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At latitudes nearer the Equator, the outward centrifugal force produced by Earth's rotation is larger than at polar latitudes. This counteracts the Earth's gravity to a small degree – up to a maximum of 0.3% at the Equator – and reduces the apparent downward acceleration of falling objects.
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 Tracker Component Library from the United States Naval Research Laboratory is a free Matlab library with a number of gravitational synthesis routines.
Green curves show hypothetical Earths with density constant (dashed) and decreasing linearly from center to surface (stippled) The preliminary reference Earth model (PREM) plots the average of Earth's properties by depth. [1] It includes a table of Earth properties, including elastic properties, attenuation, density, pressure, and gravity.
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression.
These changes can be the result of mass displacements inside the Earth, or of vertical movements of the Earth's crust on which measurements are being made. [c] The first gravimeters were vertical accelerometers, specialized for measuring the constant downward acceleration of gravity on the Earth's surface. The Earth's vertical gravity varies ...
The precise strength of Earth's gravity varies with location. The agreed-upon value for standard gravity is 9.80665 m/s 2 (32.1740 ft/s 2 ) by definition. [ 4 ] This quantity is denoted variously as g n , g e (though this sometimes means the normal gravity at the equator, 9.7803267715 m/s 2 (32.087686258 ft/s 2 )), [ 5 ] g 0 , or simply g ...
A gravity map is a map that depicts gravity measurements across an area of space, which are typically obtained via gravimetry. Gravity maps are an extension of the field of geodynamics . Readings are typically taken at regular intervals for surface analysis on Earth . [ 1 ]
If that sphere were then covered in water, the water would not be the same height everywhere. Instead, the water level would be higher or lower with respect to Earth's center, depending on the integral of the strength of gravity from the center of the Earth to that location. The geoid level coincides with where the water would be.