Research On The Key Technology Of GNSS High-Precision Positioning And Heading Determination

Global Navigation Satellite System(GNSS)receiver can provide high-precision positon and heading information for a vehicle.Availability and accuracy are the key indicator to judge a GNSS receiver.The accuracy of position and heading depends on the error control,therefore GNSS error control technique improve accuracy at the source.Carrier phase measurement contains integer ambiguity,therefore integer ambiguity resolution technique is the precondition of carrier phase relative positioning.Baseline length information constraint technique can improve availability and accuracy by means of combining baseline length information and measurement information.This work is focus on researching the key technology to improve the availability and accuracy in GNSS high-precision positioning and heading in consideration of the current development direction of multi-constellation and multi-frequency.1)For GNSS error control technique,the research is carried out to improve the positioning accuracy of the two main positioning mode in GNSS receiver.The raw measurement is modeled and its error characteristic is analyzed.Different parameter estimation methods are deduced and their performance is analyzed.Then modified algorithms are proposed to improve the accuracy in pseudo-range point positioning and carrier phase relative positioning according to the error characteristic and estimation method performance analysis.A positioning algorithm assisted by different GNSS time bias is proposed.The pseudo-range point positioning model based on different GNSS time bias is designed.The Extended Kalman Filter(EKF)for the designed positioning model is deduced.The proposed algorithm takes full advantage of the prior information that the GNSS time bias is more stable than receiver clock bias to improve the position accuracy in multi-constellation pseudo-range point positioning.A carrier phase measurement quality control algorithm is proposed based on Double Differenced(DD)Geometry Free(GF)model.The measurement error is modeled and the theoretical error detecting threshold is designed to detect abnormal large multipath and gross error in DD carrier phase measurement.The proposed algorithm improves the accuracy of the carrier phase relative positioning.2)For integer ambiguity resolution technique,the research is carried out to improve the performance of two common integer ambiguity methods.The original performance,advantages and disadvantages of different methods are analyzed.Then modified algorithms are proposed to improve the performance for Integer Least Squares(ILS)and Integer Bootstrapping(IB)integer ambiguity resolution methods.A Wide Lane(WL)and Narrow Lane(NL)dual frequency Least-squares AMBiguity Decorrelation Ajustment(LAMBDA)algorithm is proposed.The searching space is constrained by means of the relationship between the WL and dual frequency integer ambiguity.The Ratio test is improved by means of the relationship between the WL,NL and dual frequency integer ambiguity.The proposed algorithm improves the success rate of dual frequency ILS integer ambiguity resolution method.A self-corrected integer ambiguity resolution algorithm based on WL rounding is proposed.The error detector and theoretical detection threshold is designed according to the specific characteristic of WL and dual frequency integer ambiguity to fix one cycle WL integer ambiguity error.The proposed algorithm solves the problem of the low WL integer ambiguity resolution success rate in IB integer ambiguity resolution method.3)For baseline length information constraint technique,the characteristic and shortage of baseline length information constraint are analyzed.The modified algorithms for helping integer ambiguity resolution and improving the baseline vector parameter accuracy are proposed.A dual frequency long-short baseline ambiguity resolution algorithm is proposed.The harsh requirement of short baseline length in original long-short baseline method is loosened according to the WL constraint and dual frequency error strip constraint.The proposed algorithm solves the problem that the size of high-precision antenna is not suitable for the long-short baseline method.A dynamic baseline vector resolution algorithm based on previous baseline length information is proposed.The model for combining previous baseline length information and current measurement is designed.The optimal weight and the theoretical gain are deduced.The proposed algorithm improves the carrier phase relative positioning accuracy in baseline length constant environment by means of the full usage of the previous baseline length information.