Objectives Recognizing that the seriously occluded global navigation satellite system (GNSS) signals in urban environments and the rapidly accumulated micro-electro-mechanical system inertial measurement unit (MEMS IMU) errors would lead to the decline of GNSS/inertial navigation system (INS) positioning accuracy, a real-time precise positioning method named GNSS real-time kinematic (RTK) + time-differenced carrier phase (TDCP) /INS is proposed.
Methods In this method, the RTK positioning with fixed ambiguity is coupled with INS tightly to generate the navigation results when GNSS signals are well tracked. If GNSS signals are seriously blocked and the RTK solution fails but the TDCP solution succeeds, the TDCP measurements are coupled with INS tightly for navigation. Moreover, if TDCP solution also fails, the INS is used for reckoning navigation.
Results Vehicle experiments have been carried out on the campus of Wuhan University and its surroundings. The results show that the success rate of TDCP solution with multi-GNSS is close to 90% on urban roads except for tunnels and other closed scenes.More importantly, even in an adverse scene where the continuous time of RTK solution failure is less than 45 s, the root mean square errors of the TDCP/INS solution are only 0.30 m and 0.21 m, and its maximum errors are 0.69 m and 0.72 m, respectively, in the horizontal and vertical directions.
Conclusions The experimental results have demonstrated that a decimeter-level real-time navigation accuracy is achievable with this method.
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