Abstract
The tropospheric delay is one major error source affecting the precise positioning provided by the global navigation satellite system (GNSS). This error occurs because the GNSS signals are refracted while travelling through the troposphere layer. Nowadays, various types of model can produce the tropospheric delay. Among them, the globally distributed GNSS permanent stations can resolve the tropospheric delay with the highest accuracy and the best continuity. Meteorological models, such as the Saastamoinen model, provide formulae to calculate temperature, pressure, water vapor pressure and subsequently the tropospheric delay. Some grid-based empirical tropospheric delay models directly provide tropospheric parameters at a global scale and in real time without any auxiliary information. However, the spatial resolution of the GNSS tropospheric delay is not sufficient, and the accuracy of the meteorological and empirical models is relatively poor. With the rapid development of satellite navigation systems around the globe, the demand for real-time high-precision GNSS positioning services has been growing dramatically, requiring real-time and high-accuracy troposphere models as a critical prerequisite. Therefore, this paper proposes a multi-source real-time local tropospheric delay model that uses polynomial fitting of ground-based GNSS observations, meteorological data, and empirical GPT2w models. The results show that the accuracy in the zenith tropospheric delay (ZTD) of the proposed tropospheric delay model has been verified with a RMS (root mean square) of 1.48 cm in active troposphere conditions, and 1.45 cm in stable troposphere conditions, which is significantly better than the conventional tropospheric GPT2w and Saastamoinen models.
Highlights
The troposphere is an important part of the Earth’s space environment and exerts an important control to the functioning of the global navigation satellite system (GNSS) technology
Local tropospheric models significantly affect the performance of the differential global positioning system (DGPS), and the real time kinematic (RTK) and network RTK positioning systems [2,3,4]
In order to address the issue, three types of real-time model of the troposphere are commonly used: the first type comprises empirical models of tropospheric key parameters, by which the tropospheric delay can be calculated without any additional information; the second type includes the traditional models based on meteorological data observed from the ground; the third type comprises the models established by the GNSS continuously operating reference stations (CORS) networks
Summary
The troposphere is an important part of the Earth’s space environment and exerts an important control to the functioning of the global navigation satellite system (GNSS) technology. Dousa et al developed a new concept for providing tropospheric augmentation corrections, by which a two-stage correction model is used to combine data from a Numerical Weather Model (NWM) and precise ZTDs estimated from GNSS permanent stations in regional networks [25]. In this way, the accuracy of ZTD estimates is improved by a factor of 2.5 or higher. The assessment and outcomes of the strategies adopted are discussed, while considerations are presented in the conclusion
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