Basics of symbolization 133
Yield!, Do not enter!—no further analysis is necessary, and no legend is required on
the sign. This is basically symbol matching, not interpreting (Figure 7.2). It is this
kind of symbolization that is proposed for emergency response maps. To interpret a
map, however, the reader must not only identify the symbols from the legend, but also
recognize the spatial relationships between the objects symbolized; this is a three-
level problem in perception: identify symbols, recognize patterns, and then interpret
patterns.
Because of this multilevel perception, the cartographer must choose symbols that
are distinct and easily identified in the legend and must also choose the symbol system
that most effectively portrays the relationships featured. Well-chosen symbols result
in a map that is readily understood because it states its message clearly and unam-
biguously. A poor choice of symbolism produces a map that is confusing and may
even mislead the reader.
We must distinguish between two terms that are sometimes used synonymously:
phenomena and
data.
Phenomena are the features and attributes of the real world
that are being mapped. They are the features to be conceived and communicated,
such as rivers, roads, and countries, and the attributes of those features, such as form,
continuity, and location.
Data are facts gathered by measuring, counting, calculating, or derivation. Geo-
graphic, or spatial, data are those that describe or measure aspects or attributes of
geographic phenomena. It is important to remember that we are portraying spatial
data,
rather than phenomena, on maps.
In this chapter the nature of the geographic phenomena and data being symbol-
ized, the measurement of data, and the nature of symbols are discussed so that an
appropriate symbol can be chosen.
fIgURe 7.2.
Qualitative pictorial symbols. These symbols require little or no interpretation
and may be grasped quickly.
