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last updated
July 25, 1999
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The Apoala/GeoVISTA Tclet home page
Tclets created by Rob Edsall
July 1999
This page contains links to interactive widgets written in Tcl/Tk, a
graphical user interface prototype development language available for free
at www.scriptics.com. The widgets
here are scaled-down versions of the original widgets; certain functionality
of the original widgets are impossible to implement for display on the
web. Please email Apoala
with comments.
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The web versions of the widgets are so-called "Tclets"
-- Tcl applets -- for which you need the Tcl plug-in, downloadable for
free here. At the
site, you will find versions of the plug-in for Mac, Windows, and Unix
platforms, as well as many nifty demos.
If you are ready to view these pages, there should be a green
circle here: ...
If the cicle blinks red/orange, you have an old version installed.
If there is a blank square, you don't have the plug-in installed and need
to download it. |
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Temporal query and display time indication widgets.
Critical to the understanding of a representation of temporal data (say,
in a temporal GIS) is the ability to discern the location in real-world
time shown in the display. For example, animated satellite images
in weather reports are much easier to understand and interpret if the time
represented in each frame is indicated. In an interactive system
like a GIS or a geographic visualization environment (GVE), indicators
of temporal location can also serve as interactive query and display mechanisms.
The design of these "temporal legends," we argue, may have a subconscious
(or conscious) impact on the way the data is interpreted and explored by
the user of the display. Here, we present two quite different designs
of widgets for temporal querying and display:
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The linear timeline: with
features for linking multiple themes. This design may encourage the
exploration of trends and linear changes, like the progression of a storm
across a continent or the increase in population of a developing country.
The "timeline" is a classic temporal representation utilizing the metaphor
of time as a line, or, more poetically, as an "arrow." |
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The cyclical timewheel.
In an ideal design, users would be able to explore data for cyclical temporal
patterns. Perhaps an traffic analyst is only interested in congestion
information for weekdays, 4:00 pm to 6:00 pm. The timewheel may facilitiate
invsetigations of cycles like rush hour traffic; by arranging a display
according to known cycles, an analyst may be able to discern correlated
patterns in other variables. For example, by querying only times
of rush hour, an environmnetal scientist may notice that there is a corresponding
increase in toxic material in a stream nearby a highway during - or perhaps
offset by an hour from - those times. This "timewheel" concept treats
time not as an "arrow," but more like a series of circles and cycles. |
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Statistical graphics widgets.
A spatial (or spatiotemporal) database typical of GIS or GVE is typically
large, with many different variables, each of which might be related in
some way to another. Often, an analyst is unaware of these realtions
until the data is explored. A well-designed GIS or GVE will provide
an analyst with a variety of tools for exploring these multivariate relations.
Two examples are shown here: |
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The brushable scatterplot matrix.
Each observation is a point, represented on a series of two-dimensional
scatterplots arranged in a matrix. Each pair of variables has its
own scatterplot. A user can drag a box over any set of points, and
the points representing the brushed observations are highlighted in all
other scatterplots. |
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The parallel coordinate plot.
Each observation is a series of connected line segments, passing through
a series of parallel axes arranged like fenceposts or frets on a guitar.
The observation's line passes through each axis according to its value
of the variable of that axis. Each observation, thus, has its own
multivariate "signature," crossing an axis near the top if it is high in
that variable, near the bottom if it's low. |
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