Screen arcs widen view
Technology Research News
Viewing a large map on a small screen can
be frustrating, especially if you're trying to keep track of positions
and distances of locations that fall far beyond the range of the screen.
Researchers from Palo Alto Research Center (PARC) have hit upon
a simple solution that allows people to keep a sense of the relative distances
of key offscreen locations. The software, dubbed Halo, was inspired by
the arc of light that appears around streetlights.
As a person navigates a map on a handheld computer, the software
causes arcs representing selected offscreen locations to appear on the
edge of the screen, as if the locations were surrounded by circles large
enough that a portion of the arc just reached onto the screen. The user
can sense how far away an offscreen location is by the curve and translucence
of its arc, which indicates the size of the full circle and thus the distance
to its center.
The software could make it easier to use small screens to navigate
maps, three-dimensional environments, and keep track of moving targets
like hazards, or even friends, according to Patrick Baudisch, now a researcher
at Microsoft Research.
"Halo is a visualization technique that supports spatial cognition...
by surrounding offscreen objects with rings that are just large enough
to reach into the border region of the display window," said Baudisch.
"Users can infer the offscreen location of the object at the center of
the ring," he said. The arcs also become more translucent as they grow
larger to give users a second distance clue.
The researchers hit on the idea while trying to use small dots
at the window border to show distance. "Then I thought of street lamps
and how they cast a halo of light onto the street," said Baudisch.
There are several other methods for providing offscreen information
on small-screen devices, including overviews with detailed insets, fisheye
views, and arrows. However, insets divide the user's attention, fisheye
views distort distances and directions, and arrows fail to provide distance
information, said Baudisch
The researchers tested their prototype software with 12 study
participants who used it on a laptop and a relatively large handheld computer.
The participants compared Halo and a second program that used arrows to
point to offscreen objects.
The participants carried out four tasks: estimating where an offscreen
object would lie in space, locating the closest of several offscreen objects,
selecting five offscreen targets in the order that would form the shortest
delivery path, and selecting a route to the closest of several on- and
offscreen hospitals that would best avoid several on- and offscreen traffic
The participants rated the difficulty of the tasks and the ease-of-use
of the interfaces. The participants performed the tasks 16 to 33 percent
faster, and a majority preferred the Halo interface for each of the four
tasks, according to Baudisch.
Error rates were slightly lower for the Halo interface on the
second, third and fourth tasks, but somewhat higher on the first task,
even though 80 percent of the participants said they preferred Halo for
that task. "The difference in accuracy was caused almost exclusively by
subjects underestimating distances when using the Halo interface," said
The researchers are currently working to change the circles to
ovals, which may allow people to perceive distance more accurately, Baudisch
said. They are also working on a three-dimensional version of the software,
The method could solve a potential problem in navigating complicated
environments through a small handheld computer screen, according to Baudisch.
"If I use... editing tools to move a graphical object around in [a] potentially
infinite plane, how can I make sure I find it again?" he said. "Halo could...
solve the problem."
The researchers are also working to adapt the method to real-time
environments. "Halo gets really useful if offscreen objects move or change
their relevance," said Baudisch. "Think of a handheld system that informs
you about the availability of attractions in a theme park [or] hazards
in a hostile environment."
On a handheld connected to a wireless network, halos could also
represent the movements of people, for instance, the users' friends, Baudisch
The method is also appropriate for games, said Baudisch. "Think
of a football game -- where are my teammates? -- is a player of the opposite
team at a location where he or she could intercept my pass?"
The basic method is ready for practical use now, said Baudisch.
Baudisch's research colleague was Ruth Rosenholtz of Palo Alto
Research Center. They presented the research at the Association of Computing
Machinery Computer-Human Interaction (ACM-CHI) conference in Fort Lauderdale,
Florida in April 5-10, 2003. The research was funded by PARC Inc.
TRN Categories: Human-Computer Interaction
Story Type: News
Related Elements: Technical paper, "Halo: A Technique for
Visualizing Offscreen Locations," presented at the Association of Computing
Machinery (ACM) Computer-Human Interaction (CHI) Conference 2003 Fort
Lauderdale, Florida April 5-10, 2003, and posted at www.ipsi.fhg.de/~baudisch/Publications/2003-Baudisch-CHI03-Halo.pdf.
May 7/14, 2003
Screen arcs widen view
Light show makes 3D
Net scan finds like-minded
Sound forms virtual
Touchy-feely goes remote
Light mix makes
Metal expands electrically
fill virus with metal
Gold connectors stretch
Research News Roundup
Research Watch blog
View from the High Ground Q&A
How It Works
News | Blog
Buy an ad link