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or 'familiar' scenes (Gee
et al.
, 1998; Robertson, 1990), which more closely represent the
real world. One basis for this argument is that the vertical viewpoint used in the traditional
printed map is unnatural for humans who spend most of their lives moving around a world
that is seen largely in oblique view from ground level. Another is that the symbolic forms
of representation widely adopted on paper maps to represent familiar surface features are
too divorced from the everyday experience of buildings, roads or trees.
There are many recent examples where 2.5D and 3D data visualizations have been used
to communicate environmental problems and issues to the general public more effectively
than conventional 2D maps. The extent and impact of flooding, both in the case of actual
floods (e.g. the impact of hurricane Katrina in New Orleans in 2005) and also predicted
floods (e.g. the effect of global warming on central London), are often given a greater impact
by being visualized using oblique views that show surface variations of the areas involved.
However, some caution is needed here, because although Sweet and Ware (2004) suggest
that an oblique viewpoint enables better judgements to be made about surface orientation,
other interpretive benefits of adding perspective are questioned by Cockburn (2004).
Even where data are spatially referenced, it may be more appropriate to construct
metaphoric spatial scenes to visualize such data rather than reproduce the actual 3D en-
vironments from which these data are derived. Over 20 years ago, for example, the rooms
metaphor was proposed for a general computer interface (Henderson and Card, 1986), and
the BBC Domesday system adopted a museum metaphor for the display of images stored on
videodisc (Rhind, Armstrong and Openshaw, 1988). More recently, e-commerce web sites
have introduced the virtual shopping mall as a context for browsing purchasable products,
collaborative learning websites have adopted 3D virtual worlds (e.g. B orner
et al.
, 2003;
Penumarthy and Borner, 2006), while some 3D social networking web sites have adopted
familiar 3D environments such as landscapes (e.g. Second Life) or hotels (e.g. Hotel Habbro)
for their avatars to inhabit.
In experiments undertaken to visualize telecommunications network data, Abel
et al.
(2000) suggest that specific tasks may be better supported with 3D scenes built using visual
metaphors such as buildings, cities and the solar system, rather than on the inherent geo-
graphical structure of the network infrastructure. Their research suggests that an analysis
should be undertaken of task requirements in order to determine the utility of adopting
natural rather than unconventional spatial representations. Similar considerations also ap-
ply to the choice between 3D interfaces that mimic natural human actions and those that
overturn conventional principles. Pierce (2000), for example, argues for the need to break
existing assumptions about how people interact in the real world when designing interaction
methods for virtual 3D worlds, suggesting that '3D worlds are governed by more complex
laws than 2D worlds, and in a virtual world we can define those laws as we see fit'.
10.2.4 Resolving the hidden-symbol problem
One of the largely unrecognized problems of displaying large numbers of point symbols
on a conventional 2D map is that they often obscure one another. Where this results from
overlaps in the extent of proportional or graduated symbols, then various techniques may
be used to resolve the problem, including transparency and symbol cut-outs (e.g. Rase,
1987). However, where symbols obscure one another because the objects they represent
share identical locations, an alternative solution is required. An example of this problem is
illustrated in Figure 10.1(a), in which the social classes of individual families living in part
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