A method for retrieving soil moisture from GNSS-R by using experiment data

摘要

Soil moisture is a key parameter in agricultural irrigation.The L band（1.58GHz）on board global position system（GPS） satellite is well suited for monitoring the change of soil moisture.In order to investigate the potential of retrieving soil moisture using the L-band GPS bistatic radar,this paper analyzed a retrieval method by using field experiment data.In order to investigate the relationship between the soil moisture（corresponding roughly to the 05cm top soil layer） and the signalto-noise ratio(Pr-SNR) to the direct GPS signal-to-noise ratio(Pd-SNR),an experiment was conducted in Hulunber grassland of China in 2009 and 2011.Six field sites in the soil moisture experiment were utilized to analyze the relationship between soil moisture and the ratio of Pr-SNR to Pd-SNR and the square of correlation coefficient was about 0.9 when the surface type was known and the elevation angle of the satellite ranged from 65 to 85 degrees approximately.The analysis shows that ratio of Pr-SNR to P（d-SNR） can be used to monitor the soil moisture,because the ratio of P（r-SNR） to P（d-SNR） maximized the elimination of the influence of different signals from different GPS satellites.The estimation accuracy could be improved if we make full use of the empirical knowledge on elevation angles of GPS satellites and ground roughness of different surface types.