Validations of Three Global Gravity Field Models Using the QDaedalus System Observed Astrogeodetic Vertical Deflections in the Munich Region, Germany

Abstract

<p>The total station-based QDaedalus system, developed in 2014 by ETH Zurich in Switzerland, incorporates a charge-coupled device (CCD) camera in support of daytime geodetic and nighttime astrogeodetic observations. The successful realization of astrogeodetic observations has resulted in astrogeodetic vertical deflection (VD) data collection in Germany, Italy, Hungary, Australia, and Turkey. Astrogeodetic observations carried out in Munich, Germany were used to determine the precision and accuracy of the newly installed QDaedalus system, which was found to be ~0.2 arcseconds for both the North-South (N-S) and East-West (E-W) VD components. In this study, 10 benchmark observations in the Munich region were also used to assess the quality of three global gravity field models—Global Gravitation Model Plus (GGMplus), Earth Residual Terrain Modelled 2160 (ERTM2160) and Earth Gravitational Model 2008 (EGM2008)—through comparison with the QDaedalus observations. The results of these comparisons between the predicted and observed VD data are: (i) The GGMplus predicted VD values were found to be closer to the observed VDs, with the differences for both the N-S and E-W VD components being ~0.2″, and reaching a maximum of 0.3″ and 0.4″ for the N-S and E-W components, respectively; (ii) The ERTM2160 predicted values were also found to be closer to the observed VDs, with differences of 0.4″ or less for the N-S component, with the exception of one benchmark (BM 8), and 0.2″ or less for the E-W component, with the exception of one benchmark (BM 9); and, (iii) When the predicted VDs computed using EGM2008 were analysed, we found that they were less accurate than the predicted GGMplus and ERTM2160 values. Therefore, the maximum differences between the observed and EGM2008 predicted VD data were for 0.9″ N-S and 1.8″ for E-W. Finally, we conclude with a comparison of the results of this Munich Region study with the results of a prior QDaedalus study, which was conducted in Istanbul (Albayrak et al. 2020), to assess the accuracy of the EGM2008 and GGMplus models.</p><p> </p><p>Albayrak, M., Hirt, C., Guillaume, S., Halicioglu, K., Özlüdemir, M.T., Shum, C.K., 2020. Quality assessment of global gravity field models in coastal zones: a case study using astrogeodetic vertical deflections in Istanbul, Turkey, Studia Geophysica et Geodaetica, <strong>64</strong>(3), 306–329. doi: 10.1007/s11200-019-0591-2</p>