Knowra Geoid Geoid The geoid is an equipotential surface of Earth’s gravity field that approximates global mean sea level. It serves as a reference surface for measuring elevations.
Gravitational potential : The potential energy per unit mass associated with a gravitational field. The geoid is a surface of constant gravitational potential, including the effect of Earth’s rotation.
Orthometric height : The height of a point above the geoid, measured along the local direction of gravity. It is the standard physical elevation that geoid models help derive from satellite heights.
Reference ellipsoid : A mathematically defined ellipsoid used to approximate Earth’s overall shape. Unlike the geoid, it is smooth and defined by geometry rather than gravity.
Carl Friedrich Gauss : A German mathematician and physicist whose work shaped geodesy, mathematics, and physics. Gauss introduced the geoid concept in 1828 as a physical representation of Earth’s figure.
Topographic surface : The irregular physical boundary between Earth’s solid surface and the atmosphere or water. The geoid is a reference surface, not the landforms and structures that elevations describe.
Earth's gravity field : The spatial pattern of gravitational acceleration around and within Earth. Variations in this field determine the geoid’s departures from a smooth reference ellipsoid.
Ellipsoidal height : The height of a point above a reference ellipsoid, measured along the ellipsoid’s normal. Satellite positioning yields this height, which differs from geoid-based elevation.
Equipotential surface : A surface on which a scalar potential has the same value at every point. The geoid is one particular equipotential surface of Earth’s gravity field.
Johann Benedict Listing : A German mathematician who studied topology and Earth’s physical shape. Listing coined the term “geoid” in 1873 for the equipotential surface associated with mean sea level.
Dynamic ocean topography : The ocean surface’s deviation from an equipotential surface caused by currents, temperature, and salinity. Real ocean circulation produces sea-surface height differences above or below the geoid.
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