Height Transfer Across the Storebælt (Eastern Channel) Using Geometric Levelling, Trigonometric Heighting and Astronomic Methods in Combination with GPS (GPS Levelling)

The combination of GPS measurements and levelling yields information on the inclination of the geoid relative to the WGS84 ellipsoid (deflections of the vertical). The same holds for the combination of GPS measurements and astronomic azimuth and latitude determination. Once the inclination components of the geoid are known for an area of operation GPS derived ellipsoidal height differences can be transformed into orthometric height differences. Based on this knowledge the orthometric height difference between the Danish islands Sjælland and Sprogø has been determined. This value is crucial for the setting out of the two 8 km railway tunnels being constructed to establish a fixed link across the Great Belt waterway. Compared with hydrostatic levelling the employed methods offer clear cost advantages.