Environmental data have inherent uncertainty which is often
ignored in visualization.
For example, meteorological stations measure wind
with good accuracy, but
winds are often averaged over minutes or hours.
As another example, doppler radars (wind profilers and ocean current radars)
thousands of samples and average the possibly spurious returns.
time series data have a wealth of uncertainty information,
that the traditional vector visualization methods such as
using wind barbs and arrow glyphs simply ignore.
We have developed new vector
glyphs to visualize uncertain winds and ocean currents.
Our approach is to include uncertainty in direction and
magnitude, as well as the mean direction and length,
in vector glyph plots.
Our glyphs show the variation in uncertainty,
and provide fair comparisons of
data from instruments, models, and time averages of varying certainty.
We use both qualitative and quantitative methods to compare
our glyphs to traditional ones.
Subjective comparison tests
with experts (meteorologists and oceanographers) are provided,
as well as objective tests (data ink maximization), where the
information density of our new glyphs and traditional glyphs are compared.
We have shown that visualizing data together with their uncertainty
information enhances the understanding of the continuous range of
data quality in environmental vector fields.
Glyphs for visualizing uncertainty in vector fields
, Craig M. Wittenbrink,
A. T. Pang and S.K. Lodha. In the IEEE
Transactions on Visualization and Computer Graphics, Vol. 2, No. 3, pages
266-279, 1996. Short version in the
proceedings of the IS&T/SPIE Symposium on Electronic Imaging: Visual Data
Exploration and Analysis, Vol.
2410, pages 87-100, color plate page 206, San Jose, CA 1995.
in small multiples (ala Tufte), glyphs are shown with traditional
arrow glyphs compared to new uncertainty glyphs,
C.M. Wittenbrink, A.T. Pang, and S. K. Lodha, IEEE Transactions on
Visualization and Computer Graphics, Vol. 2, No. 3, Sept. 1996,
pages 266-279. Shown here are Figures 9-14 as intended:
A postscript version of the paper presented at the
SPIE'95 conference on Visual Data Exploration and Analysis
can be obtained by clicking
or by anonymous ftp to
then get pub/reinas/papers/spie95_glyph.ps.Z.
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