page_title: Normalhöhennull
section_title: Definition
hierarchical_section_title: Normalhöhennull / Definition
context_page_description: Normalhöhennull or NHN is a vertical datum used in Germany.
  In geographical terms, NHN is the reference plane for the normal height of a topographical eminence height above mean sea level used in the 1992 German Mean Height Reference System. The plane is in the shape of a quasi-geoid. The reference height is a geodetic, fixed point on the New Church of St. Alexander at Wallenhorst in the German state of Lower Saxony. The geopotential height of this point was calculated in 1986 as part of the United European Levelling Network, based on the Amsterdam Ordnance Datum, which represents the average level of the North Sea.
context_section_description: The NHN plane is a theoretical reference plane. It is derived by deducting normal heights from the normal plumb line. The difference between the resulting quasi-geoid and the reference ellipsoid is called the height anomaly or quasi-geoid height.
caption: The curved blue line is the quasi-geoid Normalhöhennull reference plane.
   Key: Erdoberfläche - earth's surface
   Normalhöhe = normal height
  ellipsoidische Höhe - ellipsoidal height
   Quasigeoidhöhe - quasi-geoid height.