Comparision of Target Detection Capabilities of the Reson Seabat 8101 and Reson Seabat 9001 Multibeam Sonars

Swath multibeam sonar systems (MBSS) are commonly described as being capable of producing full-bottom coverage (100 % coverage). However, there is finite dimension to their multiple narrow beams, and therefore, this places a limit on the minimum target size that can be successfully detected. Multibeam sonars are being used more frequently to provide information regarding short wavelength features on the seafloor, and since these feautures are similar is size or smaller than the beam footprint, their adequate detection is not always possible. Numerous other issues inherent to the use of multibeams complicate the successful detection and delineation of small scale features, including but not limited to the changing size of the projected beam footprint tied to water depth, the nature of the bottom detect algorith used at nadir or obliques portions of the swath, and the difficulty of maintaining high data sounding densities from a moving platform. This papers explores the capabilities of two different multibeam sonars to detect short wavelength features on the seafloor, whose dimensions approaches that of or are less than the beam spacing in the horizontal dimensions. The survey site was offshore of the Bamfield Marine station, in a region where an underwater pipeline had recently been installed. Due to the shallow nature of the survey region, several dives were conducted using underwater video equipment to record the actual size of the concrete collars for ground truthing purposes. This allowed for the comparison of the actual target size with the results provided from the MBSS, as a means of determining the effectiveness of target detection of these two system