The height and distance to an obstacle must be known or at
least estimated for the Scoutrobot to successfully jump over it. If
the obstacle is too large, the robot must avoid it by detouring.
The robot determines whether jumping or detouring is more
appropriate based on the distance to the obstacle, height of
the obstacle, and shape of the obstacle. In most robots, a set
of ultrasonic sensors is used to measure the distance to an object,
but the signal from these sensors is sometimes poor due
to the narrow view angle and unexpected noise. In addition,
the dimensions of an object cannot by easily measured with
ultrasonic sensors. Thus, a camera is sometimes combined with
the ultrasonic sensors to obtain two-dimensional values of the
vertical and horizontal lengths of the object by considering the
geometric relation between the camera and image frames, which
is known as a forward projection. Fig. 9 illustrates the computations
used to determine a point on an object based on the focal
length f and the coordinates of the point with respect to the
camera frame, Z and Y.