## 3 Results
### Regression-Based LAI and \(\mathrm{LUE_{Canopy}}\) Retrieval  
We now present the results of the retrieval of LAI and \(\mathrm{LUE_{Canopy}}\) from LANDSAT EVI2 by Equations (4) and (5) via leave-one-site-out cross validation. In Figure 3, we present the leave-one-site-out performance for all sites combined in separate scatterplots for the LAIGROUND and FLUX datasets (prediction performed with leave-one-site-out site-by-site and then combined into a single scatter plot). Figure 3a shows the LAI retrieval scatterplot for the LAIGROUND dataset, while Figure 3b,c show the LAI and \(\mathrm{LUE_{Canopy}}\) retrieval scatterplots for the FLUX dataset.  
Figure 3 shows LAI retrieved with a \(\mathrm{R^{2}}\) performance between 0.41 and 0.69 and an RMSE between 1.07 and 1.22, while \(\mathrm{LUE_{Canopy}}\) is retrieved with an \(\mathrm{R^{2}}\) performance of 0.74 and an RMSE of 0.17. In addition, the site-by-site leave-one-site-out retrieval performance and regression coefficients for the LAIGROUND dataset are shown in Table 3, while the corresponding information for the FLUX dataset is shown in Table 4. Tables 3 and 4 also show the confidence intervals for the determined leave-one-site-out coefficients.  
Figure 2: (**a**) Comparison of actual versus Hybrid-Maize modeled \(\mathrm{LUE_{Canopy}}\). The color bar represents the number of points at each marker on the scatter plot. (**b**) \(\mathrm{R^{2}}\) of actual versus Hybrid-Maize modeled \(\mathrm{LUE_{Canopy}}\) and \(\Delta\mathrm{LUE_{Canopy}}\) at different levels of smoothing and values of \(\Delta\). N = 2384.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**Best-Fit**} & \multicolumn{3}{c}{**Lower Bound**} & \multicolumn{2}{c}{**Upper Bound**} \\  & & \multicolumn{3}{c}{**Coefficients**} & \multicolumn{3}{c}{**Confidence Interval**} & \multicolumn{3}{c}{**Confidence Interval**} \\ \hline
**Site Name** & **LAI RMSE** & **N** & **a** & **b** & **a** & **b** & **a** & **b** \\ \hline Beltsville & 0.85 & 26 & 8.41 & \(-\)0.92 & 7.73 & \(-\)1.18 & 8.94 & \(-\)0.65 \\ CEFLES2 & 0.60 & 26 & 8.55 & \(-\)1.04 & 7.76 & \(-\)1.31 & 9.10 & \(-\)0.79 \\ California & 1.32 & 59 & 8.19 & \(-\)1 & 7.60 & \(-\)1.43 & 9.22 & \(-\)0.77 \\ Italy & 1.58 & 35 & 8.49 & \(-\)1.20 & 7.82 & \(-\)1.49 & 9.33 & \(-\)0.92 \\ Mead & 1.03 & 92 & 7.27 & \(-\)0.71 & 5.86 & \(-\)0.9 & 7.67 & \(-\)0.03 \\ Missouri & 0.98 & 10 & 8.13 & \(-\)0.87 & 7.57 & \(-\)1.18 & 8.81 & \(-\)0.64 \\ NAFE06 & 0.31 & 14 & 8.08 & \(-\)0.85 & 7.50 & \(-\)1.42 & 9.19 & \(-\)0.61 \\ SEN3 EXP2009 & 0.89 & 10 & 8.20 & \(-\)0.94 & 7.61 & \(-\)1.26 & 8.90 & \(-\)0.77 \\ SMEX02-IA & 1.23 & 21 & 8.66 & \(-\)1.06 & 8.03 & \(-\)1.35 & 9.27 & \(-\)0.83 \\ SPARC & 1.74 & 45 & 9.17 & \(-\)1.31 & 8.67 & \(-\)1.55 & 9.73 & \(-\)1.03 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Leave-one-site-out LAIGROUND LANDSAT regression retrieval performance using Equation (4). a and b are the leave-one-site-out regression coefficients defined in Equation (4).  
Figure 3: Comparison of retrieved versus actual (**a**) LAI from LAIGROUND dataset, (**b**) LAI from FLUX dataset, and (**c**) LUE\({}_{\text{Canopy}}\) from FLUX dataset from LANDSAT measurements via leave-one-site-out cross validation. The color bars represent the number of points at each marker on the scatter plot.