The HapBack: Evaluation of Absolute and Relative Distance Encoding to Enhance Spatial Awareness in a Wearable Tactile Device

For the significant global population of individuals who are blind or visually impaired, spatial awareness during navigation remains a challenge. Tactile Electronic Travel Aids have been designed to assist with the provision of spatiotemporal information, but an intuitive method for mapping this information to patterns on a vibrotactile display remains to be determined. This paper explores the encoding of distance from a navigator to an object using two strategies: absolute and relative. A wearable prototype, the HapBack, is presented with two straps of vertically aligned vibrotactile motors mapped to five distances, with each distance mapped to a row on the display. Absolute patterns emit a single vibration at the row corresponding to a distance, while relative patterns emit a sequence of vibrations starting from the bottom row and ending at the row mapped to that distance. These two encoding strategies are comparatively evaluated for identification accuracy and perceived intuitiveness of mapping among ten adult participants who are blind or visually impaired. No significant difference was found between the intuitiveness of the two encodings based on these metrics, with each showing promising results for application during navigation tasks.