Apollo's celestial navigation relied on standard spherical trigonometry and the measurement of angles between stars and horizons, which is fundamentally the same geometric foundation used in marine navigation for centuries.
The claim that space navigation via sextant shares its underlying geometry with marine navigation is a foundational fact of spherical geometry and celestial mechanics. Both marine and Apollo-era space navigation rely on lines of position derived from the angles between celestial bodies and a reference horizon or spacecraft coordinate frame, governed by spherical trigonometry. No citation is needed for this basic geometric fact, making it common knowledge.