University of Edinburgh

Tactile Graphics

CHAPTER EIGHT: Tactile graphics design

[Please note the first part of this chapter has been substantially changed since the technology mentioned in the original is now obsolete]

8.1 Tactile graphics and Braille

Because of the great shortage of tactile diagrams and the vast numbers of diagrams which may be required by blind students in formal education, particularly those at university, production methods which are computer based are obviously attractive. The microcapsule process lends itself to computer drawing and also to the use of scanned images as working templates.  In this way diagrams can be shared easily.

It is of course be possible for an experienced designer to use any graphics software on any computer to produce designs for tactiles.

8.2 Contextual factors

Microcapsule (Zychem) diagrams have a maximum relief height of 1 mm while faint dotted lines and light, stippled infill patterns are raised lo about half of this height. In order to maximise the effectiveness of the diagram format it is necessary to work within these restrictions in such a way that the user can discriminate the essential components of the diagram. In doing this, the designer has to keep the word 'context' constantly in mind; for context is all-important. Components that can be identified or differentiated in isolation or in one context may behave differently in a different context. To illustrate this, and the way it can be manipulated to good effect, the following series of maps may provide a simple example.

The UK maps

The first illustration (Figure 5) shows a map of the UK as it may appear on the computer screen after scanning in. The visual quality of the image could be enhanced but this is not necessary, because the image shown will only be used as a template to guide the designer.

first map

Figure 5 Scanned image with outline begun

First the designer may draw around the coast line to produce a simple map outline (Figure 6). In tactile form this is not so simple for a blind user because (a) the raised line becomes an 'object' to be identified, and (b) the shape of the enclosed void is difficult to appreciate.

second map

Figure 6 Simple black outline

It is possible to fill this outline with a solid black infill (as in Figure 7 a strategy would give an excellent strong coastline and the shape of the land mass would be easier to appreciate. However, in doing this the designer has lost all chance of adding other features internally.

third map

Figure 7 Solid black map

One alternative would be to infill with a light stippled pattern which would only partially rise under the heat treatment, because the individual dots do not receive enough heat during the normal exposure time. To leave the coastal boundary line on would risk confusion with rivers or internal boundaries (eg; of counties, or river catchment areas). So the coastal boundary can be left out entirely, except that this results in a coastline which is rather difficult to follow. (Fig 8).

fourth map

Figure 8 Light stipple

A strategy for overcoming this problem is to substitute a narrow strip of a more dense stippled pattern for the original black solid line coastal boundary (Fig 9). This has the effect of making the edge rather more distinct to the touch and yet still giving good contrast with other features of the map.

fifth map

Figure 9 Light stipple with denser edge

Thus in Figure 10 the Rivers Thames and Severn have been added to the map as solid black lines, with a selection of cities as small black squares. All of these features are distinct from one another in the tactile version.

sixth map

Figure 10 Map with rivers and cities

Sometimes quite small differences in diagram components are all that is required to ensure successful discrimination. A relatively thick, meandering line of a river may be easy to differentiate from a finer, straighter political boundary. The overall context in which these diagram components are used ensures successful reading.

However, in the vast majority of maps and diagrams the totally blind student may need some initial assistance to interpret what he or she feels, although this assistance may simply be a Braille title or note, or the diagram may contain some feature that is already known and which provides the key to the rest. In some cases a taped description may augment the map or the interpretation may be assisted by a tutor in person.

The Loughborough Research Unit has made a vast range of diagrams which all have their own particular challenges to discrimination and interpretation, but it is the kind of approach suggested in the example above which nearly always provides a solution.

One other practical detail that ought to be mentioned at this point is the effect of strong cross-hatching or other unidirectional infill patterns. Any raised line in a tactile diagram may develop a meaning of its own. It may be perceived as a piece of string, a river or a wall (for example) depending on the context. For this reason any raised line must be used with care.

Also in visual diagrams adjacent areas of an illustration are commonly marked off with boundary lines. Where areas of a tactile diagram are in filled with a pattern to produce a perceivable texture the limits of that infill mark the boundary without the necessity for an added line. The author generally avoids tactile boundary lines altogether unless some special circumstance requires their use.

Cross-hatching can lead the finger in a particular direction which may not be congruent with the structure of the diagram component which they are filling, so this style of infill is probably best avoided except in highly stylised diagrams like pie-charts. Safer and more generally useful are the more diffuse. 'non-directional' infill patterns illustrated.

8.3 Use of the graphics software and scanner

Although it is easy to draw diagrams of simple structures freehand, our research unit commonly scanned in the more complex diagrams on a fiat-bed scanner. The presence of a draft image that can be used as a template may save much time when extensive alterations and re-drawing are required. This scanned image can be displayed on screen at will, or hidden and omitted when the final computer drawn diagram is printed.

Educationally speaking, a tactile that is as near as possible to the diagram that sighted students are using is a good thing, provided that the resulting tactile is effective for the blind student. It is also important that teachers and lecturers using such diagrams and encountering difficulties with individual students or groups enquire why this is happening. Is the diagram badly designed or do the students lack some preparatory experience or simple guidance that would equip them to interpret it?

Even visual diagrams differ in their ease of interpretation for the sighted student, and considerable effort may be required to come to terms with them, although that effort may be worthwhile for the understanding gained from the diagram. When working with tactile diagrams blind users must not expect every one to be easy and immediate in its impact. It may demand careful exploration and thoughtful consideration for full understanding.

Of course tactile diagram makers must always consider whether the diagram is the best way of communicating information to a blind student as compared to oral methods, Braille text or type. (The subject of judicious selection by teachers and designers is considered separately below)

Normally the designer's first step with the scanned image is to define the limits of the main structures of the diagram. Even if the boundary lines are going to disappear in the final print they may be required (earlier) for the application of infill patterns. The boundary line can later be replaced by a narrow band of stippled infill or it can be made to disappear.

Fairly early in the designing process the Braille labels and titles are applied, because Braille is a bulky script and to work properly the diagram may have to be designed around the Braille. If the Braille is positioned early there is still an opportunity for adjustment later as the diagram evolves. In particular, the finger which is reading the Braille must not be obstructed by adjacent diagram components. Braille labels and key letters must be placed in such a way that their presence is obvious to the blind user. In general the rules about Braille label placement are the same as those already described for thermoformed diagrams.

Grade I Braille directly corresponds with normal type, whereas Grade II Braille has many short forms and contractions, which will reduce the bulk of labelling and titles.

Some useful diagram types like flow charts are almost entirely Braille, but laid out with boxes and link lines or arrows. These can easily be designed on-screen by an experienced operator.

This description is deliberately not going into fine detail about the computer package because software writers are continually improving their product and readers may wish to use other software.

8.4 The designer's selection process

Tactile diagrams are generally more expensive to reproduce than their print counterparts. They frequently require more effort from a blind person attempting to read and interpret them for the first time. It seems wise, therefore, to be thoughtful and selective when producing the material so that the result is genuinely useful and worth the effort for designer and user.

Nevertheless it is important to bear the following points in mind when making the selection:

(a) Any selection process denies the blind user access to diagrams which the sighted person has and must be carried out with care and thought and for sound reasons.

(b) Diagrams remaining must add more to the user's understanding than words alone, at least for some users.

(c) Perceived difficulties with diagrams may often be overcome by the use of preparatory material or by breaking the subject matter of the original print diagram down into smaller parcels which are more easily understood.

(d) For many blind users, the diagram may provide the blind users with a conceptual framework which makes the information more easy to understand and often more easy to translate into a new setting. This is often very important for the understanding of the sciences and technical subjects.

It is perhaps worth making the point that every aspect of the transcription of a print diagram into a tactile format entails some form of selection process. So the above comments are just as relevant to diagram components as they are to the whole diagram.

Ron Hinton
First published 1996
ISBN: 0901580775