Relative navigation of an autonomous underwater vehicle using a light-section profiling system

Autonomous underwater vehicles (AUV) are suitable for condition survey of artificial structures such as pillars and caissons in harbors. This paper describes a method to trace the structure's surface using a light-section profiling system. This profiling system determines the continuous shape of the target objects over a wide area by the light sectioning method. The vehicle navigates referencing the principal shape of the structure, tracing its surface while taking video images. This method also enables three-dimensional mapping of traced structures and the seabed. The method is implemented using testbed AUV "Tri-Dog 1" and verified by tank tests. The AUV navigates robustly against trivial objects such as small obstacles and floating particles. Precise depth mapping of the tank bottom is carried out.