A procedure is suggested in which a relative calibration for the intensity output of a multibeam echo sounder (MBES) can be performed. This procedure identifies a common survey line (i.e., a standard line), over which acoustic backscatter from the seafloor is collected with multiple MBES systems or by the same system multiple times. A location on the standard line which exhibits temporal stability in its seafloor backscatter response is used to bring the intensity output of the multiple MBES systems to a common reference. This relative calibration procedure has utility for MBES users wishing to generate an aggregate seafloor backscatter mosaic using multiple systems, revisiting an area to detect changes in substrate type, and comparing substrate types in the same general area but with different systems or different system settings. The calibration procedure is demonstrated using three different MBES systems over 3 different years in New Castle, NH, USA.
An extended calibration target has been developed for calibrating the intensity output of a multibeam echo sounder (MBES). The target was constructed of chain links arranged similar to a curtain, providing an extended surface target with a mean scattering strength of −17.8 dB at 200 kHz. The target was used to calibrate a 200 kHz MBES, and the MBES was subsequently used to collect seafloor backscatter over sand and gravel seafloors. Field results were compared with calibrated split-beam echo sounder measurements at an incidence angle of 45°. The results suggest that the chain target is a viable MBES calibration tool.
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