At first approximation the Earth has the shape of a sphere with radius 6,371 km.
The so called International Earth Ellipsoid as a rotation ellipsoid with flattened poles optimally represents the real shape of Earth.
The Earth's corpus can not be represented exactly by a simple geometrical figure; instead of this one speaks of a geoid.
The geoid is not symmetrical to the equatorial plane: It differs from the rotation ellipsoid at the North Pole about +10 m, at the South Pole about -30 m (pear shape). The equator is not exactly circular either (potato shape, with differences up to -113 m in the Indian Ocean and up to +81 m in the west of the Pacific Ocean).
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spheroid |