The Research Of The Influence Of Environmental Loading On Non-linear Motion Of European GPS Stations

Due to the redistribution of the surface physical fluid loading,the GPS stations are influenced by geophysical effects such as Atmospheric Loading(ATML),Non-Tidal Ocean Loading(NTOL),and Continental Water Storage(CWS),all of which can cause non-linear motion of the GPS stations and introduce some errors in the high-precision geodesy.In order to study the tectonic movement at millimeter scale,the interference of geophysical effects must be removed.The study of environmental loading can explain the nonlinear motion of GPS stations due to natural environmental factors,resulting in velocities of GPS stations and reflecting more realistic coordinates.However,the established environmental loading models are not accurate enough,and the differences of them are usually large in some areas.So environmental loading models are need to execute the comparative analysis and quantitative evaluation.Based on the GGFC and QOCA environmental loading models,this thesis calculated ATML,NTOL and CWS,correcting European regional GPS coordinate time series(2001 to 2010).For the ATML,NTOL and CWS calculated by the GGFC and QOCA models,this thesis analyses the regional feature.The environmental loading are added to GPS coordinates corrections as the corrective numbers,and this thesis quantitates the correcting effect and the impact of the GGFC and QOCA environmental loading on the non-linear variation in the Up component of GPS coordinate time series.By the end,the thesis' s main works and contributions are as follows:(1)Elaborates the basic theories and methods of the non-linear variation analysis on GPS coordinate time series systematically,including the terrestrial reference frame,commonly used coordinate systems and the three methods of the different non-linear motion analysis,which consists of the geophysical effects analysis method,the technical system error analysis method and the noise characteristic analysis method.Finally,this thesis introduces the theory of environmental loading,GGFC and QOCA environmental loading models.(2)Calculates and preprocesses GGFC and QOCA environmental loading time series of 58 stations in European region.After using the GGFC grid model and QOCA software to obtain the original GGFC and QOCA environmental loading,this thesis need to preprocess the original GGFC and QOCA environmental loading time series.In order to ensure the consistency of time resolution,GPS coordinate time series as the standard,and the cubic spline function is used to unit the time resolution of GGFC environmental loading.To ensure reliable data interpretation,some GGFC and QOCA environmental loading's linear trend are removed.Therefor,it can be better evaluate the impact of environmental loading on the non-linear motion of the station.(3)Discusses the relationship between ATML,NTOL,CWS,the total environmental loading and the geographical environment of the station and calculates the RMS of the GGFC and QOCA environmental loading time series.The results show that the main influencing factors of the environmental loading are the latitude and the distance from the coastline.In general,the magnitude and amplitude of environmental loading displacement of the high-latitude area stations is larger than those of the low-latitude area stations;At the same latitude,the magnitude and amplitude of the environmental loading displacement of the stations located inside the European continent is larger than those of the coastal stations.The main influencing factors of RMS of the environmental loading are the latitude and the distance from the coastline.The RMS of GGFC is smaller than that of QOCA.The linear relationship between the latitude and the RMS of QOCA is relatively weak,and the RMS of the coastal stations' environmental loading is overall high.(4)Quantifies the contribution and correction effect of GGFC and QOCA environmental loading on the non-linear motion in coordinate time series of IGS stations.Results show that the correlation coefficient of GGFC environmental loading time series and GPS coordinate time series is 57%(vs.QOCA 49%).The average annual amplitude contribution of GGFC environmental loading time series to GPS coordinate time series can reach 80%(vs.QOCA 64 %).After GGFC environmental loading is corrected,the WRMS of GPS coordinate time series decreases and the average correcting rate can reach to 18%(vs.QOCA 13%).Therefore,compared with QOCA model,GGFC model is more suitable for the environmental loading correction of European regional stations' GPS coordinate time series.