Spacing Standards for Tactile Maps
Research on tactile maps and tactile graphics has long emphasized that minimum spacing between symbols is one of the key factors determining readability for users with visual impairments. Most studies approach this issue from three complementary perspectives: tactile perception thresholds, ergonomic usability of tactile graphics, and practical cartographic design guidelines.
Early perceptual studies focused primarily on the physiological limits of touch recognition. Research by Roberta Klatzky and Susan Lederman demonstrated that two tactile points can typically be distinguished only when separated by approximately 2.4 mm. This finding became one of the foundational references for later tactile cartography guidelines because it established a baseline for minimum separability of tactile stimuli (Klatzky and Lederman 2003).
Later works in tactile cartography expanded these findings into practical map design recommendations. Ruth Edman, in her influential publication Tactile Graphics, stressed that tactile symbols must remain simple, sufficiently separated, and free from excessive density in order to reduce confusion during map exploration (Edman 1992). Similar principles were adopted in guidelines developed by the Braille Authority of North America (BANA) and the Canadian Braille Authority (CBA), where recommended spacing between tactile symbols and labels generally ranges from 3 to 6 mm, depending on symbol complexity and production technology (BANA and CBA 2010).
Polish studies also contributed significantly to this field. Anna Więckowska and collaborators proposed spacing recommendations of approximately 3–4 mm between tactile elements and labels, emphasizing the importance of balancing map detail with tactile clarity (Więckowska et al. 2012). Other researchers, including Jehoel et al. (2006, 2009), investigated not only spacing but also the relationship between symbol height and tactile discrimination, suggesting that varying symbol elevations may improve readability and reduce confusion between neighboring objects.
A recurring limitation in earlier studies is that many recommendations were based either on theoretical assumptions or on traditional embossed-map production techniques. Relatively few studies tested spacing parameters directly with users with visual impairments in the context of modern 3D-printed tactile maps. Furthermore, earlier guidelines often proposed universal spacing values without considering the influence of symbol height differentiation or specific map content complexity.
The solutions developed within our project address these gaps. The proposed spacing recommendations were established through a detailed review of international literature and existing tactile cartography standards and subsequently verified during practical testing sessions with users with visual impairments. Unlike many earlier approaches, the project introduced differentiated symbol heights, making it possible to safely reduce some distances between neighboring elements while maintaining tactile readability.
As a result, the project recommends:
- 2.0–2.2 mm spacing between symbols of different heights (2.2 applies when the graphic symbol is larger than the tactile symbol),
- 4.0 mm spacing between symbols of the same height.
These values constitute practical, empirically validated recommendations for tactile maps produced using contemporary 3D-printing technologies and represent an important step toward more evidence-based standards in modern tactile cartography.
References
- BANA (Braille Authority of North America) and CBA (Canadian Braille Authority). 2010. Guidelines and Standards for Tactile Graphics. Pittsburgh: BANA.
- Edman, Polly. 1992. Tactile Graphics. New York: American Foundation for the Blind.
- Jehoel, Sandra, Janneke McCallum, Huib de Haan, and Frans Verwey. 2006. “An Evaluation Tool for Tactile Maps.” The Cartographic Journal 43 (3): 256–266.
- Jehoel, Sandra, Huib de Haan, Janneke McCallum, and Frans Verwey. 2009. “The Importance of Tactile Map Variables for Visually Impaired People.” Cartography and Geographic Information Science 36 (4): 399–410.
- Klatzky, Roberta L., and Susan J. Lederman. 2003. “Touch.” In Handbook of Psychology, edited by Irving B. Weiner. New York: Wiley.
- Więckowska, Anna, et al. 2012. Tyflomapy – zasady opracowania i użytkowania. Warszawa: GUGiK.