A METHOD OF MICROWAVE SOIL MOISTURE INVERSION WITHOUT DEPENDENCE ON THE FIELD MEASUREMENT DATA

Abstract. In the process of retrieving soil moisture (M_v) by active microwave, surface roughness is an important parameter affecting the accuracy of m_v retrieval.Using effective roughness to replace the original measurement value of surface roughness can effectively avoid the error. In the existing methods of soil water inversion, the value of fixed mean square root height (S) was used to retrieve the surface of different types and vegetation coverage, neglecting the difference of different ground surface. This paper proposed a LUT (look up table) soil moisture inversion method based on the pixel scale effective roughness. First, the effective roughness was obtained by using the measured soil moisture value of the sampling point based on the LUT method. And then the empirical function between the optimum roughness (S, Correlation length-l) and the backscattering coefficient of VV/HH polarization was obtained. The value of each pixel's S and L was obtained by using the empirical function. Finally, the soil moisture was retrieved by the LUT method. Using the measured data of the Linze sample area to verify, the results showed that the proposed method was superior to the LUT inversion method using the S fixed value without dependence on the measured data of the roughness. It was also proved that the inversion method proposed in this paper is not only applicable to the bare soil area, but still maintained a high precision in the soil moisture inversion results in the area with large vegetation coverage.