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Figure 5.18. vOICe system: visual image to soundscape mapping

is placed over an image, as in Figure 5.18, then each square in the grid can be considered to have the visual attributes {(x,y) (indicating position), brightness, colour}. The principle of the vOICe system is to map each of these visual attributes to the aural attributes {left/right ear, pitch, loudness, time duration of the sound}. The summation of the sounds from the different grid squares in the image produces a soundscape version of the image.

The soundscape images can be refreshed at the rate of one image per second and the visual images can be supplied to the vOICe system from a PC camera, an image file or a computer screen. This technology raises the question of the ability of the auditory system to process and make sense of this type of very complex information. There is also the further question of whether this ‘sense making’ is dependent on training at an early age, since sighted people ‘learn’ to process complex images from birth. If the auditory sense is able to process the information, even if only with training, then this approach could be used to enhance the experience of blind people by giving them a sound picture of their environment.

5.7 Orientation Assistive Technology Systems

Designing and constructing a long-range orientation aid for visually impaired and blind people poses a significant challenge. Past projects in the US and Europe have led to the development of prototypes and currently, at least two commercial devices are available. However, this is an area where the basic enabling navigational technologies are maturing and entering mainstream consumer products. Although there are now a number of commercially available orientation devices for visually impaired and blind people, generally based on global positioning systems (GPS), published research on what the enduser community would like to have or actually need in an electronic orientation and navigation assistive technology device seems rather sparse. Clearly, long-range orientation aids need to be easily portable and, if purely devoted to providing orientation information, to leave at least one hand free to allow use of a long cane. As with obstacle avoidance systems, the device has to perform two main functions:

•Obtaining way-finding information and the relationship of the user to landmarks.

•Communicating this information to the user.

Unlike obstacle avoidance systems, (portable) assistive orientation and navigation systems are of great interest to sighted people. The existence of this very large user community has led to a number of important developments in the past few years, generally based on the use of GPS. Developments have included hand-held GPS devices, in-car navigation and map systems and position data features in mobile phones. However, GPS technology is only one option for acquiring position data and other communication technology methods are well advanced and ready for application. The popularity of this type of device has led to a reduction in prices and will undoubtedly lead to further development of the different technologies. However to exploit these technologies in an orientation and navigation system for visually impaired and blind people, an understanding of the differences in the requirements of the sighted and visually impaired communities is needed. This includes the following factors:

•System accuracy. Blind and visually impaired people will frequently need to know their location to a much greater degree of accuracy than sighted people do. For instance, an accuracy of one metre or less will be required to ensure that blind and visually impaired users are able to locate the door of the house they are looking for.

•Information frequency and quantity. Blind and visually impaired people often use a greater number and variety of landmarks than sighted people when on a journey. It is not likely that all the most appropriate landmarks, such as pedestrian crossing location data, will be available from the digital maps so often used in these systems.

•Spatial orientation resolution. Blind and visually impaired people may require information on the direction they are facing. This type of information was not provided by the earlier GPS systems. This problem can be resolved by the user travelling a short distance and being informed whether the distance to their destination has increased or decreased. However this is not a particularly user-friendly solution.

•Unambiguous audio and tactile information interfaces. Many visually impaired people will not be able to use the visual information often provided by these systems, particularly while travelling and will therefore need all the information in verbal or tactile form. This will require the verbal information and descriptions to be presented in a particularly clear and unambiguous way, as this is the sole source of information and ambiguities cannot be resolved by looking at a visual route map.

•Back-up system provision. Blind and visually impaired people are likely to experience problems that are more serious than those experienced by sighted people if the electronic orientation system fails. For example, the GPS system can fail in built-up areas, due, for instance, to the line of sight to the satellites being

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blocked by high buildings. Therefore electronic orientation systems designed for blind and visually impaired people will require a backup system.

5.7.1 Global Positioning System Orientation Technology

GPS systems use information from at least three satellites to detect the user’s location. The satellite system is interfaced with a digital map that can then relate the detected location to appropriate landmarks. In-car systems incorporate speech delivered information, as well as visual information to try to avoid the driver being distracted from concentrating on the road. Therefore, systems of this type are potentially equally relevant to visually impaired, blind and sighted people and some GPS devices are available.

The satellite system currently used in GPS is a military system belonging to the US Department of Defense. This system was originally available to civilians at a reduced accuracy, called selective availability, of ±100 m rather than ±5 m. Selective availability was removed in May 2000, enabling all users to benefit from the full accuracy of the system. Accuracy can be increased by the use of differentially corrected GPS (DGPS) which corrects bias errors at one location using measured bias errors at another location and also eliminates static errors from satellite signals entering the earth’s atmosphere. The DGPS services are provided commercially with different services giving accuracies of ±1 m to ±4 m, with corresponding prices. Therefore, in principle, DGPS is able to provide sufficient accuracy to be used by blind and visually impaired people. However, there will still be a need for modification of existing digital maps to provide sufficient and appropriate information for blind and visually impaired people. There is also a need for further development of the information interface to provide sufficient and appropriate information to enable the user to navigate to their destination safely while being aware of any landmarks of interest on the route.

Braille Notetaker with GPS

This device has the advantage of being useable by deafblind as well as blind people. Chapter 8 contains a more detailed presentation of the development history for this device.

5.7.2 Other Technology Options for Orientation Systems

Mobile telecommunication technology orientation systems

Another potential approach to obtaining position data is the use of mobile phone signals in combination with the technical development resulting from legislation to ensure that the emergency services are able to pinpoint the location of calls made from a mobile telephone. As with GPS, the resulting information has to be interfaced with a digital map in order to relate the location to appropriate landmarks. In addition, as in the GPS case, it is not always possible to obtain the location using mobile phone signals. Combining the two approaches might prove a solution. Alternatively, a backup system would be required.