Syn: Normal Earth, Reference Earth
Mathematical earth models are described by stereometric bodies.
The main mathematical earth models are spheroids:
C) Normal earth, or reference earth, or earth
model. Mathematically the simplest model is an
ellipsoid of revolution, which therefor is practically almost exclusively used. Physically the
reference for describing the small, more or less elastic, temporal variations (free and forced
oscillations such as earth tides), is a hydrostatic equilibrium figure. Figures of hydrostatic
equilibrium for the earth are very close to ellipsoids, but do not exactly coincide with an ellipsoid...