Abstract
Recently, microwave remote sensing has become a strong tool for monitoring the surface of the earth. As a potential application, the monitoring of the surface distribution of soil moisture content is an important factor in hydrology. The differential scattering coefficient data obtained from a satellite borne scatterometer depend on the complex dielectric constant, which is related to the moisture content in the soil. This paper describes the results of the investigation of the soil moisture content characteristics of Kanto loam. The dielectric constant of wet soil is measured by using the S-parameter method which has a large aperture waveguide compared with the wavelength.
In order to model the characteristics of dielectric constant to soil moisture content, two adjustable parameters α and β in the semi-empirical model proposed by F.T. Ulaby et al. are determined from the results of above experimental data. The parameter a agrees with the a of the soil in the USA, but the parameter β is different from the β in the USA. From the result of comparison between the measured result by Hirosawa et al. and our result, it is noted that the real part of the complex dielectric constant does not agree well. Then the Fresnel reflection coefficient of Kanto loam is also measured by using a modified detecting method of reflected wave. In the general case, the scattering coefficient is directly proportional to the power reflectivity. A good agreement is obtained between the reflection coefficient calculated by the semi-empirical model and the above result. So it is concluded that soil moisture content of Kanto loam can be estimated by using the semi-empirical model based on our experimental results by taking the roughness and the incident angle into account.
