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Normal altitude, quasigeoid and altitude anomaly

The quasigeoid is the reference surface for the normal heights . It results from the normal heights determined on the earth's surface being removed downwards (see Fig.). Normal heights are determined from the geopotential elevation ( potential difference to the geoid ) and the normal gravity .

The quasigeoid is a unique model of the geoid that can be used for height measurements . In contrast to the geoid, the quasigeoid can be determined without hypothesis, because the geoid cannot be determined at every point without hypotheses about the mass distribution between the earth's surface and geoid. The Quasigeoid is different from the geoid no equipotential surface of gravity. The differences compared to the geoid are usually in the range of centimeters to decimeters; they are smallest on the sea and in the lowlands and can be in the meter range in the high mountains .

The quasigeoid in the German Main Elevation Network 1992 is referred to as normal height zero .

Since the introduction of the Integrated Spatial Reference in 2016 , the German Combined Quasigeoid 2016 (GCG2016) has been the height reference surface of the national survey above the reference ellipsoid of the Geodetic Reference System 1980 (GRS 80).


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