Some of the predisposing factors can be characterized using standard GIS data processing techniques. For instance, primary topographic attributes (such as slope gradient, slope aspect, planform curvature, and profile curvature) can be derived from DEM data using standard terrain analytical methods in GIS. Lithology type and strata information can be digitized from geological maps. However, some predisposing factors are easy for human experts to recognize but hard for the computer to characterize. Slope shape, an important predisposing factor in landslide-susceptibility mapping for some study areas, is an example. Landslide experts/researchers can easily identify different shapes of slope such as straight slope and upper convex–lower concave slope. However, characterizing these features using computer programs in an automated way is not straightforward. Customized techniques are needed (see Section 3.2.2).