Height Differentiation on Tactile Maps
One of the greatest challenges in tactile cartography is balancing map readability with the amount of information that can be presented. Traditional tactile maps require sufficient spacing between neighbouring symbols to ensure they can be reliably distinguished by touch. Although this improves legibility, it also limits the amount of information that can be included on a single map sheet.
Recent research has demonstrated that symbol height can be treated as an additional tactile cartographic variable rather than merely a production parameter. Experimental studies showed that differentiating the height of point, line, and area symbols significantly improves tactile discrimination, allowing symbols to be placed closer together without reducing readability (Wabiński et al. 2022). Based on user testing, three height levels proved particularly effective for FDM-printed tactile maps: 0.56 mm for area symbols, 1.12 mm for line symbols, and 1.68 mm for point symbols. These findings provide practical guidelines for increasing the information density of tactile maps while maintaining comfortable tactile exploration.
The concept of height differentiation was subsequently incorporated into the development of tactile maps of historic gardens. In addition to applying different height levels, every tactile symbol was subjected to a structured validation procedure based on iterative testing in isolation and in the context of complete tactile maps (Mościcka et al. 2025). The validation process resulted in a standardized library of 52 tactile cartographic symbols optimized for DLP 3D printing. During this process, the final symbol heights were refined to improve tactile recognition and consistency across the complete symbol set.
| Symbol type | Final recommended height |
|---|---|
| Area symbols | 0.5 mm |
| Line symbols | 1.0 mm |
| Building walls | 1.5 mm |
| Point symbols | 2.0 mm (2.2 mm)* |
These values represent the final design recommendations obtained after iterative user testing and refinement of the tactile symbol library. While the earlier study demonstrated the potential of height differentiation as a cartographic variable, the later research translated this concept into a practical, validated symbol system suitable for real-world tactile maps.
References
Wabiński, Jakub, Emilia Śmiechowska-Petrovskij, and Albina Mościcka. 2022. “Applying Height Differentiation of Tactile Symbols to Reduce the Minimum Horizontal Distances Between Them on Tactile Maps.” PLOS ONE 17 (2): e0264564. https://doi.org/10.1371/journal.pone.0264564