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Optimizing ZWD estimation strategies for enhanced PPP-RTK performance

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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.

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Data availability

The RINEX data acquired from the National Geodetic Survey (NGS) in the USA can be downloaded at https://www.ngs.noaa.gov/CORS/. The GFS products can be accessed at https://rda.ucar.edu/datasets/ds084.1/.

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Funding

This work was funded by the National Natural Science Foundation of China (Grant Nos. 42022025 and 42304038). This work was supported by the Science and Technology Innovation Program of Hunan Province, China (No. 2023RC3217). This work was also supported by the Hubei International Science and Technology Cooperation Project “Research and Development of Key Technologies of Multi-data Positioning System in Middle and low Latitude Areas” (No. 2023EHA004).

Author information

Authors and Affiliations

  1. Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, China

    Rui Gao, Fei Ye & Baocheng Zhang

  2. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China

    Rui Gao

  3. BeiDou High-Precision Satellite Navigation and Location Service Hunan Engineering Research Center, Hunan Institute of Geomatics Sciences and Technology, Changsha, China

    Fei Ye

  4. Guangzhou Urban Planning & Design Survey Research Institute, Guangzhou, China

    Yang Liu & Jiuping Zha

  5. School of Surveying, University of Otago, Dunedin, New Zealand

    Robert Odolinski

  6. Mapping And Positioning from Space (MAPS) Technology Research Center, Department of Survey Engineering, Chulalongkorn University, Bangkok, Thailand

    Chalermchon Satirapod

Authors
  1. Rui Gao
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  2. Fei Ye
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  3. Yang Liu
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  4. Jiuping Zha
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  5. Robert Odolinski
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  6. Chalermchon Satirapod
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  7. Baocheng Zhang
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Contributions

RG designed the experiments, carried out the data analysis, and wrote the main manuscript text; FY and JZ contributed to the paper writing and the data analysis; RO and CS revised the manuscript; BZ designed the algorithm, offered supervision, and revised the manuscript. All authors reviewed the manuscript.

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Correspondence to Baocheng Zhang.

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Gao, R., Ye, F., Liu, Y. et al. Optimizing ZWD estimation strategies for enhanced PPP-RTK performance. GPS Solut 28, 86 (2024). https://doi.org/10.1007/s10291-024-01629-3

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  • DOI: https://doi.org/10.1007/s10291-024-01629-3

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