The last two decades have witnessed a sharp rise in the amount of data available to business, government and science. Data visualisations play a crucial role in exploring and understanding this data. They provide an initial grasp of the data and allow the assessment of findings of data analytics techniques. This reliance on visualisations creates a severe accessibility issue
for blind people (by whom we mean people who cannot use graphics even when magnified).

Guidelines for accessible information provision recommend the use of raised line drawings, called tactile graphics, to show spatial data, such as maps or charts. However, tactile drawings must be explored sequentially using touch, making it difficult to quickly obtain an overview of the graphic. To overcome this, guidelines recommend that tactile graphics come with a textual (braille) description. However, such descriptions are fixed and do not allow the blind reader to ask questions about the graphic or the underlying data.