Work

Soil Moisture Retrieval Using Single-Frequency Dual-Polarization GNSS-R Data From Airborne GLORI Experiment

Year: 2025

Type: article

Abstract: In global navigation satellite system reflectometry (GNSS-R) research, polarization was historically overlooked. However, it has garnered increasing attention in recent years. This article focuses on analyzing the first publicly available dual-polarization, single-frequency dataset from the airborne global navigation satellite system reflectometry instrument (GLORI), collected during the summer of 2021. Based on theoretical analysis, multiple soil moisture retrieval algorithms were implemented. Initially, only the surface reflectivity of LHCP-receiving/RHCP-transmitting (LR) and RHCP-receiving/RHCP-transmitting (RR) polarizations was investigated. As additional surface parameters, such as surface roughness and vegetation, were integrated into the algorithm, the retrieval accuracy, measured by root mean square error (RMSE), improved significantly from approximately 0.07 cm3/cm3to 0.03 cm3/cm3. The retrieval accuracy of RR polarization is slightly better than that of LR polarization. Nevertheless, when both dual polarizations were considered, the retrieval accuracy was comparable to that of using only one polarization. When surface roughness, leaf area index, and incidence angle are taken into account, the soil moisture retrieval accuracy, indicated by RMSE, reaches 0.0344 cm3/cm3. This clearly demonstrates the great potential of dual polarization in soil moisture estimation. GLORI data is the first publicly available dual-polarization GNSS-R data that encompasses not only coherent and but also noncoherent scattering scattering information. This article further discusses the noncoherent scattering properties of LR and RR polarizations. In the context of coherent scattering, it is found that the scattering properties at LR polarization are stronger than those at RR polarization. Conversely, for noncoherent scattering, the scattering properties at LR polarization are weaker than those at RR polarization for corresponding land surface types. By employing both cohrent and noncoherent scattering properties with the consideratons of LR and RR polarizations, the soil moisture retrieval accuracy indicated by RMSE and correlation coefficients (R) will be 0.0316 and 0.9043, respectively. The analysis of dual-polarization data incorporating both coherent and noncoherent scattering mechanisms holds significant potential for advancing soil moisture retrieval accuracy through future data mining efforts, while also informing the design of next-generation polarimetric GNSS-R payloads, such as ESA’s HydroGNSS and China’s GNSS-ReSAR.

Source: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing

DOI: 10.1109/jstars.2025.3597333

Authors: Xuerui Wu, Shumin Han, Xinming Huang, Kuo Cao

Institutions: Chinese Academy of Sciences, Shanghai Astronomical Observatory, Dalian Maritime University, National University of Defense Technology

Language: English

Topic: Soil Moisture and Remote Sensing

Subfield: Environmental Engineering

Field: Environmental Science

Domain: Physical Sciences

SDG: Climate action

Open Access status: gold

Estimated APC paid: $1,800