Imaging sonar based navigation method for backtracking of AUV

We propose an imaging sonar-based backtracking method as a navigation strategy for an underwater investigation of AUVs. The purpose of backtracking method is to reduce a drift error caused by the inaccuracy of navigation sensors when an AUV returns to its previous position. The AUV divides the trajectory into several intervals and returns to the previous position while correcting small drift error for each interval. For the backtracking, we suggest a method obtaining terrain information using an imaging sonar. We create a 3D point cloud by scanning the seafloor. We can use the 3D point cloud to detect objects and to select natural landmarks. The selected natural landmark can be used as a reference in the backtracking process. To verify the feasibility of proposed methods, we conducted field experiments using a hovering-type AUV `Cyclops'.