S2 can also output interior coverings, which will return only the cells in a covering that are fully contained in a polygon. So if you encounter a point (or any

S2 can also output interior coverings, which will return only the cells in a covering that are fully contained in a polygon. So if you encounter a point (or any cell) whose parent is in an interior covering, you don't have to do any additional checks to produce an exact result (whereas on the boundary, you may want to do a point-in-polygon test to be exact).