Kinematic GPS as a source for airborne gravity reduction in the airborne gravity survey of Switzerland

An airborne gravity survey of Switzerland was performed in a joint project between the Swiss Federal Institute of Technology, Zurich and LaCoste and Romberg Gravity Meters, Inc. The survey was flown in a Twin‐Otter aircraft equipped by the Swiss Federal Directorate of Cadastral Surveying. The aircraft was outfitted with three Global Positioning System receivers, one for navigational purpose and two as sources of positioning, velocity, and vertical acceleration for airborne gravity reduction. Four receivers were installed on the ground as reference stations. The gravity data were recorded with a modified LaCoste and Romberg marine gravimeter at a sampling rate of 1 s. Modifications included anti‐alias filters and an absolute encoder for the measuring screw. The flights were performed at a barometric altitude of 5100 m above sea level. An airborne Bouguer anomaly map, computed at flight altitude with topographic corrections of up to 167 km and a density of 2670 kg/m 3 , is presented. Bouguer anomaly values at crossing points between lines flown at comparable altitudes (Δ H <10 m) show differences varying between 1.1 and 2.7 mGal (10 −5 m/s 2 ). Comparison of the ground Bouguer anomaly map, upward continued to 5100 m, and the one computed from airborne data shows a strong similarity both in amplitude and wavelength.