Sensitivity Analysis of Multi-Temporal Sentinel-1 SAR Parameters to Crop Height and Canopy Coverage

Abstract

The Polarimetric Synthetic Aperture Radar technique has provided various opportunities<br> and challenges in agricultural activities mainly on crop management. The aim of this study is<br> to investigate the sensitivity of 10 parameters derived from multi-temporal Sentinel-1 Synthetic<br> Aperture Radar (SAR) data, to crop height and canopy coverage (CC) of maize, sunflower, and wheat.<br> The correlation coefficient values indicate a high correlation for maize during the early growing<br> stage. The coefficient determinations (R 2 ) of 0.82 and 0.81 indicate that there is a strong relationship<br> between the maize height and SAR parameters including VV + VH and VV, respectively. The maize<br> CC is well correlated with VV parameter (R 2 = 0.73), but it is observed that at the later growing stage<br> the correlation became weaker. This means that the sensitivity decreases with increasing vegetation<br> cover growth. Compared to maize, the sensitivity of SAR parameters to wheat variables is often<br> good at the early stage. However, the highest correlation with wheat height represented by Alpha<br> (α) decomposition parameter (R 2 = 0.67). The sunflower height has an insignificant correlation<br> with the majority of SAR parameters and only VH polarization shows low sensitivity (R 2 = 0.31).<br> The sunflower CC shows relatively higher correlation with VV polarization (R 2 = 0.46) at the early<br> stage while no considerable correlation is observed at the later stage. It is found that Sentinel-1 has a<br> high potential for estimation of crop height and CC of the maize as a broad-leaf crop. The same is not<br> true for sunflower as another broad-leaf crop.