Ellipsoidhöjd

ellipsoidhöjd refers to the height of a point above a reference ellipsoid. A reference ellipsoid is a mathematical model of the Earth's shape, approximating it as an oblate spheroid. This height is distinct from orthometric height, which is the height above mean sea level. Ellipsoidhöjd is directly calculated from geodetic survey measurements, such as those obtained from GPS receivers. GPS satellites transmit signals that allow receivers to determine their position relative to the Earth's center, and the resulting height is an ellipsoidhöjd. This type of height is fundamental in geodetic positioning and is used in various applications including navigation, surveying, and mapping. The difference between ellipsoidhöjd and orthometric height is due to the Earth's irregular gravity field and is accounted for by the geoid, which represents equipotential surfaces of gravity. The relationship between these heights can be expressed by the formula: orthometric height = ellipsoidhöjd - geoid height. Therefore, understanding ellipsoidhöjd is crucial for accurate geodetic work and for converting between different height systems.