Knowledge Bank

This study developed a geostatistical method to determine the required extent of terrain corrections for gravity gradients under the criterion of different applications. We present the different methods to compute the terrain corrections for gravity gradients for the case of ground and airborne gravity gradiometry. In order to verify our geostatistical method and study the required extent for different types of terrain, we also developed a method to simulate topography based on the covariance model. The required extents were determined from the variance of truncation error for one point, or furthermore from the variance of truncation error difference for a pair of points, and these variances were verified with that from the deterministic method. The extent of terrain correction was determined for ground gradiometry based on simulated, ultra-high resolution topography for very local application, and also was determined based on mountainous topography of large areas. For airborne gradiometry, we compute the terrain corrections and the required extent based on Air-FTG observations at Vinton Dome, LA and Parkfield, CA area; also they were verified with the results of Bell Geospace. Finally, from the mostly flat, medium rough and mountainous areas, an empirical relationship was developed which has the properties that the required extent has 4 times relationship corresponding to the amplitude of PSD has 100 times relationship between mountainous and mostly flat areas, and it can be interpolated for other types of topography from their geostatistics.