NormalhöhenNull

Normalhöhennull, often abbreviated as NHN, is the official vertical reference system used in Germany for surveying and geodetic purposes. It defines the zero point for height measurements nationwide. The system is based on a mean sea level established from tidal observations at the Amsterdam tidal gauge. Specifically, it represents the mean water level of the North Sea as determined by the Amsterdam tidal gauge in the period 1872-1977. This reference level is crucial for many applications, including infrastructure planning, construction, flood control, and hydrological studies. Heights above NHN are used to indicate elevations of land surfaces, water bodies, and man-made structures. The adoption of NHN ensures a consistent and unified understanding of elevation across Germany, facilitating accurate spatial data integration and collaborative projects. It replaced older, localized height systems that could lead to discrepancies. The NHN system is maintained and updated by the Federal Agency for Cartography and Geodesy (Bundesamt für Kartographie und Geodäsie - BKG).