138 sYMBOLizaTiOn
The
form may be representational, such as an
airplane to designate airports,
trees to symbolize forests, or a pick and shovel to represent a mine. These shapes
have also been called
pictorial,
replicative, or
mimetic symbols. A subgroup of pic-
torial symbols gives an impression of movement or action; these are called
dynamic
symbols. Examples are bomb bursts, flames, arrows, and the like. In other instances
a geometric shape is used to represent types of objects; the form of the symbol has
no relationship to the form of the object symbolized. Thus,
a square can be used
to represent an airport, a star a capital city, or a triangle a mine. These are called
abstract,
arbitrary, or
geometric symbols. In still other instances the form of the sym-
bol may suggest in some way the feature symbolized: a triangle for a mountain peak
or regularly spaced green dots for an orchard. These have been called
associative or
semimimetic symbols. Although the pictorial–associative–abstract
description is a
useful device for visualizing symbols, there is considerable overlap between the cat-
egories, which might better be thought of as points on a continuum than as mutually
exclusive categories.
Linear symbols are not usually thought of as having shape other than the con-
tour of the feature represented. However, the form of the line symbol can be varied
by making it solid, broken, dotted, and so on. Linear symbols may also be classed as
pictorial,
associative, and abstract.
Shape does not directly apply to area symbols because the shape of the polygon
corresponds to the area represented; however, the symbol may be made up of a vari-
ety of smaller marks that themselves have shape and form patterns. In such cases, the
symbol that is applied may be a tree, a dot, or a line, and these can be seen to have
pictorial, associative, and abstract elements. Some books use cartograms as examples
of shape, but in this book cartograms are considered as a separate type of map.
Size is normally used to show the magnitude of the data represented, that is, for
ordinal, interval, and ratio representations; it is not appropriate to use size to distin-
POINT
SYMBOLS
LINE SYMBOLS
AREA SYMBOLS
