Rotational Geoid

Rotational Geoid: a surface perpendicular at every point to the direction of the vertical—that is, to the direction of gravitational force. This surface best represents the average surface of the oceans (excluding the effects of tides, currents, and weather conditions), and thus the Earth’s mean surface. It is defined as the equipotential surface (where the gravitational potential is constant) that shows the smallest deviations from mean sea level.

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