Special Considerations for Blind Travelers using GPS
by Larry Skutchan
Global Positioning Systems (GPS) are so common now that most people either use one in their car or employ a hand-held unit on a daily basis. These devices pinpoint your position on earth by triangulating signals from three or more satellites. When this positional information combines with detailed maps and the appropriate software, a powerful tool emerges.
Typically, the maps and software provide capabilities such as finding nearby businesses, or routing you to your desired destination. Preferences for distance and speed, including turn-by-turn directions during the journey, or just discovering what attractions of interest happen to be nearby, are other benefits of this technology.
In addition to the road details, typical maps contain millions of points of interest. These features make searching for a destination by name or category possible.
While most sighted drivers agree that the use of GPS helps them find where they need to go, the implications for a blind traveler are more critical. Consider the fact that most blind people do not see well enough to be able to read signs that mark the world for the rest of us. By cleverly designing software, such systems provide the blind pedestrian with the information she needs to detect the proximity of buildings, businesses, and other items of interest, in an alternative way. Specialized GPS software for blind users arranges these points of interest by proximity and the direction of travel and presents the information as relevant to her current position. For example, the location of Starbucks might be stated as ahead and to the right 50 feet.
Typical GPS software shows the sighted user a map to help her find a particular destination. A blind user, however, cannot look at a graphical representation of a map, but software designed to let her explore the map virtually would give her the same navigation capability. In other words, instead of scrolling a map into view, the blind user employs a device with directional keys to traverse the map. Typical systems use the Up Arrow key to move the traveler from one point to the next in the direction of virtual travel. Most commonly, these points are intersections, but they can be points of interest or even a specific distance.
Along with the special "move by intersection" commands, a system for blind users must provide a means for the traveler to change her virtual direction. One way software helps is with the use of the Left Arrow and Right Arrow keys. Positioned at an intersection, a user presses the Right Arrow key, for instance, to change the direction of travel toward the next intersecting street or path clockwise from the original direction. Similarly, the Left Arrow key changes the direction of travel toward the first intersecting street in the counterclockwise direction.
APH is working on such a system of maps and software in a tri-phase project. The first phase provides the kinds of capabilities just described for outdoor space.
The second phase involves the development of a social web site designed to share points of interest. As users discover interesting or useful sites and landmarks, they can make that information available to others with this networking tool.
In addition to providing signage information, the GPS lets the blind user find objects that might not be of interest to a typical user. When the software supports sharing points of interest, data from municipalities integrated with map data provide information about other kinds of landmarks. Things such as mailboxes, traffic lights, and even trashcans, become "visible" to the blind user, allowing her to find objects in her path that she might ordinarily miss.
In the third phase of the project, research begins on indoor mapping. Obviously, the same problem of identifying businesses indoors exists as well, but satellites seldom penetrate buildings enough to be able to provide an accurate position. Several companies have devised ingenious ways to augment the satellite signal to obtain precise positional information using cell phone towers and even Wi-Fi hotspots. Nevertheless, one of the biggest problems for indoor navigation is the lack of indoor mapping standards. In a road network, it is clear where paths lead but building interiors may need more attention, especially large open areas. There is also no standard for representing characteristics specific to indoor space. Rooms, stairs, elevators, and exits are some that come immediately to mind.