A system and method for landmark navigation employing optical beacons
deployed at locations throughout a field of operation of a vehicle. The
optical beacons emit or reflect an optical signal at a predetermined
blink frequency. The locations of the optical beacons may or may not be
known to the vehicle. At least one imaging device on the vehicle, such as
a digital camera, captures images in the field of operation, and in
particular a pair of image frames such that the time interval between the
image frames of the pair is equal to one-half of the blink period of the
optical signal. Data is generated that represents a difference frame
between two image frames captured by the imaging device. Pixel locations
of optical beacons in the difference frame are identified. The position
and orientation of the vehicle is determined from data representing pixel
locations of optical beacons in the difference frame.