Method for advancing a colonoscope within a colon of the body of a patient, the method including the procedures of acquiring a stereoscopic image pair of a region of the interior of the colon, identifying topographical features in the stereoscopic image pair, determining the depth of each of the topographical features in the stereoscopic image pair, and indicating the appropriate direction to advance the colonoscope, the direction being toward at least a selected one of the topographical features with greater depth than others of the topographical features.