Tightly Coupled Integration of BDS-3 B2b RTK, IMU, Odometer, and Dual-Antenna Attitude

Real-time kinematic (RTK) based on single-frequency observation is still widely used in many fields due to the characteristics of low-cost and low-power consumption. However, the positioning performance of single-frequency RTK in terms of accuracy, stability, and continuity would be significantly degraded during the harsh satellite environments. To improve the performance, this contribution presented a model of multisensor and analytical observations augmented the single-frequency RTK tightly based on a modified Psi-angle state model. In such a model, the single frequency observations of the new signal of third generation BDS (BDS-3) B2b are tightly integrated with inertial measurements, odometer data, dual-antenna attitude, and nonholonomic constraint (NHC). To evaluate the presented model, the typical navigation performance and the ambiguity resolution (AR) performance are analyzed based on a set of vehicle-borne data. Results illustrated that the inertial navigation system (INS) would bring about 13.5%, 16.2%, and 12.3% position enhancements to the BDS-3 B2b RTK mode. Such improvements could be up to 15.9%, 16.2%, and 25.2% while adding the NHC and odometer data. Besides, NHC and odometer also upgrade the attitude accuracy visibly in pitch and heading directions, with enhancements of about 16.9% and 62.9%. In contrast, augmentations from the dual-antenna attitude are mainly presented in terms of heading angle with about 29.5% compared to the RTK/INS/Odometer/NHC tight integration mode. Besides, the convergence time of yaw angle is visibly enhanced while using the odometer/NHC, the dual-antenna heading, or the two together. Moreover, the AR performance could also be improved while using the presented model. Due to the enhancements in position and attitude brought by different sensors, the ADOP performance would be improved to varying degrees. Besides, the fixed rate and reliability of AR could also be enhanced.