|
|
|
| Registros recuperados: 32 | |
|
|
| 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 |
| |
|
|
| 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 |
|
| |
|
|
| Lamarche, Geoffroy; Lurton, Xavier; Verdier, Anne-laure; Augustin, Jean-marie. |
| A comprehensive EM300 multibeam echo-sounder dataset acquired from Cook Strait, New Zealand, is used to develop a regional-scale objective characterisation of the seafloor. Sediment samples and high-resolution seismic data are used for ground-truthing. SonarScope (R) software is used to process the data, including signal corrections from sensor bias, specular reflection compensation and speckle noise filtering aiming at attenuating the effects of recording equipment, seafloor topography, and water column. The processing is completed by correlating a quantitative description (the Generic Seafloor Acoustic Backscatter-GSAB model) with the backscatter data. The calibrated Backscattering Strength (BS) is used to provide information on the physical... |
| Tipo: Text |
Palavras-chave: Backscatter; Multibeam echo-sounder; Sediment waves; Habitat mapping. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00031/14260/11552.pdf |
| |
|
|
| Montereale-gavazzi, Giacomo; Roche, Marc; Lurton, Xavier; Degrendele, Koen; Terseleer, Nathan; Van Lancker, Vera. |
| To characterize seafloor substrate type, seabed mapping and particularly multibeam echosounding are increasingly used. Yet, the utilisation of repetitive MBES-borne backscatter surveys to monitor the environmental status of the seafloor remains limited. Often methodological frameworks are missing, and should comprise of a suite of change detection procedures, similarly to those developed in the terrestrial sciences. In this study, pre-, ensemble and post-classification approaches were tested on an eight km2 study site within a Habitat Directive Area in the Belgian part of the North Sea. In this area, gravel beds with epifaunal assemblages were observed. Flourishing of the fauna is constrained by overtopping with sand or increased turbidity levels, which... |
| Tipo: Text |
Palavras-chave: Multibeam; Seafloor backscatter; Change detection; Seafloor integrity; Marine Strategy Framework Directive; Reference calibration area. |
| Ano: 2018 |
URL: http://archimer.ifremer.fr/doc/00387/49807/50379.pdf |
| |
|
|
| 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 |
| |
|
| |
|
| |
|
|
| 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 |
|
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00115/22601/20308.pdf |
| |
|
|
| Lurton, Xavier; Deruiter, Stacy. |
| Currently, more and more attention is focusing on the impact of anthropogenic sound sources on marine life, particularly marine mammals. Indeed, several unusual cetacean strandings linked to the use of high-power sonar have been observed over the past years. Hydrography and seafloor-mapping make extensive use of acoustic sources; this paper aims to present the order of magnitude of sound radiated by such echosounders, and hence estimate their potential impact on marine mammals. The paper begins with a presentation of the main issues related to sound-mediated risks to marine life and a reminder of echosounder characteristics and geometry. Next, the numerical results from several case studies are compared with currently accepted threshold values for marine... |
| Tipo: Text |
|
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00115/22607/20313.pdf |
| |
|
|
| 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 |
| |
|
| |
|
|
| Le Bouffant, Naig; Berger, Laurent; Lurton, Xavier. |
| Bathymetric multibeam echosounders (MBES) classically improve their bottom detection resolution by increasing the number of beams with narrower beamwidths. Many independent detections are thus obtained when extracting one sounding in each beam. However when the pulse footprint on the bottom gets narrower than the beamwidth, which often happens at high incidence angles, it is possible to extract several independent bottom detections within the same beam. These high-density soundings extraction methods present a still higher interest for MBES designed with rather “wide” beams (say 3° or more), so as to offer other benefits, such as compacity, low-cost, or low sidelobe levels as for fishery applications. This paper presents a simple way to derive multiple... |
| Tipo: Text |
Palavras-chave: Multibeam; Bathymetry; Interferometry; Beamwidth. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00146/25719/23801.pdf |
| |
| Registros recuperados: 32 | |
|
|
|
