Research On Real-time Estimation And Prediction Methods Of The Ionosphere TEC

The ionospheric error is one of the main sources of error in GNSS navigation and positioning.Although the system itself provides the ionospheric correction model to improve the impact of a certain degree of ionospheric delay to meet the users' real-time positioning needs and it has high timeliness.But the accuracy of the model correction is very limited and only 70% error could be corrected,it can not meet the needs of high-precision navigation and positioning for single-frequency navigation positioning users.IGS analysis center can provide high-precision ionospheric TEC grid products to meet the high-precision single-frequency navigation and positioning users.But the update time of IGS ionospheric TEC grid products is greater than 24 hours,it's difficult to meet single-frequency navigation and positioning users for timeliness.In view of this problem,this paper focuses on the single-station and global ionospheric real-time estimation method and ionospheric prediction method and test.The main contents of the paper are as follows:(1)The real-time parameter estimation method based on Kalman filter is introduced.Combined with the single-station and global ionospheric estimation function model,the method of real-time ionospheric delay modeling is realized.The experimental results show that the accuracy of real-time ionospheric TEC is within 5TECu,which can achieve the purpose of real-time estimation of ionospheric TEC.(2)There are a large number of global IGS tracking stations,all involved in satellite real-time orbit and clock offset determination will greatly reduce the efficiency of the solution,so that it is generally only selected part of the tracking stations.In this paper,based on the global grid model and data quality of the station selection strategy,the global IGS tracking station for a regular choice,to ensure the accuracy of the solution while improving the efficiency of the solution.(3)This paper summarizes the three regularity and characteristics of the global TEC's diurnal change,season change and annual change.Based on the understanding of global ionospheric TEC period change,the concept of time series is introduced.And the ionospheric TEC is predicted by time series model.Based on the general characteristics of global ionospheric TEC cycle variation,the time series ARMA model was used to predict the ionospheric TEC.The experimental results show that the predicted residuals account for about 51% of the range of 1TECu and 93% in the range of 3TECu.(4)This paper analyse the effect of ionospheric error correction in standard single positioning using real-time ionospheric TEC estimation through measured data,which provides a reference for single-frequency users.The experimental results show that the plane accuracy of the standard single point is about 0.75 m,and the elevation direction accuracy is 1.4-2.0m.At the same time,The results show that the accuracy of the wide-area differential pseudorange is better than 2m.