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| Registros recuperados: 32 | |
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| Malik, Mashkoor; Lurton, Xavier; Mayer, Larry. |
| Multibeam echosounders (MBES) have become a widely used acoustic remote sensing tool to map and study the seafloor, providing co-located bathymetry and seafloor backscatter. Although the uncertainty associated with MBES-derived bathymetric data has been studied extensively, the question of backscatter uncertainty has been addressed only minimally and hinders the quantitative use of MBES seafloor backscatter. This paper explores approaches to identifying uncertainty sources associated with MBES-derived backscatter measurements. The major sources of uncertainty are catalogued and the magnitudes of their relative contributions to the backscatter uncertainty budget are evaluated. These major uncertainty sources include seafloor insonified area (1–3 dB),... |
| Tipo: Text |
Palavras-chave: Multibeam echosounder; Calibration; Incidence angle. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00429/54018/57435.pdf |
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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; Ladroit, Yoann; Augustin, Jean-marie. |
| Swath sonar bathymetry accuracy depends on the intrinsic performance of acoustic signal processing. We propose here a quality factor, quantifying the accuracy associated with every sounding computation. This descriptor is derived from simple models either for amplitude (variance of the centre-of-gravity instant of a fluctuating bell-shaped envelope) or for interferometric phase (local variance for a number of processed samples). The purpose is to attach to each individual sounding an objective quality level that is sonar independent, and directly applicable in bathymetry processing, either in data editing, or as an input parameter to statistical post-processing. This concept is illustrated by examples from experimental data. |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00115/22601/20308.pdf |
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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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| Lurton, Xavier; Eleftherakis, Dimitrios; Augustin, Jean-marie. |
| The sediment backscatter strength measured by multibeam echosounders is a key feature for seafloor mapping either qualitative (image mosaics) or quantitative (extraction of classifying features). An important phenomenon, often underestimated, is the dependence of the backscatter level on the azimuth angle imposed by the survey line directions: strong level differences at varying azimuth can be observed in case of organized roughness of the seabed, usually caused by tide currents over sandy sediments. This paper presents a number of experimental results obtained from shallow-water cruises using a 300-kHz multibeam echosounder and specially dedicated to the study of this azimuthal effect, with a specific configuration of the survey strategy involving a... |
| Tipo: Text |
Palavras-chave: Azimuth dependence; Seafloor backscatter; Multibeam echosounder; Sand ripples. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00386/49782/50326.pdf |
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| Le Chenadec, Gilles; Boucher, Jean-marc; Lurton, Xavier. |
| Backscattered signal statistics are widely used for target detection and seafloor characterization. The K-distribution shows interesting properties for describing experimental backscattered intensity statistics. In addition to the fact that its probability distribution function accurately fits actual sonar data, it advantageously provides a physical interpretation linked to the backscattering phenomenon. Sonar systems usually record backscattered signals from a wide angular range across the ship's track. In this context, previous studies have shown that backscatter statistics strongly depend on the incidence angle. In this paper, we propose an extension of previous works to model the angular evolution of the K-distribution shape parameter. This evolution... |
| Tipo: Text |
Palavras-chave: K distribution; Sonar statistical analysis; Seafloor classification. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-2599.pdf |
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| Lurton, Xavier. |
| Les phénomènes de propagation liés à l'utilisation de sonars actifs par petits fonds sont décrits de façon adéquate par un modèle géométrique de l'énergie moyenne. Cette approche, classique pour l'évaluation des pertes de propagation, est étendue ici aux aspects temporels du signal transmis, en particulier les niveaux de réverbération: le calcul ainsi défini permet une amélioration très significative par rapport aux méthodes usuelles par rayons propres, tant en charge de calcul qu'en fiabilité des résultats. Une autre extension est proposée pour l'évaluation de l'influence du relief de surface, dont l'effet est de diffuser l'énergie incidente vers des directions angulaires voisines: ce phénomène est traité sous forme d'un couplage entre les différentes... |
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| Ano: 1989 |
URL: http://archimer.ifremer.fr/doc/00281/39250/37823.pdf |
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| Guillon, Laurent; Lurton, Xavier. |
| Signals received by low-frequency multibeam echosounders are strongly affected by sound penetration inside the upper sediment layers and by backscattering from buried layers down to depths of a few meters; this may lead to serious ambiguities and misinterpretations of experimental data. These phenomena are modeled here using a concept of equivalent input backscattering strength (EIBS), based on a combination of classical models of local backscattering strength and propagation inside fluid layered media. The local backscattering strength at a buried interface is expressed first to account for the impedance adaptation due to the overlying layers, for the angular refraction effects due to the velocity profile, and for the layered structure of the underlying... |
| Tipo: Text |
Palavras-chave: Sound propagation; Sediment structure; Multibeam sonar; Echosounding; Backscatter; Acoustic properties; Sediment properties. |
| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/2001/publication-729.pdf |
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| Demer, Da; Berger, Laurent; Bernasconi, M; Bethke, E; Boswell, K; Chu, D; Domokos, R; Dunford, A; Fassler, S; Gauthier, S; Hufnagle, Lt; Jech, Jm; Le Bouffant, Naig; Lebourges-dhaussy, Anne; Lurton, Xavier; Macaulay, Gj; Perrot, Yannick; Ryan, T; Parker-stetter, S; Stienessen, S; Weber, T; Williamson, N. |
| Acoustic instrument calibration is fundamental to the quantitative use of its data for estimating aquatic resource abundance. Regular calibrations also allow instrument performance to be monitored to detect changes due to the environment or component dynamics, degradation, or failure. This is the second ICES Cooperative Research Report (CRR) focussed on calibrations of acoustic instruments. The first, CRR No. 144 (Foote et al., 1987), was published during the era of analogue electronics more than a quarter of a century ago. Since then, not only has the acoustic equipment improved vastly with digital electronics and signal processing, but the techniques for applying them to studies of marine organisms have both advanced and diversified. Motivating,... |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00586/69821/67711.pdf |
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| Fabri, Marie-claire; Loubrieu, Benoit; Dupre, Stephanie; Opderbecke, Jan; Lurton, Xavier. |
| Ce document a pour objectif de préparer une réunion sur le choix du type de charge utile "Acoustique" pour le H-ROV. Ce document s'intéresse à la charge utile "cartographie acoustique". Il est réalisé avec l'objectif de préparer une réunion du groupe de travail scientifique du H-ROV. Il propose un bilan des différentes charges utiles acoustiques embarquables sur un engin sous-marin, ainsi que leur avantages et leurs inconvénients au regard des caractéristiques techniques du H-ROV. Au final un SONDEUR MULTIFAISCEAUX a été le choix considéré comme étant le plus adapté à l'environnement probable d'exploration du HROV (milieu à fort relief) ainsi qu'à ses caractéristiques techniques (autonomie réduite). Lors de l'intégration sur le SKID "Acoustique", il faudra... |
| Tipo: Text |
Palavras-chave: H-ROV; Cartographie acoustique. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00233/34382/32753.pdf |
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| Ladroit, Yoann; Lurton, Xavier; Sintes, Christophe; Augustin, Jean-marie; Garello, Rene. |
| For modern multibeam echosounders, the use of a robust and reliable quality estimator associated with each sounding is an absolute necessity. Indeed, due to the large volume of data acquired, a lot of time is lost, both during the survey and the post-processing. This is a costly problem for hydrographers. The definition of a quality estimator based on the characteristics of the beamformed signal gives an answer to this problem. It has been successfully implemented by several sonar manufacturers and its relevance in measuring the quality of each sounding has been demonstrated. The defined Quality Factor can also be used directly in the sonar measurement process, such as in detection algorithm, in order to improve the performance of the systems. This makes... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00106/21728/20275.pdf |
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| Sinquin, Jean-marc; Lurton, Xavier; Vignaud, Christophe; Mathieu, Gregory; Bisquay, Herve. |
| Hydrographic and geosciences surveys, using acoustic devices, need to use accurate water sound velocity profiles. Because the acoustic path depends on the sound velocity profile (SVP), the use of the most accurate SVP is one of the keys to conducting effective surveys (with multibeams, for instance). To date, the existing software available does not answer to both the needs of efficiency and simplicity (sometimes not so easy to operate, sometimes not so accurate). DORIS provides a handy freeware to post-process SVP for the hydrographic communities. |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00339/45065/44473.pdf |
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| Ladroit, Yoann; Sintes, Christophe; Lurton, Xavier; Garello, Rene. |
| Sonar signal simulation is an important area of research for industrials and scientific of the domain. Indeed, it can be used in many ways by sonar manufacturers, both for designing a system or in order to explain physical phenomenon on data. Therefore, by minimizing the expensive testing time at sea, a well designed simulator can be a very interesting financial asset. Traditional sonar signal simulation also contains problems to be dealt with. It is often necessary to find a balance between the computational power consumption, the needed accuracy of the physical phenomenon description and the scale at which simulated signals are relevant. In our simulation model we propose a solution based on a very dense grid (resolution of about the concerned... |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00106/21727/20274.pdf |
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| Fettweis, M; Toorman, E; Verney, Romaric; Chapalain, Marion; Legrand, S; Lurton, Xavier; Montereale-gavazzi, G; Roche, M; Shen, X; Van Den Eynde, Dries; Van Lancker, Vera. |
| Context To protect the marine environment more effectively, the European Union adopted the Marine Strategy Framework Directive (MSFD) in 2008, aiming to achieve the Good Environmental Status (GES) of the EU's marine waters by 2020 and to protect the resource base upon which marine-related economic and social activities depend. A major challenge in the implementation of the MSFD is to achieve the necessary scientific knowledge on the marine environment, its processes and the methods to monitor them. The focus of INDI67 is on the evaluation and development of indicators to monitor GES of descriptor 6 and 7. Seafloor integrity (descriptor 6) refers to the structure and functions of the benthic ecosystems. It relates to the comprises physical, chemical and... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00634/74632/74526.pdf |
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| Registros recuperados: 32 | |
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