This paper introduces one method to obtain super detailed sea floor acoustic image with an autonomous underwater vehicle and its result on the 2,000m depth mud volcanoes in Kumano Trough 50km offshore of Japan. Ocean going autonomous underwater vehicle "Urashima" was used as a platform to equip a high frequency side scan sonar system and its latitude, longitude and altitude was programmed and controlled keeping constant to unify the resolution of acoustical image. As the result, the vehicle was controlled successfully, and acoustic image of mud volcanoes was proved that the autonomous underwater vehicle has high capability for detailed deep seafloor scientific survey.
The frequency of the sound wave for seafloor investigations by surface vessels are getting lower and even though narrow beams would be used, its footprints at seafloor are getting larger by becoming of depth is increasing, so that it is well known that the resolution of the acquisition data is decreasing by ocean depth. Recently, to obtain high resolution sea floor image, autonomous underwater vehicles have been developed by many institutions and companies instead of deep towing vehicles, because the vehicle motion is not restrained to its towing cable. Autonomous underwater vehicle "Urashima" (Hereafter, it is called ("AUV") shown in Table 1 by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing to research underwater engineerings as the energy storage system which composed from close polymer membrane fuel cell, metal hydride and cogeneration system, inertial navigation system with ring-laser gyro and acoustical digital telemetry system since 2000. The data obtained by sea tests is offered not only a technological research but also the science section of a precise inquiry in seafloor etc. is executed co-operation with Ocean Research institute of the Tokyo University (ORI), the National Institute of Advanced Industrial Science and Technology, Institute for Research Earth Evolution (IFREE) and Center for Deep Earth Exploration (CDEX) in JAMSTEC since 2005.
