Modeling And Performance Analysis Of GNSS Regional Ionosphere

Global Navigation Satellite System(GNSS)has the advantages of all-weather global monitoring and high precision,which makes it possible to accurately extract the total electron content(TEC)of the ionosphere and further research on the ionospheric activities by using GNSS observation data.At the same time,the ionospheric delay error is also one of the main error sources in GNSS positioning.Therefore,the development of ionospheric TEC model and GNSS promotes each other,which is beneficial to improve the navigation and positioning accuracy of GNSS users,and can also provide data reference for ionospheric monitoring and prediction.The ionospheric structure and variation characteristics are complex.Based on GNSS dual-frequency observation data,this paper focuses on the establishment method of regional ionospheric TEC model,and makes comparison and application analysis.The main research contents are summarized as follows:1.Briefly introduce the current status of ionospheric modeling research,analyze the ionospheric structure and change characteristics,and discuss the principle of extracting ionospheric TEC from GNSS observation data and using functions to establish TEC model.The dual-frequency carrier phase smoothing pseudorange algorithm is researched.Experiments show that the use of carrier phase smoothing pseudorange can improve the calculation accuracy of TEC.2.The Ionospheric TEC model of single station area is established based on polynomial function.BDS / GPS data of IGS MGEX observation network are used for modeling.The accuracy of DCB and VTEC obtained by single GPS,single BDS and BDS/ GPS modeling are analyzed.The results show that the accuracy of BDS/GPS dual-system data in solving TEC and DCB is better than that of single system;VTEC modeling results are in good agreement with IGS,and the difference between VTEC and IGS is more than70% within-2TECU to 4TECU.Finally,the influence of polynomial model order on TEC modeling is researched.The results show that the accuracy of modeling increases with the increase of model order,but after a certain order,the increase of order has little effect on the accuracy of the model.3.Based on the spherical harmonic function,the multi-station establishment of the regional ionospheric TEC model is realized.Aiming at the possible abnormal phenomena of TEC,an algorithm of ionospheric modeling with additional virtual observations and inequality constraints is proposed,and the ionospheric TEC model in the region of 15° ?45° N and 105° ? 135° E has been established;The DCB results of receivers calculated by6 IGS stations prove that DCB is basically stable within 7 days,and the average deviation of DCB calculation results from CAS is basically less than 0.5ns.Using the established model to perform single-frequency single-point pseudorange;For static positioning applications,the correction effect at the BJFS station and JFNG station is better than that of IGS ionospheric grid products,and the correction effect at the HKWS station is equivalent to that of IGS.4.Based on the Kalman filter,the GNSS dual-frequency observation data is used to achieve the DCB and TEC calculation.The deviation from the satellite DCB released by IGS is about-0.7?0.62 ns.The results show that the Kalman filter is effective for DCB and TEC.The calculation is reliable,and the extracted ionospheric TEC can be used for TEC modeling and ionospheric morphology and disturbance research.