Considering different recent advancements in GNSS on real-time zenith troposphere estimates
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ORIGINAL ARTICLE
Considering different recent advancements in GNSS on real‑time zenith troposphere estimates Tomasz Hadas1,2 · Thomas Hobiger1 · Pawel Hordyniec2,3 Received: 11 May 2020 / Accepted: 21 July 2020 © The Author(s) 2020
Abstract Global navigation satellite system (GNSS) remote sensing of the troposphere, called GNSS meteorology, is already a wellestablished tool in post-processing applications. Real-time GNSS meteorology has been possible since 2013, when the International GNSS Service (IGS) established its real-time service. The reported accuracy of the real-time zenith total delay (ZTD) has not improved significantly over time and usually remains at the level of 5–18 mm, depending on the station and test period studied. Millimeter-level improvements are noticed due to GPS ambiguity resolution, gradient estimation, or multi-GNSS processing. However, neither are these achievements combined in a single processing strategy, nor is the impact of other processing parameters on ZTD accuracy analyzed. Therefore, we discuss these shortcomings in detail and present a comprehensive analysis of the sensitivity of real-time ZTD on processing parameters. First, we identify a so-called common strategy, which combines processing parameters that are identified to be the most popular among published papers on the topic. We question the popular elevation-dependent weighting function and introduce an alternative one. We investigate the impact of selected processing parameters, i.e., PPP functional model, GNSS selection and combination, inter-system weighting, elevation-dependent weighting function, and gradient estimation. We define an advanced strategy dedicated to real-time GNSS meteorology, which is superior to the common one. The a posteriori error of estimated ZTD is reduced by 41%. The accuracy of ZTD estimates with the proposed strategy is improved by 17% with respect to the IGS final products and varies over stations from 5.4 to 10.1 mm. Finally, we confirm the latitude dependency of ZTD accuracy, but also detect its seasonality. Keywords GNSS · Meteorology · Real time · ZTD
Introduction The global navigation satellite system (GNSS) signal delay depends on pressure, temperature, and water vapor content along the propagation path, which creates a link between GNSS and meteorology. Although troposphere delay is treated as an error source in precise GNSS positioning, there is a great potential of exploiting troposphere delays * Tomasz Hadas [email protected] 1
Institute of Navigation, University of Stuttgart, Breitscheidstrasse 2, 70174 Stuttgart, Germany
2
Institute of Geodesy and Geoinformatics, Wroclaw University of Environmental and Life Sciences, Grunwaldzka 53, 50‑357 Wroclaw, Poland
3
SPACE Research Centre, RMIT University, 402 Swanston Street, Melbourne, VIC 3001, Australia
for weather and climate monitoring (Bianchi et al. 2016; Guerova et al. 2016). This is because the tropospheric wet delay is representative of the quantity of water vapor integrated along the signal path. As a
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