Nonvisual Route Following with Guidance from a Simple Haptic or Auditory Display

A path-following experiment, using a global positioning system, was conducted with participants who were legally blind. Onand off-course confirmations were delivered by either a vibrotactile or an audio stimulus. These simple binary cues were sufficient for guidance and point to the need to offer output options for guidance systems for people who are visually impaired. Personal navigation systems using global positioning systems (GPS) are now commercially available for persons who are visually impaired (that is, those who are blind or have low vision). Some of the more widely used systems are BrailleNote GPS from Sendero Group, StreetTalk from Freedom Scientific, and Trekker from HumanWare (see, for example, product evaluations by Denham, Leventhal, & McComas, 2004; and NFB Access Technology Staff, 2006). All these systems use textual information to communicate with the user, in the form of either synthetic speech or electronic braille. Loomis (1985) proposed that sounds that are perceived as coming from spatial This research was supported by Grant SB020101 from the National Institute on Disability and Rehabilitation Research awarded to the Sendero Group (Michael May, principal investigator). The authors thank Jerry Tietz for configuring the hardware and developing the custom software that was used in the experiment, Ethan Smith for assisting with the experiment, and Tom Wiegand for recommending the tactile stimulator used in this research. ©2007 AFB, All Rights Reserved Jou locations (so-called virtual sounds) could be used to guide people who navigate without sight as an alternative to guidance information provided by synthesized speech. He and his colleagues (Golledge, Klatzky, Loomis, Speigle, & Tietz, 1998; Golledge, Loomis, Klatzky, Flury, & Yang, 1991) later developed a Personal Guidance System (PGS) using virtual sound and subsequently experimented with a range of different display devices, in addition to virtual sound, to determine the effectiveness of using different modes and guidance information cues. Three field experiments have shown that virtual sound and a haptic/auditory interface are well liked by users and effective in guiding them along paths. Some of the experiments compared display modes that had the directional compass mounted on the head, hand, or trunk of users (Loomis, Golledge, & Klatzky, 1998; Loomis, Marston, Golledge, & Klatzky, 2005; Marston, Loomis, Klatzky, Golledge, & Smith, 2006). Most recently, Klatzky, Marston, Giudice, Golledge, and Loomis rnal of Visual Impairment & Blindness, April 2007 203 (2006) found that virtual sound imposes considerably less of a cognitive load (the level of effort on working memory associated with thinking and reasoning, which potentially interferes with other thought processes) than does speech in a routefollowing task. In addition to our group, the SWAN project at the Georgia Institute of Technology has been investigating the potential of virtual sound as part of the user interface of wayfinding devices (Walker & Lindsay, 2003, 2005, 2006). Because the virtual sound and haptic/auditory interfaces just mentioned all involve auditory signals, often with language, we were interested in whether a minimal haptic display that does not involve audition would be effective in guiding users along a route. Such a display may be useful for people in noisy environments, people who are deaf-blind, and people who are visually impaired who want to keep their auditory channels open only for environmental sounds and for conversing with others. Of course, using haptic information for route guidance does not preclude the use of audition for providing other sorts of information, such as the names and locations of streets or points of interest, but it would still be useful for minimizing the use of the auditory channel of users. Two studies established the feasibility of using haptic displays for route guidance. Ertan, Lee, Willets, Tan, and Pentland (1998) showed that a 4 4 array of vibrotactile stimulators placed on the backs of users allowed the users to traverse indoor paths successfully. Successive pulsing of vertical columns within the array specified the direction of the turn toward the next waypoint along the route. In a more systematic study using a GPS navigation system outdoors, Van 204 Journal of Visual Impairment & Blindness, April 2007 Erp, Van Veen, Jansen, and Dobbins (2005) showed that sighted users could easily walk over routes that were defined by invisible waypoints that were sensed by way of vibratory signals. The display used in their investigation consisted of eight vibrotactile stimulators that were spaced evenly about the waist, with the current direction to the next waypoint specified by the active stimulator at the corresponding direction around the waist. The distance to the next waypoint was specified by the spacing between successive one-second pulses of the active stimulator (which operated using a frequency of 160 Hz). With a little practice, the participants were able to walk over paths at acceptable walking speeds. The vibrotactile display that was used in our study relies on an electronic compass that is attached to a visor worn on the user’s head so that the direction to the next waypoint is relative to the head. Since it is worn on the wrist and uses a single vibrotactile stimulator, the display we used is minimal in comparison to previous vibrotactile displays that were worn on the torso. When the head is facing the next waypoint, the vibrator conveys a signal indicating a correct or incorrect headfacing orientation. Thus, the user makes use of both cutaneous information from the vibrator and kinesthetic information from the head to determine the direction to the next waypoint. Because the direction to the next waypoint is not mapped to body locus, the stimulator can be worn on any part of the body. In our study, we compared the vibrotactile display with an auditory display that provided the same binary corrective information. The auditory display did not use directional virtual sound; rather, it used a chime as the cue for correctness. The minimal vibrotactile and ©2007 AFB, All Rights Reserved auditory displays were tested in two different modes. The cue was activated either only when the user was headed in the correct direction and deactivated when the user headed in another direction (“on-course cue” mode) or only when the user was off course and deactivated when the user was on course (“off-course cue” mode). In addition to the two displays, we also tested a display that had been evaluated in previous experiments, which is described later.