Study On Soil Moisture Retrieval Based On GPS-R Remote Sensing Technology

Soil moisture plays an important role in global carbon cycle,and in agriculture,too high or too low soil moisture can adversely affect crop yield,therefore,the research of soil moisture determination is of great significance in the fields of timely and reasonable irrigation and meteorology.With the continuous development and improvement of the global satellite navigation system,the inversion technique based on GPS-R(Global Positioning Satellite System-Reflectmetry)has been used to monitor soil moisture,snow thickness and tide position.Based on GPS multi-path and signal-to-noise ratio(SNR),this paper explores the Theory and Method of soil moisture inversion using GPS-R technique.GPS data and portable sensors are used to collect soil moisture data.the relationship between multi-path characteristic parameters(amplitude,frequency and phase)and soil moisture is analyzed qualitatively and quantitatively.The influence factors of height angle,soil moisture and band were analyzed.The results show:(1)The measured data of five satellites before and after one rainfall at the same location show,with the increase of soil moisture,the characteristics of multi-path reflection component of satellite are as follows:frequency and amplitude decrease,and delay phase increase.(2)From the quantitative analysis of five satellites,it is found that the amplitude of the multi-path component of three satellites(G01,G22 and G23)is moderately correlated with soil moisture,and the exponential function model is better than that of linear function model.The frequency of multi-path components of three satellites(G01,G22 and G30)is moderately correlated with soil moisture,the linear function model is superior to the exponential function model in the model of soil moisture.The phase of two satellites has a moderate correlation with soil moisture.The phase of the multi-path component of G23 satellite is linearly correlated with the soil moisture at 2cm and 5cm,and the determining coefficient R2(5cm)>R2(mean soil moisture)>R2(2cm)(3)In the selection of original data,the correlation coefficients of SNR multi-path component amplitudes of four satellites(G01,G22,G23 and G27)in height angle(5?-25“)are-0.759,-0.532,-0.671 and-0.833 respectively.The correlation coefficients of multi-path component frequency and soil moisture of three satellites(G01,G22 and G30)were-0.761,-0.761 and-0.736,respectively.The correlation coefficients between the multi-path component phase and soil moisture of two satellites(G23 and G27)are 0.631 and-0.760,respectively.Soil moisture corresponding to the height angle of 5°-25°was selected to correlate with satellite parameters,the correlation coefficient of amplitude was-0.494?-0.833;phase was 0.513?-0.760;frequency was-0.627?-0.761.If SI SNR is chosen,too long and too short can reduce the inversion effect.Figure[43]table[7]reference[78]...