Key Techniques Of BDS/GNSS Multi-frequency Carrier Phase Differential Positioning

The focuses of research are quality control of observations,mathematical modelling,and integer ambiguity validation revolved around Chinese Bei Dou Navigation Satellite System(BDS),capitalizing on multi-system and multi-frequency signal construction of gloabal navigation satellite system(GNSS),to improve BDS/GNSS carrier phase differential positioning performance in terms of precision,integrity,continuity,and availability,in order to satisfy required navigation performance of high-precision navigation and positioning fields under challenging signal environments.The outline of the thesis is as follows:(1)Cycle slip detection and repair method based on epoch-between double differential modelling for a single frequency receiverUnder the coexistence of multiple severe conditions including single frequency,single receiver,kinematic situations,and active ionosphere period,cycle slip detection and repair is a challenge for the traditional methods.In order to solve the problem,the satellite-related,atmospheric-related,and receiver-related errors on cycle slip is analyzed under the multiple severe conditions.The suppression of atmospheric errors is explored by the epoch-between double differential model and the cycle slip detection and repair method based on epoch-between double differential modelling for a single frequency receiver is proposed.The proposed method is tested by using single frequency BDS observations in static and kinematic environments.The results show that,under the active ionosphere and long interval conditions,the proposed method can achieve better performance of cycle slip detection and repair than the traditional methods,which reflects the proposed method can further improve the quality control performance of carrier phase observation.(2)Measurement-domain inter-satellite-type bias(ISTB)detection and repair for BDSCarrier phase differential positioning between mixed BDS recievers is adversely affected by the inter-satellite-type bias(ISTB).In order to eliminate the influence of the ISTB,a measurement-domain ISTB detection and repair method is proposed by analyzing the relation between ISTB and carrier phase observations.BDS receivers from different manufacturers are used for testing performance of carrier phase differential positioning with unrepaired ISTB and repaired ISTB,respectively.The results show that,the proposed method can detect and repair ISTB rapidly and accurately.Meanwhile,repairing ISTB can effectively guarantee the reliability of BDS carrier phase positioning.(3)Mutli-system and multi-frequency tightly coupled differential positioning by calibaring inter-system and inter-frequency biasesCarrier phase differential positioning may be undermined under the challenge signal environments.In order to further improve the positioning performance,multi-system and multi-frequency GNSS tightly coupled models with overlapping frequency and non-overlapping frequency are proposed by calibrating the inter-system and inter-frequency biases(ISB/IFB)in multi-system and multi-frequency GNSS.The ISB/IFB are estimated by analyzing their temporal and spatial variation characteristics.Because of non-overlapping frequency bias(NOFB)is a crutial factor for non-overlapping frequency case,minimizing the difference between non-overlapping frequency and optimal estimation of pivot single differential ambiguity resolution are conducted to eliminate the influence of NOFB on the ambiguity resolution.The proposed method is tested by collecting the kinematic data.The results show that,the proposed method can achieve better positioning performance than the traditional method in the challenge signal environments with limited available satellites.(4)Adaptive ionospheric weighted model based on the constraints of ionospheric rate.Ionospheric weighted model with fixed empirical parameters cannot achieve optimal positioning performance under different ionospheric environments.In order to solve the problem,a real-time adaptive ionophseric weighted model based on the ionospheric rate is proposed.The ionospheric rate is computed by analyzing the relation between multi-frequency observations and ionospheric delay errors.The weighted parameters of the proposed method can adaptively adjust according to different ionospheric conditions.The proposed method is tested by collecting the BDS data under peace and active ionospheric conditions.The results show that,the proposed method can adaptively adjust the weighted parameters according to the variation of ionospheric delay and obtain the optimal ambiguity resolution and positioning performance.(5)Multi-frequency ionosphere-free and variance-restricted modelExcessive amplification of combined noise is a limiting factor of the traditional ionosphere-free model for ambiguity resolution.In order to solve the problem,analyzing the relation between the combined wavelength and the combined noise,and according to minimization criterion of ratio of combined noise and combined wavelength,an ionosphere-free and variance-restricted model is proposed by using ultra-wide lane(EWL)and wide lane(WL)ambiguity constraints.The proposed method is tested by using a series of BDS data with different baseline lengths.The test results show that,the proposed method can better restrict the combined noise and improve the success rate and rapidity of ambiguity resolution.(6)False alarm and missed detection probability controllable GNSS ambiguity validationSimultaneous control of false alarm and missed detection probability is a challenge for ambiguity resolution to satisfy the positioning continuity and integrity.In order to solve the problem,false alarm and missed detection probability controllable GNSS ambiguity validation is proposed for the integer rounding(IR)method and integer least-squares(ILS)method,respectively.By analyzing distribution characteristics of the IR method and the ILS method in ambiguity-domain,statistics and detection thresholds are constructed based on false alarm and missed detection probability requirement,to achieve the simultaneous control of false alarm and missed detection probability.The proposed method is tested by using BDS kinematic data.The results show that,the proposed method can satisfy both the requirements of false alarm and missed detection probability and achieve the optimal balance between the positioning integrity and continuity.