Validation of the New Earth Gravitational Model EGM08 Over the Baltic Countries

Abstract

AbstractThe Earth’s geopotential models (EGM) in conjunction with regional terrestrial gravity data are often used in regional geoid determination. Thus, significant enhancements are expected due to the release of the new high resolution Earth Gravitational Model EGM08. Accordingly, this study validates the performance of the EGM08 model over the Baltic Sea region with an emphasis to Estonaia, Latvia and Lithuania. Three different sets of the “ground truth” are used in the comparisons. First, the EGM08-derived height anomalies are compared with an existing regional geoid model. The detected discrepancies range within ±0.3 m with a mean of –0.02 m, whereas the standard deviation (STD) of the discrepancies amounts to 0.08 m. The largest discrepancies are related to the areas where only a few data were available either for the regional geoid modeling or at the EGM08 compilation, or both. Second, the free-air gravity anomalies at the terrestrial data-points are compared with the EGM08 – derived anomalies. The STD of the anomaly discrepancies is 2.6 mgal. Finally, the EGM08 model is validated with respect to GPS-levelling data. The STD of detected discrepancies is 0.06 m, with a mean of 0.49 m. Thus, the EGM08 based quantities agree reasonably well with the tested datasets. Evidently, most of the available gravity data in the Baltic Sea region appear to be utilised at the EGM08 construction.KeywordsGeopotential modelGeoidGPS-levelling