Geodetic altitude to a triaxial ellipsoidal planet

An efficient theoretical model for determining geodetic altitudes with better than millimeter accuracy is proposed, with application to the TOPEX/Poseidon project. The triaxial ellipsoidal subsurface point of a satellite is used as the initial trial solution to achieve an efficient and simple iterative solution. It is found that the second-iteration solution is exact to an accuracy of at least 10 to the -9th km.