ABSTRACT
In previous chapters we have seen that maps are geospatial images that can influence people’s conception of space. Maps have this influence partly because of convention and partly because of the general characteristics of the graphic cues used, either on paper or on the monitor screen. Convention especially plays a role in topographic mapping: most of the symbols used on topographic maps (see Chapter 6) have come down to us in a form conditioned by eighteenth-century examples and we have stuck to them ever since. Among these conventions are the rendering of water by a blue colour, forests by a dark green and built-up areas by a red, grey or pink colour. Association may have been at the root of this usage, but may not be valid any more, and so it has changed into convention. The convention of using specific symbols on topographic maps originated in the example provided by French topographic mapping practice in the eighteenth century. This convention has been strengthened by the fact that in the nineteenth century all topographic maps were produced with the same objective, i.e. infantry warfare.
