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O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING (OAWRS) Helen Dickson
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R EVIEW : A CTIVE A COUSTIC S ENSING An acoustic signal is generated Sound waves travel through the water and scatter off objects Backscattered sound is recorded
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R EVIEW : C ONVENTIONAL F ISH F INDING S ONAR (CFFS) Uses active acoustic sensing Sends sound waves straight down through the water column
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P ROBLEMS OF C ONVENTIONAL F ISH F INDING S ONAR Attenuation Frequency Image size Sampling frequency
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O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING Method of active acoustic sensing Developed by MIT Sends sound waves horizontally through the water column
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A COUSTIC W AVEGUIDES Physical structures for guiding waves Allow acoustic waves to travel long distances with little attenuation The continental shelf as a waveguide
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O CEAN A COUSTIC W AVEGUIDE R EMOTE S ENSING Little attenuation Lower frequency Much larger image (1,000s of square km’s) Images created every minute (or less)
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I MAGE GENERATED BY OAWRS
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M OVIE GENERATED BY OAWRS
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A PPLICATIONS Shoal Characteristics: Formation (critical density) Migration Leaders Monitor and conserve fish populations Identify fish species based on return signal
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A PPLICATIONS Acoustic clutter Acoustic returns from objects in the water other than the intended target Is it a submarine or is it a school of fish? Important in Navy operations OAWRS allows more detailed information to be gathered
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R EFERENCES Holden, Constance. Sound Sightings. 2006. Science. 313(5788):777 Makris, Nicholas C., et al. Fish Population and Behavior Revealed by Instantaneous Continental Shelf-Scale Imaging. 2006. Science. 311(5761):660-663. Makris, Nicholas C. et al. Critical Population Density Triggers Rapid Formation of Vast Oceanic Fish Shoals. 2009. Science. 323(5922):1734-1737. Makris, Nicholas C. Acoustic Clutter and Ocean Acoustic Waveguide Remote Sensing (OAWRS) in Continental Shelf Environments. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/oamakris.pdf Makris, Nicholas C. Continuous Monitoring of Fish Population and Behavior by Instantaneous Continental-Shelf-Scale Imaging with Ocean Waveguide Acoustics. http://www.onr.navy.mil/sci_tech/32/reports/docs/08/npmakris.pdf Ratilal, Purnima et al. Long range acoustic imaging of the continental shelf environment: The Acoustic Clutter Reconnaissance Experiment 2001. 2005. Journal of The Acoustic Society of America. 117(4):1977-1998. Woods Hole Oceanographic Institution. 2007. http://www.whoi.edu/page.do?pid=10897&i=2041&x=131
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