CS 533 Assignment 1
Mik Kersten

bad visualization

This image of Venus was released from NASA's Jet Propulsion Lab from in the early 1990s.  It has since made its way into textbooks such as Sir Robert Wilson's Astronomy Through the Ages, where it is described as how "Venus would look to the human eye".  The image is a visualization of Venus terrain data.  This particular picture is a snapshot taken from a 3D computer generated from topographical photographs of Venus taken by the Magellan spacecraft.  This model was also used to make a fly-over video of the planet.

I saw the fly-over video when I was 17, and it made a lasting impression on me.  I was amazed at the ability of computers to make an accurate relief map of another planet.  But it turns out that this image, as well as the video, is very misleading.  The vertical scale is exaggerated 22.5 to 1.  Both the picture and a fly-over video would be quite boring if Venus was accurately represented.  This visualization is most remarkable for what it fails to show: any sort of indication of scale and attitude.  If the authors of the work had considered this picture and video a scientific visualization, and not a simple picture, perhaps the results would not have been as misleading.  The potential for a visualization to create a lasting misconception is made evident by this impact of this image, and by the resulting foundation of a "Flat Venus Society".


good visualization

There is potential for asteroids to collide with the earth and hope to avoid those collisions by nudging the asteroid away from the collision orbit, as shown in this diagram (Scientific American, November 2003, p. 57).  The diagram depicts how a "space-tug" can be used to alter the trajectory of an asteroid on a collision course with earth (enlarge the image to read the text).  The blue arc show's earth's orbit, the red arc shows the asteroid's collision orbit, and the green arc an altered safe orbit of the satellite.

This diagram makes careful use of iconography and color, without overwhelming the reader.  The direction of each trajectory is made clear with arrows.  The meaning of each trajectory is implicitly encoded in its color, and the colors have a clear semantic mapping (earth = blue, bad = red, good = green).  The only icons used are that of the sun, earth, asteroid, and spacecraft.  These are small, clear, accurate, and don't take away from the textual descriptions of the diagram.  The diagram also shows time, made clear by the numbered sequences and descriptions.  The text doesn't obscure the diagram thanks to a consistent use of font & color (e.g. orange for headings).  Finally, the inset pictures do a good job at showing the details of the interesting points in the trajectories without taking away from the bigger picture, and maintain context by not introducing any new elements (just scaling icons and trajectories).
 Last modified on January 14, 2003.