Geography Reference
In-Depth Information
another location on the map, and thus the numerical data can be displayed in another table,
in a further window. There are other terms in the literature that have specific meaning.
For instance,
alternative representations
has been used to explain multiple forms (Koua and
Kraak, 2004a-c), but the phrase is also used to promote multiple opinions (Roberts and
Ryan, 1997). Users may have a different understanding of the data and hence provide various
interpretations of the phenomenon; for example, historic information may be sparse, there
may be disagreements between eye-witness reports or interpretations of the data may vary.
In archaeology, experts may disagree and their suppositions may change over time as they
become influenced by other people's opinions. Alternative representations are also useful in
education, in that the learner better understands a process if it is explained or demonstrated
in multiple ways.
Multiple views are also used for control. Many of the views utilize direct manipulation,
where the user directly controls the information in the window. Consequently, a user may
find it easier to manipulate the data in one type of representation in comparison to another;
for instance, the user is given two views, one being a three-dimensional network view
showing the position of objects found from an archaeological excavation and the other an
alphabetical list of the objects found. If the user wished to see where all the pottery vessels
were located, then they could select 'pottery vessels' from the textual list to highlight all those
in the three-dimensional view. However, if they wanted to see what information is located
near a specific location then drawing a bounding box on the plot would be easier. This is
also a demonstration of a
master and slave
relationship, where one view directly controls
another. Another use of multiple views is to create
focus and context
, where one view depicts
a summary of all the information with the other showing detail. In addition, both focus and
context information can be displayed in one unified view using distortion techniques.
In a windows environment it is possible to gain information on demand through popup
information; these popup views provide specific information dependent on the context in
which it was requested (Geisler, 2000). In virtual reality a similar style of master and slave rela-
tionship exists. The concept is named
view on a bat
or
worlds in miniature
(Stoakley, Conway
and Pausch, 1995). In this case the user has a virtual bat that moves around the virtual world
with the user. Different pieces of information can be mapped onto the bat such as a geograph-
ical map of the area or some extra information that is relevant to the context of the user at that
point in time. Similar concepts occur in other domains. For instance augmented table-top
environments use markers to instantiate additional information (Hedley
et al
., 2002).
Finally, the last type is
small-multiples
(Tufte, 1990). By displaying the data in many
different small representations, the user can perceive trends in the data. It is through an
overall perception of the texture that the user perceives trends in the information.
3.3.2 Multiple forms
There are many types of geographical visualizations. Inspired by the categorization of
Lohse
et al.
(1994), the various geovisualizations can be divided into seven categories:
Maps/Cartograms, Networks, Charts/Graphs, Tables, Symbols, Diagrams and Pictures.
Maps
communicate spatial meaning and there is a direct association between the physical
space and the represented space. There are clearly many different types of maps that are used
in geovisualization. Geographical maps aim to represent proportions and the geography of
our world and can be two- or three-dimensional. For example, elevation information, such
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