Referenzeellipsoid
The Referenzeellipsoid, or reference ellipsoid, is a mathematically defined ellipsoid used as the reference surface in geodesy to approximate the Earth's shape and to define geodetic coordinate systems. It provides a smooth, global surface on which latitude and longitude are defined and serves as the basis for many map projections and spatial calculations.
It is characterized by its equatorial radius a and flattening f (or inverse flattening 1/f). Flattening describes
Common reference ellipsoids include WGS 84 (a = 6378137.0 m, 1/f = 298.257223563), GRS80 (a = 6378137.0 m, 1/f
Usage: The referenzeellipsoid underpins GPS and GNSS positioning, map projection definitions, and cadastral surveying. A datum
Selection: Global applications often use WGS 84; regional or national projects may adopt a local ellipsoid