Research And Application Of Real-time Precision Point Positioning Based On SSR Corrections

Precise Point Positioning(PPP)is a hot topic in the field of GNSS in the past 20 years..Compared to traditional relative positioning,it is not limited by base station,the problem of high cost,so the precise point positioning technology are widely used in aerial photogrammetry,fast map updating,monitoring system,alarm system and other large projects.Compared to the precise point positioning technology,real time precise point positioning(RT-PPP)technology highlights the characteristics of real-time processing and obtains the current epoch results.It needs real-time and high-precision track and clock error data to solve.In the orbit clock difference products provided by IGS,the ultra fast and precise ephemeris prediction section is real-time product,but the accuracy is low.How to choose the right real-time track and clock error products is a problem.Due to the environmental impact of satellite signal in the process of propagation,there may be cycle slips and larger gross errors.Therefore,data preprocessing is necessary.In the process of locating and calculating,it is necessary to choose the appropriate mathematical model and parameter estimation method and take all the error items into consideration and correct them.In view of the above problems,this paper has done a systematic study,and the main contents are as follows:(1)The real-time precise point positioning is systematically studied: the ionosphere free combination model,UofC model,combination model based on non-original observations and comparative analysis of their advantages and disadvantages,this paper analyzes several commonly used stochastic model;studies the method of data preprocessing,mainly introduces the gross error detection,detection and repair the clock jump,cycle slip detection method;analysis and research on the real-time precise point positioning error and error correction model.(2)Two methods of sequential least squares and Calman filtering commonly used for parameter estimation are systematically studied.The design methods of the experiment estimation of these two parameters were studied.The results show that the Calman filter has higher computational efficiency than the sequential least squares method.Single and double system are investigated under the condition of dynamic and static precise point positioning based on BDS system and GPS system respectively.The results show that the precision of the positioning accuracy of double fusion system the single system has been improved to a certain extent,shorten the convergence time.(3)Real time precise single point positioning is realized based on real-time SSR correction information.First,the method of obtaining real-time ephemeris and clock error is studied,and compared with the super-fast extrapolation ephemeris and clock difference,the accuracy of the product is analyzed.By using these two real-time products,the real-time precise point positioning is realized,and the accuracy analysis is carried out respectively.The results show that the accuracy of the SSR real time ephemeris is close to that of the ultra-fast extrapolated ephemeris,and the accuracy of the clock difference is higher.In the positioning process,the use of SSR real-time product positioning accuracy is higher.(4)For receiving real-time streaming products in short time when broken,several clock error prediction methods are studied and two polynomial models are selected as the clock error by positioning the experimental analysis of the prediction accuracy,which provide solutions for future similar problems.At last,a set of real-time precision single point positioning software is written,which realizes the function of real-time data acquisition and recovery,precision single point positioning and quality analysis and evaluation.