Find the k nearest neighbors for points on a sphere for .NET
sphere-knn is a .NET module that provides fast nearest-neighbor lookups on
a sphere. This is useful if, for example, you have a database of geographic
points (latitude, longitude) and want to swiftly look up which of those points
are near a given latitude, longitude pair.
This is based on the NodeJS model sphere-knn (https://github.com/darkskyapp/sphere-knn)