As presented in Fig. 4, the results of tropical peatlands classification from four combinations of data were generated by means of the decision tree classifier. The classification results showed six land use/cover classes, i.e., water, artificial, bareland with peat, bareland without peat, vegetation with peat, and vegetation without peat. The “bareland with peat” and “vegetation with peat” classes represented land use/cover classes identified with the existence of peatland, whereby the “bareland without peat” and “vegetation without peat” classes represented land use/cover classes identified as having no peatland. The classification results of data combinations (i), (ii), (iii), and (iv) had 53.6%, 40.4%, 50.9%, and 32.3% of the total area identified as having peatland, respectively. The results of tropical peatlands classification derived by the dual-polarization data generated the biggest area identified as having peatland, whereas those derived by the combination of dual-polarization data, fully polarimetric data, and the additional feature “distance to river” produced the smallest area identified as having peatland. Thus, in this study, the dual-polarization data tended to generate more peatland area, whereas the full polarimetric data tended to generate less peatland area. In addition, the feature “distance to river” was added to the algorithm of decision tree classification to ignore the existence of peatland from the river stream, so that it influenced the classification results of data combination (iv) producing the smallest area of peatland.