Fig. 2.

Seasonal variation in spectral patterns and spatial probability maps for the Hamoukar region (Fig. 3E). Spectra for anthrosols (red) and other pixels (blue) are shown in the left column; lines represent medians, boxes quartiles (TIR has a different offset than the other channels; VNIR combines channels V and NIR). The anthrosol probability maps of observations A–C are shown in the right column (black 100%, white 0%; 50% threshold outlined red). The bottom row shows the feature ranking for all ASTER images of the study using the Gini importance (22, 24) as measure (boxes represent quartiles; black lines median; green crosses observations A–C). The final probability map—also shown in Fig. 3E—is obtained by averaging A–C and two more observations (which are similar to B and C).