a mathematical figure generated by the revolution of of an ellipse about one of its axes

a mathematical structures that define the shape of the earth and that are associated with different datum's

an ellipse rotated around one of its axes

an equipotential surface of a rotating, homogeneous body

an N dimensional generalization of an ellipse

a smooth, mathematically perfect surface that is used to approximate the shape of the earth

a sphere scaled along its X-, Y- or Z-axes

Athree-dimensional ellipse which is used to represent the shape of the surface of the earth. A more complete explanation is available in the Standards Section.

A three-dimensional mathematical model which approximates the shape of the geoid. Many different ellipsoids have been developed for continents or individual countries to minimize local deviations from the geoid. The standard global ellipsoid is the World Geodetic System of 1984 (WGS 84). Reference: Peter Dana, The Geographer's Craft

The Earth surface is approximately described by an ellipsoid, a closed surface all planar sections of which are ellipses. In general, an ellipsoid has three independent axes, and is usually specified by the length of the three semi-axes. If the lengths of two axes are the same, the ellipsoid is called “ellipsoid of revolution” or spheroid. Due to the rotation around its axis, the Earth has the shape of a spheroid. Several spheroids are used to model the Earth surface and project it onto a two-dimensional map; the choice of the reference spheroid depends on the region of the Earth to be represented and the required precision. The spheroids quoted in this work are Clarke 1866, WGS72 and WGS84. Clarke 1866 is used to map the North America and the Philippines. The World Geodetic System (WGS) spheroids have been developed to be used for global mapping; the number indicates the year of calculation. WGS84 is the most recent version, and is also used by the Global Positioning System.

a smooth mathematical surface which resembles a squashed sphere and is used to represent the earth's surface

A mathematical figure formed by revolving an ellipse about its minor axis. It is often used interchangeably with spheroid.

spheroid The mathematical function used to describe the shape of the earth for geodetic computations. The figure is formed by rotating an ellipse about its minor (shorter) axis and is typically described by dimensions for the semimajor axis (a) together with the semiminor axis (b) or flattening (f) = (a-b)/a.

A mathematically defined quadratic surface used to model the earth.

a squashed or stretched sphere in which each of the three axes can be of different lengths. (Contrast to a spheroid, in which two of the three axes have the same length.) An ellipsoid has the equation x²/a² + y²/b² + z²/c² = 1

An oblate spheroid used to roughly model the surface of the Earth. There are many possible ellipsoids available, parameterized by eccentricity and semi-major axis. When used as a datum, an ellipsoid also has an XYZ offset from the center of the Earth.

the surface obtained rotating an ellipse around one of its axes.

A geometric solid that simplifies the geoid's bulges and depressions to a smoother surface that is slightly wider at the equator than at the poles, and much more adaptable to mapping and survey measurements (see also Geodesy). Various reference ellipsoids have been developed and used in different parts of the world for large scale mapping purposes. the United states uses the Geodetic Reference System (GRS80) as the reference ellipsoid for surveying and topographic mapping.

An ellipsoid is a type of quadric surface that is a higher dimensional analogue of an ellipse.