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A Method for Real-Time Decimeter Solutions Over Long Baseline With BDS Triple-Frequency Signals

Relative positioning with global navigation satellite system (GNSS) is one of the main techniques to achieve high precision positioning, however, due to the influence of spatial errors such as atmospheric errors, there are still some problems with a single reference station over long baseline. In this paper, based on the BDS triple-frequency carrier, a real-time decimeter-level positioning method for long-distance under a single reference station is proposed to meet the requirements in daily life. Firstly, the ambiguity of extra-wide-lane (EWL) observation is fixed by a single epoch, which is characterized by long wavelength and small error. Then, the initial value of the ionospheric delay is solved on this basis, and the idea of smoothing is introduced to further optimize the ionospheric delay by Hatch filter. Finally, the optimal combined observation with a minimum standard deviation (STD) of positioning is constructed. Both static and kinematic tests are conducted to verify the effectiveness and performance of the proposed method. The results show that under different lengths of baseline, the positioning accuracy of each epoch can be controlled within 0.5m in the north (N), east (E), and up (U) three directions and is uniform among all epoch. In the long baseline, the positioning result based on the optimal combined observations is much better than the pseudo-range and other combined observations in terms of accuracy and stability. Moreover, the method can realize real-time and decimeter-level positioning in static and low kinematic environments, especially in the time when the ionosphere is more active.