algorithms in Boost Geometry library following the paper Algorithms for geodesics by Charles Karney. An in-depth analysis of the inaccuracy in current implementation is provided in this blog post.