The Research Of The Ionospheric Based On Dual-frequency GPS Receiver

With the development of global positioning systems and the improvement of positioning technologies, its application has gone deep into all aspects of people's lives and productions. China has also become the third country with independent navigation satellite after United States and Russia. Reducing errors to improve accuracy of satellite positioning has become a hotspot which many scholars and institutions are researching. The impact of the ionosphere on the accuracy is particularly significant in many factors of positioning errors. In this theme, using the GPS signals to calculate the electron content and analyze the change is a realizable basis of researching for delay modeling of ionosphere and reducing errors. It also plays a helpful role for monitoring the ionospheric electron content and predicting their trends.Firstly, this paper introduces the structure of the ionosphere, related principles of the GPS and error sources. On this basis, it discusses the theoretical basis of using the GPS dual-frequency to calculate the ionospheric electron content in detail. Dual-frequency receiver can receive different frequencies carrier signals with L1 and L2. Using the different delay amounts between two signals when they pass through the ionosphere, the electron content can be calculated. Based on this result, the vertical electron content can be reckoned with using satellite real-time location data. At the same time, the text also illuminates the command format and data structure of the GPS receiver.Secondly, this theme introduces the implementation methods of the regional vertical electronic content in detail. The GPSolution software is used to receive specified GPS data log and store it. The codes are writed to deal with the GPS data in VC++6.0 environment. According to the data protocol of the dual-frequency GPS receiver, the corresponding data is extracted, calculated, displayed and so on. At the beginning, the figure of electronic content is displayed with the time changes. After the data smoothing and other appropriate treatment, a relatively clear tendency of the vertical electronic content is gained.Finally, in order to find out the change law of the ionospheric electron content, the local weather conditions are recorded, such as temperature, pressure, etc. We compare vertical electron content with local weather factors in one day and discuss the tendency of electronic content between different weather conditions.This topic's research is from the national 863 projects "the new technology research of using the multi-diameter signal to enhance the performance of the GNSS receiver", which is undertook by the navigation research institute and this result provide a reference data for positioning algorithm of GPS receiver.