Terrain corrections are critical for airborne gravity gradiometer data

Abstract

Several developments aim to produce airborne gravity gradiometers with sufficient sensitivity to detect mineral deposits of several millions of tonnes at shallow depths. In a conventional ground gravity survey, a Bouguer slab correction is always necessary, with the terrain component of the full Bouguer correction often not needed unless the topography is severe. For airborne gravity gradiometers, however, the slab correction is exactly zero but the terrain corrections prove to be critical even with subdued or moderate topography. This paper reports on research into airborne gravity gradiometer corrections, especially aspects that assessed the importance of regolith and its constraints of surface and bedrock topography, together with predicted target anomalies. Using an example of topography typical of the Western Australian shield, calculations show that densities of both regolith and bedrock need to be determined to better than 0.1 t/m3 for adequate correction to be made to raw gravity gradiometer data. Topography also needs to be defined to about ±3 m on 10 m pixels for adequate gravity corrections.