Normalnull
{{Short description|Outdated official vertical datum used in Germany}}
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File:Borne de nivellement Kriegstor.JPG
{{lang|de|Normalnull}} ("standard zero") or {{lang|de|Normal-Null}} (short N. N. or NN) is an outdated official vertical datum used in Germany. Elevations using this reference system were to be marked {{lang|de|Meter über Normal-Null}} (“meters above standard zero”). {{lang|de|Normalnull}} has been replaced by {{lang|de|Normalhöhennull}} (NHN).
History
In 1878 reference heights were taken from the Amsterdam Ordnance Datum and transferred to the New Berlin Observatory in order to define the Normalhöhenpunkt 1879. {{lang|de|Normalnull}} has been defined as a level going through an imaginary point 37.000 m below {{lang|de|Normalhöhenpunkt 1879}}. When the New Berlin Observatory was demolished in 1912 the reference point was moved east to the village of Hoppegarten (now part of the town of Müncheberg, Brandenburg, Germany).{{langr|de|S. German}}: {{lang|de|Was ist "Normal-Null"?}}. In: {{lang|de|Physikalische Blätter}} 1958, vol 14, issue 2, p. 62–66 {{ISSN|1521-3722}} {{doi|10.1002/phbl.19580140203}}
References
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