Geography Reference
In-Depth Information
of definitions (Peuquet, 2002). In that sense time is a phenomenon that is actually per-
ceived by its consequences and can therefore be described through the changes that it
induces. These changes can be broadly distinguished as occurring in the spatial domain
and in the temporal domain (Blok, 2005). Changes in the spatial domain include: (a) ap-
pearance or disappearance, e.g. the emergence or vanishing of phenomena; (b) movement,
e.g. change in position (location) or/and in geometry (shape) of the phenomenon; and (c)
mutation (nominal: change in the character of a phenomenon; ordinal or interval/ratio:
increase/decrease). Changes in the temporal domain refer to (a) moment in time, e.g. the
instant (or interval) a change starts to occur; (b) pace, e.g. the rate of change over time; (c)
sequence, e.g. the order of phases in a series of changes; (d) duration, e.g. the length of time
during which a change takes place; and (e) frequency, e.g. the number of times a phase is
repeated.
Some other aspects related to time should be also mentioned at this point, since they are
closely related to spatio-temporal representations (such as the space-time cube) and to func-
tionality and interaction with these representations. They are related to different descriptions
or classifications of time (time granularities), interrelated varying resolutions and temporal
uncertainties. Regarding the former, time can be described with varying different units, such
as dates (absolute chronology) or historical/archaeological/geological periods (e.g. 'Roman',
'bronze age', 'Pleistocene', etc.). These different units for measuring (or describing) phenom-
ena are known as 'granularities'. Examples of time granularities are calendar dates and hours,
but also specialized units such as business days or academic years (Bettini
et al.
, 2000). The
latter relates to space (spatial zoom) and time (temporal zoom), while it could also relate to
thematic content ('semantic' zoom, as used in information visualization terminology; Ware,
2004). The third refers to inaccuracy in assigning a time-stamp in a phenomenon, event or
record.
The changes in the temporal domain as described above can be represented graphi-
cally in many ways. These representations are based on alternative conceptions of time
(Langran 1993); each one of them offers a different view of temporality and emphasizes
the representation and effectiveness of different spatio-temporal aspects (Kousoulakou
and Kraak, 1992). The main categories are (a) use of a single map (use of visual vari-
ables for understanding of changes); (b) use of small multiples ('spatial' deduction of
changes, although in a discontinuous manner); and (c) animation (use of dynamic vari-
ables for the deduction of changes via memory). The space-time cube allows changes
to be traced spatially, via the third dimension, a somewhat separate category combining
elements from (b) and (c). Many other not strictly geographically oriented representa-
tions can be used in combination with map-based representations (M uller and Schumann,
2003).
In cartography the application of methods and techniques from other disciplines has
led to geovisualization. It integrates approaches from scientific visualization, (exploratory)
cartography, image analysis, information visualization, exploratory data analysis, visual
analytics and GIScience to provide theory, methods and tools for the visual exploration,
analysis, synthesis and presentation of geospatial data (Dykes
et al.
2005). The visualiza-
tions should lead to insight that ultimately helps decision making. In this process maps and
other graphics are used to stimulate (visual) thinking about geospatial patterns, relation-
ships and trends, generate hypotheses, develop problem solutions and ultimately construct
knowledge.
Search WWH ::
Custom Search