GNSS reflectometry for remote sensing of soil moisture

Global Navigation Satellite System Reflectometry (GNSS-R) is an emerging technique for remote sensing of soil surfaces. In this work, the data collected by a GNSS receiver prototype mounted on a small aircraft are analyzed to retrieve soil moisture. Based on GNSS-R bi-static configuration, direct and reflected GPS signals were measured by a right hand (RHCP) and a left hand (LHCP) circular polarized antenna, respectively. The direct signal was used to calibrate the system. The soil moisture was retrieved from the power ratio of LHCP reflected SNR over RHCP direct SNR regardless of the surface roughness and incoherent components. A over-water calibration method was applied to improve the estimation accuracy. Results showed good correlation with the types of underlying terrain.