Abstract
Indoor localization and navigation systems for individuals with visual impairments (VI) typically rely upon extensive augmentation of the physical space or heavy, expensive sensors; thus, few systems have been adopted. This work describes a system able to guide people with VI through buildings using inexpensive sensors, such as accelerometers, which are available in portable devices like smart phones. The method takes advantage of feedback from the human user, who confirms the presence of landmarks. The system calculates the user's location in real time and uses it to provide audio instructions on how to reach the desired destination. Previous work suggested that the accuracy of the approach depended on the type of directions and the availability of an appropriate transition model for the user. A critical parameter for the transition model is the user's step length. The current work investigates different schemes for automatically computing the user's step length and reducing the dependency of the approach to the definition of an accurate transition model. Furthermore, the direction provision method is able to use the localization estimate and adapt to failed executions of paths by the users. Experiments are presented that evaluate the accuracy of the overall integrated system, which is executed online on a smart phone. Both people with visual impairments, as well as blindfolded sighted people, participated in the experiments. The experiments included paths along multiple floors, that required the use of stairs and elevators.