The Research On Ionosphere Modeling Based On GPS/BDS Navigation System

The ionosphere is an important part of the space environment of the day, which interferes the radio navigation information dissemination, in particular, it has a major impact on the single frequency receiver, The ionosphere error has become one of the most troublesome source of error in the global navigation s atellite system(GNSS) data processing. Recently, with the increasing of satellit e navigation system and the continuous development of human space activities,mastering the variation characteristics of ionospheric, then to monitor and inv ert the law of ionosphere has been paid more and more attention. Therefore, t here has important significance to study the ionosphere.In recent years, the construction and application of China’s BDS GNSS ha s brought new opportunities and challenges with ionospheric research. On one hand, because of the special geographical position of our country, our ionosphe re situation is more complex than the global average level of the ionosphere. China’s BDS monitoring stations distribute in domestic territory, the station ove rseas are very limited. In addition, the BDS constellation is out of completion,so it cannot achieve global positioning. Compared with GPS, BDS is unable t o complete the global ionospheric independent modeling. On the other hand, in the competitive international environment, the establishment of high precision i ndependent ionospheric delay correction model has important significance to ou r BDS for achieving a dominant position in the international navigation market.Based on the above points, this paper carried out the research on the modelin g method of ionospheric delay based on global GNSS data. Using GNSS techn ology to establish the principle of global ionospheric model and to analysis the method of data processing. We established the TEC model of global ionosphe ric based on the observation data of single GPS system and GPS/BDS dual sy stem. In addition, considering current situation which Beidou station is not yet more and the constellation is out of completion, thus it is unable to model sep arately. In this paper, the method of pseudo spherical harmonic function was pr oposed to establish China regional ionospheric model. The main work and achi evements can be summarized as follows:1. The pretreatment method of GNSS observation data is studied. Kalman filter method, high order difference method and polynomial method were the focused research for detecting cycle slip.A comparative analysis had been done t hat Kalman filtering method had the advantages of superior and timeliness in d istinguishing gross errors and cycle slips. The ionospheric TEC formula had be en calculated with GNSS data, and the phase smoothing pseudorange algorithm was researched. The experimental results showed that the modeling accuracy c an be improved by using carrier phase smoothing pseudo range.2. The principle of global ionospheric model and the method of data proc essing based on the GNSS observation data were summarized. The TEC model of global ionospheric was established based on the observation data of single GPS system and GPS/BDS dual system. Through the experimental analysis, co mpared with the single mode GPS, the accuracy of global ionospheric modelin g using the GPS/BDS dual system was improved to a certain degree. While th e BDS system has no yet ability to establish the global ionospheric model ind ependently, so it is needed to be combined with other system to model.3. Using the GPS/BDS dual system observation data, pseudo spherical har monic function was proposed to establish China regional ionospheric model me thod. The hardware delay deviation parameters of BDS satellite was estimated accurately in China, and the accuracy and reliability were also analyzed. These provide an important reference for the development of ionospheric delay corre ction in BDS wide area of China.