Gravity anomaly field over Estonia

Abstract

Different gravity reference frames, methods and instruments have been used by several institutions for conducting gravimetric measurements in Estonia within the past 70 years. Accordingly, a careful evaluation of the obtained gravity data is required before their use in applied science and scientific research. The focus of this study is on (i) the determination and elimination of discrepancies between different gravity datasets and (ii) the prediction of a high-quality gravity anomaly grid for the Estonian territory and adjacent areas. About 144 000 gravity points were evaluated with outlier detection and removal. Some high-resolution data sets were also low-pass filtered to meet the requirements of geodetic applications like the determination of regional and national geoid models. Remaining 31 850 high-quality data points (22% of initial data) with additional metadata were used in the compilation of the Estonian Gravity Database (EGDB). Recent international cooperation (NKG2015 geoid and FAMOS marine survey projects) resulted in additional 17 339 points in the neighbouring countries and marine areas. These were used as auxiliary data to the EGDB in the computation of gravity anomaly grids. The conversion of gravity data to the residual terrain model anomaly (RTMA) values is a novel approach to improve the prediction accuracy of the regional gravity anomaly grids in Estonia. The resulting RTMA model obtained for the Estonian territory from the least-squares collocation prediction indicates high accuracy (low uncertainty) according to the statistical estimates and geostatistical analysis. As examples, some gravity field-related products were derived from the RTMA model for possible application in geosciences and other fields.

Keywords

• gravity reference frame
• gravimetric database
• gravity anomaly
• residual terrain model anomaly
• stochastic spatial prediction
• least-squares collocation.