Accuracy and Resolution of the Local Geoid Determined from Airborne Gravity Data

During the past five years, gravity measurements from airborne systems have become a viable alternative to terrestrial gravity measurements for applications where local or regional modeling of the gravity field of the Earth is required. One of these applications is local geoid determination where data taken along regular flight profiles can replace the use of point gravity values measured on the ground. Although the importance of this application was realized early in the development of airborne gravimetry, only limited results of comparisons between the local geoid derived from airborne gravity data and the local geoid derived from ground gravity data in the same area have so far been published. This is mainly-due to the fact that airborne gravity surveys are typically done in areas with no or sparse ground gravity, so that a direct comparison cannot be done. It is the objective of this paper to provide such a comparison and to analyze the accuracy and resolution of the geoid, currently achievable by airborne gravimetry. The airborne data used cover a 100 km by 100 km area in the Canadian Rocky Mountains with large changes in topography and gravity. It represents therefore a worst-case scenario in terms of the high-frequency spectrum of the gravity field and the geoid variations resulting from it. Results indicate that even under such extreme conditions, the root-mean-square differences between the two the geoids is at the level of two centimeters for the short-wavelength part of the geoid.