Open Session - SWISS GEOSCIENCE MEETINGs

316
Symposium 12: Data acquisition, Geo-processing, GIS, digital mapping and 3D visualisation
12.18
The National Gravity Network of Switzerland
Urs Marti
Federal Office of Topography swisstopo, Geodesy, Seftigenstrasse 264, CH-3084 Wabern (urs.marti@swisstopo.ch)
In 2003, a project LSN2004 (Landesschwerenetz 2004) was started by swisstopo to modernize the national gravity network of
Switzerland. This new network is based on the existing gravity network of 1995 and is connected to several stations of the
European gravity network UEGN. In this project, 4 new absolute stations were established and some existing ones were remeasured
with the FG5 absolute meter of the Federal Office of Metrology (Metas). So today, the Swiss absolute (zero order)
gravity network consists of about 15 stations, which are mostly located in stable buildings and far away from traffic and
ground water zones.
In order to improve the accuracy and stability of the network, additional high precision relative measurements between the
absolute stations are performed with SCINTREX-CG5 gravity meters in collaboration with the University of Lausanne and ETH
Zurich. With repeated observations, the accuracy of LSN2004 should also allow the first determination of gravity changes
and derived vertical movements in Switzerland.
The densification of the zero order network (1st and 2nd order network) is performed by relative measurements on stable
levelling and GPS benchmarks. This network consists of about 120 stations.
Based on this national gravity network (LSN), the detailed observations are performed. One data set of more than 5000 points
is located along the national levelling lines and is used for the reduction of levelling observations and the determination of
rigorous orthometric heights.
The second important detailed data set of more than 32'000 points was collected and re-processed by the Swiss Geophysical
Commission and the University of Lausanne. It covers the whole country and is presented in the form of 1:100'000 gravity
anomaly maps. This data set is a very important contribution to the determination of the Swiss geoid model and is used for
geophysical and geological interpretation.
The poster shows the concepts of LSN2004, presents the observations performed so far and gives an overview of the available
gravity measurements in and around Switzerland.
Figure 1. Absolute gravity stations in and around Switzerland.