Potential and Complementarity of Dense SAR and Optical Data for Rapeseed Crops Monitoring

This paper aims to investigate the potential of SAR and optical satellite data for high temporal monitoring of rapeseed crops and the retrieval of biophysical parameters. To do so, dense temporal series of Landsat-8, Sentinel-2 and Sentinel-1 have been used to derive NDVI, GAI and backscattering coefficients, respectively. These signals have been physically interpreted and compared each other and to in situ measured crop biophysical parameters (i.e., height, dry biomass, fresh biomass and plant water content) for two rapeseed fields. This study pointed out the complementarity of multi-orbit SAR and multi-sensor optical data for rapeseed crop monitoring throughout its phenological cycle. We also demonstrated that the SAR derived VH-VV ratio could be successfully used for biomasses retrieval ( $\mathrm{R}^{2}\geq 0.7$ ) thus showing its potential for assimilation in crop models.