Tactile maps and diagrams need to be carefully designed in order to be readable by the visually impaired user. In the Tactile Inkjet Mapping Project, we attempt to provide a new orientation for tactile map design through a rigorous programme of experimental research on design issues (cognitive tactualization approach). In this article we discuss three of our studies. The first study evaluates the use of different background materials for tactile graphics. The second study looks at the minimal perceptible distance between two lines. The third study investigates the optimal elevation (height off the paper) at which graphics are produced. We argue that experimental studies like these represent a necessary basis for the design of tactile maps.

This study evaluated the relative suitability of a range of base materials for producing tactile maps and diagrams via a new ink-jet process. The visually impaired and sighted participants tactilely scanned arrays of symbols that were printed on seven substrate materials, including paper, plastic, and aluminum. In general, the rougher substrates were scanned faster than the smoother substrates, and the majority of participants preferred the rougher substrates over the smoother ones.

No abstract

Objective: To determine the optimal elevation of tactile map symbols. Background: Tactile perception research predicts that symbol elevation (vertical height) and texture on tactile maps could influence their readability. However, while research has shown that elevation influences detection and discrimination thresholds for single tactile stimuli, and that the physiological response of fingertip receptors varies with texture, little is known about the influence of these parameters on the identification of stimuli in the context of multiple symbols as found on tactile maps. Method: Sighted and visually impaired participants performed tactile symbol identification tasks. In Experiment 1, we measured the effect of elevation on identification accuracy. In Experiment 2, we measured the effect of elevation and symbol texture on identification speed. Results:Symbol elevation influenced both speed and accuracy of identification with thresholds being higher than found in work on detection and discrimination but lower than on existing tactile maps. Further, as predicted from existing knowledge of tactile perception, rough features were identified more quickly than smooth ones. Finally, visually impaired participants performed better than sighted ones. Conclusion: The symbol elevations necessary for identification (0.040 to 0.080 mm) are considerably lower than would be expected on the basis of existing tactile maps (generally 0.5 mm or higher) and design guidelines (0.4 mm). Application: Tactile map production costs could be reduced and map durability increased by reducing symbol elevation.Further, legibility of maps could be improved by using rough features, which are read more easily, and smaller symbols, which reduces crowding of graphics.

Symbols that could effectively designate direction have the potential to show routes, geographic phenomena, aid scientific explanation and generally enhance understanding of tactile maps and diagrams. In this study, 41 tactile symbols, including subsets of arrow symbols and stair symbols, were investigated for effectiveness at indicating direction. The symbols were presented to blind or blindfolded participants, and qualitative and quantitative responses regarding the symbol orientation and meaning were recorded. The arrow symbols with the greatest agreement across participants as to which direction the symbol intended to convey were basic arrows and the arrowhead. In the case of a line with a saw-tooth surface profile that felt rough when traced by the finger in one direction and smooth in the opposite, participants were split between those intuitively thinking the rough or the smooth was the direction being indicated. Stair symbols with a greater degree of threedimensionality gave marginally increased agreement as to which way was up.