Computer-Based Navigation System for Blind People

At the 10th ICCHP conference held July 12-14 at the University of Linz, Austria, Bettina Pressl and Manfred Weiser, the staff of the Institute of Navigation and Satellite Geodesy of Graz University of Technology, presented their paper on the development of a navigation system specifically designed to meet the requirements of visually impaired pedestrians. This research project is funded by the Austrian Federal Ministry of Transportation, Innovation and Technology, to promote the development of applications for the Galileo System, which is proposed to be Europe’s future satellite-based navigation and positioning system.

Blind people encounter difficulties in navigating independently in urban areas, especially in an unknown environment. The aim behind creating PONTES (positioning and navigation of visually impaired pedestrians in an urban environment), an assistive technology solution, is to develop a demonstrator navigation system to meet the special requirements of blind and visually impaired individuals. PONTES provides the much-desired accessibility to blind people in terms of manipulating their physical environment. The components of the navigational map include the entire data for the navigation system and a positioning module that determines the current position of the blind pedestrian. The Pedestrian Navigation Module includes a GPS receiver, a gyrocompass, an accelerometer triad, a barometric altimeter and a magnetometer triad for absolute single point positioning, course determination, step detection and height determination respectively. Navigable Map, Path Network, Pedestrian Navigation Module, Routing and Guidance are the system components of this assistive technology solution.

In order to enable blind and visually impaired people to rely on this system in every situation, high data and position accuracy is a must. More importantly, the data has to include details to create an imaginary map of the surroundings as close to reality as possible. People who became blind in later life encounter more difficulty in determining their course as compared to people blind by birth. Since all objects are divided into object classes and categories, they can be switched on and off randomly as desired by the user. Apart from guidance instructions, obstacle warnings are necessary for objects that the white cane cannot sense, such as postboxes, traffic signs and gates. Bicycle paths, construction sites and scaffolding are other sources of threat to the blind pedestrian. Object recognition via head mounted camera is required to include these sources of threat to the obstacle warnings in the navigation system. This system includes only one warning for each obstacle to avoid too much of outputs. The system includes a cost function for the route planning algorithm for people preferring safer routes.

This system has vital difficulties in the design of the user interface like the fact that it is difficult to transmit accurate information of the surrounding space as blind people have a different cognitive imagination. They do not like to wear headphones as it makes them unable to hear background noises of the environment. Speech input is not reliable enough as it is yet to be used for blind pedestrians. Vibrating wristbands and a one-hand keypad with Braille output are some of the user interface devices that can counter these difficulties. Work on ODILIA, another assistive technology solution, will start in July 2006. The aim is to solve the difficulties encountered in PONTES.