Graphic content, including images, drawings, schematics and maps, is effective in providing a considerable amount of information concentrated in a small space, allowing a better organization of data and information series so that they are easily understood. They are widely used in the teaching process at all levels of education. Naturally, visually impaired people do not have easy access to such contents. Other strategies are used by visually impaired people to access graphic contents, one of them is the use of tactile drawings that enable to explore graphic representations using the sensory touch system for this task. However, it is difficult for visually impaired people to be autonomous in reading and exploring tactile drawings usually needs the help of a sighted person to provide initial information, such as the general message conveyed by the tactile drawing, and to guide the individual in step-by-step reading. The absence of such a person may make it impossible or considerably difficult for visually impaired people to use tactile drawings. Assistive technologies have been developed to make it easier for visually impaired people to access graphic data and even to make displays more dynamic. In this paper we list some of the main assistive technologies that aim at helping visually impaired people to read and interpret tactile graphs using various forms of feedback for vision substitute sensory systems. After studying different strategies for exploring tactile designs adopted by visually impaired people, we proposed to develop an application for ordinary tablets exploring the benefit of multimodal interactions by overlaying tactile designs printed on touchscreens intended to assist the visually impaired people in reading tactile drawings. After confirming that interactions with current touchscreens devices are possible through the papers used to explore tactile designs superimposed on the screen. In a case of study, the application prototype was tested with three blind students demonstrating that the solution has a promising approach to improve exploration of tactile designs. It also raised improvement requirements. After the implementation of these improvements, a controlled experiment with 8 blind participants was performed to compare the exploration of tactile designs with braille subtitles with multimodal tactile designs, using the developed application, and to evaluate the application usability through a SUS (System Usability Scale) questionnaire. The results showed that the application has excellent usability, according to the participants, and that the task of tactile exploration is more enjoyable, easier and faster with multimodal tactile designs, demonstrating also a performance gain and improved understanding of tactile design, and at last that user satisfaction was higher when using the application.
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