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Presenter(s)
Helen Petrie
City University London
Northampton Square
London, EC1V 0HB United Kingdom
Email: h.l.petrie@city.ac.uk
Introduction
Technologies for providing access to text for blind people are well developed - high quality Braille production, refreshable Braille displays, DAISY talking books and screenreaders. However, access to graphics is more problematic. This is particularly unfortunate, as with the use of electronic publishing tools, the amount of graphic material available to sighted readers is increasing. Numerous methods for producing tactile versions of graphics exist - thermoforming, microcapsule paper and Braille dot-based embossing - but all have inherent limitations. There is also a lack of psychophysical, and psychological knowledge about how blind people process information from tactile graphics and in the case of tactile maps, cartographic knowledge relevant to the design and use of tactile maps. The TIMP Project (Tactile Inkjet Mapping Project) is focusing on the production and use of tactile maps for two reasons: firstly, tactile maps are a particularly valuable source of information about the environment for VI people, and secondly, any findings relating to maps, as a specific subcategory of graphics, should also generalise to other kinds of graphics.
The aims of the TIMP Project are:
• to develop a manufacturing process which produces raised tactile print using new inkjet technology.
• to establish principles for the design of tactile maps grounded in research on tactile perception and non-visual spatial cognition.
• to develop a palette of tactile symbols (point, line & area) using the new tactile print technology that are consistent with the cognitively based principles.
• to evaluate the pool of tactile map symbols with a sample of blind and partially sighted people to determine their effectiveness in terms of identification and discriminability, and to test maps in ecologically valid, real world tasks.
To achieve these aims, a multi-disciplinary team comprising materials and system engineers, psychologists and a cartographer are working collaboratively on the following areas.
Materials/Systems Engineering
In order to incorporate the best aspects of current popular tactile production methods (thermoform and microcapsule) in a single common technique we felt it was necessary that the new technology combine:
• Speed, reliability and efficiency, with maps generated by computer.
• An ability to produce symbols at different elevations, textures and profiles.
• Robust output that can withstand repeated, heavy use in many kinds of environments.
• Desk top capability and affordability.
The project has developed a printer capable of producing raised ink surfaces on a variety of substrates. This is achieved by laying down a polymer via an adapted jet head, which is then cured under UV light.
Current work is focusing on:
• The potential to differentiate between ink and substrate to maximise haptic contrast.
• Controlling the spread of inks that will enable the efficient manufacture of symbols with vertical walls. Sharper leading edges and textures will increase symbol discriminability, permitting more control over the three-dimensional profile of tactile symbols.
• Combined with the ability to print maps direct from electronic copy, such factors will help us reduce the height of raised print in the long term, leading to lower production costs and increased production speeds.
Cartography
Building on previous work, the current work is:
• Establishing an initial set of tactile symbols derived from existing literature sources and information on current best practice based on a survey of tactile map producers, designers and researchers.
• Evaluating user needs and preferences via a survey of tactile map users and potential users.
• Via an iterative process of evaluation and redesign, obtaining a set of symbols that is empirically shown to be effective in use, both individually and in combination.
• Testing these symbols in combination on tactile maps and map-like layouts, to determine criteria for arranging map symbols that facilitate user access to map information (e.g. facilitate scanning the map, or organising map information).
• Deriving from this testing a set of design principles or criteria that can be applied independently to guide selection or construction of effective tactile symbols (for all types of graphics, not only for maps) and their distribution on the map surface.
Psychology
The psychologists is working closely with the cartographer to develop tactile symbol sets based on input from information processing theory. Current work is concentrating on:
• Developing evaluation methodologies for assessing tactile symbol characteristics based on properties including size (lateral dimensions), elevation and heights, and line weight and profiles.
• Conducting psychophysical tests on individual symbols generated by the tactile printer using point, line and area (texture) samples.
• Evaluating tactile symbols in combination according to their discriminability and identifiability.
• Testing tactile symbols and maps for their effectiveness in real world tasks.
• Articulating a set of cognitive principles relating to tactile map design.
Conclusions
The presentation will present latest findings in each of these areas of work and illustrate them with a range of tactile materials developed with the new printing process. Plans for future work to lead to a commercially available desk top printer, both a mass production and a personal version, will be discussed.
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