GLORIA

GEOMAR Library Ocean Research Information Access

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 117, No. 4 ( 2005-04-01), p. 1977-1998
    Abstract: An active sonar system is used to image wide areas of the continental shelf environment by long-range echo sounding at low frequency. The bistatic system, deployed in the STRATAFORM area south of Long Island in April–May of 2001, imaged a large number of prominent clutter events over ranges spanning tens of kilometers in near real time. Roughly 3000 waveforms were transmitted into the water column. Wide-area acoustic images of the ocean environment were generated in near real time for each transmission. Between roughly 10 to more than 100 discrete and localized scatterers were registered for each image. This amounts to a total of at least 30 000 scattering events that could be confused with those from submerged vehicles over the period of the experiment. Bathymetric relief in the STRATAFORM area is extremely benign, with slopes typically less than 0.5° according to high resolution (30 m sampled) bathymetric data. Most of the clutter occurs in regions where the bathymetry is locally level and does not coregister with seafloor features. No statistically significant difference is found in the frequency of occurrence per unit area of repeatable clutter inside versus outside of areas occupied by subsurface river channels.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2005
    detail.hit.zdb_id: 1461063-2
    detail.hit.zdb_id: 219231-7
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2002
    In:  The Journal of the Acoustical Society of America Vol. 112, No. 5_Supplement ( 2002-11-01), p. 2280-2280
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 112, No. 5_Supplement ( 2002-11-01), p. 2280-2280
    Abstract: In the Geoclutter experiment of April–May 2001, an active sonar system was used to remotely and rapidly image geomorphology over wide areas in continental shelf waters by long-range echo sounding. The bistatic system, deployed in the strataform area south of Long Island, imaged extensive networks of buried river channels and inclined subseafloor strata over tens of kilometers in near real time. Bathymetric relief in the strataform area is extremely benign. The vast majority of features imaged apparently correspond to sub-bottom geomorphology that sound waves reach after tunneling as well as propagating through the overlying sediment. Returns from buried river channels were often found to be as discrete and strong as those from calibrated targets placed in the water column. Since buried river channels are expected to be ubiquitous in continental shelf environments, sub-seafloor geomorphology will play a major role in producing ‘‘false alarms’’ or clutter in long-range sonar systems that search for submerged objects such as underwater vehicles or marine mammals. Wave guide scattering and propagation are inherent to this new remote sensing technology because source signals are transmitted over hundreds of water-column depths in range to image sub-seafloor and seafloor geomorphology.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2002
    detail.hit.zdb_id: 1461063-2
    detail.hit.zdb_id: 219231-7
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 114, No. 4_Supplement ( 2003-10-01), p. 2375-2375
    Abstract: Results from the three-ship, April–May 2003 Main Acoustics Experiment of the ONR Acoustics Clutter Program are presented. A long-range bistatic sonar system was used to image extensive clutter over wide areas of the New Jersey Continental Shelf in the low- to mid-frequency range in near real-time. A downward-directed high-frequency fish-finding sonar was also simultaneously operated from one of the ships to determine whether fish schools occur in the location of the clutter events. Tracks of the long-range sonar were repeated over days throughout the experiment. Most of the clutter features were observed to evolve both in time and in space moving throughout the survey area and therefore do not consistently correlate with static geologic features. The clutter features were observed to cluster, disperse, and gradually disappear and then re-emerge in the general vicinity at later times. The long-range active sonar data show that the primary source of clutter corresponds to objects moving in the waveguide. This was made certain by our ability to accurately register a number of fixed point targets deployed as controls throughout the experiment. The preliminary finding of this experiment is that the dominant source of clutter in this Continental Shelf environment is marine life, particularly fish schools.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2003
    detail.hit.zdb_id: 1461063-2
    detail.hit.zdb_id: 219231-7
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...