Regional Gps Ionospheric Tec Monitoring, Modeling, And Applications

In Global Positioning System (GPS), one of the major error sources is Ionospheric propogation delay. Especially after the USA government declared off the SA policy, the error caused by ionosphere has become the largest fraction which influence the accuracy of GPS positioning. Using suitable Ionospheric models, this error can be corrected and position accuracy using GPS can be improved. From the angle of actual application, this paper described the principles and methods of monitoring the ionosphere by GPS in detail, presented several correcting models for ionosphere delays, established the regional ionospheric model software system ,and then, constructed the database of long time series of VTEC using observations data, including the CMONC and SCGAN. With deep research on the characteristic of VTEC diurnal variation and data method, we have formed long-time series of characteristic parameters diurnal variation of VTEC above Yang-zi delta, and then summarized the law of it. Especially according to the actual needs of Chinses GNSS development, we pointed out inaccuracy of the parameters setting, and improved the Klobuchar Ionospheric Model broadcast by GPS satellites to provide a more accurate forecast model for correcting the Ionospheric propogation delay in GNSS. On the base of these GPS data, we researched and monitored the ionopheric disturbances, and enunciated the spatio-temporal variation characteristic of ionosphere over china area in magnesicstorm of Nov10, 2004. It can be generalized as follows:1. This paper described the data processing methods of getting ionspheric delay using dual-frequency observation of GPS. It described the method to deduct the hardware delay from TEC, introduced the ionosphere single layer model and the algorithm of Grid based Ionospheric model. And then it introduce the way of how to make use of dual-frequency observations to set up ionosphere model in local area. After that, we mainly focused on VTEC polynomial model(POLY), generalized trigonometric series function (GTSF) model, low degree and order spherical harmonic function (TSF) model etc. Then the verification results are presented.2. This paper attempts to study the variations and actions of the ionospheric TEC above Yanzi-Delta by using a span of one-year series of absolute TEC, which is obtained from Shanghai Comprehensive GPS Application Network (SCGAN) and Crustal Motion Observation Network of China (CMONC) in 2004. From the TEC data, using several kinds of data processing methods, such as Gauss weight function and running smooth, the diurnal, seasonal, annual variations of ionosphere above Yanzi-Delta area analyzed and discussed, and the winter anomaly is also revealed. Meanwhile, using the method of spectrum analysis, such as Fast Fourier Transform (FFT), the periods of TEC variation have come out.3. In Global Positioning System (GPS), the 8 parameter Klobuchar type ionospheric delay model is broadcast to predicts the global vertical TEC distribution at a given time period for real-time correcting the ionospheric effect on for single frequency GPS measurements. Using the original Klobuchar model, about 60% of the ionosphere delay effects can be corrected...