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The Korean Earth Science Society (한국지구과학회)
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Soil Moisture Retrieval Method Utilizing GPS Ground Reflection Signals

  • Young-Joo Kwon (Moon Soul Graduate School of Future Strategy, Korea Advanced Institute of Science and Technology) ;
  • Hyun-Ju Ban (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Sumin Ryu (Satellite Application Division, Korea Aerospace Research Institute) ;
  • Suna Jo (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Han-Sol Ryu (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Yerin Kim (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Jeong-Eun Park (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Yun-Jeong Choi (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Kyung-Hoon Han (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Yeonjun Kim (Department of Environment, Energy, and Geoinfomatics, Sejong University) ;
  • Sungwook Hong (Department of Environment, Energy, and Geoinfomatics, Sejong University)
  • Received : 2024.07.16
  • Accepted : 2024.08.18
  • Published : 2024.08.31
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Abstract

This study proposes a soil moisture retrieval method from ground reflection signals received by Global Positioning System (GPS) antenna modules consisting of an up-looking (UP) right-hand circular polarization (RHCP) and two down-looking (DW) RHCP and left-hand circular polarization (LHCP) signals. Field experiments at four different surface types (asphalt, grassland, dry soil, and moist soil) revealed that the DW RHCP and LHCP signals are affected by antenna height and multipath interference signals. The strength differences between the DW LHCP and UP RHCP signals were in good agreement with the DW LHCP signals. Methodologically, this study applied a spectrum analysis to the detrended surface-reflected signals for RHCP and LHCP. The study indicated that the down-looking antenna exhibited greater sensitivity to reflected GPS signals than the up-looking antenna. We demonstrated the feasibility of estimating soil moisture using GPS signals, by comparing LHCP signals received by the down-looking antenna with theoretical values. This study presents a novel method for estimating soil moisture in vegetated areas, leveraging the advantage of cross-polarization comparisons to achieve stronger signal strength than single-polarization reflection signals. With further research, including long-term observations and detailed analysis, the proposed method has the potential to enhance performance significantly.

Keywords

Acknowledgement

The authors thank anonymous reviewers for their helpful and constructive comments on the manuscript. This study was funded by the Korea Meteorological Administration Research and Development Program under Grant KMI2018-05710 and supported by a grant from the National Institute of Environment Research (NIER), funded by the Ministry of Environment (MOE) of the Republic of Korea (NIER-2024-01-02-035).

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