We empirically evaluate the extent to which people perceive non-constant time and speed encoded on 2D paths. In our graphical perception study, we evaluate nine encodings from the literature for both straight and curved paths. Visualizing time and speed information is a challenge when the x and y axes already encode other data dimensions, for example when plotting a trip on a map. This is particularly true in disciplines such as time-geography and movement analytics that often require visualizing spatio-temporal trajectories. A common approach is to use 2D+time trajectories, which are 2D paths for which time is an additional dimension. However, there are currently no guidelines regarding how to represent time and speed on such paths. Our study results provide InfoVis designers with clear guidance regarding which encodings to use and which ones to avoid; in particular, we suggest using color value to encode speed and segment length to encode time whenever possible.


author={C. Perin and T. Wun and R. Pusch and S. Carpendale},
journal={IEEE Transactions on Visualization and Computer Graphics},
title={Assessing the Graphical Perception of Time and Speed on 2D+Time Trajectories},
keywords={Data visualization;Encoding;Guidelines;Image color analysis;Trajectory;Two dimensional displays;Visualization;Trajectory visualization;graphical perception;movement data;quantitative evaluation;visual encoding},

Evaluated time and speed encodings

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Short (1:40) video illustrating the study details

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Study Data

Pre-study questionnaire

Contains participant demographic information.

Post-study questionnaire

Contains participant subjective preferences.

Quantitative Data

Contains the quantitative results to the study.


Charles Perin
Charles is a lecturer in the Department of Computer Science at City, University of London, and part of the giCentre research group. He is a computer scientist specializing in information visualization and human computer interaction. He is particularly interested in designing and studying new interactions for visualizations; in understanding how people may make use of and interact with visualizations in their everyday lives; and in sports visualization.

Tiffany Wun
Tiffany is a Bachelor of Science, 5th Year at the University of Calgary under the supervision of Sheelagh Carpendale.

Richard Pusch
Richard is a research engineer in the Interactions Lab at the University of Calgary. He is interested in exploring new interfaces and methods for collaboration on large displays, and investigating how people build and interact with data in visualizations.

Sheelagh Carpendale
Sheelagh is a Professor at the University of Calgary where she holds a Canada Research Chair: Information Visualization and an NSERC/iCORE/SMART Industrial Research Chair: Interactive Technologies. She directs the Innovations in Visualization (InnoVis) research group and her research focuses on information visualization, collaborative visualization, and large interactive displays.