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The geoid (/ ˈ dʒ iː. ɔɪ d / JEE-oyd) is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent.
A data set which describes the global average of the Earth's surface curvature is called the mean Earth Ellipsoid. It refers to a theoretical coherence between the geographic latitude and the meridional curvature of the geoid. The latter is close to the mean sea level, and therefore an ideal Earth ellipsoid has the same volume as the geoid.
The ellipsoid is a mathematically defined regular surface with specific dimensions. The geoid, on the other hand, coincides with that surface to which the oceans would conform over the entire Earth if free to adjust to the combined effect of the Earth's mass attraction (gravitation) and the centrifugal force of the Earth's rotation.
The result is a smooth but irregular geoid surface, providing a mean sea level as a reference level for topographic measurements. ... Earth's biosphere produces many ...
Earth Gravitational Model 2008 (EGM2008) GeographicLib provides a utility GeoidEval (with source code) to evaluate the geoid height for the EGM84, EGM96, and EGM2008 Earth gravity models. Here is an online version of GeoidEval.
The Indian Ocean Geoid Low (IOGL) is a gravity anomaly in the Indian Ocean. A circular region in the Earth's geoid, situated just south of the Indian peninsula, it is the Earth's largest gravity anomaly. [1] [2] It forms a depression in the sea level covering an area of about 3 million km 2 (1.2 million sq mi), almost the size of India itself.
Determination of the figure of the Earth, positioning, and navigation (geometric satellite geodesy) [1]: 3 Determination of geoid, Earth's gravity field and its temporal variations (dynamical satellite geodesy [2] or satellite physical geodesy) Measurement of geodynamical phenomena, such as crustal dynamics and polar motion [1]: 4 [1]: 1
The geoid is essentially the figure of the Earth abstracted from its topographic features. It is an idealized equilibrium surface of sea water, the mean sea level surface in the absence of currents, air pressure variations etc. and continued under the continental masses.