52A55: Spherical Geometry
This section is supposed to be for "spherical and hyperbolic convexity" but it appears to be the only geometric area focusing on things spherical! So we use it to hold a few posts on spherical geometry.
Parent field: 52A: General convexity. But there is not yet a page for that; see its parent page, 52: Convex and discrete geometry
There is a considerable collection of useful formulas for global navigation and so on at the Aviation Formulary.