## 3 Results
### OLI vs. ETM+  
The scatterplot standing for the comparison between paired surface reflectance pixel values of satellites Landsat-8 and Landsat-7 (training dataset) was reported in Figure 4. This inter-comparison between sensors has the best grade of agreement, as evidenced by the dashed line representing the ODR slope values which--in some cases--coincides with the 1-to-1 line (Blue band) (Figure 4; Table 13). The NIR band has the higher degree of disagreement (0.9992). The mean difference values for all band comparisons (Table 13) are statistically significant (\(p\)-value < 0.05). The RMSD values range from 0.0186 (Blue band) to 0.0366 (SWIR1 band). A statistical difference was observed applying adjustment coefficients of the regression models from this study (OLS/RMA) (Table 14) and those available in the literature by [PERSON] et al. [39]. The coefficients available in the literature and applied to our dataset revealed statistically significant differences (\(p\)-value < 0.05) (Table 15a) for all comparisons between OLI and ETM+ bands adjusted, RMSD ranging from 0.0173 (blue band) to 0.0446 (NIR band) for [PERSON] et al. (2019) [39] transformation functions (Table 15b). The regression models developed in this study (OLS and RMA) both improved the fitting of the data for all band pairs (Table 15). No statistically significant difference was \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Band** & **ODR Slope** & **Mean Difference** & **RMSD** \\ \hline Blue & 1.0026 & \(-\)0.0141 * & 0.0186 \\ Green & 1.0467 & \(-\)0.0131 * & 0.0196 \\ Red & 1.0566 & \(-\)0.0169 * & 0.0256 \\ NIR & 0.9992 & \(-\)0.0060 * & 0.0267 \\ SWIR1 & 1.0322 & \(-\)0.0159 * & 0.0366 \\ SWIR2 & 1.0569 & \(-\)0.0130 * & 0.0327 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Statistical differences in surface reflectance between the OLI and ETM+ band values. ODR slope, mean difference, and RMSD values for each pairwise band of the training set, comprising a total of 25,640 data points. The asterisk (*) indicates the significance of the \(t\)-test, with a \(p\)-value < 0.05. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Regression Model** & **Blue** & **Green** & **Red** & **NIR** & **SWIR1** & **SWIR2** \\ \hline OLS Intercept & \(-\)0.0083 & \(-\)0.0037 & \(-\)0.0041 & 0.0065 & 0.0038 & 0.0067 \\ OLS Slope & 0.9375 & 0.934 & 0.9325 & 0.959 & 0.9416 & 0.9246 \\ RMA Intercept & \(-\)0.0119 & \(-\)0.0067 & \(-\)0.0067 & \(-\)0.0063 & \(-\)0.0054 & 0.0010 \\ RMA Slope & 0.9764 & 0.9554 & 0.9464 & 1.0009 & 0.9688 & 0.9462 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Intercept and slope values obtained by applying both OLS and RMA regression models for each pair of OLI surface reflectance as a function of ETM+ surface reflectance. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Band** & **OLS** & **RMA** & **[PERSON] et al. [PERSON]** \\ \hline Blue & \(1.06\times 10^{-7}\) & \(4.88\times 10^{-6}\) & \(-\)0.0118 * \\ Green & \(-\)5.29 \(\times 10^{-7}\) & \(-\)3.68 \(\times 10^{-5}\) & \(-\)0.0136 * \\ Red & \(3.49\times 10^{-5}\) & \(-\)4.85 \(\times 10^{-6}\) & \(-\)0.0186 * \\ NIR & \(-\)1.80 \(\times 10^{-5}\) & \(1.49\times 10^{-5}\) & \(-\)0.0326 * \\ SWIR1 & \(-\)5.56 \(\times 10^{-5}\) & \(3.79\times 10^{-6}\) & \(-\)0.026 * \\ SWIR2 & \(-\)3.72 \(\times 10^{-5}\) & \(4.33\times 10^{-5}\) & \(-\)0.0293 * \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Statistical differences in surface reflectance between the OLI and ETM+ band values after transformation functions. Mean difference (a) and RMSD values (b) for each pairwise band of the training set subjected to OLS and RMA regression models in this study and to the [PERSON] et al. [39] transformation functions. The asterisk (*) indicates the significance of the \(t\)-test, with a \(p\)-value < 0.05.  
revealed by the \(t\)-test \(p\)-value. An improvement can be observed compared to the initial RMSD values (Table 13) and post-transformation RMSD values (Table 15).