# Sensitivity Analysis of Multi-Temporal Sentinel-1 SAR Parameters to Crop Height and Canopy Coverage
## 4 Conclusions  
In this study, three different crop types that have \"broad\" and \"narrow\" leaves were selected to investigate the sensitivity of the Sentinel-1 dual polarimetric SAR parameters to plant height and CC. Maize and sunflower is selected as broad leaf and wheat as narrow leaf crop. The reason for studying two broad-leave crops was to validate the high sensitivity of SAR polarimetric data to early stages of broad-leave crops and then comparing the findings for wheat as narrow-leave crop. We demonstrate that maize presents higher correlation during the early stages of the crop growth when the crop height is less than 150 cm. It is strongly correlated with the SAR parameters including VV + VH (R\({}^{2}\) = 0.82), VV (R\({}^{2}\) = 0.81), and VH (R\({}^{2}\) = 0.80). Besides, CC of maize was well correlated with VV polarization (R\({}^{2}\) = 0.73) at the early stage before the heading stage although at the later growing stage the correlation becomes weaker after the heading stage. From the backscatter analysis, the same result is not observed in the sunflower. The sunflower height has very low correlation with the most of SAR parameters. Only VH polarization shows slightly better sensitivity when its height is below 92 cm before the ending of flowering and the inflorescence reaches to full size. The sunflower CC is relatively correlated with VV polarization at the early stage (during the flowering stage) while any considerable correlation between SAR parameters and sunflower height and CC is observed at the later stage. The sensitivity of SAR parameters to wheat variables is often low compared to maize and sunflower. The high, but negative correlations are related to the VH/VV intensity ratio and VH polarization. However, Alpha (\(\alpha\)) decomposition parameter shows highest correlation at the beginning stage and represents absence \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**SAR Parameters**} & \multicolumn{2}{c}{**Maze CC**} & \multicolumn{2}{c}{**Sunflower CC**} & \multicolumn{2}{c}{**Wheat CC**} \\ \cline{2-7}  & CC \(\pm\) 75\% & CC \(\geq\) 75\% & CC \(\pm\) 85\% & CC \(\geq\) 85\% & CC \(\leq\) 60\% & CC \(\geq\) 60\% \\ \hline Linear Polarization & & & & & & \\ C\({}_{11}\)-Intensity (VH) & 0.25 & \(-\)0.41 & 0.07 & 0.18 & \(-\)0.01 & \(-\)0.15 \\ C\({}_{22}\)-Intensity (VV) & **0.73** & \(-\)0.49 & 0.46 & 0.09 & 0.10 & \(-\)0.06 \\ H-Alpha Decomposition & & & & & & \\ Entropy (H) & \(-\)0.28 & 0.36 & \(-\)0.06 & \(-\)0.01 & \(-\)0.09 & \(-\)0.01 \\ Anisotropy (A) & 0.30 & \(-\)0.31 & 0.06 & 0.01 & 0.05 & 0.02 \\ Alpha (a) & 0.29 & \(-\)0.32 & 0.07 & 0.00 & 0.07 & 0.04 \\ Radar Vegetation Index & & & & & & \\ RVI & \(-\)0.29 & 0.29 & \(-\)0.07 & 0.01 & \(-\)0.08 & \(-\)0.03 \\ Intensity Ratio & & & & & & \\ VH/VV & \(-\)0.30 & 0.28 & \(-\)0.07 & 0.00 & \(-\)0.06 & \(-\)0.05 \\ (VV \(-\)VH)/(VV + VH) & 0.29 & \(-\)0.29 & 0.07 & 0.00 & 0.07 & 0.04 \\ Intensity Arith. Oper. 1 & & & & & & \\ VH \(-\)VV & \(-\)0.69 & 0.48 & \(-\)0.41 & \(-\)0.07 & \(-\)0.15 & 0.02 \\ VV + VH & **0.73** & \(-\)**0.49** & 0.47 & 0.10 & 0.05 & \(-\)0.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Coefficient of determination (R\({}^{2}\)) between CC and Sentinel-1 SAR parameters. Figure 11: Correlation between \(\sigma^{0}_{\rm VV}\) (**a**), and VV + VH (**b**), backscatter values of maize, and VV + VH (**c**) backscatter value of sunflower with their CC during growing stages. of SAR parameters sensitivity with wheat height at the later growing stage and CC at both stages. The results we have obtained reveals that Sentinel-1 dual polarimetric SAR (C-band) has a high potential for identifying growth stages and estimation of crop height, canopy coverage of maize as a broad-leaf crops. However, this is not proven for sunflower, that may be due to the crop structure and leaves geometry since they may change the SAR backscatter value in any stages of crops.