Abstract
According to the problem that the positioning error increased with the increase of navigation time in the environment of complete lack of satellite signals such as viaduct and tunnel, the precise point positioning (PPP) / inertial navigation system (INS) tight coupled continuous positioning with non-holonomic constraint (NHC) and zero velocity update (ZUPT) in BeiDou navigation satellite system (BDS) was proposed. Firstly, the ionospheric composite model was analyzed from the aspects of observation equation, parameter estimation, fuzziness, degree of freedom and noise. The BDS PPP dynamic positioning model of ionospheric composite was established, and the errors that affect the positioning accuracy and convergence rate were analyzed. According to the motion characteristics of land vehicles, a scheme of velocity NHC was proposed to limit the accumulation of system positioning error with time, and ZUPT was used to increase the navigation accuracy of the integrated system when the vehicle was in the static state at the traffic light. The experimental results showed that the horizontal positioning accuracy of converged BDS PPP was better than 5 cm, the vertical positioning accuracy was better than 10 cm, and the dynamic positioning results are different from the high-precision real-time kinematic (RTK) / INS integrated navigation results by centimeters. The positioning accuracy of the system could be effectively improved by the BDS PPP/INS tight coupling method of NHC+ZUPT. Compared with the PPP/INS tight coupled positioning results without any constraints, the accuracy of the method in the three directions of East, North, and Up was increased by 0.08 m, 0.02 m and 0.01 m respectively.
Highlights
Precise point positioning (PPP) is the technique that enables centimeter- or decimeter-level positioning accuracy with only one receiver on a global scale [1], and was implemented on GIPSY software developed by themself, with positioning accuracy of 1-2cm
The results showed that the positioning accuracy could reach centimeter level after ambiguity fixed, the velocity and attitude accuracy were equivalent to DGNSS/inertial navigation system (INS) combination accuracy, and INS could speed up the re-fixed time of PPP under the condition of poor signal [24]
The nonholonomic constraint (NHC)+zero velocity update (ZUPT) BeiDou navigation satellite system (BDS) PPP/INS tight coupled continuous positioning method was proposed, which the velocity NHC was used to limit the accumulation of errors, and the ZUPT correction principle was used to increase the navigation accuracy of the integrated system when the vehicle was stationary at the traffic lights
Summary
Precise point positioning (PPP) is the technique that enables centimeter- or decimeter-level positioning accuracy with only one receiver on a global scale [1], and was implemented on GIPSY software developed by themself, with positioning accuracy of 1-2cm. Liu et al [21] implemented a tight coupling model of GNSS single-frequency PPP and low-cost INS, and analyzed the positioning performance when the number of satellites seen in the vehicle experiment was insufficient. The vehicle experimental results showed that the positioning accuracy of the loose coupling was dm level, the velocity accuracy was cm/s level, and the attitude angle error was better than 0.15◦. The experimental results showed that the tight coupled positioning accuracy was better than the loose coupling and the convergence rate of PPP under the constraints of INS could be accelerated [28]. BDS PPP MODELING AND ACCURACY ANALYSIS PPP technology uses the pseudorange and phase observations of a single receiver in combination with the precise products provided by the international GNSS service organization (IGS) to obtain the positioning results at centimeter level.
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