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Environmental data have inherent uncertainty which is often ignored in visualization. Meteorological stations and Doppler radars, including their time series averages, have a wealth of uncertainty information that traditional vector visualization methods such as meteorological wind barbs and arrow glyphs simply ignore. We have developed a new vector glyph to visualize uncertainty in 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 glyph shows the variation in uncertainty, and provides fair comparisons of data from instruments, models, and time averages of varying certainty. We also define visualizations that incorporate uncertainty in an unambiguous manner as verity visualization. We use both quantitative and qualitative methods to compare our glyphs to traditional ones. Subjective comparison tests with experts are provided, as well as objective tests, where the information density of our new glyphs and traditional glyphs are compared. The design of the glyph and numerous examples using environmental data are given. We show enhanced visualizations, data together with their uncertainty information, that may improve understanding of environmental vector field data quality.

Uncertainty and error of data an important aspect of a data set and is often overlooked during visualization due to the difficulties of actually rendering these values in a manner that is informative and concise. There are two approaches to the visualization of uncertainty, one is to overload current visualization approaches by using color or transparency to indicate uncertainty, and the other approach, presented here as verity visualization, is to derive new techniques that integrates the uncertainty and data visualization together in a way that allows the user to easily understand all data values. The specific method presented here is the creation of new glyphs that convey both the direction and magnitude information from the data, as well as indicate the uncertainty of the data. These new glyphs use area, direction, length, and extra lines to convey all relevant information. In addition to a technique for creating uncertainty glyphs, the method is evaluated using both a quantitative and a qualitative measure. The quantitative measure compares the data-to-ink ratio of normal glyphs to the new glyphs. The qualitative analysis looks at how well users visually decode the information. Overall the glyphs displayed more information using about the same amount of ink, and they were as easy to decode as normal glyphs.

Verify visualization, wind profilers, Doppler radar, wind barbs, icons.

uncertainty specific glyphs, glyph overloading

@Article{	wittenbrink:1996:GVUV,
author =	"Craig M. Wittenbrink and Alex T. Pang and Suresh K. Lodha",
title =	"Glyphs for Visualizing Uncertainty in Vector Fields",
journal =	"IEEE Transactions on Visualization and Computer Graphics",
volume =	"2",
number =	"3",
pages =	"266--279",
month =	"September",
year =	"1996",
}