“…These and related model-based techniques have been applied to a range of difficult image analysis problems, such as locating, interpreting, and measuring structures in medical images (Cootes et al, 1994;Redhead, Kotcheff, Taylor, Porter, & Hukins, 1997;Solloway, Hutchinson, Waterton, & Taylor, 1997), tracking and performing measurements on the nematode worm Caenorhabditis elegans (Butcher, Cootes, Courtney, Gill, & Lithgow, 1999), locating and tracking farm animals (Bulpitt, Boyle, & Forbes, 2000;Magee & Boyle, 1999;Marchant & Onyango, 1995;Sumpter & Bulpitt, 1998), and tracking pedestrians (Baumberg & Hogg, 1994). The important defining feature of such model-based approaches is that the model is first trained on a set of example images containing instances of the object of interest.…”