Analysis and Evaluation of Network Real-time Kinematic Positioning Performance Based on Standalone BDS Receivers

Objectives: With the completion and operation of China's Beidou-3 navigation satellite system (BDS-3), the BDS provides all-time, all-weather and high-accuracy positioning, navigation and timing services to global users. Network real-time kinematic (NRTK) technology, as the primary means of high-precision positioning for BDS, has been widely used in various fields. And the demand for development and promotion of the homemade standalone BDS receivers has been increasingly growing in recent years. Methods: The data of standalone BDS receivers will be process by the NRTK software PowerNetwork, which developed independently by Wuhan University, to analyze and evaluate the NRTK performance. Sinan M300 Pro standalone BDS receiver is used to collect data at four stations in Wuhan, and then the performance in three aspects, namely the ambiguity resolution between reference stations, generation of regional augmentation products, and real-time positioning for rover stations are comprehensively evaluated. In the first aspect, the ionospheric-free three-carrier ambiguity resolution (IF TCAR) method is used to process the three-frequency observations of BDS-2, while the B1I+B3I dual-frequency observations of BDS-2/3 are processed by the MW method. In the second aspect, the corrections including dispersive and non-dispersive errors for the rover station are obtained by linear interpolation algorithm. In the positioning calculations, the Kalman method is employed to determine the float ambiguity, and then the optimal position of the rover station is obtained after the ambiguity is processed by the LAMBDA algorithm. Results: The experimental results show that the average standard deviation of the wide-lane ambiguity and the original double-difference ambiguity residuals of the three baselines is better than 0.1 cycle, which can determine the ambiguity reliably in the first aspect. In the second aspect, the accuracy of the ionospheric delay and non-dispersive errors for all visible satellite pairs is better than 1.00 cm and 0.5cm; In the last aspect, the fixed rate and correctly fixed rate of the ambiguity for the rover are 99.72% and 96.55%, respectively. And the RMS values in the horizontal and elevation directions are better than 1cm and 5cm, respectively. Conclusions: The service performance of the homemade standalone BDS receivers in the above three aspects is not significantly different from that of multi-system GNSS receiver, and the final positioning accuracy can meet the needs of high-precision surveying and mapping.