An Evaluation of Side-Looking 12 and 100kHz Sonars for Continuous Surveillance of a Shallow Channel

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Authors
  1. Trevorrow, M.V.
Corporate Authors
Defence R&D Canada - Atlantic, Dartmouth NS (CAN)
Abstract
This study evaluates data from two high-frequency (12 and 100 kHz) side-looking sonars which were operated for extended periods in March and October 1997 in Drogden Channel, near Copenhagen, Denmark. This busy shipping channel, 1-km-wide by 12-m-deep, connects the Baltic Sea with the North Sea through the Kattegat. The original purpose of these tests was to demonstrate continuous surveillance for migratory herring, however a variety of shipping traffic was also observed. Quantitative acoustic measurements of ship characteristics and low-grazing-angle seabed reverberation were made with both sonars under a variety of conditions. The sonar measurements were supplemented by simultaneous water temperature, salinity, and current profiles and surface meteorological measurements, allowing some understanding of the environmental influences. The general characteristics were that under normal, homogeneous flow conditions, ships and fish schools were routinely observed up to 400 m range with the 100 kHz sonar and up to 2000 m range with the 12 kHz system. Occasional saline intrusions near the seabed were observed to create strong upward-refracting conditions that significantly altered the available range for target detection, especially for the 100 kHz sonar. Example echograms and reverberation results from both normal and upward refracting conditions are shown. TRUNCATED

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Keywords
Side looking sonar;Boundary reverberation;Target strength;Ray tracing analysis
Report Number
DRDC-ATLANTIC-TM-2002-149 — Technical Memorandum
Date of publication
01 Sep 2002
Number of Pages
44
DSTKIM No
CA021917
CANDIS No
518661
Format(s):
CD ROM

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