Construction And Precision Analysis Of Ionospheric Delay Correction Model Based On Ground-GPS

As an important part of the near-earth space environment, ionosphere has a close relationship with modern radio system and satellite navigation system. Ionospheric delay is the main error sources for the navigation, positioning and timing of global satellite system. The effect of ionosphere delay on electromagnetic wave propagation and using GNSS signals to research the characteristics of ionosphere and monitor the change of ionosphere have become the hot topic. In this paper, we use GPS data provided by IGS to study the law of the daily changes of global TEC. And we establish a global ionospheric delay model based on GPS data by a set of software. Comparing the results of software with those issued by CODE, we can see the model accuracy is consistent with that of CODE. The primary contents of this paper are as follows:1. It briefly introduces the basic knowledge and research status of ionosphere, systematically studies the current common ionospheric delay models and analyzes the implementation methods and the advantages and disadvantages of some models.2. It explains the basic theories and methods to research the ionosphere by using GPS, which mainly includes the relevant principles of GPS, the methods of parameterizing and mathematical modeling of ionospheric delay, and the deep analysis of the character of differential code bias (DCB).3. It uses GPS dual-frequency observation data provided by IGS global observation stations to establish global ionospheric delay correction model based on spherical harmonics. The model calculating results are accordance with those of the global ionospheric products of CODE. Residuals of TEC calculated by model minus CODE TEC almost fall in-5TECU-5TECU and the accuracy is less than 2TECU. The RMS of all satellite DCB estimates is 0.07ns, and the residuals of receiver DCB are all less than 2ns.4. Using the normal equation superposition algorithm, only non-zero elements involved in normal matrix calculation, to solve the problem of storage difficulty and low computational efficiency of the large matrix.5. We focus on the negative VTEC in global ionosphere maps, which is caused by uneven distribution of global IGS observation stations, by using inequality-constrained least squares (ICLS).