Uncertainty Glyphs


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) take thousands of samples and average the possibly spurious returns. Others, including 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.

Journal Paper:

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.

Correction to illustrate technique 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: postscript or pdf1 or pdf2 .


A postscript version of the paper presented at the SPIE'95 conference on Visual Data Exploration and Analysis can be obtained by clicking here , or by anonymous ftp to ftp.cse.ucsc.edu then get pub/reinas/papers/spie95_glyph.ps.Z.


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