Scatterometer performance with polarization discrimination ratio approach to retrieve crop soybean parameter at X‐band

Abstract

Microwave remote sensing is an important tool because it can penetrate into cloud independent of weather and it can acquire day or night time data. One of the important applications is the estimation of crop parameters and another main point of research is to know which crop parameter [i.e. plant height (PH), biomass (Bm) leaf area index (LAI) crop‐covered soil moisture (Sm)] is interacting more with microwave for radar remote sensing because these crop parameters regulate the crop health. For this purpose, an experiment using ground‐based X‐band scatterometer was carried out to understand the interaction mechanism and to retrieve the soybean parameters. In this paper, angular variation and polarization dependence on soybean crop have been observed at X‐band microwave frequency. It was found that soybean biomass is highly correlated with microwave frequency at X‐band than the other plant parameters. As the biomass increases in the soybean, the scattering coefficient increases for both polarizations (i.e. HH‐ and VV‐pol.). It was noticed that VV‐pol provides better results than HH‐pol. An incidence angle less than 40° shows better results for observing crop‐covered soil moisture, while an incidence angle greater than 40° is good for observing the effect of soybean parameters at X‐band. A polarization‐based model is also proposed to retrieve the crop parameter. The crop parameter retrieved by the polarization‐based model is compared by another model based on least square (LSE) optimization. The results retrieved with the polarization‐based approach yielded very good agreement with observed results in comparison with LSE optimization approach.