Abstract

PPP–RTK, a synthesis of precise point positioning (PPP) and real-time kinematic (RTK) techniques, achieves fast integer ambiguity resolution-enabled positioning using, among others, satellite clocks, biases, and ionospheric corrections generated in a reference network. When formulating a network model to estimate these products, one usually considers a receiver as the pivot and selects its receiver-related parameters as the datum to address the rank deficiency problem. This work demonstrates that the precision of ambiguity-float combined PPP–RTK products relates to the pivot receiver selection. The combined product encompasses the summation of satellite clocks, satellite phase biases, and ionospheric delays at a certain station. Specifically, we find that the precision of ambiguity-float combined products at the pivot receiver surpasses that at non-pivot receivers by a significant margin. Consequently, user positioning becomes inhomogeneous in the network, as users far away from the pivot receiver perform worse than those close to the pivot receiver. To relieve this pivot receiver dependency, we emphasize the necessity of network integer ambiguity resolution, which improves the precision of products and ensures the homogeneity of user positioning. For verification purposes, we performed a one-week experiment involving 12 global positioning system (GPS) receivers to generate network products and 23 receivers to perform user positioning. The results showed that the precision of ambiguity-float combined products at the pivot receiver was better than 2 cm, whereas that at non-pivot receivers reached several decimeters. With these ambiguity-float products employed on the user side, the time-to-first-fix (TTFF) of the positioning near the pivot receiver was less than 5 epochs, but that away from the pivot receiver exceeded 15 epochs. Network integer ambiguity resolution improved the quality of PPP–RTK products, as the precision of combined products at an arbitrary receiver reached several millimeters. User positioning with ambiguity-fixed products became homogeneous with an average three-dimensional root-mean-square (3D RMS) of 1.5 cm, and the mean TTFF decreased to 4 epochs.

中文翻译：

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网络整数模糊度解析带来的同质 PPP–RTK 用户定位性能

摘要

PPP-RTK 是精确单点定位 (PPP) 和实时运动学 (RTK) 技术的综合体，利用参考网络中生成的卫星时钟、偏差和电离层校正等，实现快速整数模糊度分辨率定位。在建立网络模型来估计这些乘积时，通常将接收器视为枢轴，并选择与接收器相关的参数作为数据来解决秩不足问题。这项工作表明，模糊度-浮点组合 PPP-RTK 产品的精度与枢轴接收机的选择有关。组合产品包括卫星时钟、卫星相位偏差和某个站的电离层延迟的总和。具体来说，我们发现枢轴接收器处的模糊度-浮动组合产品的精度大大超过非枢轴接收器处的精度。因此，用户定位在网络中变得不均匀，因为远离枢轴接收器的用户比靠近枢轴接收器的用户表现更差。为了缓解这种枢轴接收器依赖性，我们强调网络整数模糊度消解的必要性，这提高了产品的精度并保证了用户定位的同质性。为了验证目的，我们进行了为期一周的实验，涉及 12 个全球定位系统 (GPS) 接收器来生成网络产品和 23 个接收器来执行用户定位。结果表明，枢轴接收器处的模糊浮点组合产品精度优于2厘米，非枢轴接收器处的模糊浮点组合产品精度达到数分米。通过在用户侧使用这些模糊浮动产品，靠近枢轴接收器的定位的首次定位时间（TTFF）小于5个epoch，但远离枢轴接收器的定位超过15个epoch。网络整数模糊度分辨率提高了PPP-RTK产品的质量，任意接收机处组合产品的精度达到了几毫米。模糊固定产品的用户定位变得均匀，平均三维均方根 (3D RMS) 为 1.5 厘米，平均 TTFF 下降到 4 个时期。