Much of the work at CCOM/JHC involves the use of highly sophisticated sonar systems like multibeam echo sounders (MBES) and phase differencing bathymetric sonars (PDBS). The Center constantly strives to better understand the characteristics and fundamental performance limitations of the systems we use, and to develop new capabilities for existing systems. Much of this work involves aspects of sonar calibration, both in the acoustic test tank at the Chase Ocean Engineering Lab and in the field.
The facility at Chase Ocean Engineering Lab takes advantage of our 18Lx12Wx6D meter tank, outfitted with a computer controlled transducer rotor (0.025 degree resolution) and custom-build data-acquisition system. MBES and PDBS systems are characterized running standard calibrations (e.g., beam patterns, sensitivity), but research efforts also strive to extend these techniques to the field with the use of standard target spheres that can be positioned using an ‘auxiliary’ split-beam transducer. The goal is to perform in situ calibrations at an accuracy that is close to what we can achieve in the calibration tank. The initial results for a 200 kHz Reson 7125 MBES (shown below) look promising. The results of the calibration work are used to refine our understanding of how these systems work and allow us to increase the fidelity of some of the data products generated by these systems.
As this research indicates, not all work at CCOM/JHC occurs in a laboratory setting. In the field, scientists and students work to increase the utility of these sonar systems. For example, the Center has developed software routines to turn the Simrad ME70 MBES, which was originally designed for mapping pelagic fish schools, into a hybrid multibeam / phase differencing system capable of collecting thousands of soundings per ping. Researchers also work in the opposite direction, testing the ability of MBES’s designed for hydrography to collect acoustic backscatter from targets (e.g., marine organisms, gas plumes) within the water column. These aspects of our work are closely related to the Center’s IOCM and midwater mapping efforts.