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Jean Guillard - One of the best experts on this subject based on the ideXlab platform.
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survey boat effect on yoy fish schools in a pre alpine lake evidence from Multibeam Sonar and split beam echosounder data
Ecology of Freshwater Fish, 2010Co-Authors: Jean Guillard, Pierre Balay, Michel Colon, Patrice BrehmerAbstract:Guillard J, Balay P, Colon M, Brehmer P. Survey boat effect on YOY fish schools in a pre-alpine lake: evidence from Multibeam Sonar and split-beam echosounder data. Ecology of Freshwater Fish 2010: 19: 373–380. © 2010 John Wiley & Sons A/S Abstract – Hydroacoustic methods are widely employed by fish scientists for assessing fish stocks. The method most often used is echosounding, beaming vertically. Nowadays the Multibeam Sonar, and therefore the 3-D presentation of fish schools, has yielded better knowledge of school morphology. Using the data collected simultaneously by both Sonar and echosounding in a lake, we have identified boat-induced behavioural changes in small pelagic fish schools. Using high resolution Sonar data, we showed that the fish schools detected under the boat have a significantly larger volume than those alongside the boat. This finding is explained according to behavioural response due to the theoretical characteristics of the boat diagram sound pressure, and the existence of a strong thermocline. Then we compared two descriptors, the height of the fish school and the backscatter energy. We found significant differences, which reveal vertical fish school compression occurring simultaneously with the horizontal and sidelong escape behaviour.
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daily migration cycles of fish populations in a tropical estuary sine saloum senegal using a horizontal directed split beam transducer and Multibeam Sonar
Fisheries Research, 1998Co-Authors: Jean GuillardAbstract:The tropical Sine-Saloum estuary (Senegal) is an ecologically important area for fish population dynamics. Daily cycles of fish movements in a tidal channel were observed using both split-beam and Multibeam Sonar. A trap-net was set and lifted regularly and simultaneously with the acquisition of acoustic data. The relationship between the two sets of data was satisfactory when acoustic records for single targets were separated from those containing fish schools. The heterogeneity of fish spatial and temporal distributions is examined, as well as the rapidity of changes of fish population density in an environment subject to tides. The consequence of this on sampling strategies is discussed.
Daniel Ierodiaconou - One of the best experts on this subject based on the ideXlab platform.
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Multibeam Sonar backscatter data processing
Marine Geophysical Researches, 2018Co-Authors: Alexandre C. G. Schimel, Jonathan Beaudoin, Iain Parnum, Tim Le Bas, Val E. Schmidt, Gordon Keith, Daniel IerodiaconouAbstract:Multibeam Sonar systems now routinely record seafloor backscatter data, which are processed into backscatter mosaics and angular responses, both of which can assist in identifying seafloor types and morphology. Those data products are obtained from the Multibeam Sonar raw data files through a sequence of data processing stages that follows a basic plan, but the implementation of which varies greatly between Sonar systems and software. In this article, we provide a comprehensive review of this backscatter data processing chain, with a focus on the variability in the possible implementation of each processing stage. Our objective for undertaking this task is twofold: (1) to provide an overview of backscatter data processing for the consideration of the general user and (2) to provide suggestions to Multibeam Sonar manufacturers, software providers and the operators of these systems and software for eventually reducing the lack of control, uncertainty and variability associated with current data processing implementations and the resulting backscatter data products. One such suggestion is the adoption of a nomenclature for increasingly refined levels of processing, akin to the nomenclature adopted for satellite remote-sensing data deliverables.
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Granitic coastal geomorphology: applying integrated terrestrial and bathymetric LiDAR with Multibeam Sonar to examine coastal landscape evolution
Earth Surface Processes and Landforms, 2014Co-Authors: David M. Kennedy, Daniel Ierodiaconou, Alexandre C. G. SchimelAbstract:Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long-term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of Multibeam Sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with Multibeam Sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (
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granitic coastal geomorphology applying integrated terrestrial and bathymetric lidar with Multibeam Sonar to examine coastal landscape evolution
Earth Surface Processes and Landforms, 2014Co-Authors: David M. Kennedy, Daniel Ierodiaconou, Alexandre C. G. SchimelAbstract:Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long-term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of Multibeam Sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with Multibeam Sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (<2 m apart) or the bedrock is highly weathered can semi-horizontal surfaces form. Copyright © 2014 John Wiley & Sons, Ltd.
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Granitic coastal geomorphology: applying integrated terrestrial and bathymetric LiDAR with Multibeam Sonar to examine coastal landscape evolution
Earth Surface Processes and Landforms, 2014Co-Authors: David M. Kennedy, Daniel Ierodiaconou, Alexandre SchimelAbstract:Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long-term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of Multibeam Sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with Multibeam Sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (<2 m apart) or the bedrock is highly weathered can semi-horizontal surfaces form
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habitat suitability for marine fishes using presence only modelling and Multibeam Sonar
Marine Ecology Progress Series, 2010Co-Authors: J Monk, Daniel Ierodiaconou, Alex Rattray, Vincent L Versace, Alecia Bellgrove, Euan S Harvey, Laurie Laurenson, Gerry P QuinnAbstract:Improved access to Multibeam Sonar and underwater video technology is enabling sci- entists to use spatially-explicit, predictive modelling to improve our understanding of marine ecosys- tems. With the growing number of modelling approaches available, knowledge of the relative perfor- mance of different models in the marine environment is required. Habitat suitability of 5 demersal fish taxa in Discovery Bay, south-east Australia, were modelled using 10 presence-only algorithms: BIOCLIM, DOMAIN, ENFA (distance geometric mean (GM), distance harmonic mean (HM), median (M), area-adjusted median (Ma), median + extremum (Me), area-adjusted median + extremum (Mae) and minimum distance (Min)), and MAXENT. Model performance was assessed using kappa and area under curve (AUC) of the receiver operator characteristic. The influence of spatial range (area of occupancy) and environmental niches (marginality and tolerance) on modelling performance were also tested. MAXENT generally performed best, followed by ENFA-GM and -HM, DOMAIN, BIO- CLIM, ENFA-M, -Min, -Ma, -Mae and -Me algorithms. Fish with clearly definable niches (i.e. high marginality) were most accurately modelled. Generally, Euclidean distance to nearest reef, HSI-b (backscatter), rugosity and maximum curvature were the most important variables in determining suitable habitat for the 5 demersal fish taxa investigated. This comparative study encourages ongo- ing use of presence-only approaches, particularly MAXENT, in modelling suitable habitat for demer- sal marine fishes.
Richard A Pickrill - One of the best experts on this subject based on the ideXlab platform.
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image based classification of Multibeam Sonar backscatter data for objective surficial sediment mapping of georges bank canada
Continental Shelf Research, 2011Co-Authors: Craig J Brown, B J Todd, Vladimir E Kostylev, Richard A PickrillAbstract:Abstract Developments in acoustic survey techniques, in particular Multibeam Sonar, have revolutionised the way we are able to image, map and understand the seabed environment. It is now cost effective to image large areas of the seafloor using these techniques, and the information from such surveys provides base line data from which thematic maps of the seabed environment, including maps of surficial geology, can be derived when interpreted in conjunction with in-situ ground truthing data. Traditional methods for the interpretation of acoustic backscatter rely on experienced interpretation by eye of grey-scale images produced from the data. However, interpretation of data can be subjective, and new developments in semi-automated backscatter classification software offer an objective method of segmentation of acoustic backscatter data into acoustically similar regions, but are not yet well tested or accepted. A large Multibeam Sonar data set from Georges Bank, Canada, was classified using the backscatter classification software, QTC-Multiview. Data from 4800 km 2 of seabed were classified and results were compared with 110 ground truthing stations to assess the performance of the classification for geological discrimination. The relationship between backscatter metrics derived from the classification software and benthic geological characteristics were explored using statistical methods. Results suggest that image-based backscatter classification shows considerable promise for interpretation of Multibeam Sonar data for the production of geological maps.
Alexandre C. G. Schimel - One of the best experts on this subject based on the ideXlab platform.
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Multibeam Sonar backscatter data processing
Marine Geophysical Researches, 2018Co-Authors: Alexandre C. G. Schimel, Jonathan Beaudoin, Iain Parnum, Tim Le Bas, Val E. Schmidt, Gordon Keith, Daniel IerodiaconouAbstract:Multibeam Sonar systems now routinely record seafloor backscatter data, which are processed into backscatter mosaics and angular responses, both of which can assist in identifying seafloor types and morphology. Those data products are obtained from the Multibeam Sonar raw data files through a sequence of data processing stages that follows a basic plan, but the implementation of which varies greatly between Sonar systems and software. In this article, we provide a comprehensive review of this backscatter data processing chain, with a focus on the variability in the possible implementation of each processing stage. Our objective for undertaking this task is twofold: (1) to provide an overview of backscatter data processing for the consideration of the general user and (2) to provide suggestions to Multibeam Sonar manufacturers, software providers and the operators of these systems and software for eventually reducing the lack of control, uncertainty and variability associated with current data processing implementations and the resulting backscatter data products. One such suggestion is the adoption of a nomenclature for increasingly refined levels of processing, akin to the nomenclature adopted for satellite remote-sensing data deliverables.
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Granitic coastal geomorphology: applying integrated terrestrial and bathymetric LiDAR with Multibeam Sonar to examine coastal landscape evolution
Earth Surface Processes and Landforms, 2014Co-Authors: David M. Kennedy, Daniel Ierodiaconou, Alexandre C. G. SchimelAbstract:Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long-term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of Multibeam Sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with Multibeam Sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (
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granitic coastal geomorphology applying integrated terrestrial and bathymetric lidar with Multibeam Sonar to examine coastal landscape evolution
Earth Surface Processes and Landforms, 2014Co-Authors: David M. Kennedy, Daniel Ierodiaconou, Alexandre C. G. SchimelAbstract:Coasts composed of resistant lithologies such as granite are generally highly resistant to erosion. They tend to evolve over multiple sea level cycles with highstands acting to remove subaerially weathered material. This often results in a landscape dominated by plunging cliffs with shore platforms rarely occurring. The long-term evolution of these landforms means that throughout the Quaternary these coasts have been variably exposed to different sea level elevations which means erosion may have been concentrated at different elevations from today. Investigations of the submarine landscape of granitic coasts have however been hindered by an inability to accurately image the nearshore morphology. Only with the advent of Multibeam Sonar and aerial laser surveying can topographic data now be seamlessly collected from above and below sea level. This study tests the utility of these techniques and finds that very accurate measurements can be made of the nearshore thereby allowing researchers to study the submarine profile with the same accuracy as the subaerial profile. From a combination of terrestrial and marine LiDAR data with Multibeam Sonar data, it is found that the morphology of granite domes is virtually unaffected by erosion at sea level. It appears that evolution of these landscapes on the coast is a very slow process with modern sea level acting only to remove subaerially weathered debris. The size and orientation of the joints determines the erosional potential of the granite. Where joints are densely spaced (<2 m apart) or the bedrock is highly weathered can semi-horizontal surfaces form. Copyright © 2014 John Wiley & Sons, Ltd.
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An Overview of Multibeam Sonar Data Processing for Benthic Habitat Mapping at Deakin University
2013Co-Authors: Alexandre C. G. Schimel, Daniel Lerodiaconou, Alex Rattray, Jacquomo Monk, Rozaimi Che Hasan, Sean BlakeAbstract:Deakin University has been carrying out research in habitat mapping techniques applied to the coastal regional Victoria since 2007, using primarily bathymetry and backscatter data from Multibeam Sonar, coupled with video ground-truth. Contrary to the traditional seafloor-mapping approach of backscatter imagery segmentation, our research has been focused on the implementation of ecological modeling approaches, which consist in letting ground-truth data drive a modeling algorithm using a varied set of "predictor" data layers that include –but are not limited to - bathymetry and backscatter data from Multibeam Sonars. Slight modifications can be implemented to these approaches to produce two types of outputs presenting different ecological interests: "benthoscapes" (maps of seafloor bio-physical properties) and "habitat suitability maps" (habitat preference maps for single species). Such ecological approach to mapping the seafloor presents the main advantage to allow for any geographical dataset and its derivatives to be implemented and tested for its predictive power. Tested variables to-date include Multibeam and Lidar bathymetry data and derivatives (slope, rugosity, etc.), Multibeam backscatter data and derivatives (HSI, textural features, 1st-order statistics, etc.), but also backscatter angular response features, hindcast oceanographic conditions, etc. Our most recent work has been focusing on (1) processing backscatter angular response to create additional layers of information, (2) implementing random-forest as classification algorithm to allow for the estimation of the relative importance of each variable, (3) developing procedures to ensure the repeatability of our studies, that is, the reliability of results, and allow for detection of changes over time. Deakin University recently launched its own research vessel MV Yolla and equipped it with a Kongbserg EM2040c Multibeam Sonar aided with a POS MV positioning/attitude system. Future research directions include exploring the new capabilities of this next-generation Multibeam Sonar in terms of water-column imaging and wide bandwidth, in order to derive new data layers for our classification processes. The lack of calibration of Multibeam Sonar backscatter remains a major obstacle, especially affecting our development of repeatable procedures across different systems and study sites.
Patrice Brehmer - One of the best experts on this subject based on the ideXlab platform.
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Efficient Multibeam Sonar calibration and performance evaluation
2014Co-Authors: Yannick Perrot, Patrice Brehmer, Gildas Roudaut, Peter Gerstoft, Erwan JosseAbstract:Quantitative applications of mobile Multibeam Sonar in aquatic ecology and fisheries require accurate and efficient in-tank calibration methodologies. Calibration factors for a Simrad SM20 Multibeam Sonar are experimentally extracted thereby enabling Sonar estimation of target strength and volume backscattering strength. Measured and modeled Sonar characteristics are systematically compared and show good overall correlation. Due to the limited angular span of the Sonar head array, well quantified Sonar operation is restricted to an equatorial angular sector of only 80° (vs. rated 120°) in 'imaging' mode. In 'echo-sounder' mode, the 'high' power transmit setting appears to introduce artifacts. A routine in-tank measurement procedure is described which for given Multibeam Sonar minimizes the time required for quality Multibeam calibration.
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survey boat effect on yoy fish schools in a pre alpine lake evidence from Multibeam Sonar and split beam echosounder data
Ecology of Freshwater Fish, 2010Co-Authors: Jean Guillard, Pierre Balay, Michel Colon, Patrice BrehmerAbstract:Guillard J, Balay P, Colon M, Brehmer P. Survey boat effect on YOY fish schools in a pre-alpine lake: evidence from Multibeam Sonar and split-beam echosounder data. Ecology of Freshwater Fish 2010: 19: 373–380. © 2010 John Wiley & Sons A/S Abstract – Hydroacoustic methods are widely employed by fish scientists for assessing fish stocks. The method most often used is echosounding, beaming vertically. Nowadays the Multibeam Sonar, and therefore the 3-D presentation of fish schools, has yielded better knowledge of school morphology. Using the data collected simultaneously by both Sonar and echosounding in a lake, we have identified boat-induced behavioural changes in small pelagic fish schools. Using high resolution Sonar data, we showed that the fish schools detected under the boat have a significantly larger volume than those alongside the boat. This finding is explained according to behavioural response due to the theoretical characteristics of the boat diagram sound pressure, and the existence of a strong thermocline. Then we compared two descriptors, the height of the fish school and the backscatter energy. We found significant differences, which reveal vertical fish school compression occurring simultaneously with the horizontal and sidelong escape behaviour.
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Omnidirectional Multibeam Sonar monitoring: applications in fisheries science
Fish and Fisheries, 2006Co-Authors: Patrice Brehmer, Erwan Josse, François Gerlotto, Stratis Georgakarakos, Thierry Lafont, Christophe ColletAbstract:Data exploitation, acquired by medium-frequency omnidirectional Multibeam Sonar, enables original studies in fisheries research but is seldom used despite the fact that such equipment is found on most fishing vessels and a number of research vessels. This is the only system for real-time monitoring of fish schools within a horizontal omnidirectional plane about a vessel or a buoy. Between 1996 and 2001, we used two standard omnidirectional Sonars and developed new methodologies for exploiting their specific acoustic data according to two main sampling schemes: 'prospecting', including fishing and searching operations, and 'drifting', as with an instrumental buoy system or aboard a stationary vessel. We present a complete method for continuous data acquisition from aboard a research vessel or commercial boat, with automated data extraction by picture analysis and a data processing method. Two cases of data analysis are considered: the first on a school-by-school basis, the 'single school' mode; the second taking into account all fish schools detected within the Sonar sampling volume, the 'cluster' mode. Elementary Sonar information is divided into five categories that comprise 24 survey and Sonar parameters and 55 school, cluster and fisher behaviour descriptors. We review the applications of these categories and discuss perspectives for their use in fisheries science. If the Sonar system enables the evaluation of the effects of vessel avoidance on fish school biomass assessment, no accurate abundance estimate can be provided by a simple Sonar echo-integration process. Omnidirectional Sonar data can be used to analyse collectively the fish schools' swimming speed, kinematics in terms of diffusion and migration, aggregative dynamics as school splitting and merging indexes, spatial characteristics of clusters such as school density, 2D structure and fisher behaviour. The prospect of integrating such data into a fish school database, including multifrequency echo-sounder and lateral Multibeam (3D) Sonar data combined with a species recognition method, will enable a complete view of fish school behaviour and consequently the adoption of accurate fisheries management methods.
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Application of Multibeam Sonar in marine ecology and fisheries research: New fields and limitations
Journal of the Acoustical Society of America, 2003Co-Authors: François Gerlotto, Patrice Brehmer, Stratis Georgakarakos, Paul G. Fernandes, David G. Reid, Philip Copland, Jorge ParamoAbstract:Multibeam Sonars have been used since the mid 90s for three dimensions and a dynamic observation of fish schools and shoals in their environment. A 455 kHz Reson Seabat 6012, with 60 beams of 1.5×22 deg, was used. It has allowed the quantification of school avoidance in acoustic surveys; the three‐dimensional description of school structure and position in the water column; the noninvasive study of the real schooling behavior of fish in the wild; the observation and quantification of fish in relation to survey gear; and the predation on mussels in aquaculture by fish schools; the fish school distribution in relation to ecological factors, even in very shallow water. These observations showed that a Multibeam Sonar can be a useful tool for improving the quality of stock assessment surveys and studying the behavioral ecology of important commercial species. To date all these applications are essentially observational. The next stage in the development of these systems will be to produce quantitative biomass estimates. To achieve this, calibration systems and side aspect TS measurements for the fish will be required. The paper presents the current uses of this instrument described above, and discuss the research requirements for use in fisheries science.