1 Earth Ellipsoid Coordinates
The Earth is more accurately modeled as an oblate ellipsoid of revolution. If the symmetry axis is
taken as OZ, then the Cartesian equation with respect to its center is
The definition of longitude λ is exactly the same as on the sphere. The geodetic latitude ϕ, which
we will simply call latitude, is the angle at which the Normal at P intersects the equatorial plane
(Z = 0).
Figure 1. Cross-section of an oblate Earth ellipsoid showing the geodetic latitude ϕ.
References
[1] This article is a derivative work of material in: P. Osborne, The Mercator Projections.
Zenodo, 2013. DOI: 10.5281/zenodo.35392
