RELATIONSHIP BETWEEN SAR/SENTINEL-1 POLARIMETRIC AND INTERFEROMETRIC DATA WITH BIOPHYSICAL PARAMETERS OF AGRICULTURAL CROPS
Keywords: microwave, LAI, height, soybean, wheat, coherence, backscatter, polarization
Abstract. The use of SAR (Synthetic Aperture Radar) data in agricultural applications has not yet been adequately explored, due to the complexity of the processing required, the lower diversity and availability of SAR data, and the difficulty in interpreting this data. The interactions between microwave energy and vegetation are influenced by factors related to plant structure, dielectric properties of the canopy, planting density and line orientation, and the angle of incidence and polarization of the wave. These differences between the recorded phases are used in data analysis techniques such as polarimetry and interferometry. Thus, the objective of this research is to analyse the relationships between the biophysical attributes of two agricultural crops (soybean and wheat) and the polarimetric and interferometric parameters of the SAR/Sentinel-1 data. The backscatter coefficients sigma and gamma in the VV polarization have inversely direct relation with the height of the crops, that is, as cultures grow, the interaction of energy in this polarization increases and the return signal decreases. For the cross polarization VH, the behaviour is the opposite, the larger the canopy height, the greater the interaction of vertical polarization and the greater the return on horizontal polarization. The interferometric coherence had small values, characterising a temporal decorrelation between the image pairs, due the canopy development. This preliminary study serves as a basis for future research with SAR/Sentinel-1 data focused on crops.