Acoustic phase characteristics and phase centers of the acoustic transducers for seafloor geodetic observation

Abstract

Institute of Industrial Science, University of Tokyo and Hydrographic and Oceanographic Department, Japan Coast Guard have been conducting seafloor geodetic observations since 2000. Sufficient observational results to discus the system and the observational method have been established as we accumulated the experiences of the observations. Issues and knowledge that we have through the observations should be fed back to the system and further observation for improvement. One of such issues is one inherent in acoustic transducers for acoustic ranging. Ranging errors were caused by the operational principles of the transducers and the reference point set on the point at the top center of the transducers. In order to take measure to this issue, tank tests were conducted to evaluate the ranging characteristic curves of the acoustic transducers. And then the acoustic phase centers of the transducers were deduced from these curves. The comparison of the acoustic phase centers of two types of the acoustic transducers, that is, the cylindrical and the spherical curved disk transducers should be needed to retain the continuity of the long‐term seafloor geodetic observation.