Biomass estimation of oilseed rape using simulated compact polarimtric SAR imagery

Plant biomass is an important parameter for crop management and yield estimation. The potential of compact polarimetric (CP) synthetic aperture radar (SAR) data in estimating biomass of oilseed rape crop (Brassica napus L.) is investigated in this study. Five CP SAR imagery was simulated using five fully polarimetric Radarsat-2 data, and the dynamic evolution of polarimetric features, relying on different polarimetric decomposition methods (m-χ, m-δ, and Freeman-Durden), with the crop growth, was compared. It was found that the Dbl indicator, by the m-χ decomposition method, can reflect well the dynamic growth of canola. Therefore, a method of monitoring fresh and dry biomass of canola was put forward. The result showed that the root mean square error (RMSE) was 56.5g/m², 448.2g/m², and the relative error (RE) was 23.9%, 25.0% for fresh and dry biomass, respectively. In addition, the precision of the model will be affected when the crop becomes mature since its vegetation water content declines. The results were also compared with those of the fully polarization SAR. It revealed that the performance of CP SAR on rapeseed monitoring can achieve the level of fully polarization SAR, considering the advantages of CP SAR, such as wider coverage and less data volume etc. It revealed that the polarization information was necessary in quantitatively monitoring of broad leaf crops, such as rapeseed, and CP SAR has a great potential in crop monitoring.