Airborne gravimetry for geoid determination

In this dissertation, the potential contribution of an airborne gravity system consisting of a strapdown inertial navigation system and differential global positioning system is investigated. Specifically, its contribution to geoid determination in terms of wavelength resolution and achievable accuracy is studied from a numerical and operational point of view.; Gravity values in various areas with typical topographic features were used for the spectral analysis of the requirements of geoid determination on gravity data. Results indicate that a cm-geoid can be achieved if the minimum wavelength resolved on the ground is about 14 km in flat areas and 5 km in mountainous areas.; The achievable accuracy and resolution of airborne gravimetry in geoid determination is studied through an assessment of INS and GPS errors in the spectral range of interest. The results show that the total GPS/INS induced geoid error is less than 1 cm for wavelengths between 5 km and 100 km and less than 10 cm for wavelengths between 5 km and 5 00 km.; To verify these results, an airborne test was flown over a very rugged area. Airborne gravity disturbances were collected above a 100 km x 100 km area and were downward continued to the ground level. The downward continued gravity disturbances agree with ground gravity data at the level of 3.8 mGal (1σ) and 2.5 mGal (1σ) for a wavelength resolution of 10 km and 20 km respectively. In the test area, the local airborne geoid agrees with the reference solution at the level of 1 ∼ 2 cm (1σ). The regional geoid computed from the downward continued gravity disturbances and 30&feet; x 30&feet; mean gravity anomalies in the outer area agrees with the reference geoid computed from ground gravity data on a 5&feet; x 5&feet; grid at the 5 cm level (1σ). The same level of agreement exists between the reference geoid and a GPS/levelling-derived geoid when fitting out the systematic trend. Thus, airborne gravimetry is capable of geoid determination at the 2 cm level for wavelengths between 10 km and 100 km and at the 5 cm level for wavelengths above 10 km when the systematic trend is removed.