Halo (visualization technique)

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A personal digital assistant (PDA) showing a street map enhanced with the halo visualization technique. The PDA screen shows five arcs, each indicating one off-screen location. This screenshot was enhanced such that it shows the actual locations of the off-screen locations--in reality users only see the arcs on the actual PDA screen. However, the arcs convey all information required to reconstruct the off-screen locations. The higher curvature of the arc at the bottom, for example, allows users to conclude that this location is closer to the car (marked in blue) than the other four locations.

For other uses, see Halo (disambiguation).

In information visualization, the halo technique is a method for viewing large documents on small screens or display windows, which functions by pointing users to the locations objects out of the visible field. Off-screen objects are surrounded by rings which reach into the border visible field (or window). From the position of the arc-shaped marker, combined with its curvature, users can infer the off-screen location of the object.

Halo has been used to display maps on personal digital assistants and mobile phones. The name of the technique was derived from the metaphor of a streetlamp shining a halo onto the street. The technique was invented by Patrick Baudisch in 2001, while at Xerox PARC,

A similar concept is arrow location, where the direction of objects is represented by a directional marker shown in the border. This variant has been used in 3D video games for several years. Arrow-based techniques convey the direction to off-screen locations, but require additional scale-dependent annotations in order to convey distance. Halo arcs, in contrast, point to a location, which implies direction and distance.

[edit] Advantages

• Faster and more reliable comprehension than techniques based on arrows.
• Halo is scale-independent, because arcs point to a location, rather than indicate a (scale-dependent) distance.
• Application designers can use arc color, thickness and texture to convey additional parameters, such as type of off-screen location or desirability.

[edit] Disadvantages

• More prone to clutter than arrow-based techniques
• Notion of distance decreases for objects located far away

[edit] References

• Patrick Baudisch, Ruth Rosenholtz (2003). "Halo: A Technique for Visualizing Off-Screen Locations". Proceedings of ACM CHI Conference on Human Factors in Computing Systems: 481-488. 
• Smalley, E. Screen arcs widen view. In Technology Research News (TRNs). May 7, 2002.

[edit] See also

• Halo interactive Flash prototype

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