Moving edge is the edge of moving objects.
Difference image can be regarded as time gradient,
while edge image is space gradient. Moving edge can
be defined by the logic AND operation of difference
image and the edge image [6].
The advantage of frame difference method is its
small calculation, and the disadvantage is that it is
sensitive to the noise. If the objects do not move but
the brightness of the background changes, the results
of frame difference methods may be not accurate
enough. Since the edge has no relation with the
brightness, moving edge method can overcome the
disadvantage of frame difference method.
The flow chart of the detecting process by moving
edge method is as Figure 2.