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The gravitational effects of the Moon and the Sun (also the cause of the tides) have a very small effect on the apparent strength of Earth's gravity, depending on their relative positions; typical variations are 2 μm/s 2 (0.2 mGal) over the course of a day.
Geoid undulations based on satellite gravimetry. Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest. The study of gravity changes belongs to geodynamics.
Gravitational field strength within the Earth Gravity field near the surface of the Earth – an object is shown accelerating toward the surface If the bodies in question have spatial extent (as opposed to being point masses), then the gravitational force between them is calculated by summing the contributions of the notional point masses that ...
Readings are typically taken at regular intervals for surface analysis on Earth. [1] Other methods include analysis of artificial satellite orbital mechanics, which can allow comprehensive gravity maps of planets, as has been done for Mars by NASA. [2] Gravity maps typically are based on depictions of gravity anomalies or a planet's geoid. [3]
Vector field (blue) and its associated scalar potential field (red). Point P between earth and moon is the point of equilibrium. In physics, a gravitational field or gravitational acceleration field is a vector field used to explain the influences that a body extends into the space around itself. [1]
However, a spherical harmonics series expansion captures the actual field with increasing fidelity. If Earth's shape were perfectly known together with the exact mass density ρ = ρ(x, y, z), it could be integrated numerically (when combined with a reciprocal distance kernel) to find an accurate model for Earth's gravitational field. However ...
For such problems, the rotation of the Earth would be immaterial unless variations with longitude are modeled. Also, the variation in gravity with altitude becomes important, especially for highly elliptical orbits. The Earth Gravitational Model 1996 contains 130,676 coefficients that refine the model of the Earth's gravitational field.
The official Earth Gravitational Model EGM2008 has been publicly released by the National Geospatial-Intelligence Agency (NGA) EGM Development Team. Among other new data sources, the GRACE satellite mission provided a very high resolution model of the global gravity.