“…This is generally followed by a process that classifies these regions as pedestrian or non-pedestrian. Objects can be filtered according to, for example, aspect-ratio (since pedestrians are generally expected to be taller than they are wide) (Xu et al, 2005), inertial parameters (total rotational momen tum of a candidate with respect to its centre) (Fang et al, 2004), horizontal and vertical grey-level intensity profiles (Fang et al, 2004), or, as humans display bilateral symmetry, grey-level symmetry and edge symmetry of pedestrians can also be used to segment regions of interest (Bertozzi et al, 2004). Edge density can also be analysed as pedestrians in far-IR images are usually much brighter than the background, and there can be a sharp change in image intensity at their edges (Bertozzi et al, 2004).…”