Page 272 - Concise Encyclopedia of Robotics

Range Plotting
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Range
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Range of function

To do one-dimensional (1-D) range plotting, a signal is sent out, and
the robot measures the time it takes for the echo to come back. This signal
can be an acoustic wave, in which case the device is sonar. Or it can be a
radio wave; this is radar. If it is visible light in the form of a laser beam, it
is ladar.
Two-dimensional (2-D) range plotting involves mapping the distances to
various objects, as a function of their direction in a defined plane. One
method is shown in the illustration. The robot is at the center of the plot, in
a room containing three desks (rectangles) and two floor lamps (circles).
The range is measured every 10° of azimuth around a complete circle,result-
ing in the set of points shown. A better plot would be obtained if the
range were plotted every 5°, every 2°, or even every 1° or less. But no mat-
ter how detailed the direction resolution, the 2-D range plot can show
things in only one plane, such as the floor level or some horizontal plane
above the floor.
Three-dimensional (3-D) range plotting requires the use of spherical coor-
dinates. The distance must be measured for a large number of directions at
all orientations. A 3-D range plot in a room such as that depicted in the

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