Research On Tropospheric Delay Modeling Based On GNSS And ERA5 Data

Tropospheric delay error is one of the main error sources affecting the positioning accuracy of Global Navigation Satellite System(GNSS).In practical applications,the tropospheric model method is usually used to reduce the influence of tropospheric delay errors on positioning.Based on this,this paper evaluates the fifth-generation meteorological reanalysis data(ERA5)in China,and establishes a Zenith Tropospheric Delay(ZTD)height change model based on ERA5 data;and on this basis,the VMF(Vienna mapping functions)interpolation algorithm is improved to solve the problem of poor interpolation accuracy in areas with large elevation dispersion.In addition,in order to improve the accuracy of ZTD calculation by GPT3,the Kalman filter data assimilation algorithm is used to assimilate the tropospheric delay(GNSS＿ZTD)and GPT3＿ZTD grid data calculated by GNSS data.The specific work and innovations of this paper are as follows:(1)Evaluate the accuracy of ERA5 data in China from two aspects of meteorological elements and integral ZTD.The experimental analysis of the ERA5 data in 2021 shows that the surface meteorological data extracted using the ERA5 pressure stratification data has a high accuracy,and the root mean square errors of the air pressure,air temperature and relative humidity are within 0.45 hpa,0.59℃ and 5.9%respectively.Using ERA5 data to integrate ZTD also has high accuracy.The average deviation of the eight reference stations in China is 9.21 mm,and the root mean square error is 18.32 mm.The average deviation and root mean square error have seasonal variations,showing a larger variation pattern in summer and smaller in winter.(2)Using ERA5 data to establish a grid model of ZTD height change in China,with a spatial resolution of 2.0°x2.5° and a temporal resolution of 6h.In January 2021,the average deviation of all grid points is 6mm,and the average root mean square error is 8.5mm.The VMF interpolation model is improved by using the ZTD elevation change grid model.After the improvement,the ZTD interpolation accuracy of stations with large elevation dispersion such as URUM and BJFS is significantly improved.(3)Use the Kalman filter data assimilation algorithm to assimilate the tropospheric delay(GNSS＿ZTD)calculated from the GNSS data and the ZTD grid data(GPT3＿ZTD)calculated by the GPT3 model.In the assimilation area,the mean square error of GPT3＿ZTD is reduced from 19.55 mm to 12.34 mm,and the accuracy is increased by about 36%.