SeaMARC II is a long-range, side-scan sonar system which produces geometrically correct acoustic images o f the seafloor. In addition, the system has the unique capability of being able to measure the direction to a seafloor reflector. When the range and direction to a reflector are accurately determined these data can be converted to position and depth, so that bathymetry can be calculated for the ensonified swath of seafloor. Thus, the SeaMARC II system provides the acoustic equivalent of an aerial photograph of the seafloor accompanied by a high resolution bathymetric map. The system is being jointly developed by International Submarine Technology Ltd. (IST), of Redmond, Wash., and the Hawaii Institute of Geophysics (HIG), of the University of Hawaii.