Research On Main Algorithm Of GPS/GLONASS/BDS Integrated Navigation And Positioning

Satellite Navigation and Positioning has been gradually walking into the era of a integrated system,with whose developing rapidly.The integrated system contribute to solving the single system in certain cases that insufficient number of visible satellites,poor geometric satellite distribution,not high reliability and disability in resisting the gross error.Therefore,combining GPS,GLONASS and BDS into a GPS/GLONASS/BDS integrated system(hereafter referred to as Three Integrated System)is a trend of Satellite Navigation and Positioning.When the GPS,GLONASS and BDS are combined,it easily occurs fault satellites and affect the accuracy and reliability of navigation and positioning with multiple satellites,on account of different performance and character of system.Therefore,the problem that how to reasonably combine different system and how to evaluate the performance of integrated system has to be settled urgently.This article has analyzed the error of integrated navigation and positioning and the computing method of satellite coordinate,established the functional model of Three Integrated System,and studied the weight ratio in stochastic model and performance evaluation of integrated system,starting from the time system and coordinate system of GPS,GLONASS and BDS.The main content are as following:Firstly,according to the error analysis of orbit determined by broadcast ephemeris of Three Integrated System,the weight of different satellite navigation and positioning system and different style of satellite orbit is researched.The weight of coefficient matrix of WTLS and initial weight of Robust Helmert VCE are determined by it.Secondly,in consideration of the time system and coordinate system,this article has established the functional model of single epoch algorithm and multiple epoch algorithm in Three Integrated System.The least squares-total least squares(LS-TLS)and the weighted total least squares(WTLS)are studied,and whose application in the functional model of integrated system is researched,considering the error of coefficient matrices.Analysis from experimental data shows that the precise of LS-TLS is lower and the precise of WTLS is equal,compared with the least squares(LS),on account of no ephemeris gross error.The gross error can be removed through total least squares(TLS)on account of existing ephemeris gross error.Thirdly,considering the weight ratio of observed value in combining GPS,GLONASS and BDS,on condition that the observed values are independent of each other of different navigation and position system,the traditional equal weight model and elevation model are researched..And the method of determining the weight ratio in pseudo-range observations of Three Integrated System through robust Helmert variance component estimation(Robust Helmert VCE).Then the effect of resisting gross error of pseudo-range observations is studied.Analysis from measured data shows that Robust Helmert VCE is more suitable for Three Integrated System.Fourthly,On account of the problem that the method of traditional algorithm about dilution of precision(DOP)is not accurate,the algorithm of DOP based on posterior weight(PW-DOP)and satellite selection algorithm based on PW-DOP are proposed.And the algorithm of integrated navigation and positioning about preserving accuracy and promoting the computing efficiency is discussed via combining satellite selection algorithm and Robust Helmert VCE.Fifthly,on consideration that ‘fault satellite' will appear easily when combining the GPS,GLONASS and BDS,the application of receiver autonomous integrity monitoring(RAIM)about detecting ‘fault satellite' through the method of least squares residuals(LSR)and correlation analysis(CA)based on hypothesis testing of linear regression are studied.The experimental data shows that the two methods are equal in detecting fault of satellite navigation and positioning.And the availability of RAIM in GPS is better than that in Three Integrated System according to the measured data.Finally,according to the analysis of experimental data,the effect of different method of combining,different measured environment in shade of tree or beside high-rise building,different measured district and different measured time span,epoch and interval is studied in navigation and positioning.