A blind reader who explores a tactile graphic using a methodical approach will understand the image more successfully than if it was done randomly as the user will gain a more thorough view of the image. As a tactile reader gains experience they will develop navigation strategies which will help them become even more skilled.
Here are some beneficial strategies that a tactile reader can use when navigating an image:
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An initial scan to gather quick information about the graphic.
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Being systematic in exploring when searching the whole display.
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Being systematic in exploring specific features through line tracing and distinctive features analysis.
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Focussing on spatial relationships - including patterns and relationships between features.
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Using a frame of reference.
Initial scan
The initial scan is a preliminary activity which involves running both hands over the entire tactile graphic to quickly gather information. The kinds of information the user will gain include:
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the overall size of the graphic
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an idea of how many elements/symbols are featured and the spread/density of these elements on the page
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any particularly distinctive features, which may be used as reference points.
Systematic approach
Exploration of a tactile graphic in a systematic manner will benefit the users encounter. A blind reader who uses a seemingly random, unsystematic approach when studying a tactile image, such as tracing in different directions is likely to have a poorer experience. as a haphazard exploration is likely to cause a jumbled impression of what is being felt.
In this approach users will start with an initial scan and then scan using both hands, or use a reference hand, with the other hand scanning the graphic. The scanning can be horizontal or vertical.
Line tracing and distinctive features analysis
Line tracing and distinctive features analysis is a strategy where the outline of a shape on an image is traced by the user to identify the distinctive features of that shape which can aid recognition. This will also identify distinctive features of the image which can provide a reference point to help user's recognise when they have traced all around the shape.
Focus on spatial relationships
An awareness of spatial relationships within the tactile graphic can aid the user's understanding of an image by referencing positions of components of a map (eg these three roads make a triangle), or referencing shapes or patterns made up by the components of an image, and then noting the relative positions of the components to each other (eg the farm is next to the river).
Frames of reference
Using frames of reference to understand spatial information is important because it helps the user to arrange the information they are viewing. Using body-centred frames of reference and external references are the most reliable cues for learning spatial information.
Body centred references: this is when a tactile reader uses a reference hand to carry out a systematic search of the graphic. For example, if scanning across the graphic, one hand would be used as an anchor on one side to maintain the level at which to scan the map, and guide the scanning hand back to start the next strip at the correct level.
External reference frames: for example using a frame on the tactile graphic itself or use of a locator dot on the graphic to assist the user to learn the orientation and location of components on the image.
For further information you can download Exploring Tactile Graphics - which strategies work? (Word, 212KB) from research carried out by the Centre for Accessible Information.