Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- n. The hypothetical surface of the earth that coincides everywhere with mean sea level.
Century Dictionary and Cyclopedia
- n. An imaginary surface which coincides with the mean sea-level over the ocean, and extends under the continents everywhere at that level at which the mean surface of the sea would stand if it were allowed to flow in through a small subterranean canal. The geoid has no simple geometrical form, but bulges out from the mean spheroid in some places (under the continents and some of the deeper parts of the ocean) and is depressed beneath the mean spheroid in other places.
- n. See geode.
Wiktionary
- n. A surface of constant gravitational potential at zero elevation.
Etymologies
- German, from Greek geoeidēs, earthlike : gē, earth + -oeidēs, -oid.
Examples
“Let the term geoid apply to the natural irregular surface of the earth and the term spheroid to the ideal regular sur - face of the geodesist which coincides nearly with sealevel and is necessarily a level surface.”
Internet Archive: Transactions - American Philosophical Society
“That span can then, in theory, be subtracted from the distance between those satellites and a kind of theoretical sea level known as the geoid, which is what the sea level would be at each point on Earth if undisturbed by weather, tides and currents.”
The Wall Street Journal: Why Measure a Mountain? Because It's There
“A new map shows the Earth's "geoid" - the map of its gravitational pull.”
“Technically speaking, the model at the top of this page is what researchers refer to as a geoid.”
“The geoid is the shape of an imaginary global ocean dictated by gravity in the absence of tides and currents.”
“The geoid is a model of global mean sea level that is used to measure precise surface elevations.”
“Goce data will be used to construct an idealised surface called a geoid”
“This will result in a unique model of the geoid, which is the surface of equal gravitational potential defined by the gravity field.”
“This will result in a unique model of the geoid, which is the surface of equal gravitational potential defined by the gravity field - crucial for deriving accurate measurements of ocean circulation and sea-level change, both of which are affected by climate change.”
“The geoid is the equipotential surface of the earth’s gravitational field that approximates the mean sea surface.”
State of fear
Lists
These user-created lists contain the word ‘geoid’.
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Logolepsy
"Luciferous Logolepsy is a collection of over 9,000 obscure English words. Though the definition of an 'English' word might seem to be straightforward, it is not. There exist so many adopted, deriv...
Anschauung, Areopagus, Argus, Briarean, Dei gratia, Dei judicium, Deo volente, Duecento, Foehn, Geflugelte Worte, Gegenschein, Hakenkreuz and 9230 more...
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Carl Friedrich Gauss
"Gauss, Karl Friedrich 1777-1855. German mathematician and astronomer known for his contributions to algebra, differential geometry, probability theory, and number theory."
--American ...Gauss, Carl Friedrich Gauss, Karl Friedrich Gauss, Johann Carl Fried..., Carolus Fridericu..., Princeps mathemat..., Gaussian gravitat..., degaussing, Gauss–Newton algo..., Gaussian noise, Gaussian prime, quadratic residue and 33 more...
ruzuzu "There have been many definitions of the "geoid" over 150 years or so. Here is the one currently adopted at the National Geodetic Survey:
geoid: The equipotential surface of the Earth's gravity field which best fits, in a least squares sense, global mean sea level
Even though we adopt a definition, that does not mean we are perfect in the realization of that definition. For example, altimetry is often used to define "mean sea level" in the oceans, but altimetry is not global (missing the near polar regions). As such, the fit between "global" mean sea level and the geoid is not entirely confirmable. Also, there may be non-periodic changes in sea level (like a persistent rise in sea level, for example). If so, then "mean sea level" changes in time, and therefore the geoid should also change in time. These are just a few examples of the difficulty in defining "the geoid"."
--What is the geoid?
Mar 31, 2011
ruzuzu See discussion on potato Earth. Mar 31, 2011