Geography Reference
In-Depth Information
P1
Replace
On a parameter change
the old visualization
is replaced by the new.
View
P2
P3
View
Replicate
On a parameter change
the new visualization
is placed in a separate
window.
P1
View
P2
View
P3
P1
Overlay
On a parameter change
the new visualization
is merged with the old.
View
View
P2
Merge
P3
Figure 3.2
On a parameter change the information in the view can be replaced by the new infor-
mation (replace), displayed in a new window (replicated) or merged with the existing representation
(overlay)
3.4.1 Where is the information displayed?
The simple answer to 'where is the result displayed?' is that the information contained within
the current view is
replaced
completely by the new information, i.e. when the user changes
a parameter a single display is updated. This is often achieved interactively, such that, when
the user changes the position of a value slider, the display instantly updates. Such dynamic
query interfaces provide pre-attentive visualization of the information. However there are
two further models of re-representation:
replicate
and
overlay
(Roberts, 2004), see Figure
3.2. Replication occurs when, on a parameter change, a new window appears with the new
information. This is useful when it is imperative to compare information from one param-
eterization to another; but if unrestricted the screen can get cluttered with many windows
and then it is difficult to understand what view represents which parameterization. Over-
laying the information is the final strategy. There are several ways to overlay information
or join information together from different parameterizations. The information could be
stacked on top in another layer, or the new information could be merged together to provide
a
difference view
(a difference view explicitly demonstrates the difference between the two
parameterizations). Some systems are better at allowing the user to change where the out-
put goes. Module visualization environments (MVE), such as AVS
TM
(www.avs.com/) and
IRIS Explorer
TM
(www.nag.co.uk/), allow the developer to adapt the flow of information by
changing the configuration of the modules. The data flows through different modules (filter,
map, render, etc.), concluding in a display module. When the user changes a parameter in
a module, the new data flows through the system and the display is updated. However, to
create a new view (a replication), the user needs to copy and connect multiple modules in
order to perform the operation. The data flow is split and the modules provide a fan-out
flow.
Overlaying the information, especially generating difference views, is extremely useful for
the user. It shows unambiguously the changes between two parameterizations or between two
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