Symbolisation

Because it is not possible to create a reduced image of the real world without devising a set of symbols that stand for real-world things, mapmaking requires symbolisation. Symbolisation can be defined as the graphic coding of the summarisation resulting from classification and the coding of the essential characteristics, comparative significance, and relative positions that result from simplification.

Two major classes of symbols are used:

Representational Symbols:

Representational symbols are symbols whose form is derived from the appearance or nature of the feature or phenomena represented. They are designed to look like their real-world counterparts. Various forms of representational symbols exist:

Pictorial symbol	Stylised symbol
A symbol whose form is a simplified portrayal of the feature or phenomena it represents.	A symbol whose form is derived from the salient characteristics of the feature represented.

For further representational symbols examples, download here a PDF form of the Swisstopo conventional signs to the Swiss topographic maps (optional).

Abstract Symbols:

Abstract symbols are symbols whose form bears little or no relationship to the form of the feature represented. For this purpose geometric symbols are often used, e.g. circle, square, rectangle, triangle, or semi-circle. The following map of microseismicity localisation is a typical example for abstract symbols.

The symbolisation process is shaped by the influence of scale: at smaller scales, it is impossible to represent geographical features at true-to-scale likeness. Therefore, distortions are necessary when changing the scale. Symbol distortion should be based on the logical association between the level of measurement of the map’s data and certain graphic variables, conventions or standards, appropriateness, reader’s abilities to use the symbols, ease of construction, and similar considerations.