Development and feasibility testing of an acoustic buried cable detection system

Minehunting, ordinance disposal, cable and pipeline relocation, and route survey operations often require the ability to detect and locate objects buried in the seafloor. A high-resolution acoustic subbottom imaging system capable of locating targets buried up to three meters deep, from altitudes of ten-meters or more in a variety of sediments has been tested. The system uses bistatic geometry, wide bandwidth, multiple-beam processing, and multiple-aspect oversampling to create profile imagery of the subbottom with centimeter-level resolution. Multi-aspect data were examined separately and found to provide target classification information using predictable backscatter pattern differences between linear targets (uniform cylindrical cables and pipelines) and small and large discreet lump scatterers. The system uses a separated wide-band transmitter, a poly-vinyl difluoride (PVDF) line-array hydrophone, and a data acquisition system. Sixteen individual channels of data were continuously recorded enabling the formation of steered multiple beams for multiple-aspect examination of target backscatter characteristics in post-processing. Tests were conducted using small buried cylindrical targets ranging in diameter from 12 to 40 millimeters as well as targets-of-opportunity in the sediments. Cylindrical target characteristics and sediment characteristics within a Puget Sound test range were measured independently. Detailed backscatter measurements for a subset of these targets were acquired in an acoustic test tank prior to burial of targets in a natural environment