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Analysis of seafloor backscatter strength dependence on the survey azimuth using multibeam echosounder data ArchiMer
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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Backscatter calibration of high-frequency multibeam echosounder using a reference single-beam system, on natural seafloor ArchiMer
Eleftherakis, Dimitrios; Berger, Laurent; Le Bouffant, Naig; Pacault, Anne; Augustin, Jean-marie; Lurton, Xavier.
The calibration of multibeam echosounders for backscatter measurements can be conducted efficiently and accurately using data from surveys over a reference natural area, implying appropriate measurements of the local absolute values of backscatter. Such a shallow area (20-m mean depth) has been defined and qualified in the Bay of Brest (France), and chosen as a reference area for multibeam systems operating at 200 and 300 kHz. The absolute reflectivity over the area was measured using a calibrated single-beam fishery echosounder (Simrad EK60) tilted at incidence angles varying between 0° and 60° with a step of 3°. This reference backscatter level is then compared to the average backscatter values obtained by a multibeam echosounder (here a Kongsberg EM...
Tipo: Text Palavras-chave: Calibration; Seafloor backscatter; Multibeam echosounder; Single-beam echosounder.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00429/54016/57434.pdf
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