GNSSGPSAltitudenmessung

GNSSGPSAltitud, often referred to as GNSS-based altitude, denotes the height component obtained from Global Navigation Satellite System data, including GPS, during a three‑dimensional position fix. It can be expressed as height relative to a reference ellipsoid (ellipsoidal height) or converted to height above mean sea level (orthometric height) using geoid models.

In GNSS positioning, the receiver computes a coordinate triplet: latitude, longitude, and ellipsoidal height h relative to a reference ellipsoid such as WGS84. To obtain an altitude above sea level, the geoid height (undulation) N is subtracted: H = h − N. Geoid models like EGM96, EGM2008, or EGM2020 provide N values to enable this conversion for local vertical datums.

Altitude determination can be enhanced by differential techniques. Real-time kinematic (RTK) and precise point positioning (PPP) use additional corrections from reference stations or satellite data to improve vertical accuracy, often to centimeter or decimeter levels in ideal conditions. Wide-area augmentation systems and SBAS provide broadcast corrections to improve both horizontal and vertical components.

Accuracy and reliability depend on receiver quality, satellite geometry, and atmospheric conditions. Vertical accuracy is typically worse than horizontal due to less favorable geometry and sensitivity to ionospheric and tropospheric delays, multipath, and datum mismatches. In practice, many devices report both h and H, along with uncertainty estimates, enabling users to work with the height meaning required for a given application.

Applications range from surveying, geodesy, and aviation to mapping, agriculture, and consumer navigation. Proper use requires awareness of the reference datum and geoid model employed to ensure consistent altitude interpretations.