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Real-time wide-area precise tropospheric corrections (WAPTCs) jointly using GNSS and NWP forecasts for China

Abstract

Real-time precise tropospheric corrections are essential for global navigation satellite system (GNSS) positioning with centimetre-level precision. This study presents a new method for generating real-time wide-area precise tropospheric corrections (WAPTCs) for China. Compared with previous models, the new WAPTC has features such as high accuracy, a small number of coefficients and good continuity of service. The new WAPTC utilizes the complementary advantages of numerical weather prediction (NWP) forecasts and GNSS-derived zenith tropospheric delays (ZTDs) with the aid of machine learning and a new polynomial approximation method. The results indicate that (1) the spatially varying biases of NWP-ZTDs can be effectively calibrated using machine learning trained on sparse real-time GNSS-ZTDs, thereby generating a tropospheric data set that is improved in both accuracy and spatial coverage over China, and (2) by incorporating the improved tropospheric data set and the modern empirical IGGtrop model, we succeed in expressing the tropospheric corrections across China using a new polynomial approximation method, thereby reducing the high-volume gridded corrections to only a small number of coefficients to permit easy transmission via satellite. Cross-validation results show that the real-time WAPTCs offer accuracies of 10.0 mm in winter and 16.0 mm in summer in terms of the root mean square (RMS) error across China. The superiority of the proposed WAPTCs to the conventional models is illustrated in both delay and BeiDou-3 positioning domains. These findings can facilitate the provision of tropospheric corrections in BeiDou/GNSS satellite-based PPP services.

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Data availability

Real-time GNSS data streams are obtained from CMONOC and GBAS. IGS final orbit and clock products are available at public repositories: https://cddis.nasa.gov/. Stream-based real-time orbit and clock corrections are provided by CNES via the SSRA00CNE0 mount point and WHU via SSRA00WHU0. The GFS data are available at https://www.nco.ncep.noaa.gov/pmb/products/gfs/. The ERA5-derived ZTD data are obtained from ftp.gfz-potsdam.de/GNSS/products/gfz-vmf1/.

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 41904041, 42074037, 42074045), the China Postdoctoral Science Foundation (No. 2019M660192), the National Key Research & Development Program (No. 2017YFE0131400), and HuBei Natural Science Funds (No. 2020CFB329). The authors acknowledge CMONOC/GBAS/Shanghai Huace Navigation Technology Ltd and Chinese Meridian Project for supplying GNSS data and IGS/CNES/WHU for supplying postprocessed/real-time GNSS orbit and clock corrections. The GRNN model was developed using the MATLAB software. The NWP data were obtained from the NCEP Products Inventory. The authors appreciate the discussions with Florian Zus of GFZ, Yong Wang, Jiuping Zha and Gongwei Xiao of CAS and Dingcheng Wu of North Information Control Research Academy Group CO., LTD. on this work.

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Authors

Contributions

HXZ and YBY initiated the study; HXZ designed the research and processed the data; YBY supervised the research; HXZ wrote the paper; and WL reviewed and improved the manuscript.

Corresponding authors

Correspondence to Hongxing Zhang or Yunbin Yuan.

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Zhang, H., Yuan, Y. & Li, W. Real-time wide-area precise tropospheric corrections (WAPTCs) jointly using GNSS and NWP forecasts for China. J Geod 96, 44 (2022). https://doi.org/10.1007/s00190-022-01630-z

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  • DOI: https://doi.org/10.1007/s00190-022-01630-z

Keywords

  • Global navigation satellite system (GNSS)
  • Numerical weather prediction (NWP)
  • Real-time tropospheric delay modelling
  • Machine learning
  • Polynomial approximation