GISdevelopment.net ---> AARS ---> ACRS 1992 ---> Poster Session R Combining Bathymetric Mapping with Side Scan Sonar Yoshiaki Igarashi Metal Mining Agency of Japan, Japan. Toshiaki Ueki Sanyo Techno Marine, INC. Japan Introduction It is critically important to map the detailed seafloor topography in order to evaluate the potential of manganese nodule resources because of presence of obstacles on the seafloor such as cliffs and hills considerably reduces minable areas. Two systems have been widely used for detailed topographic surveys: Multi Beam Echo Sounder (MBES) can provide a bathymetric map twice as wide as the water depth; on the other hand, side Scan Sonar (SSS) can provide a high-resolution acoustic image of the seafloor. We present 3-D views generated by combining the Multi beam Echo Sounder map with the Side Scan Sonar imagery. Survey of Manganese Module Since 1963, the Metal Mining Agency of Japan (MMAJ) has always strived towards the promotion of metal mining industries in Japan and throughout the world in the field of mineral exploration, mine developments, technological R&D, prevention of mining related polluted and much more. In 1975, MMAJ commenced exploration activities for manganese modules in the Clarion Clipperton Fracture Zone in the Pacific Ocean at the request of the ministry of international trade and Industry (MIT). The activities were reinforced with the launch of the research vessel. Hakurei-muru No. 2 in 1980, which is exclusively designed for exploration of deep-sea mineral resources. MMAJ has been involved in not only exploration of manganese nodules but also development of undersea technologies, ore processing, post-processing of data and environmental impact research. In addition, MMAJ has explored polymetallic sulfide deposits in the high seas of the East Pacific Rise and cobalt – rich manganese crusts in the north western part of the Pacific Ocean. Here, we present our R/V Hakurei – muru No. 2 and MMAJ’s various activities relating to deep – sea mineral resources. From 1989 to 1991, detailed surveys were concentrated in the western region of the Japanese Application areas in the Pacific Ocean using R/V Hakurei-maru No. 2. Also, locations of the survey lines and points are summarized in fig. 1. Side scan sonar was towed totally 280 nautical miles long at the speed of 1 or 2 knots, while the towfish was 80 meters off the bottom. The side scan sonar image shows cliffs on the seafloor as gray stain in fig. 2. The topography of the seafloor was mapped by Multi Narrow Beam Echo Sounder, while the interval of each ship’s track is 2 -3 miles so that ten-meter contoured map can be made (fig. 3). Fig 1. SSS towfish, CDC vehicle and MFES track lines Fig 2. SSSmosaics. SSS image shows obstcles as "gray stains". Multi-frequency Exploration system (MFES) estimated nodule abundance from seafloor acoustic reflectivity using three frequencies, 2.5, 12 and 30 KHz. In addition, the side scan sonar image can detect detailed nodule abundance that Multi-frequency Exploration System can; however, continuous photographs show that nodule abundance often changes from dense to space within 80 meters, while the side scan sonar imagery shows uniforms shade. As ground truth data, more than 3,500 photographs of sea – bottom were taken with deep-sea cameras attached to the deep-tow vehicle, continuous Deep-sea camera (CDC). Positioning correction Prior to mosaiking, preprocessing corrections such as radiometric, geometric and slantrage, are carried out. Moreover, in order to correct the position of the side scan sonar image, the mosaics are adjusted to the Multi Beam Echo Sounder map following a rough positioning by catenary calculations. As a result, correctional coefficient between the multi beam echo sounder and the side scan sonar bathymetry represents upto 0.93 in some lines. (fig. 4).] 3-D view 3-D view are presented by combining the Multi Beam Echo sounder map with the side scan sonar imagery (fig. 5- 6). This combination is helpful in understanding the relationship between topography and morphology of seafloor features. Nodules abundance calculated by Multi-frequency exploration system and bottom photographs along track lines are super imposed on the views so that the side scan sonar imagery can be compared with these abundance data. As a result, dark portions of the acoustic image are consistent with high manganese nodule abundance areas. The suggests side scan sonar imagery probably reflects on the abundance of manganese nodules. Fig 5. 3-D view with nodule abundance calculated by CDC data Fig 6. 3-D view with module abundance calculated by MFES data.