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Dick G Simons - One of the best experts on this subject based on the ideXlab platform.
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multi beam Echo Sounder bathymetric measurements implications of using frequency modulated pulses
Journal of the Acoustical Society of America, 2018Co-Authors: Tannaz H Mohammadloo, M Snelle, Dick G SimonsAbstract:In this contribution bathymetric uncertainties induced by the use of frequency modulated (FM) signals for multi-beam-Echo-Sounder (MBES) measurements are quantified and their relevance for MBES bathymetric uncertainty predictions is assessed. When switching to FM, the quality of depth measurements can get deteriorated due to the Doppler effect and baseline decorrelation. The uncertainty due to the former is divided into second-order (imperfectness of the Doppler-range correction) and first-order (effect on beamsteering) effects. The latter also holds for continuous wave (CW) signals. Here, situations of relevance for measurements in the continental shelf and ship dynamics associated to rough and calm sea-states are considered, and the vertical uncertainty induced by the above sources is quantified. The influence of the Doppler effect depends on the sea state, but is found to potentially have a significant contribution to the MBES error budget for both FM and CW [nearly 82% (rough) and 68% (calm) of the total uncertainty]. The effect of baseline decorrelation depends on the actual pulse shape. For the specifications investigated, vertical uncertainties induced by this source are predicted to be larger for FM than that of CW. This is confirmed by a comparison between the modelled and measured effect on depth uncertainties when switching to FM.
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observations regarding coarse sediment classification based on multi beam Echo Sounder s backscatter strength and depth residuals in dutch rivers
Journal of the Acoustical Society of America, 2014Co-Authors: Dimitrios Eleftherakis, Dick G Simons, M Snelle, A R Amirisimkooei, Kersti SiemesAbstract:This contribution investigates the behavior of two important riverbed sediment classifiers, derived from multi-beam Echo-Sounder (MBES)—operating at 300 kHz—data, in very coarse sediment environments. These are the backscatter strength and the depth residuals. Four MBES data sets collected at different parts of rivers in the Netherlands are employed. From previous research the backscatter strength was found to increase for increasing mean grain sizes. Depth residuals, however, are often found to have lower values for coarser sediments. Investigation of the four data sets indicates that these statements are valid only for moderately coarse sediment such as sand. For very coarse sediments (e.g., coarse gravel) the backscatter strength is found to decrease and the depth residuals increase for increasing mean grain sizes. This is observed when the sediment mean grain size becomes significantly larger than the acoustic wavelength of the MBES (5 mm). Knowledge regarding this behavior is of high importance when using backscatter strength and depth residuals for sediment classification purposes as the reverse in behavior can induce ambiguity in the classification.
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an inter comparison of sediment classification methods based on multi beam Echo Sounder backscatter and sediment natural radioactivity data
Journal of the Acoustical Society of America, 2013Co-Authors: M Snelle, A R Amirisimkooei, Dimitrios Eleftherakis, Ronald L Koomans, Dick G SimonsAbstract:This contribution presents sediment classification results derived from different sources of data collected at the Dordtse Kil river, the Netherlands. The first source is a multi-beam Echo-Sounder (MBES). The second source is measurements taken with a gamma-ray scintillation detector, i.e., the Multi-Element Detection System for Underwater Sediment Activity (Medusa), towed over the sediments and measuring sediment natural radioactivity. Two analysis methods are employed for sediment classification based on the MBES data. The first is a Bayesian estimation method that uses the average backscatter data per beam and, therefore, is independent of the quality of the MBES calibration. The second is a model-based method that matches the measured backscatter curves to theoretical curves, predicted by a physics-based model. Medusa provides estimates for the concentrations of potassium, uranium, thorium, and cesium, known to be indicative for sediment properties, viz. mean grain size, silt content, and the presence of organic matter. In addition, a hydrophone attached to the Medusa system provides information regarding the sediment roughness. This paper presents an inter-comparison between the sediment classification results using the above-mentioned methods. It is shown that although originating from completely different sources, the MBES and Medusa provide similar information, revealing the same sediment distribution.
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improving riverbed sediment classification using backscatter and depth residual features of multi beam Echo Sounder systems
Journal of the Acoustical Society of America, 2012Co-Authors: Dimitrios Eleftherakis, A R Amirisimkooei, M Snelle, Dick G SimonsAbstract:Riverbed and seafloor sediment classification using acoustic remote sensing techniques is of high interest due to their high coverage capabilities at limited cost. This contribution presents the results of riverbed sediment classification using multi-beam Echo-Sounder data based on an empirical method. Two data sets are considered, both taken at the Waal River, namely Sint Andries and Nijmegen. This work is a follow-up to the work carried out by Amiri-Simkooei et al. [J. Acoust. Soc. Am. 126(4), 1724–1738 (2009)]. The empirical method bases the classification on features of the backscatter strength and depth residuals. A principal component analysis is used to identify the most appropriate and informative features. Clustering is then applied to the principal components resulting from this set of features to assign a sediment class to each measurement. The results show that the backscatter strength features discriminate between different classes based on the sediment properties, whereas the depth residual features discriminate classes based on riverbed forms such as the “fixed layer” (stone having riprap structure) and riverbed ripples. Combination of these two sets of features is highly recommended because they provide complementary information on both the composition and the structure of the riverbed.
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principal component analysis of single beam Echo Sounder signal features for seafloor classification
IEEE Journal of Oceanic Engineering, 2011Co-Authors: Ali R Amirisimkooei, Mirjam Snellen, Dick G SimonsAbstract:Acoustic remote sensing is a useful tool for seafloor characterization. This contribution presents the results of seafloor sediment classification using single-beam Echo-Sounder (SBES) data based on a phenomenological method. Basic concepts of principal component analysis (PCA) and its applicability to the sediment classification using acoustical data are studied. This mathematical tool, which retains most of the variation of the data, is applied to the SBES Echo shape parameters such as total energy, time-spread, skewness and flatness on three low (12 kHz), moderate (38 kHz), and high (200 kHz) frequencies, making 12 features in total. These parameters are dependent on sediment types and can therefore be used as attributes for seafloor classification. To decrease the statistical fluctuations of the extracted features, an averaging over a sufficiently large number of consecutive pings have been applied to the features. The SBES classification results based on the PCA and K-means clustering approach can clearly discriminate between different sediment classes. The signal at 12 kHz contains information on sediment layers (5 m depth). The performance of the method and the results obtained are assessed using the following independent criteria: 1) inspection of the track crossings indicates stable feature extraction and processing strategy; 2) comparison between the class numbers of the classification results and of the grab samples shows a significant correlation coefficient of 0.90; and 3) an error matrix verifies the stability and independence of the classification results from the features considered.
Simons D.g. - One of the best experts on this subject based on the ideXlab platform.
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Assessing the performance of the multi-beam Echo-Sounder bathymetric uncertainty prediction model
'MDPI AG', 2020Co-Authors: Mohammadloo, Tannaz H., Snelle M., Simons D.g.Abstract:Realistic predictions of the contribution of the various sources affecting the quality of the bathymetric measurements prior to a survey are of importance to ensure sufficient accuracy of the soundings. To this end, models predicting these contributions have been developed. The objective of the present paper is to assess the performance of the bathymetric uncertainty prediction model for modern Multi-Beam Echo-Sounder (MBES) systems. Two datasets were acquired at water depths of 10m and 30m with three pulse lengths equaling 27 μs, 54 μs, and 134 μs in the Oosterschelde estuary (The Netherlands). The comparison between the bathymetric uncertainties derived from the measurements and those predicted using the current model indicated a relatively good agreement except for the most outer beams. The performance of the uncertainty prediction model improved by accounting for the most recent insights into the contributors to the MBES depth uncertainties, i.e., the Doppler effect, baseline decorrelation (accounting for the pulse shape), and the signal-to-noise ratio.Aircraft Noise and Climate Effect
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Assessment of reliability of multi-beam Echo-Sounder bathymetric uncertainty prediction models
2019Co-Authors: Haji Mohammadloo T., Snelle M., Amiri Simkooei A., Simons D.g.Abstract:Nowadays Multi-Beam Echo-Sounder (MBES) systems are used for obtaining information of the sea/river bed bathymetry and sediment composition. For the latter, use is usually made of the backscatter strength and depth derivatives, such as depth residuals. However, the depth derivatives are affected by the uncertainties inherent to the MBES varying with the sensors used, survey configuration and operational environment. Although models are available for the vertical uncertainty prediction, the question is how well these models can capture the estimated uncertainties of real observations. The present contribution addresses this issue by comparing the measured with modelled depth uncertainty accounting for the most recent insights of the error contributors. Data was acquired in water depths of around 2m, 10m and 30m with pulse lengths of 27 μs, 54 μs and 134 μs in the Oosterschelde estuary, the Netherlands, enabling the assessment of depth and pulse length dependence of the uncertainties. In general, the predicted and measured uncertainties are in the same order of magnitude. With increasing depth the discrepancy between the modelled and measured uncertainties increases. The effect of changing pulse length is found to be captured by the model, except for the angles close to nadir. The most dominant contributors to the vertical uncertainty are those induced by the angle of impact and range measurements. These contributors thus require further investigation to obtain a more realistic estimate of the vertical uncertainties.Aircraft Noise and Climate Effect
Knu Landmark - One of the best experts on this subject based on the ideXlab platform.
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acoustic seabed classification using qtc impact on single beam Echo Sounder data from the norwegian channel northern north sea
Continental Shelf Research, 2013Co-Authors: E J Eidem, Knu LandmarkAbstract:Eidem, Ellen Johanne; Landmark, Knut. Acoustic seabed classification using QTC IMPACT on single-beam Echo Sounder data from the Norwegian Channel, northern North Sea. Continental Shelf Research 2013 ;Volum 68. s. 1-14
Laurent Dagorn - One of the best experts on this subject based on the ideXlab platform.
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Environmental preferences of tuna and non-tuna species associated with drifting fish aggregating devices (DFADs) in the Atlantic Ocean, ascertained through fishers’ Echo-Sounder buoys
Deep-Sea Research Part II: Topical Studies in Oceanography, 2017Co-Authors: Jon Lopez, Cleridy Lennert-cody, Mark Maunder, Ainhoa Caballero, Gala Moreno, Igor Sancristobal, Laurent DagornAbstract:Understanding the relationship between environmental variables and pelagic species concentrations and dynamics is helpful to improve fishery management, especially in a changing environment. Drifting fish aggregating device (DFAD)-associated tuna and non-tuna biomass data from the fishers’ Echo-Sounder buoys operating in the Atlantic Ocean have been modelled as functions of oceanographic (Sea Surface Temperature, Chlorophyll-a, Salinity, Sea Level Anomaly, Thermocline depth and gradient, Geostrophic current, Total Current, Depth) and DFAD variables (DFAD speed, bearing and soak time) using Generalized Additive Mixed Models (GAMMs). Biological interaction (presence of non-tuna species at DFADs) was also included in the tuna model, and found to be significant at this time scale. All variables were included in the analyses but only some of them were highly significant, and variable significance differed among fish groups. In general, most of the fish biomass distribution was explained by the ocean productivity and DFAD-variables. Indeed, this study revealed different environmental preferences for tunas and non-tuna species and suggested the existence of active habitat selection. This improved assessment of environmental and DFAD effects on tuna and non-tuna catchability in the purse seine tuna fishery will contribute to transfer of better scientific advice to regional tuna commissions for the management and conservation of exploited resources.
Gala Moreno - One of the best experts on this subject based on the ideXlab platform.
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Environmental preferences of tuna and non-tuna species associated with drifting fish aggregating devices (DFADs) in the Atlantic Ocean, ascertained through fishers’ Echo-Sounder buoys
Deep-Sea Research Part II: Topical Studies in Oceanography, 2017Co-Authors: Jon Lopez, Cleridy Lennert-cody, Mark Maunder, Ainhoa Caballero, Gala Moreno, Igor Sancristobal, Laurent DagornAbstract:Understanding the relationship between environmental variables and pelagic species concentrations and dynamics is helpful to improve fishery management, especially in a changing environment. Drifting fish aggregating device (DFAD)-associated tuna and non-tuna biomass data from the fishers’ Echo-Sounder buoys operating in the Atlantic Ocean have been modelled as functions of oceanographic (Sea Surface Temperature, Chlorophyll-a, Salinity, Sea Level Anomaly, Thermocline depth and gradient, Geostrophic current, Total Current, Depth) and DFAD variables (DFAD speed, bearing and soak time) using Generalized Additive Mixed Models (GAMMs). Biological interaction (presence of non-tuna species at DFADs) was also included in the tuna model, and found to be significant at this time scale. All variables were included in the analyses but only some of them were highly significant, and variable significance differed among fish groups. In general, most of the fish biomass distribution was explained by the ocean productivity and DFAD-variables. Indeed, this study revealed different environmental preferences for tunas and non-tuna species and suggested the existence of active habitat selection. This improved assessment of environmental and DFAD effects on tuna and non-tuna catchability in the purse seine tuna fishery will contribute to transfer of better scientific advice to regional tuna commissions for the management and conservation of exploited resources.
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evolution and current state of the technology of Echo Sounder buoys used by spanish tropical tuna purse seiners in the atlantic indian and pacific oceans
Fisheries Research, 2014Co-Authors: Jo Lopez, Gala Moreno, Igo Sancristobal, Jefferso MuruaAbstract:Abstract Despite important technological changes in the tropical tuna purse seine fishery industry since the 1980s, the influence of these changes on the fleet efficiency and behaviour has not yet been investigated in depth. In this study, the practical use, fishing strategy and state of Echo-Sounder buoy technology applications were studied using personal interviews over three consecutive years (2010–2012) with approximately half of the Spanish tropical tuna purse seine fishing masters and licensed captains operating in the Atlantic, Pacific and Indian Oceans. The results suggested that Echo-Sounder buoys have significantly impacted drifting fish aggregating device (DFAD) fishing strategies since their introduction into the fishery in the last decade, favouring the expansion of DFAD fishing grounds. In addition, fishers are starting to be able to remotely discriminate species, which increases the fleet efficiency. Additionally, the number of Echo-Sounder buoys used by each vessel has been increasing each year, which demonstrates the utility of the information provided by this tool for the Spanish fleet. Various aspects of these devices’ use, consequences for fishing strategy, search time, nominal effort and potential future applications are discussed.
