Estimation Of Electromagnetic Wave Refraction Parameters By Singular Ground-based GNSS

The Global Navigation Satellite System (GNSS) have been applied successfully not only in the traditional field such as ranging, time service, and navigation, but also in environmental monitoring, geodesy, astronomy, and meteorology and so on. Estimation of electromagnetic wave refraction parameters based on singular ground-based GNSS has been one of hot topics in the international area. On the basis of theoretical study on GNSS point positioning, real time and high accuracy estimation of electromagnetic wave refraction parameters, experimental verification and application are studied in this dissertation. The main topics and results of the study are as follows:First, main errors consist of satellite error, receiver error, and space propagation error in GNSS point positioning, and corrected methods are analyzed. The characteristic of traditional stochastic models are discussed, and a new stochastic model is introduced. Two results of zenith tropospheric delay estimation by the above two stochastic models are compared and analyzed.Second, traditional models, for example, Hopfield model, Saastaoinen model and MOPS model, and radiosonde measuring zenith tropospheric delay are discussed, as well as their limitation. Based on precise point positioning and introducing stochastic model, the zenith tropospheric delay estimation by singular ground-based GNSS is realized. Results of GNSS agree well with those of radiosonde, the precision of GNSS have the same order with IGS products which are computed by GIPSY.Third, the estimation means of real time slant path tropospheric delay calculation at very low elevation are studied systemically. The limitations of existent mapping function, experiential model and radiosonde are analyzed in detail. A method of computing real time tropospheric slant delay at low elevation by singular ground-based GNSS is introduced. Observations in August 2008 are disposed. The corresponding results have well agreement with those of radiosonde, and are better than those of conventional models. Consequently, the estimation by singular ground-based GNSS is implemented.Fourth, real time bending angle estimation by singular ground-based GNSS station is studied. The previous methods of calculating the bending angles based on refractivity profile from refractivity climatology model and radiosonde are presented. The relationship of bending angle of radio waves with Doppler frequency shift is given and analyzed in detail. Main error sources of Doppler observations are presented and discussed. Some singular ground-based GPS observation and radiosonde measurements are analyzed. The bending angles calculating from Doppler agree fairly well with those from radiosondes. The method that is based on singurlar ground-based GNSS is introduced.Fifth, the real time inversion method of refractivity profile based on singular gound-based GNSS is introduced. Emulation is achieved by ten years historical data in Shantou and the feasibility is validated initiativly. A singular ground-based GPS observation experiment in eastsouth china is carried out. The real time inversion of refractivity profile is implemented and detailed analyzed. The feasibility and effectiveness is validated.