Ellipsoidhöhen

Ellipsoidhöhen, also known as ellipsoidal heights or geodetic heights, represent the vertical distance of a point on or above the Earth's surface to the reference ellipsoid. This reference ellipsoid is a mathematical model that approximates the Earth's shape, typically an oblate spheroid. Unlike orthometric heights, which are measured from a geoid (mean sea level approximation), ellipsoidhöhen are directly derived from satellite-based positioning systems like GPS. These heights are often referred to as "ellipsoidal heights" or "GPS heights" and are a direct output of GNSS (Global Navigation Satellite System) computations. They are purely geometric and do not account for the Earth's gravity field. The relationship between ellipsoidhöhen and orthometric heights is established through the geoid undulation, which is the difference between the geoid and the reference ellipsoid at any given point. While ellipsoidhöhen are readily available from GPS measurements, orthometric heights are generally more practical for surveying and engineering applications as they represent height above sea level. The conversion from ellipsoidhöhen to orthometric heights requires a geoid model and is a crucial step in many geodetic and mapping processes.