Research And Discussion On Algorithm Of Ionospheric Delay Correction Model

The ionosphere is the atmosphere of the Earth's surface from 50 to several thousand kilometers,due to the solar radiation,the atmosphere of those regions is weakly ionized,so there are large number of free electrons and ions.These particles have a great impact on the radio waves,and there are up to several meters or even hundreds of meters in GNSS delay.Ionospheric error is currently one of the most important sources of GNSS error,thence,when navigating and positioning of radio,GNSS users need use certain algorithms for ionospheric delay correction.In addition,the satellite navigation system is entering a new era.Expect the existing global navigation system of GPS and GLONASS,China's Beidou navigation system,the European Galileo navigation system and regional navigation systems,such as QZSS,NAVIC system,are developing rapidly.Considering this situation,this paper has carried out some researching work on the ionospheric delay correction model.The main work and innovation of this paper,Firstly,in view of the current situation of each satellite navigation system using different types of broadcast ionospheric delay correction model,the paper introduces broadcasting ionospheric delay correction model of GPSK8,Galileo NeQuick G,BDSK8,BDSK14,BDSSH in detail,and evaluated several models' accuracy in different regions,which provides the necessary support and guarantee for the performance optimization of Beidou global broadcast ionospheric model.In the region of China,the BDSSH model has the best performance,the correction rate is over 75%,the RMS accuracy is within 5TECU,and the model correction effect from high to low is followed by the model of BDSSH,BDSK14,NeQuick G,BDSK8 and GPSK8.In global,BDSSH model is also the best,the correction rate is more than 70%,RMS accuracy is within 5TECU,and the model's correction effect is followed by the model of BDSSH,NeQuick G,GPSK8.Secondly,basing on the observation information of four satellite systems of GPS,GLONASS,BDS and Galileo,this paper has carried out a multi-system ionospheric modeling study,which can make better use of the current multi-GNSS navigation characteristics,to a certain extent,improve the accuracy of ionospheric information,and provide a more effective and reliable way for the satellite navigation applications and ionospheric research work.The results are better in the northern hemisphere than in the southern hemisphere,and the accuracy is relatively stable.Compared with the final GIM of the CODE,the average deviation is about 1TECU and the RMS is around 1.5TECU.Whether in the southern hemisphere or the northern hemisphere,mid-latitude and high latitudes of the modeling results are better than the low latitude,in the low latitudes of northern hemisphere,the mean deviation is 2.77 TECU,and RMS is 3.92TECU;in the low latitude area of southern hemisphere,the average deviation is 2.33 TECU,and RMS is 3.34 TECU.Thirdly,this paper carried out assessment work of GIM,mainly discusses the ultimately,fast and predictable GIM's accuracy of CODE,ESA,UPC,JPL,CAS,IGS and iGMAS,which provides a strong guarantee for the GNSS single-frequency users to develop the high-precision navigation and for scientific research workers to carry out precise research on ionospheric information.The final GIM accuracy of CODE is the best in the mid-latitude and low latitudes,and the STD is 1.78 in the mid-latitude and 2.84 TECU in the low latitudes.In the high latitudes,the final GIM of JPL is the best,and STD is 1.76 TECU.JPL's fast GIM accuracy is the best accuracy for all fast GIMs,and the STD is 1.77 TECU in the high latitudes,1.91 TECU in the mid-latitude and 3.14 TECU in the low latitudes.In addition,the forecast GIM is worse than the final and fast GIM.Fourthly,this paper uses ARMA time series model to study the modeling and prediction of ionospheric information,which provides a high-precision,real-time ionospheric delay correction model for GNSS users,at the same time,this method also provides an effective,viable way for researching the ionosphere.The results are higher in the northern hemisphere than in the southern hemisphere.In the northern hemisphere,the prediction accuracy is stable and the average RMS is 3.53 TECU.With the decrease of the latitude,the predicting accuracy is also reduced.In the region of China,the forecast accuracy within 40 days,the average RMS is 4.01 TECU.The forecasting accuracy is better in the day than in the night,the difference is between the 0.5TECU.