Cross-Track Seabed Imaging and Buried Object Detection With a Multibeam Sonar

What lies underneath the ocean floor is of interest to a wide variety of disciplines. The focus here is imaging the upper tens of meters of material beneath the seafloor. The sub-bottom profiler is a valuable tool to that end, producing a 2-D image in depth below the seafloor and along the track of the ship. Geoscientists and engineers are frequently interested in not only the subseabed beneath the ship but also either side or cross-track of the ship. We show an approach to cross-track imaging using a low-frequency multibeam sub-bottom profiler. The main result is the detection of a buried 0.2-m diameter pipeline at a range of nearly 1-km cross-track from the ship in 230-m water depth. This is a swath width coverage of eight times the water depth or nominally an angular range of ±76° from nadir. These results have implications not only for buried object detection but also for other potential applications including exploring seabed spatial variability.