From CS294-10 Visualization Fa08

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Good Example

Source: The Economist, December 8th-14th 2007


The heatmap represents customer traffic throughout a supermarket. The color choices make the interpretation effortless, leaving just the precise meaning of 'traffic' for the visualization to be specified by a comment (not explicitly mentioned in the article). But we see that there is especially high traffic near the entrance, checkout lanes, and the major arteries halfway to the back of the supermarket and at the back.


Data Model

The data set includes quantitative traffic values for 2D positions on a supermarket floor.

Image Model and Encodings

  • Position on the supermarket floor is mapped to the X and Y axes (atop a map of the supermarket for context).
  • Traffic magnitude is mapped to hue, but a narrow range of hues, presenting a clearer ordering of quantities than might otherwise be perceived.

Bad Example

Source: Z Magazine, May 2008


A diagram of the U.S. missile defense system installed in Europe. The magazine is printed in black and white, yet the key in the lower left corner looks like it was originally in color. Additionally, it's not clear how the key corresponds to the radar installations. There could be a much clearer ordering of the depicted events in time, and while length along missile trajectory is used to represent this, it is used in in an unintuitive way, especially since time proceeds right to left instead of left to right.


Data Model

The data set includes the approximate positions (Q), names (N), and types (N) of several military installations relevant to the European missile defense system, relationships between these installations, and their behavior when detecting and thwarting a missile attack, with a few time-ordered events. The data also include two malicious launch points located in the Middle East, likely for propagandistic purposes.

Image Model and Encodings

  • The approximate position of the installations, objects, and events are mapped to 3D positions via a perspective rendering of a globe and the space above it.
  • Installation type is encoded in the shape of its icon and in the nominal label adjacent to it.
  • Relationships between installations are denoted by lines connecting them.
  • Events, ordinal with nominal descriptions, are mapped to points along the enemy missile trajectory - space is overloaded to represent time in this case.


The redesign is a bit of a nasty Photoshop hack, but the ideas are there.


  • Since the data of interest are discrete time steps, I've gone with small multiples. While this is an improvement, an animation, where changes occur in the same space over time, would be a better choice.
  • One of the enemy missiles has been removed, since the defensive events (as far as I can tell) occur identically in both cases.
  • The connections to the fire control in the U.S. have been omitted, since all installations have these connections and so their existence can just be stated instead of cluttering the visualization.
  • I've removed the misleading "Surveillance and Track" from over the Black Sea. The label was next to a piece of color representing radar that corresponded to precision discrimination. As the visualization is all I have to go on, I felt omitting it was best.
  • Given that the redesign is a (nasty) photoshop of the original, much of the chartjunk remains intact: latitudinal/longitudinal lines, geographical features, and so on.

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