| The geoid is a hypothetical surface, on which the gravitational pull of the Earth is the same everywhere. |
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| Precise knowledge of marine geoid is essential for study of mantle convection of oceanic litosphere. |
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| The geoid is defined as a gravitational equipotential surface that coincides with mean sea level. |
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| To a good approximation, the geoid is an oblate spheroid whose major axis is about 0.3 per cent longer than the minor one. |
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| The geoid serves as the classical reference for all topographical features. |
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| Canada does not currently provide geoid undulation at the heliport elevation position. |
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| Over the oceans, mean sea level defines the geoid surface, but over the land areas the geoid is an imaginary sea-level surface. |
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| The position of the equipotential surfaces of the geoid are also influenced by lunar and solar tidal effects. |
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| The realization of a new vertical datum for Canada by geoid modelling, rather than by geodetic levelling. |
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| A geoid model will become the official surveying reference for heights above sea level across Canada in the future. |
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| Non graphic applications include geoid calculations, terrain modelling, flood simulations and telecommunication studies. |
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| The geoid model of mean sea level advanced through analysis of latest local and global gravity coverage. |
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| Uncertainties in TT due to uncertainties in the realization of the geoid are thus eliminated. |
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| Its data will be used to refine models in this field, improving our knowledge of the planet's interior and geoid. |
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| A major portion of this phase is the collection and scrutiny of suitable gravity and levelling data and the final modelling of a geoid. |
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| Local reference systems are the official national coordinate and height systems, the reference ellispoid, the geoid model and the map projection. |
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| In addition it would be desirable to change the definition of Terrestrial Time to remove the reference to the geoid, and thus the uncertainty associated with this surface. |
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| Updated gravity-based geoid model with accuracy of a few centimeters. |
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| We know that it is impossible to realize an errorless geoid model. |
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| The term geoid is used above to mean mean sea level, and makes a good frame of reference. |
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| Because the directions of gravity converge toward the geoid, a length of the Earth's surface measured above the geoid must be reduced to its sea-level equivalent i.e., to that of the geoid. |
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| These irregularities of the geoid would bring about serious errors in the surveyed location of control points if astronomical methods, which involve use of the local horizon, were used solely in determining locations. |
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| A geoid is a virtual Earth's surface representing the global mean sea level where gravitational potential is equal at all points, with hills and valleys formed by differences in gravity's pull. |
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| The second step is to approximate the geoid by a mathematically simpler reference surface. |
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| The simplest choice for the reference surface is a sphere, but the geoid is more accurately modelled by an ellipsoid. |
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| This height differs from the height above the geoid or a reference height such as that above mean sea level at a specified location. |
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| The relation of these different heights requires knowledge of the shape of the geoid and also the gravity field of the Earth. |
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| Points on the real surface of the earth are usually above or below this idealized geoid surface and here the true vertical can vary slightly. |
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| Also, the true vertical at a point at a specific time is influenced by tidal forces, which the theoretical geoid averages out. |
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| In geodesy, the exact shape that Earth's oceans would adopt in the absence of land and perturbations such as tides and winds is called the geoid. |
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| More precisely, the geoid is the surface of gravitational equipotential at mean sea level. |
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| Currently pursuing PhD studies related to gravity field and geoid modelling. |
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| Each coverage was projected using Polyconic Projection and Spheroid Everest geoid system for area estimation of different classes for a particular map. |
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| In a state of rest or absence of external forces, the mean sea level would coincide with this geoid surface, being an equipotential surface of the Earth's gravitational field. |
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| In the first step the physical surface is modelled by the geoid, a surface which approximates the mean sea level over the oceans and its continuation under the land masses. |
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| The horizontal datum of the SRTM data is WGS84, while the topographic heights are referred to the EGM96 geoid which approximately coincides with mean sea level. |
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| In general the true vertical at a point on the surface does not exactly coincide with either the normal to the reference ellipsoid or the normal to the geoid. |
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| Geoid of the Nordic and Baltic area from gravimetry and satellite altimetry. |
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| Symposium on Gravity, Geoid and Marine Geodesy, Tokyo, Japan. |
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