^7fDue to the relatively high speed and low costs at which measurements can be made an airborne gravity system provides an attractive alternative to conventional terrestrial and space based methods to determine the gravity field of the earth. An aircraft provides access to difficult terrain and uniform sampling, but the success of land and sea gravimetry cannot be transferred to airborne gravimetry easily. In the beginning of airborne surveys a number of difficulties emerged and aircraft applications seemed not to be very auspicious. The circumstances were and are a big challenge on flight measurement technology and filtering techniques. This has driven the research program in airborne gravimetry at the Institute of Flight Guidance and Control (IFF) since 1986. The focus of the airborne gravimetry programme at the IFF has been on the development, improvement and application of long-range surveying techniques. It is of particular importance for the future of airborne gravimetry to increase accuracy and resolution. Additionally the IFF is involved in the development of a gravity measurement system using an inertial platform, a gravity sensor, a barometric sensor and kinematic differential carrier phase based GPS positioning. Airborne gravimetry is an important part of inertial flight measurement technique. The principle of using an inertial navigation system to measure the gravity field can be found in [1], [2], [3]. The gravity disturbance signal may be obtained from the time-synchronised difference between the measurements of a precise inertial accelerometer signal (gravity sensor) and an altimeter signal (GPS differential carrier phase, barometric sensor). The gravity sensor measures specific force, which is composed of a gravity component and an aircraft acceleration component. The Global Positioning system (GPS) measures the aircraft motion only. Accuracy requirements for users in geodesy and solid earth geophysics, oceanography and exploration geophysics are described in [4]. An accuracy of 0.5 mGat to 1 mGal in the wavelength range between 1 km and 10 km is for special interest to oil exploration, white an accuracy of 1 mGal to 3 mGal in the wavelength between 10 km and 100 km is important to geodesy.
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