geoid
Sign in to savethumb|upright=1.5|Map of the undulation of the geoid in meters (based on the EGM96 gravity model and the [[WGS84 reference ellipsoid).]]
AI overview
The geoid is an imaginary surface that represents what Earth's sea level would be if it were influenced only by gravity and the planet's rotation, rather than by winds and currents. It matters because it serves as the reference surface for measuring elevation and for understanding Earth's gravitational field, which is essential for accurate mapping and navigation.
AI-generated from the Wikipedia summary — may contain errors.
Article
11 sectionsContents
- Description
- Simplified example
- Formulation{{anchor|Shape|Undulation}}
- Determination
- Relationship to mass density
- Temporal change
- Spherical harmonics representation
- See also
- References
- Further reading
- External links
thumb|upright=1.5|Map of the undulation of the geoid in meters (based on the EGM96 gravity model and the [[WGS84 reference ellipsoid).]]
The geoid ( ) 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. This surface is extended through the continents (such as might be approximated with very narrow hypothetical canals). According to Carl Friedrich Gauss, who first described it, it is the "mathematical figure of the Earth", a smooth but irregular surface whose shape results from the uneven distribution of mass within and on the surface of Earth. It can be known only through extensive gravitational measurements and calculations. Despite being an important concept for almost 200 years in the history of geodesy and geophysics, it was not defined with any degree of precision until the advent of satellite geodesy in the mid-20th century. Mathematician Gladys West was the first worker to synthesize a high-fidelity geoid from this satellite data. The geoid is one of the essential components of satellite-based global positioning systems.