scale, Compilation, and generalization 85
The selection process is not always simple. Selection is a matter of judgment and
not easily computerized. Although some algorithms (procedures) have been developed
for generalization, there are subtle decisions that cannot yet be specified precisely,
quantified, or computerized. For example, if only perennial streams are represented,
an arid area like Saudi Arabia might appear to have no drainage pattern.
simplification
A complex feature, such as a coastline or river course, cannot be shown in complete
detail on small-scale maps, nor is it desirable to do so. For most thematic maps (in
contrast to topographic maps or nautical charts), the detail of the coastline is unim-
portant. There is no need to show each tiny inlet or point for most thematic maps,
on a map of income, for example. The basic shape of the coast must be shown so
that the area is recognizable, but not other detail. On some maps the nature of the
coast—smooth, irregular, fjiorded—must be shown, but since it is impossible to be
completely accurate and show every variation, many features are simplified even in
these cases (Figure 5.6). The amount of simplification is a factor of scale; the larger
the scale, the more detail that can be included.
smoothing
Smoothing is a part of the simplification process. A road with many switchbacks is
smoothed, as are rivers with many meanders (Figure 5.6). It is important that the
character of the feature be preserved in the smoothing process, that is, the switchback
road mustn’t be drawn as a straight line and the meandering river must still show
major changes in direction.
grouping
Many small features are often grouped. In a simplistic example, individual trees are
grouped into a forest. If the scale does not permit a number of small features to be
(A)
(B)
