Seabed and sub-bottom classification using measurements of normal incidence backscatter measurements in the 1-10 kHz frequency band


  1. Osler, J.C.
  2. Hines, P.C.
  3. MacDougald, D.J.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
It has been established that the first and second normal incidence acoustic returns from the seabed can be used as a classification tool to discriminate between, for example, sand, mud, or rock bottoms. Typically this is accomplished by using mono-static echo sounder systems that operate in the range of several 10s of kHz so that bottom roughness at the seabed interface is the dominant scattering mechanism. Theoretical results indicate that at lower frequencies, returns from the sub-bottom should provide an additional discrimination tool without significantly corrupting the seabed information contained in the interface scatter returns. This paper presents an experimental methodology for making these normal incidence measurements made in the 1 to 10 kHz frequency band using a moored vertical line array of receivers and pair of projectors. The projectors have been used in tandem to create aliased cardiods that significantly reduce interference due to the sea surface reflection. The conventional classification technique relies upon treating the first bottom echo as a mono-static arrival and the second bottom echo as a bi-static arrival. The use of a vertical line array also allows a similar comparison to be made between hydrophones proximal to the source (mono-static) and hydrophones that are farther away (bi-static). Experimental results from the ONR Stratform area are presented.
Bottom properties;Buried reflectors;Geoacoustic data;LFAS (Low Frequency Active Sonar);Seabeds
Report Number
DREA-TM-2001-185-PAP-14 — Technical Memorandum
Date of publication
01 Oct 2001
Number of Pages
Hardcopy;Document Image stored on Optical Disk

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