Our plans are for a portable, self-contained system that will indicate the positions of environmental landmarks to a blind traveler by having their labels, spoken by speech synthesizer, appear as virtual sounds at the correct locations within the auditory space of the traveler. Vision serves several functions for human travelers. A primary function is in connection with geographic orientation. Before setting out, the traveler may consult a map for determining an optimal route. Once underway, the traveler uses vision to sense distant landmarks for maintaining goal orientation and to sense nearer landmarks that signify a familiar route or that can be compared with those depicted in the map.
Vision also provides access to optical flow for velocity-based dead reckoning.
A second primary function is in connection with the local aspects of wayfinding, such as keeping the observer on the selected path, detecting hazards such as dropoffs, and avoiding stationary and moving obstacles. Obviously, a traveler lacking vision is at a considerable disadvantage, for aids like tactual maps are rarely available, the traveler has little information about remote landmarks and paths that permit the selection of novel routes while underway, and obstacles and other hazards are encountered with little advance warning. In connection with geographic orientation, a missed cue can result in the traveler's becoming momentarily disoriented or indeed lost, even in familiar environments. As a consequence, the traveler can experience stress, fear, and even panic, emotions that would rarely beset a sighted traveler except perhaps in the most remote wilderness or in densest fog. The aid we have in mind will inform a traveler of his or her current position and orientation with respect to the environment being navigated, will provide information about the immediate surroundings, and will assist in route planning.