Metres above the Sea (Switzerland)
Encyclopedia
Geodetic system
Geodetic systems or geodetic data are used in geodesy, navigation, surveying by cartographers and satellite navigation systems to translate positions indicated on their products to their real position on earth....
used in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
. Both the system and the term are also used in the Principality
Principality
A principality is a monarchical feudatory or sovereign state, ruled or reigned over by a monarch with the title of prince or princess, or by a monarch with another title within the generic use of the term prince....
of Liechtenstein
Liechtenstein
The Principality of Liechtenstein is a doubly landlocked alpine country in Central Europe, bordered by Switzerland to the west and south and by Austria to the east. Its area is just over , and it has an estimated population of 35,000. Its capital is Vaduz. The biggest town is Schaan...
.
Use
In Switzerland, levelled heights from the Swiss national levelling network 1902 (LN 02) are used as official heights without compensation for gravityGravitational acceleration
In physics, gravitational acceleration is the acceleration on an object caused by gravity. Neglecting friction such as air resistance, all small bodies accelerate in a gravitational field at the same rate relative to the center of mass....
.
The reference point for the Swiss national height network is the Pierres du Niton
Pierres du Niton
The Pierres du Niton are two unusual rocks which are visible from Quai Gustave Ador in the harbor of Lake Geneva, Switzerland. They are remnants from the last ice age, left by the Rhone glacier...
(French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
: Neptune's Stones), a pair of unusual rocks in the harbour of Lake Geneva
Lake Geneva
Lake Geneva or Lake Léman is a lake in Switzerland and France. It is one of the largest lakes in Western Europe. 59.53 % of it comes under the jurisdiction of Switzerland , and 40.47 % under France...
. That height is defined from the average height of the Pegel 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, both of them widely used) is 3.26 m higher than today's official values.
At the border between Switzerland and Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
, the Swiss heights are 6 to 75 mm higher than the Austrian heights above the Adriatic
Metres above the Adriatic
Metres above the Adriatic is an elevation reference system used in Austria and some other European countries based on the average water level of the Adriatic Sea at the Molo Sartorio in Triest harbour...
.
As gravitational potential cannot be neglected for applications with high accuracy requirements, the Swiss national height network 1995 (LHN95) created a new orthometric height
Orthometric height
The orthometric height is the distance H along a line of force from a given point P at the physical surface of an object to the geoid.Orthometric heights are what are usually used in the US for ordinary engineering work. Values for measured points can be obtained from the National Geodetic Survey...
vertical reference point, fixed to the geoid
Geoid
The geoid is that equipotential surface which would coincide exactly with the mean ocean surface of the Earth, if the oceans were in equilibrium, at rest , and extended through the continents . According to C.F...
. The height of the new reference point, Zimmerwald Observatory
Zimmerwald Observatory
Observatorium Zimmerwald is an astronomical observatory owned and operated by the Astronomisches Institut der Universität Bern . Built in 1956, it is located 10 kilometers south of Bern, Switzerland near Zimmerwald.The 1 meter aperture ZIMLAT telescope was inaugurated in 1997.-External links:*...
, 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 50 cm (20 in). 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.
See also
- MetreMetreThe metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
- Normalhöhennull (NHN)NormalhöhennullNormalhöhennull or NHN is a standard reference level, the equivalent of sea level, used in Germany to measure height....
(equivalent in Germany) - Metres above the AdriaticMetres above the AdriaticMetres above the Adriatic is an elevation reference system used in Austria and some other European countries based on the average water level of the Adriatic Sea at the Molo Sartorio in Triest harbour...