Towards a Standardized Grammar for Navigation Systems for Persons with Visual Impairments

Pedestrian navigation systems are rarely accessible or suit the needs of persons with visual impairments. They usually lack a standardized grammar for their speech instructions, forcing users to learn new types of instructions for each new system. Thus, we propose (1) a German grammar with syntax rules and vocabulary for mobile pedestrian navigation systems that take into account the special requirements of people with visual impairments. (2) a set of rules for specifying what should be spoken and when, given GPS accuracy in a city [18]. We describe (3) the methodology used to obtain the grammar as well as (4) a qualitative evaluation with orientation and mobility experts and with people with visual impairments who deployed our grammar during a user study. Our approach is the first of its kind, as there is no such grammar neither for German nor for English, as far as we know. It serves as a contribution to standardize pedestrian navigation speech instructions for people with visual impairments.