Research On Environmental Loading Effect In GPS Vertical Time Series

In recent years,GPS has been widely used in geodesy because of its high precision and round-the-clock characteristics.Various organizations have set up countless GPS continuo us operating reference stations and accumulated a large number of long-term GPS coordinate time series data.However,with the high precision processing of GPS data,it is found that the GPS coordinate time series contains not only the information of structural movement of the reaction station,but also the information of non-structural deformation,which is mainly reflected in the vertical direction.When using GPS as technical means to study geodynamics and crustal movement monitoring,the non-structural deformation information in GPS coordinate time series will lead to the deviation of the research results,so it is necessary to remove it from the GPS coordinate time series.Get more real information about tectonic movement.Current research shows that non-structural information is mainly caused by environmental load,and mainly in the vertical direction of GPS coordinate time series.In this paper,the influence of environmental load on GPS coordinate time series in vertical direction is studied,including the following research contents and results:(1)In this paper,the errors involved in GPS are introduced,and the causes of environmental load,classification and three data sets of QOCA,GFZ and GGFC which can be used in quantitative calculation of environmental load effect at present,as well as the corresponding calculation methods and models are emphatically described.(2)The displacement caused by the environmental load effect of the selected stations from 2003 to 2012 is calculated by using QOCA data,and the magnitude and spatial distributio n of the stations are analyzed firstly,by selecting 277 th global IGS reference station as the research object,and using the QOCA data to calculate the displacement caused by the environmental load effect in the selected stations.The results show that the atmospheric load has the greatest influence on the environmental load,followed by the hydrological load.At the same time,the global distribution of environmental load effect is not uniform,and there is a certain relationship between environmental load effect and latitude.Then,the correction of atmospheric load and total environmental load to the station is studied respectively.It is found that the atmospheric load is the main component of the environmental load,and the WRM value and the amplitude of the annual term decrease when the atmospheric load corrects more than 70%.Then,the influence of environmental load effect on GPS coordinate time series is analyzed from the aspects of optimal noise model,velocity estimation and speed uncertainty.(3)The vertical correction effect of three different environmental load data sets,QOCA,GFZ and GGFC,on GPS coordinate time series is analyzed quantitatively.The amplitude of WRMS,periodic term before and after environmental load correction is analyzed.The optimal noise model,velocity estimation and velocity uncertainty are compared.The results show that the correction effect of GGFC is the best,followed by QOCA,and GFZ is the weakest.(4)The relationship between environmental load and geoscience factor is studied.This paper analyzes the correlation between displacement time series and latitude caused by environmental load and the distance from station to coastline.It is found that there is a statistica l correlation between the displacement time series and latitude caused by environmental load,and some physical explanations are given.