The BeiDou global navigation satellite system (BDS-3) constellation deployment has been completed on June 23, 2020, with a full constellation comprising 30 satellites. In this study, we present the performance assessment of single-epoch Real-Time Kinematic (RTK) positioning with tightly combined BeiDou regional navigation satellite system (BDS-2) and BDS-3. We first investigate whether code and phase Differential Inter-System Biases (DISBs) exist between the legacy B1I/B3I signals of BDS-3/BDS-2. It is discovered that the DISBs are in fact about zero for the baselines with the same or different receiver types at their endpoints. These results imply that BDS-3 and BDS-2 are fully interoperable and can be regarded as one constellation without additional DISBs when the legacy B1I/B3I signals are used for precise relative positioning. Then we preliminarily evaluate the single-epoch short baseline RTK performance of tightly combined BDS-2 and the newly completed BDS-3. The performance is evaluated through ambiguity resolution success rate, ambiguity dilution of precision, as well as positioning accuracy in kinematic and static modes using the datasets collected in Wuhan. Experimental results demonstrate that the current BDS-3 only solutions can deliver comparable ambiguity resolution performance and much better positioning accuracy with respect to BDS-2 only solutions. Moreover, the RTK performance is much improved with tightly combined BDS-3/BDS-2, particularly in challenging or harsh conditions. The single-frequency single-epoch tightly combined BDS-3/BDS-2 solution could deliver an ambiguity resolution success rate of 96.9% even with an elevation cut-off angle of 40°, indicating that the tightly combined BDS-3/BDS-2 could achieve superior RTK positioning performance in the Asia–Pacific region. Meanwhile, the three-dimensional (East/North/Up) positioning accuracy of BDS-3 only solution (0.52 cm/0.39 cm/2.14 cm) in the kinematic test is significantly better than that of the BDS-2 only solution (0.85 cm/1.02 cm/3.01 cm) due to the better geometry of the current BDS-3 constellation. The tightly combined BDS-3/BDS-2 solution can provide the positioning accuracy of 0.52 cm, 0.22 cm, and 1.80 cm, respectively.

中文翻译：

---

紧密结合的BDS-2和新近完成的BDS-3的单时间RTK性能评估

北斗全球导航卫星系统（BDS-3）星座部署已于2020年6月23日完成，完整的星座包括30颗卫星。在这项研究中，我们提出了将北斗区域导航卫星系统（BDS-2）和BDS-3紧密结合在一起的单周期实时运动（RTK）定位的性能评估。我们首先研究在BDS-3 / BDS-2的传统B1I / B3I信号之间是否存在代码和相位差分系统间偏差（DISB）。已经发现，对于在其端点处具有相同或不同接收器类型的基线，DISB实际上约为零。这些结果表明，当将传统的B1I / B3I信号用于精确的相对定位时，BDS-3和BDS-2是完全可互操作的，并且可以被视为一个没有其他DISB的星座。然后，我们初步评估了紧密结合的BDS-2和新完成的BDS-3的单周期短基线RTK性能。使用歧义分辨率成功率，歧义精度稀释以及运动和静态模式下的定位精度（使用在武汉收集的数据集）来评估性能。实验结果表明，相对于仅BDS-2解决方案，当前的仅BDS-3解决方案可以提供可比的歧义分辨率性能和更好的定位精度。此外，紧密结合的BDS-3 / BDS-2大大提高了RTK性能，特别是在挑战性或恶劣条件下。单频率单历元紧密结合的BDS-3 / BDS-2解决方案即使仰角截止角为40°，也可以实现96.9％的歧义分辨率成功率，表明紧密结合的BDS-3 / BDS-2可以在亚太地区实现出色的RTK定位性能。同时，运动测试中仅BDS-3解决方案的三维（东/北/上）定位精度（0.52 cm / 0.39 cm / 2.14 cm）明显优于仅BDS-2解决方案的0.83 cm（0.85 cm）。 /1.02厘米/3.01厘米），这是因为当前BDS-3星座的几何形状更好。紧密结合的BDS-3 / BDS-2解决方案可以分别提供0.52 cm，0.22 cm和1.80 cm的定位精度。运动测试中的14厘米）明显优于仅BDS-2溶液（0.85厘米/1.02厘米/3.01厘米），这是因为当前BDS-3星座的几何形状更好。紧密结合的BDS-3 / BDS-2解决方案可以分别提供0.52 cm，0.22 cm和1.80 cm的定位精度。运动测试中的14厘米）明显优于仅BDS-2溶液（0.85厘米/1.02厘米/3.01厘米），这是因为当前BDS-3星座的几何形状更好。紧密结合的BDS-3 / BDS-2解决方案可以分别提供0.52 cm，0.22 cm和1.80 cm的定位精度。