Earth ellipsoid

Geometric figure which approximates the Earth's shape

An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's shape and size, used as part of a reference frame for coordinates and computations in geodesy, astronomy, and the geosciences. Various different reference ellipsoids have been used as approximations. It is an oblate spheroid (an ellipsoid of revolution) whose minor axis (polar diameter), connecting the geographical poles, is approximately aligned with the Earth's axis of rotation.

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