Abstract

Precise Point Positioning-Real Time Kinematic (PPP-RTK), a synthesis of PPP and RTK techniques, is a highly precise positioning technique that has been extensively studied in the GNSS community. The Zenith Wet Delay (ZWD), an important estimated parameter in PPP-RTK, significantly impacts the user positioning performance. It is crucial to determine the optimal ZWD processing methods for PPP-RTK. The present study contributes to this research trend by designing and contrasting four ZWD processing strategies for PPP-RTK, confirming the benefits of Global Forecast System (GFS) products (a global numerical weather prediction (NWP) model) in both the network and user models of PPP-RTK. In this study, the full-rank ionosphere-float undifferenced and uncombined (UDUC) PPP-RTK network and user models are first derived. To determine the optimal ZWD processing method in PPP-RTK, four ZWD processing strategies are designed and a comprehensive positioning performance evaluation is conducted for the four different ZWD processing strategies using 10-day GPS observation data from 55 GPS stations in the USA. The results show that a priori GFS ZWD information into the PPP-RTK network model’s ZWD constraint significantly improves the user positioning performance. With the GFS ZWD constraint, for user stations, the average convergence time after network filter restart is reduced by 12.7%, from 55 to 48 min, the average vertical positioning RMS of the float ambiguity solution (including convergence time) is reduced by 18.8%, from 8.5 to 6.9 cm. Additionally, a priori GFS ZWD information can also offer users an absolute ZWD constraint option, which does not require communication with the network, achieving performance comparable to PPP-RTK network ZWD products.

中文翻译：

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优化 ZWD 估计策略以增强 PPP-RTK 性能

摘要

精密单点定位-实时运动学（PPP-RTK）是PPP和RTK技术的综合，是一种高精度定位技术，已在GNSS界得到广泛研究。天顶湿时延（ZWD）是PPP-RTK中的一个重要估计参数，对用户定位性能有显着影响。确定PPP-RTK的最佳ZWD处理方法至关重要。本研究通过设计和对比 PPP-RTK 的四种 ZWD 处理策略来促进这一研究趋势，确认全球预报系统 (GFS) 产品（全球数值天气预报 (NWP) 模型）在网络和用户模型中的优势PPP-RTK。在本研究中，首先推导了全秩电离层浮点无差非组合（UDUC）PPP-RTK 网络和用户模型。为了确定PPP-RTK中的最佳ZWD处理方法，设计了四种ZWD处理策略，并利用美国55个GPS站点的10天GPS观测数据对四种不同的ZWD处理策略进行了综合定位性能评估。结果表明，将先验GFS ZWD信息引入PPP-RTK网络模型的ZWD约束显着提高了用户定位性能。在GFS ZWD约束下，对于用户站，网络滤波器重启后的平均收敛时间减少了12.7%，从55 min减少到48 min，浮点模糊度解的平均垂直定位RMS（含收敛时间）减少了18.8% ，从 8.5 到 6.9 厘米。此外，先验的GFS ZWD信息还可以为用户提供绝对ZWD约束选项，无需与网络通信，实现与PPP-RTK网络ZWD产品相当的性能。