“…(Ahmed et al 2013) used Vegetation indices (optical),Global Environment Monitoring Index GEMI ,Purified Adjusted Vegetation Index PAVI and polarimetric indices SAR (CPR, HV/HH and HV/VV) to detect the subsurface hotspots. The third part of pixel level is two articles based on Hierarchical Markov Random Fields models (Hedhli et al 2015(Hedhli et al , 2017, and finally nine papers applied others different methods including layer stacking (Sameen et al 2016), Genetic algorithm image fusion technique (Ahmed et al 2016), multi-scale decomposition and sparse representation (Zhouping 2015), the combination method band 3, band 7 of Landsat ETM+ with a modified HH polarization of SAR image (Xiao et al 2014) , Closest Spectral Fit (CSF) algorithm with the synergistic application of multi-spectral satellite images and multi-frequency Synthetic Aperture Radar (SAR) data. (Eckardt et al 2013), applied learning Artificial Neural Network at pixel level ANN (Piscini et al 2017), these three typical manifold learning ; ISOMAP, Local Linear Embedding (LLE), principle component analysis (PCA) and two papers the first are not clear and the last without fusion method.…”