Research And Application Of Ionospheric Modeling Based On GNSS

The ionosphere has complex structure and diverse variation characteristics,and the spacetime structure can be studied by spherical harmonic function model.In this paper,the global ionosphere and regional ionosphere are modeled to verify the accuracy of the model and demonstrate the feasibility of the model.1)Establish the global ionospheric model by using GPS,GLONASS and Galileo system respectively through the 15 th order spherical harmonic function model,and analyze the distribution range and causes of the puncture points,and analyze the difference in the mean value of TEC in the high,middle and low latitudes of the global and the northern and southern hemispheres,as well as the correlation coefficient with the products provided by each ionospheric group.GPS-GIM,Glonass-GIM and Galileo-GIM were correlated with the daily mean of global TEC of different analysis centers,among which the GPS-GIM had a strong correlation with other analysis centers,all of which were greater than 0.91.The correlation between Glonass-GIM and other analysis centers of Galileo-GIM is extremely strong,all of which are greater than 0.7.2)To further improve the global ionospheric model,the global ionospheric model is established based on GPS and GLONASS as well as GPS and Galileo.The difference between the ionospheric grid TEC value obtained by GPS alone,GPS+GLONASS system and GPS+Galileo system is small,and the accuracy of GPS+GLONASS and CODE is the closest.3)The five-order low-order spherical harmonic function model is used for regional ionospheric modeling,and the reliability and stability of the established regional ionospheric model are analyzed.The results show that the daily variation of GPS satellite DCB in the regional ionosphere is very small,and fluctuates within 0.03 ns.The STD and RMS of all GPS satellite DCB are better than 0.06 ns and 0.07 ns.Most of the mean values of the difference between the European Regional Ionospheric Model DCB and the DCB provided by CODE are below 0.1ns,and the RMS remains relatively stable below 0.25 ns.4)The accuracy of dual-frequency precise single point positioning with the European ionospheric model in E and N directions is not significantly improved,but the PPP accuracy in U direction is greatly improved.The positioning residual in the E direction is less than 0.3cm,the U direction is less than 0.42 cm,and the U direction is less than 0.6cm.The results of PPP positioning show that the accuracy of the solution of the PPP results in U direction is greatly improved with the addition of the ionosphere.The paper has 47 pictures,18 tables,and 94 references.