Geography Reference
In-Depth Information
dispatch, where eventually they will be needed to be viewed by the dispatcher,
possibly in a time-critical situation. It is this possibility that contributes to the
extended consideration time, even when the display is less cluttered. Even with a
solution such as fisheye views (Furnas
1986
;
2006
), where the important features
are exaggerated relative to the secondary features, the decision remains on what to
prioritize. With cartographic generalisation, the expectation is that, for the scale of
the map, the objects eliminated will not be missed at some future time. After all, in
most map viewing environments, the user has the time and opportunity to view the
desired area at a larger scale, should there be an eliminated feature to be sought.
An alternative to elimination could be to add an extra transparent/translucent
layer on top of the map, thus adding to the amount of space available in which to
fit symbols; this is exactly how the MLD works. Given this, the use of the MLD
could be seen to offer an extra option for generalisation, which we will call
''promotion''. Starting in a state where all features are assumed to occupy the rear
layer, instead of applying any of the standard generalisation processes, the feature
being considered could be promoted from the rear to the front layer, possibly
resolving the source of cartographic conflict.
6.2 Other Display Principles
6.2.1 Display Legibility and Generalization
'Making displays legible' is a perceptual design principle (Wickens et al.
2004
);
the process of cartographic generalisation is aimed at achieving this goal for maps.
The information clutter scenario described in the second case study is a viable case
for cartographic generalisation. It is basically excessive display complexity, which
in turn has inputs from the system complexity. What is important here is the
perceived complexity, i.e. the amalgamated effect of display, cognitive and task
complexity, experienced by an individual, which may be greater or less than the
real or base level of complexity. If an interface or map presents information
effectively, then this perceived complexity can be reduced (Hayes
2006
).
It is a situation where too much of the real-world system floods the interface in
the form of data. With data being increasingly abundant and the amount of cog-
nitive effort needed to process it into something meaningful, information in the
correct form and amount is the most valuable commodity for the interface user in
an application such as command and control (Barnes
1997
). In generalisation, the
problem is not so much one of data display, rather too much information (i.e.
symbols), too complex information and/or in the wrong form. Choosing the
optimal form of information for a map can reduce the information density to an
acceptable level, through processes such as reduction and typification.
