Guangxi Refined Modeling Of Regional Zenith Tropospheric Delay Model And Application

As one of the key parameters of Tropospheric Zenith Delay(ZTD),it is also the error source that affects the positioning accuracy of GNSS.The research shows that ZTD information can be applied to small and medium scale meteorological forecast,precipitation forecast and GNSS precise point positioning(PPP).Therefore,it is of great significance to construct a tropospheric delay model with high temporal and spatial resolution for improving GNSS navigation and positioning accuracy and its application.In this paper,the existing tropospheric delay model has the problems of insufficient temporal and spatial resolution in local regions and does not take into account the fine variation of ZTD with elevation.Combined with the latest ERA5reanalysis data of ECMWF,the tropospheric delay model is constructed in Guangxi and applied to GNSS PPP positioning.The main contents and contributions of this paper are as follows:1.The accuracy of ZTD data obtained by ERA5 reanalysis data integration in Guangxi was evaluated.The results show that the annual bias and RMS value of ZTD data calculated by ERA5 reanalysis data integration are-0.18cm and 1.37 cm respectively under the calculation of ZTD data from Guangxi GNSS reference station as the reference value.It indicates that the ZTD data obtained by ERA5 reanalysis data integration has high accuracy and stability,and can be used as the data source for the subsequent construction of convective delay model.2.Aiming at the problem of the single elevation correction coefficient of the traditional tropospheric delay model,the gaussian and exponential regional tropospheric delay vertical correction models GXZTD-H_g and GXZTD-H_e were constructed,which take into account the fine variation of the ZTD with elevation,and verified the applicability of the two models in Guangxi region.The results show that the RMS values of GXZTD-H_g model are reduced by 0.44 cm(21%)and 0.25 cm(12%)compared with those of GXZTD-H_e under the internal and external compliance accuracy test using ERA5 reanalysis data and MERRA-2 reanalysis data,respectively.It shows that gaussian function is more refined than exponential function to express ZTD elevation changes in Guangxi region.3.A Guangxi regional ZTD model GXZTD with the same starting surface and considering the spatiotemporal variation characteristics was constructed,and its accuracy was verified by combining ERA5 and MERRA-2 reanalysis data and GNSS reference station data.GPT3 model with the highest nominal accuracy was used for comparative analysis,and The GXZTD model was applied to PPP positioning.The results show that:(1)using the ZTD value of ERA5 reanalysis data as reference value,the accuracy of GXZTD model is improved by 1.04 cm(21%)compared with GPT3-1model,and by 1.09 cm(21%)compared with GPT3-5 model.(2)Using the ZTD value of MERRA-2 reanalysis data as the reference value,the accuracy of GXZTD model was improved by 0.69 cm(16%)and 0.77 cm(18%)compared with GPT3-1 model and GPT3-5 model,respectively.(3)Compared with GPT3-1 model and GPT3-5 model,the GXZTD model showed smaller deviation and RMS value with ZTD data of GNSS reference station as reference value.(4)In the application of GNSS PPP,the convergence time of GXZTD model is shortened by 8.87 min(19%)compared with the traditional GNSS PPP positioning method by adding GXZTD model correction method.Therefore,The GXZTD model has certain application in GNSS PPP positioning in Guangxi region.