## 2 Study Area and Materials
### Landsat Image Datasets  
This study involved a total of 428 Landsat images in order to map the crop type/LC within the Chi River Basin. In particular, L5, L7, L8 and L9 Level-2 products (atmosprically corrected) were used in this work, and 78, 78, 48, 90 and 134 Landsat scenes were used for the 2001, 2011, 2016 and 2021 base years, respectively. Specific information about the Landsat mission and the corresponding number of images involved are reported in Table 2. Through the GEE platform, only the scenes characterized by having less than 30% cloud cover were selected. It is worth reminding that the L5 and L7 images are characterized by having seven and eight portions of spectral information, respectively, while a total of eleven bands, with a spatial resolution of 30 m, are present in the L8 and L9 data [31; 32]. Despite the fact that several bands are available within the Landsat data, in this work, only six bands were involved. In particular, blue: 490 nm, green: 560 nm, red: 665 nm, NIR: 842 nm, SWIR1: 1910 nm and SWIR2: 2190 nm bands were used. These six pieces spectral information are known in the literature due to the possibility to produce several vegetation indices (VIs) able to detect, monitor and map different crop types [11]. Land surface can be labelled with VIs that are able to identify and monitor phenological crop dynamics [33]. The main aims include crop type and LC classification [13; 34]. In this study, according to Table 1, nine different potential VIs were selected among the main ones present in the literature in order to separate crop type classes. As mentioned in the previous section, the Chi River Basin is characterized by high cloudiness and inclement weather. Therefore, a median composite (MC) was applied to initiate gap-free image composites that are spatio-temporally consistent. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**2001**} & \multicolumn{2}{c}{**2006**} & \multicolumn{2}{c}{**2011**} & \multicolumn{2}{c}{**2016**} & \multicolumn{2}{c}{**2021**} \\ \cline{2-10}
**Crop** & \multicolumn{2}{c}{**Color Orthophoto**} & \multicolumn{5}{c}{**Google Earth Pro**} & \multicolumn{5}{c}{**Field Campaigns**} \\ \cline{2-10}
**Type/LC** & \multicolumn{2}{c}{**Training**} & **Validation** & **Training** & **Validation** & **Training** & **Validation** & **Training** & **Validation** & **Training** & **Validation** \\ \hline Rice & 261 & 112 & 341 & 146 & 335 & 144 & 301 & 129 & 340 & 146 \\ Sugarcane & 890 & 381 & 836 & 358 & 742 & 318 & 615 & 264 & 452 & 194 \\ Cassava & 61 & 26 & 63 & 27 & 180 & 77 & 235 & 101 & 240 & 103 \\ Para rubber & 247 & 106 & 227 & 97 & 209 & 90 & 311 & 133 & 365 & 156 \\ Built-up & 350 & 150 & 350 & 150 & 350 & 150 & 350 & 150 & 350 & 150 \\ Forest & 303 & 130 & 272 & 117 & 268 & 115 & 243 & 104 & 225 & 96 \\ Water & 118 & 51 & 126 & 54 & 125 & 54 & 136 & 58 & 150 & 64 \\ Bare soil & 73 & 31 & 88 & 38 & 94 & 40 & 112 & 48 & 181 & 78 \\ \hline Total & 2303 & 987 & 2303 & 987 & 2303 & 987 & 2303 & 987 & 2303 & 987 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Reference data sets of crop type/LC over Chi River Basin, Thailand in years 2001, 2006, 2011 and 2021. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Image Data** & \multicolumn{5}{c}{**Years (Scenes)**} \\ \cline{2-5}
**(January–December)** & **Sensor** & **2001** & **2006** & **2011** & **2016** & **2021** \\ \hline Landsat-5 & TM & 45 & 78 & 48 & \\ Landsat-7 & ETM+ & 33 & & & & \\ Landsat-8 & OLI & & & & 90 & 112 \\ Landsat-9 & OLI-2 & & & & & 22 \\ \hline Total (scenes) & & 78 & 78 & 48 & 90 & 134 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Landsat image datasets deployed for mapping agricultural fields/LC in 2001, 2006, 2011, 2016 and 2021. The number of scenes show the availability for crop type/LC mapping. Landsat-5 (L5) images were applied for 2001, 2006 and 2011, and Landsat-7 (L7) data was adapted in analysis for only 2001.