What precisely do we mean when we utter the old cliché ‘A Picture Is Worth A Thousand Words‘ in the context of the applications of computer graphics to archaeology? Why are we not filling archaeological reports with pictures? If we take the saying literally, then the extra expense of graphical printing would be well justified. I am not being entirely facetious when I suggest that we ought to look at illustrations — particularly those generated by computer — and rate them according to a notional APIWATW factor, naturally a very informative picture would approach an APIWATW value of 1000.
This is no trivial point, and I want to differentiate firmly between what I call a diagram and what I shall call a picture. A picture is a representation of something with which we are familiar m our everyday perceptual experiences: a landscape, for example. I «include under the heading ‘diagram’ such things as histograms, pie-charts, maps, contours, site-plans and so on. A good example might be an Ordnance Survey map, which is so familiar to us that we forget that it uses a ‘vocabulary’ of conventional symbols to represent real objects (like telephone boxes railway stations, and hillforts). In its two-dimensional space there are rules of ‘grammar’ (for example, certain information has priority over other when an overlap occurs).
A picture should, of course, have meaning. It should have context and possess structure A picture whose constituent parts do not make sense as a whole is, to stretch die analogy like an unstructured rambling paragraph of text. Style and narrative both have graphical analogues: consistency of style helps the viewer in making comparisons and contrasts; the narrative value of a well-chosen sequence of pictures is acknowledged but often not practised because of the need for economy.