College of Information and Computer, Taiyuan University of Technology, Jinzhong, China.
Shanxi Engineering Technology Research Center for Spatial Information Network, Jinzhong, China.
PLoS One. 2021 Jan 19;16(1):e0245561. doi: 10.1371/journal.pone.0245561. eCollection 2021.
Precision point positioning (PPP) is widely used in maritime navigation and other scenarios because it does not require a reference station. In PPP, the satellite clock bias (SCB) cannot be eliminated by differential, thus leading to an increase in positioning error. The prediction accuracy of SCB has become one of the key factors restricting positioning accuracy. Although International GNSS Service (IGS) provides the ultra-rapid ephemeris prediction part (IGU-P), its quality and real-time performance can not meet the practical application. In order to improve the accuracy of PPP, this paper proposes to use the Prophet model to predict SCB. Specifically, SCB sequence is read from the observation part in the ultra-rapid ephemeris (IGU-O) released by IGS. Next, the SCB sequence between adjacent epochs are subtracted to obtain the corresponding SCB single difference sequence. Then using the Prophet model to predict SCB single difference sequence. Finally, the prediction result is substituted into the PPP positioning observation equation to obtain the positioning result. This paper uses the final ephemeris (IGF) published by IGS as a benchmark and compares the experimental results with IGU-P. For the selected four satellites, compared with the results of the IGU-P, the accuracy of SCB prediction of the model in this paper is improved by about 50.3%, 61.7%, 60.4%, and 48.8%. In terms of PPP positioning results, we use Real-time kinematic (RTK) measurements as a benchmark in this paper. Positioning accuracy has increased by 26%, 35%, and 19% in the N, E, and U directions, respectively. The results show that the Prophet model can improve the performance of PPP.
精密单点定位（PPP）由于不需要参考站而被广泛应用于航海和其他领域。在 PPP 中，卫星钟差（SCB）不能通过差分消除，从而导致定位误差增大。SCB 的预测精度已成为制约定位精度的关键因素之一。尽管国际全球导航卫星系统服务（IGS）提供了超快速星历预报部分（IGU-P），但其质量和实时性能无法满足实际应用的需求。为了提高 PPP 的精度，本文提出了使用 Prophet 模型来预测 SCB。具体来说，从 IGS 发布的超快速星历（IGU-O）的观测部分读取 SCB 序列。然后，通过减去相邻历元之间的 SCB 序列，获得相应的 SCB 单差序列。接着，使用 Prophet 模型来预测 SCB 单差序列。最后，将预测结果代入 PPP 定位观测方程中，得到定位结果。本文以 IGS 发布的最终星历（IGF）为基准，将实验结果与 IGU-P 进行了比较。对于所选的四颗卫星，与 IGU-P 的结果相比，本文模型的 SCB 预测精度提高了约 50.3%、61.7%、60.4%和 48.8%。在 PPP 定位结果方面，本文以实时动态（RTK）测量为基准。在 N、E 和 U 方向上，定位精度分别提高了 26%、35%和 19%。结果表明，Prophet 模型可以提高 PPP 的性能。
