Systematically Evaluating Equivalent Purpose for Digital Maps - Data

Digital geographic maps remain largely inaccessible to blind and low vision individuals (BLVIs), despite global legislation adopting the Web Content Accessibility Guidelines (WCAG). A critical gap exists in defining “equivalent purpose” for maps under WCAG Success Criterion 1.1.1, which requires that non-text content provide a text alternative that serves the "equivalent purpose”. This paper proposes a systematic framework for evaluating map accessibility, defining purpose through three items (Generalized, Spatial Information, and Spatial Relationships), and establishing 15 measurable criteria for equivalent information communication. Eight text map representations: turn-by-turn directions, tables, Nearby Address Searches, short text alternatives, Google Maps Interactive Alternate Text, Audiom Map Interactive Alternate Text, and audio descriptions, were evaluated against visual map baselines. Results show that legacy methods like tables and turn-by-turn directions fail to meet equivalent purpose, while Audiom Maps, MUD Maps, and Audio Descriptions satisfy the framework. The evaluation highlights the necessity of holistic, systematic approaches to ensure non-visual maps convey all generalized spatial information and relationships present in visual maps. This framework provides a replicable methodology for assessing digital map accessibility, clarifying WCAG’s equivalent purpose, and guiding compliant and usable map creation. Compliant maps will support BLVIs’ participation in map-dependent professions and civic engagement.<br><br>