GPS Ground Deformation Monitoring Data Processing Methodology Study In Active Ionospheric Area

Abstract:Geological disasters have brought huge losses to the human life. Displacement deformation information is the most intuitive information about the geological disasters and the main basis of the geological disaster forecasting and warning. Therefore, deformation monitoring is an important means of disaster prevention and mitigation. Since the advent of GPS technology, because of its all-weather, all-time, high-precision, easy operation and direct access to the three-dimensional position information of observation sites, its application in deformation monitoring of geological disasters become more and more widely. Because the SA policy has been closed, ionospheric error is the major factor affecting the accuracy of GPS positioning. In this paper, some GPS data processing problems that exist on the ground deformation monitoring in the active ionospheric area are studied.(1) Analysis the first and high order terms of ionospheric delay effects. In conventional GPS data processing, we usually eliminate the first order term impact of the ionosphere delay through ionosphere free linear combination method and neglect the remaining higher order terms. However, in the year of active ionosphere, high order terms of ionospheric residuals will produce centimeter-level positioning errors.(2) Based on triple difference cycle slip detection method, analysis the ionospheric delay, tropospheric delay, multipath effects and elevation angle effect on this method and explore the robustness of the cycle slip detection method.(3) Using single and dual mixed mode GPS network to generate regional atmospheric delay errors by a small number of dual peripheral sites and correct internal single-frequency data. Thereby reduce monitoring costs while ensuring the accuracy of deformation monitoring. Implement single and dual mixed mode data processing algorithms by programming language, numerical results show that the method in the active region of the ionosphere can effectively eliminate atmospheric delay error and improve the accuracy of single-frequency data. (4) Since in the ground deformation monitoring, it is not easy to find a stable reference point, so usually the base station is far from the monitoring station. Because the baseline is long and the correlation of the atmospheric delay is decreased, also the accuracy of baseline solution is decreased. Therefore, we propose a method like traverse, choosing the shortest baseline and finally adjust the overall results for all baselines, thereby improving the accuracy of baseline solution.