Development of split-beam sonar processing methods

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Acoustic methods used to evaluate fish size and distribution are an important component of fisheries management and oceanographic research studies. Except for some specialised applications, acoustic methods use echosounder systems that are deployed from ships to sample a survey pattern in some area of the ocean. Deployment from ships has been required because acoustic survey instrumentation consumes a lot of power and collects large quantities of data. However, over the last 10 years, ASL Environmental Sciences Inc. (ASL) has developed low power acoustic instrumentation with large recording capacity suitable for use in a self-contained package. This capability opens up two new revolutionary survey possibilities: long-term monitoring from fixed locations that are far from shore or are not easily accessible (for example under ice) and; the ability to undertake surveys using small autonomous vehicles. The proposed project will capitalise on that capability to enable fish detection in their acoustic systems by incorporating "split-beam" sonar processing. With split-beam sonar, the acoustic beam used to probe the water is divided into four quadrants which makes it possible to identify the angular position of a target in addition to its range. That additional information makes it possible to make measurements of fish size and to track fish behaviour. The project involves the development of new acoustic hardware and signal processing software suitable for operating in a self-contained autonomous package. In addition to the hardware developments, computer simulations of sonar operation will be used to explore optimal methods for signal processing. A series of field trials will be used to fine tune and demonstrate the capabilities of the approach. This research will optimize a revolutionary survey product for ASL and improve methods for extracting and understanding information contained in sonar data - advancements with potential economic and environmental benefits to Canada.