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Mathematical Earth Models Geodetic Reference System
Syn: Normal Earth, Reference Earth
Mathematical earth models are described by stereometric bodies.
The main mathematical earth models are spheroids:
On these models, geographic coordinates (longitude, latitude) are defined.
One of the 3 definitions of "figure of the earth" [Moritz 1990, p. 1]:
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 best 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...