Touchscreen devices, such as smartphones and tablets, represent a modern solution for providing graphical access to people with blindness and visual impairment (BVI). However, a significant problem with these solutions is their limited screen real estate, which necessitates panning or zooming operations for accessing large-format graphical materials such as maps. Non-visual interfaces cannot directly employ traditional panning or zooming techniques due to various perceptual and cognitive limitations (e.g., constraints of the haptic field of view and disorientation due to loss of one's reference point after performing these operations). This article describes the development of four novel non-visual panning methods designed from the onset with consideration of these perceptual and cognitive constraints. Two studies evaluated the usability of these panning methods in comparison with a non-panning control condition. Results demonstrated that the exploration, learning, and subsequent spatial behaviors were similar between panning and non-panning conditions, with one panning mode, based on a two-finger drag technique, revealing the overall best performance. Findings provide compelling evidence that incorporating panning operations on touchscreen devices -- the fastest growing computational platform among the BVI demographic -- is a viable, low-cost, and immediate solution for providing BVI people with access to a broad range of large-format digital graphical information.
Palani, H.P. and Giudice, N.A. (2017). Principles for Designing Large-Format Refreshable Haptic Graphics Using Touchscreen Devices: An Evaluation of Nonvisual Panning methods. The 19th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS’17). Oct 30 to Nov 1, Baltimore MD, USA.