Metres above the Sea (

German German(s) may refer to: * Germany, the country of the Germans and German things **Germania (Roman era) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizenship in Germany, see also Ge ...

: ''Meter über Meer (m ü. M.)'') is the

vertical datum In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum is a reference coordinate surface used for vertical positions, such as the elevations of Earth-bound features (terrain, bathymetry, water level, and built stru ...

used in

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

. Both the system and the term are also used in the

Principality of Liechtenstein Liechtenstein (, ; ; ), officially the Principality of Liechtenstein ( ), is a doubly landlocked German-speaking microstate in the Central European Alps, between Austria in the east and north and Switzerland in the west and south. Liechtenst ...

Use

In Switzerland, levelled

height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For an example of vertical extent, "This basketball player is 7 foot 1 inches in height." For an e ...

s from the Swiss national levelling network 1902 (LN 02) are used as official heights without compensation for gravity. The reference point for the Swiss national height network is the Pierres du Niton ( French: ''Neptune's Stones''), a pair of unusual rocks in the harbour of

Lake Geneva Lake Geneva is a deep lake on the north side of the Alps, shared between Switzerland and France. It is one of the List of largest lakes of Europe, largest lakes in Western Europe and the largest on the course of the Rhône. Sixty percent () ...

. That height is defined from the average height of the Marégraphe in Marseille, the reference point for height data in France, and rounded to 373.6 m. The height was only measured accurately in 1902. As the height of the Pierres du Niton had been inaccurately measured in 1845 as being 376.86 meters, height information relating to this ''old horizon'' (for example in the '' Siegfried Map'' and the ''

Dufour Map Dufour or ''variant'', may refer to: *Dufour (surname) Places *Dufourspitze or Dufour's peak, in the Swiss Alps * Julia Dufour, a village and municipality in Santa Cruz Province, Argentina Other uses * 1961 Dufour, main-belt asteroid *Dufour Aud ...

'', both of them widely used) is 3.26 m higher than today's official values. At the border between Switzerland and

Austria Austria, formally the Republic of Austria, is a landlocked country in Central Europe, lying in the Eastern Alps. It is a federation of nine Federal states of Austria, states, of which the capital Vienna is the List of largest cities in Aust ...

, the Swiss heights are 6 to 75 mm higher than the Austrian heights above the Adriatic. As

gravitational potential In classical mechanics, the gravitational potential is a scalar potential associating with each point in space the work (energy transferred) per unit mass that would be needed to move an object to that point from a fixed reference point in the ...

cannot be neglected for applications with high accuracy requirements, the Swiss national height network 1995 (LHN95) created a new

orthometric height The orthometric height (symbol ''H'') is the vertical distance along the plumb line from a point of interest to a reference surface known as the ''geoid'', the vertical datum that approximates mean sea level. Orthometric height is one of the sci ...

vertical reference point, fixed to the

geoid The geoid ( ) is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is exte ...

. The height of the new reference point,

Zimmerwald Observatory The Zimmerwald Observatory () is an astronomical observatory owned and operated by the AIUB, the Astronomical Institute of the University of Bern. Built in 1956, it is located at Zimmerwald, 10 kilometers south of Bern, Switzerland. Numerous com ...

, was chosen so that the Pierres du Niton reference point maintained its then current level. The heights of LHN95 differ from the LN02 heights by up to . Due to the danger of confusion caused by the change in the height systems, new heights for official measurement have nevertheless not been introduced. Establishment of a clearly understood common reference system is particularly important in cross-border projects involving Switzerland, because of the differing reference systems used in its neighboring countries.Spiegel article: Planning margin - Rhine bridge with stairs

References

External links

Swiss national levelling network 1902

Vertical datums Geography of Switzerland la:Super libram maris

Use

See also

References

External links