Research On High Precision Real-Time Regional Ionospheric Modeling And Short-Term Prediction In GNSS Simulation System

With the rapid development of modern communication technology, making the research and application of many science and technologies must consider the effects of the ionosphere on radio waves. In recent years, the application of GNSS seeped into almost every field of scientific research, when we study how to eliminate the ionospheric error in GNSS, GNSS also provides a new direction for the study of ionosphere. In GNSS, Global Positioning System is the most representative in the study of the ionosphere. In view of this situation, In this paper, high-precision real-time regional ionospheric model and short-term prediction were studied by GPS. The main contents can be divided into four parts:1. Studied the correlation properties of the ionosphere. Due to the internal changes of ionosphere is quite complex. To study the ionosphere is necessary to understand the relevant characteristics of the ionosphere. Therefore, this paper firstly studied the hierarchical structure of the ionosphere and its abnormal phenomena, then analyzed the factors affecting the TEC by data. At the same time, introduces the basic knowledge used in the ionospheric research.2. Studied the modeling method of real-time regional higher-order ionospheric delay model. Most of the current ionospheric delay models only consider the impacts of the first-order item, the impacts of higher-order term are not added to the model, which leads to the accuracy of the model can not meet the needs of precision measurement and positioning. In view of this situation, this paper analyzed the impacts of ionospheric higher-order term on satellite signals, the observation equation of ionospheric delay model is derived by pseudo range values and polynomial function model, the equation includes the impacts of higher-order term. At the same time, studied the algorithm used in each stage in the modeling process to ensure the high precision and real-time of the model. Since the calculation process is very complex when we calculate geomagnetic field vector by International Geomagnetic Reference Field model. Therefore, this paper studied how to use surface fitting method to simplify the calculation process of geomagnetic field vector. On this basis, eventually established a model of higher-order ionospheric delay and proved the high precision of the model through the measured data.3. Studied the modeling method of regional ionospheric short-term prediction model which based on the combination thought. This paper puts forward to forecast TEC using combination theory based on the traditional ARMA model.According to the characteristics of sequence, this paper divided into four periods throughout the year. Then analyzed the periodic characteristic of TEC sequence by using the seasonal model and analyzed the sequence that has been eliminated the seasonal effect by using the traditional ARMA model. Finally established the combination forecast model. Forecasting result shows the precision of the combination model is higher than the traditional model and the combination forecasting method put forward in this paper is not subject to time and geographical restrictions.4. Studied the design and development of the simulation software of regional ionospheric delay and ionospheric short-term prediction. The software provides a convenient way for users to calculate regional higher-order ionospheric delay and the short-term prediction of ionospheric TEC.