GNSS Regional Ionospheric Modeling And Precision Analysis

With the development of multi-mode GNSS,various satellite systems provide users with various conveniences in positioning,navigation,timing and other aspects.Ionospheric delay,as one of the most important error sources in the process of satellite signal propagation,cannot meet the user's demand for high precision.Current global ionospheric model to construct the emphasis on the trend of global ionospheric whole change,for the regional ionospheric variation characteristics and status will not be able to do good pertinence and actual effect after spread to users may not meet expectations,and the regional ionospheric model can better study ionospheric characteristics of small scale,navigation and positioning on the regional users has more applicability and pertinence.This paper focuses on the regional ionospheric model construction and model precision analysis.The main research contents are as follows:(1)The formation and structure of the ionosphere are introduced in detail.The phenomena and principles of the ionosphere in the process of satellite signal propagation are analyzed,and the related calculation principles of TEC of the ionospheric electron content are discussed.(2)The theory and method of ionospheric delay model are expounded.On the one hand,the principle and method of the ionospheric thin layer model are introduced in the construction of the ionospheric deterministic model,and the principle and effect of the mathematical model are compared.On the other hand,the principles and effects of different baselines of ionospheric fixed model,ionospheric floating point model and ionospheric weighted model are introduced in the ionospheric stochastic model,which provides ideas for the improvement of practical work.(3)For the deterministic model,the calculation method of satellite DCB based on spherical harmonic function model is studied by choosing the data of Beidou in Asia-Pacific region,and the regional ionospheric grid map is obtained by correlation coefficient.Compared with the products of the analysis center,the difference between DCB and the analysis center is 90% in the range of(±5TECU).The results are in good agreement with each other.(4)Regarding the stochastic model,a reasonable stochastic model for the single-difference ionospheric delay between receivers is established by using the single-difference ionospheric delay weighted model of receivers,and it is used as the virtual observation value in the ionospheric weighted model,so as to improve the success rate of ambiguity resolution,and a functional model for the influence of the ionospheric weighted model is constructed by combining baseline with altitude angle.The performance and effect of the new ionospheric weighted model are validated.It can fix the ambiguity better and get better positioning results.The positioning accuracy is further improved from dm/cm level in U direction to cm level,and from cm level to mm level in N and E direction...