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Underwater Navigation for Long-Range Autonomous Underwater Vehicles Using Geomagnetic and Bathymetric Information

This paper evaluates methods for the long-range navigation of autonomous underwater vehicles (AUVs) at a middle depth of deep water from the viewpoint of spatial fields-aided navigation. Motivated by experimental works on the geomagnetic field-aided navigation of aquatic animals, we focus on the application of inertia systems with reference to maps of geomagnetic and bathymetric fields of the Earth to the navigation of AUVs. The Inertia Navigation System (INS) in combination with acoustic transponders, the Doppler velocity log, normally used for navigation systems of AUVs near the sea floor, cannot be used for long-range navigation of an AUV at a middle depth of deep water. We first carried out experiments to obtain geomagnetic and bathymetric data in the Harima Sea with a gentle slope of the sea floor and geomagnetic field. At Suruga Bay, which has a steep seabed slope, however, we used a bathymetric map and digital geomagnetic map published by the Japan Coast Guard. We performed a simulation to evaluate the performance of these navigation methods, and found that the precision of navigation of an AUV in water current by the method using the geomagnetic map and bathymetric map without INS is better than by the method using INS alone or by the method using INS with a positional correction by geomagnetic and bathymetric information.