Theory And Method Of GNSS Precise Point Positioning And Its Quality Control

With the modernization of GPS and GLONASS,and the rapid development of BDS and Galileo,Multi-GNSS precision positioning urgently needs the theory and method of Multi-GNSS data processing.In this thesis,the theory and method of GNSS precision point positioning(PPP)and its quality control are studied.Firstly,the unified model expression and the performance of Multi-GNSS PPP are analyzed.Secondly,the Multi-GNSS PPP ambiguity resolution and its verification method are investigated.Furthermore,the construction method of ionospheric delay model based on PPP with original observations is presented.Finally,the theory and method of PPP quality control and quality analysis are introduced.The main innovations and works are as follows,(1)Considering the data processing strategy of IGS analysis center,all kinds of biases in GNSS PPP model are clarified and deduced.The PPP filtering model and parameter estimation method are discussed.(2)In view of the different representations of Multi-GNSS PPP model and the lack of comprehensive analysis of the Multi-GNSS PPP performance,the unified Multi-GNSS PPP model is investigated.At the same time,the performance of the ionosphere-free PPP and the zero combined PPP are compared.The experimental results show that Multi-GNSS PPP can accelerate the convergence speed and improve positioning accuracy with respect to GPS only PPP.The performance of positioning accuracy and convergence speed are consistent with different GNSS PPP model.(3)A PPP algorithm considering the influence of GLONASS pseudo-range internal frequency bias(IFB)is proposed.The unified expression of the algorithm in the ionosphere-free PPP and zero combined PPP is given.The validity of the method is verified by GLONASS data.The results show that the method can effectively weaken the influence of GLONASS pseudorange IFB.The PPP convergence speed and residual distribution of the new method are better than those of the traditional method.(4)A simplified Multi-GNSS PPP method is proposed.Based on ionosphere-free PPP model,only GPS pseudo-range observations are used.The pseudo-range observations of other GNSSs are discarded.The influence of GLONASS pseudo-range IFB and BDS pseudo-range deviation are avoided.The experimental results show that when the number of GPS satellites is enough,the positioning accuracy and convergence speed of the simplified PPP model are consistent with the traditional PPP method.(5)According to the characteristics of GPS,GLONASS and BDS observations,firstly,the PPP ambiguity resolution methods of GPS,GLONASS and BDS are studied.Secondly,the non-integer property of PPP ambiguity is discussed.Based on the zero differenced FCB separation method,the accuracy and stability of different GNSS FCBs are analyzed.Finally,the user PPP-AR method with different system combinations is analyzed.The experimental results show that 1)PPP-AR can improve the positioning accuracy with short time observations.2)The performance of initial fixed time and ambiguity fixed rate of BDS are poor,due to the slow spatial geometry change of BDS constellation.The BDS/GPS combined PPP can improve the first fixed time and fixed rate of BDS ambiguity.3)The positioning accuracy of GLONASS zero differenced PPP-AR and ionosphere-free PPP-AR are comparable to each other.The first fixed time and fixed rate of GLONASS zero differenced PPP-AR are slightly better than ionosphere-free PPP-AR.At the same time,GPS/GLONASS combined PPP-AR can effectively shorten the first fixed time of ambiguity resolution and improve the fixed rate of ambiguity.(6)The Bayesian posterior probability test is introduced into the verification of PPP ambiguity.Integrating ratio test and Bayesian posterior probability test,a quality control method of PPP-AR is proposed.The experimental results show that: 1)The PPP-AR verification method based on Bayesian posterior probability directly gives the confidence level of ambiguity resolution,which is more intuitive and more rigorous than ratio test.2)The quality control method of PPP-AR can effectively eliminate the influence of low quality ambiguity and improve the fixed rate of PPP-AR and positioning accuracy.(7)The construction method of regional and global ionospheric delay model based on PPP with original observations extend the application mode of PPP.Firstly,the ionospheric delay is estimated based on PPP without and with prior information constraints.Secondly,the spherical harmonic function is used to construct the regional and global ionosphere.The precision of the constructed ionospheric model and DCB are analyzed and evaluated.Finally,how the accuracy of ionospheric model can influence of PPP is analyzed.The experimental results show that: 1)the ionospheric model based on PPP can effectively reflect the spatial and temporal characteristics of the ionosphere,and the accuracy of ionospheric VTEC is comparable to that of GIM model published by CODE.2)When the precision of the ionospheric model is enough,it can be used as a priori information for PPP,which can accelerate the convergence speed and positioning accuracy of PPP with short time observation.(8)The theory and method of PPP quality control and quality verification are discussed.Firstly,a variety of methods are used to ensure the reliability of the PPP results in data preprocessing and parameter estimation stage of PPP.Secondly,the relationship between position parameter covariance and actual positioning accuracy of PPP are analyzed.At the same time,the cross validation method of PPP results with different GNSS combinations is studied,which can effectively check the accuracy and reliability of PPP results.Finally,due to the lack of effective evaluation method for positioning accuracy of dynamic PPP,an improved method of PPP integrity protection level calculation is proposed,which can effectively evaluate the positioning bias of PPP.