Object observation in detail by the AUV "Tri-Dog 1" with laser pointers

AUV (autonomous underwater vehicles) can be used to observe and get video images of underwater structures. This paper proposes a navigation method of AUV for observing large objects which disturb magnetic fields, based on images by a CCD camera, assuming that visibility is good enough. The AUV uses dead reckoning navigation until it comes near to the object. For detecting and observing the object, it uses two laser pointers, which are mounted in parallel on the head of the AUV, and a CCD camera. Through visual processing, the AUV calculates distances to two reflected points of laser beams, then determines angle between the object and the AUV. The AUV can then turn around the object keeping constant distance and angle. The proposed algorithm was implemented in the developed test bed AUV "Tri-Dog 1" and tested through tank tests. The vehicle successfully traced a straight wall and a curved wall, detected piles of 1 meter in diameter, and turned around them. It finds the precise distance to an object. An AUV will thus be able to carry out a survey of a target object in detail without any help from outside.