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| Registros recuperados: 10 | |
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| Lurton, Xavier; Augustin, Jean-marie. |
| The quality estimation associated with individual soundings measured and computed by swath bathymetry sonars is a paramount issue which is most often imperfectly addressed today by sonar manufacturers. In this paper, a unified definition is proposed for a quality factor usable for all swath bathymetry sonars; the depth-relative error is directly estimated from the signal characteristics used in the sounding computation. The basic algorithms are presented for both phase-difference (oblique incidence) and amplitude (normal incidence) detection, and can be readily implemented in any swath bathymetry system using these detection principles. This approach gives a direct access to the objective bathymetric performance of individual soundings, and hence avoids... |
| Tipo: Text |
Palavras-chave: Bathymetry; Interferometry; Multibeam echosounder (MBES); Sonar. |
| Ano: 2010 |
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| Lurton, Xavier. |
| Sound waves are the only practical means of remote investigation and transmission in seawater. All along the XXth century, underwater acoustics became one of the major technologies used for exploration and exploitation of the oceans for scientific, industrial, or military purposes. It is nowadays able to play, inside the oceans, the roles devoted to radio and radar in atmosphere and space, and is widely employed in the fields of navigation, fisheries, defence, oceanography and ocean engineering. This book presents, in a clear and concise way, the basic physical phenomena governing underwater acoustical waves, the general features of sonar systems, and an overview of their applications. |
| Tipo: Text |
Palavras-chave: Acoustique sous-marine; Propagation; Traitement du signal; Sonar; Sondeur; Underwater acoustics; Propagation; Signal processing; Sonar; Echosounder. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/00017/12790/9731.pdf |
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| Lurton, Xavier; Antoine, Loic. |
| The use of acoustical systems in various human activities in the ocean (industry, defence, science) raises the issue of their impact upon marine mammals populations. Several serious accidents linked to the use of naval sonars led the military, industrial and scientific communities to investigate the potential dangers of their own activity. This report aims at identifying the risks for the cetaceans linked to the use of acoustic and seismic systems currently used for oceanographic science. The analysis proposed here stays within the frame of bibliography synthesis and elementary modelling, and brings no new scientific elements on the topic. An overview of the status of cetacean populations is given first, with a summary of the possible acoustical... |
| Tipo: Text |
Palavras-chave: Seismics; Sonar; Acoustics; Oceanography; Acoustical methods; Auditory threshold; Stranding; Acoustical risks; Marine mammals. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/rapport-2390.pdf |
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| De Ruiter, Stacy; Boyd, Ian L.; Claridge, Diane E.; Clark, Christopher W.; Gagnon, Chuck; Southall, Brandon L.; Tyack, Peter L.. |
| In 2007 and 2008, controlled exposure experiments were performed in the Bahamas to study behavioral responses to simulated mid-frequency active sonar (MFA) by three groups of odontocetes: false killer whales, Pseudorca crassidens; short-finned pilot whales, Globicephala macrorhynchus; and melon-headed whales, Peponocephala electra. An individual in each group was tagged with a Dtag to record acoustic and movement data. During exposures, some individuals produced whistles that seemed similar to the experimental MFA stimulus. Statistical tests were thus applied to investigate whistle-MFA similarity and the relationship between whistle production rate and MFA reception time. For the false killer whale group, overall whistle rate and production rate of the... |
| Tipo: Text |
Palavras-chave: Noise; Sonar; Mid-frequency sonar; Whistle; Behavioral effects; Sound production; Pseudorca crassidens; Globicephala macrorhynchus; Peponocephala electra; False killer whale; Pilot whale; Melon-headed whale. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00138/24974/23185.pdf |
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| Brehmer, Patrice; Vercelli, Catherine; Gerlotto, Francois; Sanguinede, Fabien; Pichot, Yves; Guennegan, Yvon; Buestel, Dominique. |
| The exploitation of offshore mussel farms is becoming important throughout the world, but monitoring this activity remains a difficult task. Here, we propose a specific method for this purpose. A total of 140 long-lines were monitored on a mussel culture ground in the French Mediterranean Sea during four experimental surveys deploying multibeam sonar devices mounted on poles (Reson Seabat 6012, 455 kHz) on small boats. This allowed geo-referenced observations to be made of the submerged mussel long-lines, as well as three-dimensional (3D) drawings of the long-line structures and the sea bed shapes, using long-line longitudinal sonar sampling. Three sonar data-analysis methods were applied: (i) direct two-dimensional (2D) visual interpretation of raw sonar... |
| Tipo: Text |
Palavras-chave: Management; Sonar; Open sea; Long line; Mussel. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1672.pdf |
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| Casarsa, L.; Madirolas, A.. |
| The normal behavioral patterns of several fish species is altered during trawling affecting the fish spatial distribution. Sonar methods were carried out in this research work in order to study the reaction of reproductive concentrations of the Argentine hake (Merluccius hubbsi) during mid-water and bottom fishing trawls. Observations made from a trawl sonar mounted on the headrope of an ENGEL (35 m) bottom trawl, showed that this species concentrates at the lower-central sector of the net mouth. During daytime trawls fish schools with a vertical distribution exceeding ten meters were observed entering the trawl within the first two meters from the bottom. Some observations during pelagic trawls carried out at night, showed no specific pattern at the net... |
| Tipo: Journal Contribution |
Palavras-chave: Behaviour; Bottom trawling; Sonar; Echo surveys; Vertical distribution; Behaviour; Http://aims.fao.org/aos/agrovoc/c_868. |
| Ano: 2007 |
URL: http://hdl.handle.net/1834/2517 |
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| Trenkel, Verena; Handegard, Nils Olav; Weber, Thomas C.. |
| Active- and passive-acoustic methods are widely used tools for observing, monitoring, and understanding marine ecosystems. From 25 to 28 May 2015, 214 scientists from 31 nations gathered for an ICES symposium on Marine Ecosystem Acoustics (SoME Acoustics) to discuss three major themes related to acoustic observations of marine ecosystems: (i) recent developments in acoustic and platform technologies; (ii) acoustic characterisation of aquatic organisms, ecosystem structure, and ecosystem processes; and (iii) contribution of acoustics to integrated ecosystem assessments and management. The development of, and access to new instruments, such as broad bandwidth systems, enables insightful ecological studies and innovative management approaches. Unresolved... |
| Tipo: Text |
Palavras-chave: Acoustics; Broadband; Multi-frequency; Passive and active acoustics; Ecosystem approach to management; Ecosystem monitoring; Pelagic ecosystem; Echosounder; Sonar. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00347/45820/45921.pdf |
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| Guillard, Jean; Brehmer, Patrice; Colon, Michel; Guennegan, Yvon. |
| Fish schools are aggregative structures encountered in all types of aquatic environments but have as yet been little studied in freshwaters except at small spatial scales. This study represents the three dimensional description of juvenile fish schools (Perca fluviatilis and Rutilus rutilus) in a lake environment using high resolution multibeam sonar system operating at a frequency of 455 kHz, composed of 60 beams of 1.5 degrees allowing a 90 degrees observation plane. The in situ diurnal schooling behaviour of young-of-the-year fish of both species is confirmed. The morphological, energetic and spatial variables of these schools are described and related to one another. The structures described are of the same order of magnitude as those described in the... |
| Tipo: Text |
Palavras-chave: Annecy Lake; Rutilus rutilus; Perca fluviatilis; Sonar; 3 D structure; Shoaling behaviour. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-1661.pdf |
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| Registros recuperados: 10 | |
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