  On the off-the-shelf navigational assistance devices, the localization
precision is limited to the signal error of global navigation satellite system
(GNSS). During travelling outdoors, the inaccurately localization perplexes
visually impaired people, especially at key positions, such as gates, bus
stations or intersections. The visual localization is a feasible approach to
improving the positioning precision of assistive devices. Using multiple image
descriptors, the paper proposes a robust and efficient visual localization
algorithm, which takes advantage of priori GNSS signals and multi-modal images
to achieve the accurate localization of key positions. In the experiments, we
implement the approach on the wearable system and test the performance of
visual localization under practical scenarios.
