Research On Ionospheric Tomography Algorithm And Disturbance Based On GPS

The ionosphere is a special component of the atmosphere,and its changes will affect the environment that humans rely on for survival.With the completion of a new generation global navigation satellite system,the application of the satellite navigation is becoming more extensive.It is of great significance to researching on the ionosphere about its temporal and spatial distribution characteristics,internal changes and abnormal disturbances;which can provide guarantee for propagation of wireless signals,weakening of interference to navigational aids and aircrafts.The ionospheric tomography model based on GPS(Global Positioning System)groundbased observation data has unique advantages over other ionospheric detection methods.The regularity and irregularity of the ionosphere can be studied from the temporal and spatial distribution of electron density,which can reflect the changes in the ionosphere in detail.First,by using the ionospheric TEC(Total Electron Content)data extracted from GPS dualfrequency observation data,the reconstruction of the ionospheric electron density in the region is completed.Then,based on the defect of insufficient ground-based observation data,an ionospheric tomography algorithm combining virtual observation station data is proposed.Next,research and analysis of ionospheric tomographic grid resolution and tomographic model accuracy.Last,research and analysis of ionospheric disturbance during magnetic storm activity based on ionospheric tomographic model.The main research contents of this paper are as summarized follows:(1)The carrier phase smoothing pseudorange algorithm is used to extract the TEC value,in this paper,by deriving the carrier phase smoothing pseudorange formula,a new algorithm for optimal Hatch filter is constructed,which optimizes the ionosphere divergence error.At the same time,statistics and analysis are carried out on the accuracy of the DCB(Difference Code Bias)value in the extraction process,the results show that the algorithm can extract the TEC value with higher accuracy.(2)Using the initial value of the electron density provided by the international reference ionosphere(IRI2016)and the ground-based observation data,the multiplicative algebraic reconstruction algorithm is used to complete the reconstruction of the electron density in the region.In view of the restriction of the ground-based data on the inversion accuracy of the tomographic model,in this paper a tomography algorithm that combines data from a virtual observation station is proposed,the results of the region reconstruction show that the grid penetration and the accuracy of the electron density values have been improved.(3)Research on the grid resolution of the tomographic model,simulation experiments have verified that reducing the resolution of a single tomographic grid can effectively improve the accuracy of the tomographic model.At the same time,analyze and study the resolution of the mixed grid and experimental results prove that the inversion accuracy of the tomographic model can be improved by the combination of different grid resolutions.(4)By analyzing the global ionospheric anomalies during the magnetic storm,the ionospheric disturbance phenomenon during the magnetic storm was studied based on the ionospheric threedimensional tomographic model,and the three-dimensional tomographic inversion of the electron density during the magnetic storm was carried out.The experimental results showed that the disturbance of electron density was more obvious at the peak points after the occurrence of the magnetic storm,and the electron density is mainly disturbed at the peak height.The tomographic model inversion results based on ground-based observation data can reflect the actual dynamic changes of the ionosphere.