Research On Precise Point Positioning Method Based On FCB/UPD Ambiguity Fixing

With the development of society,satellite navigation and positioning users have higher and higher requirements for accuracy and real-time positioning results.Precision point position(PPP)uses high-precision precise ephemeris data,and the number of users is not limited.However,traditional PPP technology generally uses floating-point solutions,and its accuracy and convergence are not as good as network RTK(Network Real Time Kinematic,NRTK).To solve this problem,a ambiguity fixation method based on FCB/UPD(Fraction Cycle Bias / Uncalibrated Phase Delay)is proposed.This method is characterized by using the wide lane FCB and narrow lanes calculated on the network side.FCB products are sent to users,and a one-way broadcast is carried out between the reference network and users.After the users receive the products,they realize precise single-point positioning with fixed ambiguity.Starting from the basic observation model of GNSS(Global Navigation Satellite System)positioning,this article discusses the principle of precise single-point positioning and the combined model of observations,and discusses the main sources of errors in positioning and their correction methods.Analyze the parameters affecting the integer characteristics of the ambiguity,determine the network-side and user-side positioning models,use the observation data of the Beidou ground-based augmentation system reference station to realize the precise single-point positioning based on the FCB/UPD ambiguity fixed,and develop the FCB/UPD-based The precise singlepoint positioning solution software with fixed ambiguity realizes the conversion from theoretical research to practical application.The main tasks of this paper are:(1)Starting from the basic GNSS observation equation,the positioning error model is studied,the error correction method is given,and the observation model of single-difference precision single-point positioning between satellites is derived,which improves the precision single-point positioning method.(2)Aiming at the parameters that affect the integer characteristics of the ambiguity,a precise single-point positioning method that can realize the ambiguity fixation is proposed,and the specific process of the ambiguity fixation is given.(3)Based on the original observation data of the frame network reference station of the Beidou Ground-based Augmentation System,the characteristics of the satellite wide lane UPD and narrow lane UPD are studied.By discussing and analyzing the observation data and observation conditions,the ambiguity of the user terminal is fixed,and the static and imitation dynamic positioning solutions are performed.The results show that: using the FCB/UPD ambiguity fixed model to solve PPP,the positioning accuracy of static PPP and imitation dynamic PPP is improved to a certain extent,the convergence time is greatly reduced,the static PPP convergence time can reach within10 minutes,and the imitation dynamic PPP convergence time can be Within 15 min.(4)Using Visual Studio 2019 platform,the positioning software based on FCB /UPD is designed and developed.According to the requirements of software function,design software function module,optimize the operation process of each module,and analyze and verify the software output results.