GEODESY, CARTOGRAPHY AND AERIAL PHOTOGRAPHY

Abstract

A number of factors can significantly affect the accuracy of height determination when applying the GNSS leveling method. In general, it is possible to distinguish those related to the process of GNSS observations and their post-processing, and those related to the selection of the geoid/quasi-geoid height model. This work focuses on aspects of GNSS leveling accuracy when choosing global geoid models. In particular, to better ensure accuracy, it is important to understand the significance of the heights tidal system selection of global geoid models. The purpose of the work is to analyze the influence of different tide systems of global geoid models on the accuracy of height determination by the GNSS leveling method. This paper considers the heights of global geoid models EGM08, EIGEN-6C4, GECO, and XGM2019e_2159 of high degree and order calculated in the tide systems of “tide-free”, “mean-tide”, “zero-tide”. The analysis of the actual accuracy of the geoid heights was carried out on the basis of the standard and root mean square deviations of the heights differences of global geoid models in the corresponding tidal systems in relation to the GNSS leveling data. GNSS leveling data were obtained at 14 high-precision geometric leveling points of accuracy class 1-2, covering the central part of the Lviv region. Similarly, the accuracy of the geoid models was analyzed taking into account the differences of gravity anomalies concerning the high-resolution anomalies of the WGM2012 model. Data presenting differences of height and gravitational anomalies allowed us to correct the height of the models according to the weighted average principle. In addition, corresponding statistics were calculated for them. The conducted analysis shows that for the EGM08 model, the system of “mean-tide” is optimal with an accuracy assessment at the level of σ=2-3 cm and m=4 cm. For the EIGEN-6C4 model, it is best to use the “zero-tide” system which will ensure accuracy up to 4-5 cm. The accuracy of the EGM08 and EIGEN-6C4 models is confirmed by the statistical characteristics analysis results of the gravity anomaly differences. The GECO and XGM2019e_2159 models give ambiguous results within 3-9 cm by both parameters and in all tidal systems. Only after correction of the heights, their accuracy is 2-5 cm. Considering the optimal tidal system, the heights of the EGM08 and EIGEN-6C4 models can provide an accuracy of 1-3 cm after the correction by weighting coefficients.