I wrote an article about it and S2 some time ago as well for those interested: https://blog.christianperone.com/2015/08/googles-s2-geometry-on-the-sphere-cells-

I wrote an article about it and S2 some time ago as well for those interested: https://blog.christianperone.com/2015/08/googles-s2-geometry-on-the-sphere-cells-and-hilbert-curve/ https://blog.christianperone.com/2015/08/googles-s2-geometry...