Geography Reference
In-Depth Information
over a fractal-generated landscape (which mimics natural forms), annotated with three-
dimensional text placed directly on the landscape. Unlike static two-dimensional maps, few
rules have been established in how to most effectively label three-dimensional immersive
maps (Maass, Jobst and Dollner, 2007), including issues such as text size, placement, label
density and text behaviour (e.g. should the three-dimensional text 'track' the user, always
presenting an orthogonal face?). The MODIS sea surface temperature animation (upper
right) highlights the importance of the Gulf Stream in the North Atlantic by using four years
of high-resolution space-time data that captures subtle behaviours not easily seen in static
snapshots. This animation demonstrates that a well-designed map can successfully present
gigabytes of raw satellite data without overwhelming the reader, in part because individual
data points (pixels) merge to form a coherent larger picture (i.e. distinct ocean currents,
seasonality and overall north-south gradient). Ballotbank.com (lower right) can create
animated bivariate choropleth maps that allow for both temporal and attribute focusing
(both forms of information filtering) as well as on-the-fly temporal aggregation, allowing
uses to adjust the 'temporal granularity' of the animation: often what one sees in an animation
is a product of the ways in which the data are presented, especially the temporal and spatial
resolution of the data, and the look of the animation can vary dramatically by changing
either (Harrower, 2002). Thus, allowing the user to make these kinds of adjustments to
the map themselves is both useful and ethical. The map of alcohol-related incidents (lower
left) employs
temporal re-expression
controls, allowing users to animate through the data by
composite hour of day, day of the week and month to see how patterns of drinking behaviour
change as the basic unit of time changes.
4.3.1 Characteristics of animated maps
Animated maps, sometimes called movie maps or change maps, are primarily used to
depict geographic change and processes. Static maps present all of their information simul-
taneously; animated maps present information over time. Thus, animated maps have an
additional representational dimension that can be used to display information. Increasing
the running time of an animation increases the total amount of data that can be represented,
but at a cost to the user. As the length of the animation increases so too does the difficulty of
remembering each frame of the animation. Put another way, although the amount of data
that can be represented within an animation is virtually unlimited, there is a finite amount
of information the user can distil from the animation and store in their short-term visual
memory. As a result, animated maps are typically less than a minute in duration. They are
more analogous to television commercials than feature-length films. One practical reason
for this is the limitations of visual working memory (Sweller, 1988). Another reason is that
animated maps are temporal abstractions. As condensed forms of knowledge, animated
maps are intentionally scaled-down representations of the world.
Just as static maps have a spatial scale, temporal animated maps have a temporal scale.
This can be expressed as the ratio between real-world time and movie time. For example,
five years of data shown in a 10 s animation would have a temporal scale of 1:157 million.
Although it is possible to build animated maps that vary their temporal scale as they play -
to focus on important moments, or blur-out others - most animated maps keep a constant
temporal scale. Additional aspects of the map include its temporal granularity/resolution
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