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    Tracking near surface drogues using an acoustic travel time technique in shallow, highly stratified water : problems and observations

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    WHOI 81-37.pdf (6.510Mb)
    Date
    1981-05
    Author
    Churchill, James H.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/10253
    DOI
    10.1575/1912/10253
    Keyword
     Underwater acoustics; Acoustic drogue measurements 
    Abstract
    During July and August of 1980 near surface water velocities of Lake Huron were measured by tracking drogues, equipped with sonobuoys, using an acoustic travel time technique. Prior to these experiments difficulties associated with acoustic ray bending in the shallow, highly stratified environment were anticipated. Simple models were developed to predict the errors in drogue position and velocity determination resulting from ray bending. During the experiments round trip travel times of acoustic pulses transmitted between three bottom transponders and a transducer (lowered from a ship) were recorded. These combined with ray diagrams strongly suggested that, for a separation between the transducer and a bottom transponder of about 1.2 km, pulses which were detected first traveled by two paths, that of an inflected ray and that of a ray trapped beneath the thermocline. The error in position and velocity determination associated with these paths was 1 to 2%. Evidence also indicated that increased thermocline depth resulted in decreased tracking range.
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    • Physical Oceanography (PO)
    • WHOI Technical Reports
    Suggested Citation
    Churchill, J. H. (1981). Tracking near surface drogues using an acoustic travel time technique in shallow, highly stratified water: problems and observations. Woods Hole Oceanographic Institution. https://doi.org/10.1575/1912/10253
     

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