The heavy reliance of real-time precise point positioning (RTPPP) on external satellite clock products may lead to discontinuity or even failure in time-critical applications. We present an alternative approach of real-time undifferenced precise positioning (RUP) that, by combining satellite clock estimation and precise point positioning based on the extended Kalman filter, is independent of external satellite clock corrections. The approach is evaluated in simulated real time with the assistance of a variable number of IGS multi-GNSS stations located between 1359.7 and 4852.5 km from the users. The results show that even with a single auxiliary IGS station, RUP is still feasible and able to retain centimeter-level positioning accuracy. Typically, with three auxiliary IGS stations about 2000–3000 km away, an accuracy of about 2 cm in the horizontal and 5 cm in the vertical can be achieved. The performance of RUP is comparable to that of PPP using 5-s satellite clock products and notably exhibits superior short-term precision in dealing with high-rate (1 Hz) GPS/GLONASS observations. The addition of GLONASS observations reduces the convergence time by 56.9% and improves the 3-D position accuracy by 31.8% while increasing the processing latency by a factor of about 1.6. Employing three IGS stations over 2400 km away from the epicenter, RUP is applied for the rapid determination of coseismic displacements and waveforms for the 2016 Kaikoura earthquake, yielding highly consistent results compared to those obtained from post-processed PPP in the global reference frame. We also explore its potential in facilitating real-time online services in terms of real-time precise positioning, zenith tropospheric delay retrieving, and satellite clock estimation.

中文翻译：

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远程IGS多GNSS站辅助实时无差异精确定位的性能

实时精确点定位（RTPPP）严重依赖外部卫星时钟产品可能会导致对时间要求严格的应用不连续甚至失败。我们提出了一种实时无差异精确定位（RUP）的替代方法，该方法通过结合卫星时钟估计和基于扩展卡尔曼滤波器的精确点定位来独立于外部卫星时钟校正。在距离用户1359.7至4852.5 km之间的可变数量的IGS multi-GNSS台站的协助下，对该方法进行了模拟实时评估。结果表明，即使只有一个辅助IGS站，RUP仍然可行并且能够保持厘米级的定位精度。通常，在距离约2000-3000公里的地方有三个辅助IGS站，在水平方向上大约可以达到2厘米，在垂直方向上可以达到5厘米的精度。RUP的性能可与使用5 s卫星时钟产品的PPP媲美，并且在处理高速率（1 Hz）GPS / GLONASS观测时表现出卓越的短期精度。GLONASS观测值的添加将收敛时间减少了56.9％，并将3-D位置精度提高了31.8％，同时将处理延迟增加了约1.6倍。RUP在距震中2400公里以外的三个IGS台站中进行了应用，可用于快速确定2016年Kaikoura地震的同震位移和波形，与在全球参考框架中从后处理PPP获得的结果相比，该结果具有高度一致性。