additional processing in preparation for printing.
Some subprocesses are present in both
conceptual and graphic generalization, but there are
differences in the causes of their application.
Subprocesses performing graphic generalization are
interdependent and cannot be viewed separately
from other content on the map. Some activities
require concurrent compliance with the resulting
changes resulting from their implementation. For
example, polygons representing a class and being
displaced should merge with polygons of the same
class as soon as they come into contact. Such
simultaneous execution of activities can be upgraded
by dividing the whole process into stages. This
would lead to the activation of a predetermined
subprocess after each phase, which would be
executed if the given condition is fulfilled. For
example, each time after moving polygons for a
certain distance, if they are in contact with polygons
of the same class, the displaced polygons merge with
them. After that comes the second step in which the
others move further and it is checked again that now
these displaced polygons are in contact with
polygons of the same class. Another factor that can
influence the outcome of cartographic generalization
is the order in which subprocesses will be used.
Proper selection of the execution order can influence
the final appearance of the map. Also, there are a
number of different algorithms for each subprocess.
Not all subprocesses are equally represented in the
generalization process. Sublimation of two or more
operators placed in a proper arrangement is a model
of cartographic generalization (Stojanović, 2018).
It is possible to automate those forms of
generalization that can be numerically interpreted
and expressed in mathematical form, as well as those
that necessarily generalize the classifications of
mapped objects by creating models of cartographic
generalization. It is easy to automatically reduce
objects smaller than the established census or to
select objects determined by normative indicators. In
doing so, a set of choice indicators can be used on
the computer at the same time, taking into account
the correlation of an occurrence with other objects, if
it can be expressed in mathematical form (eg. by
setting a minimum distance between adjacent
objects at the expense of reducing less significant
ones) and may change the value indicators in
different regions. The census approach can also be
applied to geometric side of generalization in terms
of automatic contours generalization or other lines,
e.g. automatically reduce curves and fractures on
lines smaller than a given size (Drobnjak, 2016).
Figure 12 shows an example of automatic curvature
reduction in detail and on an entire object using the
Simplification subprocess.
Figure 12: Automatic curve reduction using simplification
subprocesses, detail view (left) and entire object (right)
(Lee & Hardy, 2005).
3.3 Requirements and Limitations for
Cartographic Generalization
Cartographic generalization is a complex process
because of subjectivity and lack of well-defined
rules in decision making processes necessary to
compensate visual problems. During this demanding
process, it is important to understand why, when,
and how to generalize, in order to select and apply
relevant subprocess to spatial objects (McMaster &
Shea, 1992).
The relevance of the generalization subprocess
depends on the particular design specifications to
which the solution applies. These specifications are
limitations that cartographers have to deal with. The
restrictions apply to the accuracy, scale, and purpose
of the map required, as well as to your visualization
medium (Stoter et al., 2008). For example, when a
tourist map is generated, priority is given to
semantic content elements that represent objects of
tourist interest in a picturesque way. This type of
object does not require the use of complex
subprocesses that offer high geometric accuracy. On
the other hand, such subprocesses may be required
when a map is generated for cadastral or military
use. Moreover, constraints also apply to handle,
readability of spatial objects (visibility threshold),
forms, spatial relationships (positioning of objects
relative to each other), and semantics. Considering
the fact that it is difficult, even impossible, to
overcome all limitations during cartographic
generalization, it is important to identify those that
are prioritized in relation to the purpose and scale of
the map (Plazanet et al, 1998).
For successful cartographic generalization, the
choice of the relevant subprocesses, as well as their
interlocation, are important. The same subprocess
will depend on where it is executed, generalize
different content in different ways. Also, a particular
subprocess may resolve a conflict that may re-occur