Soil Moisture Inversion Based on Dual-Frequency Signal of QZSS GEO Satellite

In recent years, soil moisture retrieval using GNSS reflection signals has become a topic of great concern to scholars. However, most researchers adopt GPS and BDS signals to carry out the related research. There are insufficient studies on soil moisture inversion using QZSS (Quasi-Zenith Satellite System), and the performance of soil moisture inversion with different QZSS signals has not been evaluated yet. This study aims to provide new results by conducting a soil moisture monitoring experiment of QZSS-Reflectometry (QZSS-R) using the QZSS GEO satellite signal in the experimental field of Weihai Academy of Agricultural Sciences, Shandong Province. The original Intermediate Frequency (IF) data were collected, and the experimental data on October 21, 2022 (during bare soil period) were processed by using the self-developed GNSS-R software receiver. The results of different soil moisture inversion models were evaluated for L1 C/A and L5 signals, and it is found that the signal quality of L5 is better than that of L1 C/A in QZSS-R soil moisture inversion. For the Topp model, the RMSE (Root Mean Square Error) of L5 and L1 C/A inversion results are 0.0240 cm3/cm3 and 0.1725 cm3/cm3. For the Wang model, the RMSE of L5 and L1 C/A inversion results are 0.0317 cm3/cm3 and 0.1856 cm3/cm3 respectively. These results demonstrate that the soil moisture estimations accuracy of QZSS L5 signal are superior to that of L1 C/A.