I wrote about it in the past if someone is interested in a tutorial: http://blog.christianperone.com/2015/08/googles-s2-geometry-on-the-sphere-cells-and-hilbert

I wrote about it in the past if someone is interested in a tutorial: http://blog.christianperone.com/2015/08/googles-s2-geometry-on-the-sphere-cells-and-hilbert-curve/ http://blog.christianperone.com/2015/08/googles-s2-geometry-...