Research On BDS-3 Three-frequency Cycle Slip Detection Repair And Joint GPS Precise Point Positioning Technology

With the comprehensive completion of the ‘three-step’ strategic plan of my country’s navigation satellite system,the third-generation Bei Dou-3 Navigation Satellite System(BDS-3)has been officially serving the world for more than two years.BDS-3 not only has the functions of high-precision positioning,accurate and reliable timing and speed measurement,but also provides Beidou short-message communication services for users.In addition,BDS-3 has the advantage of providing users with abundant signals(B1I,B1 C,B2a,B2 b and B3I).However,in the process of actual navigation and positioning,the cycle slip phenomenon in the carrier phase observation value will cause errors in the solution of the whole cycle ambiguity,thus affecting the positioning accuracy.Therefore,aiming at the above problems,this thesis mainly studies the BDS-3three-frequency cycle-slip detection and repair technology,and proposes a new method suitable for BDS-3 three-frequency cycle-slip detection and repair;At the same time,in order to provide more reliable and convenient high-precision positioning services in view of the imperfection of precision products in the early stage of BDS-3,this thesis combines BDS-3 with Global Positioning System(GPS)for Precision Point Positioning(PPP)and analyzes the observation data and positioning results.The main work and innovations of this thesis are as follows:(1)BDS-3 three-frequency cycle slip detection and repair.Aiming at the phenomenon that small cycle slips and insensitive cycle slips are difficult to detect and repair in the BDS-3 positioning process,based on the traditional three-frequency pseudorange-phase method,this thesis proposes an efficient and reliable BDS-3 three-frequency cycle slip detection and repair method.Firstly,to solve the problem of excessive pseudorange noise in the traditional pseudorange-phase combination,doppler observations are introduced to enhance the detection ability of small cycle slips.Secondly,the doppler-assisted pseudorange-phase combination is combined with free geometric phase combination for joint detection makes up for the lack of insensitive cycle slip detection capability.In terms of signal,B2 a was chosen to replace B2 I,together with B1 I and B3 I constituting the Beidou three-frequency observation combination with better positioning performance in BDS-3,and the threefrequency observation combination with longer wavelength,smaller ionospheric delay,and lower standard deviation was selected by comparison.The combination of frequency coefficients is used to detect cycle slips.In terms of repairing,the cycle slip value of the solution is rounded,and the accuracy of the repairing value is ensured according to the 1-norm principle.The experimental results show that: under the condition of 1s sampling rate and stable ionospheric delay,the proposed method can detect and repair all added general cycle slips,small cycle slips and insensitive cycle slips,which verifies the feasibility of joint detection and repair of cycle slips by combining doppler-assisted pseudorangephase combination and geometric phase-free combination.(2)Research on the performance of BDS-3/GPS joint three-frequency PPP model.In order to improve the positioning accuracy and convergence speed of BDS-3 precise point positioning,this thesis proposes a BDS-3+GPS combined three-frequency PPP scheme.Firstly,based on RTKLIB software,the data quality analysis of BDS-3 and GPS observation data was carried out in terms of satellite visibility,sub-satellite point trajectory,signal-to-noise ratio and multipath effect,etc.Secondly,the BDS-3+GPS three-frequency mathematical model was studied on the basis of the PPP observation model,which analyzed the deviation between the respective signal frequencies of BDS-3 and GPS and the deviation between BDS-3 and GPS systems;And completed the construction of reasonable parameter models for BDS-3+GPS three frequency ionospheric free pairwise combination(IF-1213),ionospheric free combination(IF-123),and non differential non combination(UC-123).Finally,the performance analysis of the three kinds of PPP models of BDS-3+GPS is carried out from static and pseudo-dynamic perspectives using GAMP software.The results of the PPP solution show that after adding the GPS joint positioning,the positioning accuracy and convergence speed of the static PPP and dynamic PPP solutions have been significantly improved: statically,the average positioning accuracy of the east,north,and upper directions are respectively 2 cm,1.2 cm and 3.4 cm,increased by 28.6%,31.4% and 27.9% respectively;the average static convergence time are 22.1 min,16.3 min and 27.2 min,respectively increased by 57.7%,58.8% and 57.6%;Dynamic aspect,the average positioning accuracy in the three directions are 5.3 cm,4 cm and 7.1 cm,respectively,which has been increased by 27.8%,18.8%,and 26.9% respectively;The average convergence time in the three directions are 32.7 min,25.7 min and 37.2 min,which has been increased by 54.2%,60.2% and 53.7%.