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3.7 Summary and analysis
The works presented above highlight several benefits provided by sensor
fusion. Sensor fusion techniques help to balance strong and weak points
of different types of sensors and to retrieve more reliable information
from the robot and the surrounding environment [24, 54]. Besides,
fused sensor data can be displayed to the user in a unified form.
Unified sensor representation has many advantages in respect to
visualization in separate displays. Presenting data inside a unique dis-
play, within a common reference frame, avoids competition for the
user’s attention. Interfaces that separately visualize different sensors
data force operators to continuously switch between different displays,
reference frames and visualization modalities. Instead, a unified rep-
resentation prevents this switching, thus strongly reducing the user’s
cognitive workload [9, 26].
Augmented reality is a form of unified representation which presents
a further advantage. Namely, visualizing complex data (as positions
and paths in [21]) as a graphic overlay on an image of the real worlds
permits a faster and more intuitive interpretation by a human operator.
Several approaches to AR-based representation of visual and range
data in telerobotics have been described. Some of them ([9, 24]) use
bidimensional augmentations to the video image. They use the color of
these overlays as a quick and effective way to communicate a distance
measure to the user. Though, since bidimensional overlays display in-
formation only on a single plane, their capacity to communicate a depth
value is intrinsically limited.
Others approaches [25, 26] create a bidimensional map of the envi-
ronment using laser data, and display a 3D representation of the map
by elevating virtual 3D walls. This approach has several advantages
in respect to using 2D overlays. First, a 3D map usually looks more
realistic, and can communicate depth in a more intuitive way because
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