A datum consisting of five quantities, the latitude and longitude and elevation above the reference spheroid of an initial point, a line from this point, and two constants which define the reference spheroid Azimuth or orientation of the line, given the longitude, is determined by astronomic observations Alternatively, the datum may be considered as three rectangular coordinates fixing the origin of a coordinate system whose orientation is determined by the fixed stars, and the reference spheroid is an arbitrary coordinate surface of an orbiting ellipsoidal coordinate system
A specifically oriented ellipsoid typically defined by eight parameters which establish its dimensions, define its center with respect to Earth's center of mass and its orientation in relation to the Earth's average spin axis and Greenwich reference meridian See: Ellipsoid
A mathematical model designed to fit part or all of the geoid (the physical earths surface) Defined by the relationship between an ellipsoid and a point on the topographic surface established as the origin of a datum World geodetic datums are typically defined by the size and shape of the ellipsoid and the location of the center of the ellipsoid with respect to the center of the earth
A model of the Earth used for geodetic calculations Geodesy is the science of measuring the shape and size of the Earth, together with the determination of the exact position of particular points on its surface by taking the Earth's curvature into account
A mathematical model designed to fit part or all of the geoid, defined by the relationship between an ellipsoid and a point on the topographic surface established as the origin of a datum World geodetic datums are typically defined by the size and shape of an ellipsoid and the location of the center of the ellipsion with respect to the center of the earth
A mathematical model designed to best fit part or all of the geoid It is defined by an ellipsoid and the relationship between the ellipsoid and a point on the topographic surface established as the origin of datum