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LHN95

In the course of national survey LV95, the need for a corresponding vertical reference frame arose. LHN95 is a potential-theoretic, rigorous height system which takes kinematic phenomena (uplift of the Alps) into account and is based on rigorous orthometric heights. The origin for LHN95 is the fundamental point of national survey LV95 in Zimmerwald.

National height network LHN95

LN02 (introduced in 1902) is an official height system computed from raw, levelled height differences. For the calculation of LN02, new levelling observations were constrained into the old nodal points. Since, however, there is an alpine uplift of up to 1.5 millimetres per year versus the Central Plateau, the fixed values are no longer representative today. In addition, because the influences of gravity were not taken into consideration, LN02 shows systematic deviations with respect to a potential-theoretic, rigorous height system.

In the course of national survey LV95, the need for a corresponding vertical reference frame (LHN95) arose. LHN95 contains rigorous orthometric heights. At around 220 GNSS/levelling points, both LHN95 as well as ellipsoidal heights were calculated using satellite navigation. These points support the geoid model for Switzerland (CHGeo2004), which permits transformations between LHN95 orthometric heights and ellipsoidal heights with an accuracy range of 1 to 3 centimetres. The origin for LHN95 is the fundamental point of the LV95 national survey in Zimmerwald. However, the height datum was chosen in such a manner that the reference value of the “Repère Pierre du Niton” was kept in a first approximation. These heights differ from the old LN02 heights by a maximum of 50 centimetres.

Differences between LHN95 and LN02 in [m]
Differences between LHN95 and LN02 in [m]

LHN95 is a potential-theoretic, rigorous height system which takes kinematic phenomena (uplift of the Alps) into account and is based on rigorous orthometric heights. The advantage over normal heights is that the levelled heights allow a better combination with GPS heights.

The following is a list of the central themes of LHN95:

  • kinematic adjustment of the precise levelling
  • based on geopotential heights (±15 mgpu, 1 sigma)
  • orthometric height system
  • consideration of the alpine uplift 
  • inclusion of GPS observations (with known geoid)


Federal Office of Topography swisstopo Seftigenstrasse 264
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3084 Wabern
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+41 58 469 01 11

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Relevant authority

Geodesy and Federal Directorate of Cadastral Surveying
E-mail

Federal Office of Topography swisstopo

Seftigenstrasse 264
P.O. Box
3084 Wabern

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