8.6 User Interface Design Issues

Functionality does not conceptually have to correlate with stand-alone or integrated units. Historically, if you wanted a top of the line sound system, you purchased separate components. This does not apply to computer-based technology. Functionality is more likely to be linked to the memory capacity and processing speed of the computer chip running the GPS. Functionality will have the most to do with the maturity and sophistication of the software. Sendero’s GPS software, for example, has been in the marketplace in one form or another since 1995 giving it the benefit of user input over many years. Newer GPS applications primarily developed for sighted users have basic functionality but are lacking features specific to blind users.

Mobile phones with built-in or Bluetooth GPS are likely to offer the convenience and cost benefit of integration with basic functionality. They have the benefit of more up-to-date map data residing on a server. However, the mobile phone GPS is not likely to have the power of the accessible PDA GPS for narrating location information and providing “look-around” functionality.

8.6 User Interface Design Issues

Designing a device that provides location information requires careful research and planning for the user interface. The main objective is to deliver relevant orientation information while not overloading the user. Since the definition of what is considered relevant to the end-user is different for every individual and travel situation, the user interface must be configurable but not complicated. The balance between configurability and complexity must be driven by user input. The more experience a developer has with user feedback, the better this balance will be achieved.

8.6.1 How to Present the Information

Everyone has a different preference when it comes to obtaining travel directions; this is also true for blind travellers. Generally, a blind person will get directions in two different forms. The first form uses a sound that is emitted by the source of the object. For example, to find a person in a room, a blind person might follow the sound of that person’s voice. This type of auditory cue will be referred to as 3D Sound. The other form of directional information is the type of directions obtained when on the street asking for directions. For example, “Big Mama’s Pizza is ahead of you 8 m away.” Other variations of this type of information use clock face references. So the same example from above would be “Big Mama’s Pizza is at 12 o’clock, 8 m away.” These auditory cues are referred to as Spatial Language, because they use language to describe where an object is located. According to research studies from the University of California, Santa Barbara, 3D sound and spatial language are roughly comparable in their effectiveness as auditory interfaces. For guiding a person along a route, 3D sound delivered by a virtual acoustic display led to somewhat better performance and user evaluations than spatial

282 8 Accessible Global Positioning System and Related Orientation Technologies

language (Loomis et al. 2001). With regard to monitoring and reporting off route locations, 3D sound and spatial language are very similar in their effectiveness (Loomis et al. 2002; Klatzky et al. 2003) but building up mental representations of these off-route locations takes a little longer with spatial language. Although 3D sound is slightly more effective as an interface, it suffers from these disadvantages when implemented using a virtual acoustic display: earphones are necessary, and specialized hardware is needed to implement the display.

8.6.2 When to Present the Information

Now that the best way to describe the directions has been determined, the best time to receive directional information will be considered. Again, personal preference plays a role in this issue. Some people like to receive all their directions at once and others like to be given announcements as they travel the route. Some blind people have trained to use their memory extensively when it comes to directions; however, it is still nice to have reassurance while on a route. The GPS program should have the flexibility to be able to provide information to suit the user and the situation. For example, the announcements can be quiet until the traveller approaches the destination or when a turning point or significant point is approached. On the other hand, announcements can be set to repeat every 10 s, giving the user a continuous commentary on the upcoming intersections or remaining distance to the destination. Automatic announcements keep the user from having to find a key or push a button, especially if that hand is occupied carrying something, for example a mobility device like a long cane. Manual functionality is important for the user who does not want his or her thoughts interrupted or who is concentrating on mobility information.

8.6.3 What Information to Present

Finally, it is important to identify the type of information that a blind traveller will need. Using GPS technology, every point on earth becomes an electronic landmark; every point of the Earth attains a unique name. So, there is no limit to the amount of information that can be announced. Filtering the important information for the given user in a given situation becomes the challenge. The essential location information like street names, upcoming intersections, businesses, cities, and landmarks should be the first priority in creating a GPS system designed for blind travellers. Using the example from the first section of the chapter, if the task was to find Big Mama’s Pizza, it would help to know that Big Mama’s pizza is at the intersection of Broad Street and 22nd Street. It would also be helpful to know that it is ahead of you and 38 m away. With a GPS system it is also possible to know your speed of travel, your heading direction, your distance travelled, and that you have not wandered in the wrong direction.