Microwave bistatic polarization measurements for retrieval of soil moisture using an incidence angle approach

Abstract

In this paper, the specular scattering (σOHH/VV) behaviour of ten types of plots having different percentage of moisture (mg) and roughness (hrms) has been analysed at various incidence angles with horizontal-horizontal (HH-) and vertical-vertical (VV-) polarizations by an indigenously assembled X-band bistatic scatterometer at frequency of 9.5 GHz. Still, it is very uncertain for minimizing the effect of roughness while retrieving soil moisture. For this purpose, the polarization behaviour of a radar wave has been analysed and a known polarimetric ratio (P ≤ σOHH/σOvv) and proposed polarimetric discrimination ratio have been tested for minimizing the effect of roughness for the retrieval of soil moisture. It was found that PDR has minimum effect of roughness in comparison to P. To avoid the complexity of a moisture retrieval algorithm, we have proposed the incidence angle-based approach to retrieve the soil moisture. The retrieved moisture with the proposed approach is in quite a good agreement with the observed moisture. PDR gives better results than P for retrieval of soil moisture. This type of study and the development of this algorithm will be very helpful in the near future of the Cartwheel satellite system. © 2007 Nanjing Institute of Geophysical Prospecting.