Effect of soil moisture on microwave scattering for remote sensing

Abstract

The main objective of remote sensing is to design space borne microwave sensors to sense a target and derive useful geophysical parameters. For this purpose, the knowledge of the target characteristics must be obtained through ground based remote sensing. In this paper, soil has been taken as the target. Various percentages of gravimetric soil moisture (m _g) have been taken for establishing its relation with the scattering coefficient (σ ₀) for both like polarizations at X-band frequencies. A linear model has been developed for correlating these two variables (i.e.m _g andσ ₀). Using this model, regression analysis has been done for obtaining different regression parameters and predicted values. Treating measurements from bare smooth soil fields with different soil moistures, the data were analysed to examine the effect of soil moisture on scattering co-efficient (σ ₀) at 9.50 GHz frequency in X-band. The scattering coefficient increases with increase in soil moisture content. Different regression parameters have been obtained, which show that the best look-angle is at 25° for HH-pol and 60° for VV-pol for observingσ ₀ from bare moist soil. Data analysis indicated that the basic cause and effect relationship between the sensor measurements and soil moisture can be extrapolated from theory and small-scale tests to larger resolution elements observed by the sensing aircraft. These results indirectly provide reference data for a satellite-borne remote sensor. From the results, the look angles suitable for operation with radar antennas can be suggested.