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information. This experiment is complemented with questionnaires to
identify whether observed user performance is related to personal abilities,
skills, and attitudes.
Geo-visualizations in 2D and 3D
3D visualizations in geographical context are quite self-evidently
efficacious in situations where the content to be visualized has naturally
3D spatial properties. For instance, in urban planning [4] or in landscape
planning [5] the content to be visualized consists of realistic structures
which are to be presented in an authentic way. In this context
geovisualization is not different from other applications of photo-realistic
visualizations such as games or simulator based training.
In geospatial data analysis, on the other hand, abstract information,
often numbers, is presented and evaluated in its geographical context,
whereby cartographic maps provide geographic reference frames [6].
Insight is gained from seeing relations between quantities and patterns as
they become evident in their geographic neighbourhood. The well-known
visualization of the Cholera epidemic in London in 1854 [7] is one
example which, incidentally, demonstrates a very efficient 2D graphical
design. The use of 3D maps for visualization of abstract, i.e., non-spatial
information, was popularized in geovisualizations in the 1970s with the
introduction of the 3D space-time cube by Hägerstrand [8]. The concept of
the space-time cube has recently been evaluated for spatio-temporal
analysis in various applications [9][10][11].
Concepts of 2D and 3D visualizations
In the visualization literature, various notions exist for different types of
3D visualizations. According to computer graphics textbooks, a projection
of a geometric model represented in 3D and its rendition on a 2D
projection plane are to be considered a 3D rendering as long as they provide
some of the so-called monoscopic depth-cues, such as linear perspective.
According to this concept, even a planar 2D map defined as a flat surface
in 3D can be considered a 3D visualization if it is projected back on the
2D computer screen at some angle with some perspective distortion. This
notion has been assumed by, among others, Lind et al. [12], who
investigated traditional 2D user interfaces for industrial control that were
virtually slanted in 3D. These 3D visualizations present only monoscopic
depth-cues to the observer and they fail to exploit other highly efficient 3D
cues, such as motion parallax (e.g. due to dynamic observer position), as
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