The geoid is defined by an area with constant gravity potential, which best corresponds to the mean sea level and the intended continuation in the continental area. The mean sea level is determined by level observations (e.g. Amsterdam, Trieste).
The distance between the geoid surface and a reference ellipsoid is called geoidundulation N. For Austria, geoidundulations N related to the international ellipsoid GRS80 (reference system ETRS89) and the Bessel ellipsoid (reference system MGI) were calculated: GRS80 and Bessel.
Austrian Geoid Card:
The Austrian geoid map shows in isoline representation the geoidundulations on the Austrian territory in two different representations:
a) Austrian Geoid Card GRS80: The geoidundulations GRS80 show the distances of the geoide above the international ellipsoid model GRS80 (reference system ETRS89) in a range of values between ~42 m in the northeast and ~53 m in the Ötztal Alps.
B) Austrian Geoid Card MGI: The geoidundulations NBessel show the distances of the geoides above the Bessel ellipsoid (reference system MGI). The value range is between ~-2 m in the western Innviertel and ~ + 3.5 m in the Ötztal Alps and East Tyrol.
The solder deviation is the angle between a geometrically defined ellipsoid normal and the physically defined solder direction in a point. It describes the direction of the heavy vector, represented in a north/south and an east/west component.
For the entire territory of Austria, solder deviations — more precisely, surface lot deviations — can be calculated and released in relation to the Bessel ellipsoid in the reference system MGI.
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