The existing height system LN02 from 1902 is a so-called official height system computed from raw, levelled height differences. For the adjustment of LN02, new levelling observations were constrained into the old nodal points. Since, however, there is an Alpine uplift of up to 1.5 mm per year with respect to 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 the new national control survey LV95, the need for a new vertical reference frame (LHN95) arose. LHN95 contains rigorous orthometric heights which can be transformed to ellipsoidal GPS heights with an accuracy of 1 to 3 cm using the geoid model for Switzerland (CHGEO04). The origin for LHN95 is the fundamental point of the new 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 cm.
