Monitoring underwater nourishments using multibeam bathymetric and backscatter time series

Gaida, Timo C.; Dijk, T.A.G.P. van; Snellen, Mirjam; Vermaas, Tommer; Mesdag, C.S.; Simons, Dick G.

doi:10.1016/j.coastaleng.2020.103666

Cited by 15 publications

(13 citation statements)

References 43 publications

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“…Because they are independent of human perception, they provide objective and repeatable results that cannot be achieved using traditional, manual analysis (Diesing et al 2016). Automatic classification of MBES data sets for different time steps is the foundation of change-detection analysis, which has recently been a significant research topic in the discipline of benthic habitat mapping (Montereale- Gaida et al 2020;Janowski et al 2020). The accuracy assessment based on ground-truth samples allows for the possible verification of classifier performance, which is highly desirable from a scientific perspective.…”

Section: Gaps In the Existing Knowledge That This Study Wants To Covermentioning

confidence: 99%

From acoustics to underwater archaeology: Deep investigation of a shallow lake using high‐resolution hydroacoustics—The case of Lake Lednica, Poland

et al. 2021

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One of the main challenges of underwater archaeology is to develop non-invasive research of heritage sites in order to enable their further protection for future societies. This study explores, identifies and classifies archaeological objects in a shallow lake using underwater acoustics. We solved the aforementioned challenges by developing an innovative, objectbased, fuzzy-logic classification of nine archaeological object categories based on multibeam echosounder bathymetry, 13 secondary features of bathymetry and 106 underwater diving prospections. We achieved an 86% correlation with ground-truth samples, and 49% overall accuracy. The unique and repeatable workflow developed in this study can be applied to other case studies of underwater archaeology around the world.

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Section: Gaps In the Existing Knowledge That This Study Wants To Covermentioning

confidence: 99%

From acoustics to underwater archaeology: Deep investigation of a shallow lake using high‐resolution hydroacoustics—The case of Lake Lednica, Poland

et al. 2021

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“…Rather, it relates to differences in a combination of acoustic impedance contrasts, sediment, and topographic roughness (i.e., at the level of the grain size which exhibits intrinsic roughness and at the level of sub-beam topographic roughness such as oscillatory ripples) and sediment volume inhomogeneities [68]. Refining the relationship between frequency, seafloor type (including porosity, compactness and permeability) and backscatter response is continually being improved [14,16,63,65,69,70]. Further developments to better utilise backscatter data such as angular response analysis (ARA) [71][72][73] and the hyper-angular cube (HAC) [21,74] may also increase the predictive power of acoustic data [75].…”

Section: Acoustic Discriminationmentioning

confidence: 99%

Limitations of Predicting Substrate Classes on a Sedimentary Complex but Morphologically Simple Seabed

et al. 2020

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The ocean floor, its species and habitats are under pressure from various human activities. Marine spatial planning and nature conservation aim to address these threats but require sufficiently detailed and accurate maps of the distribution of seabed substrates and habitats. Benthic habitat mapping has markedly evolved as a discipline over the last decade, but important challenges remain. To test the adequacy of current data products and classification approaches, we carried out a comparative study based on a common dataset of multibeam echosounder bathymetry and backscatter data, supplemented with groundtruth observations. The task was to predict the spatial distribution of five substrate classes (coarse sediments, mixed sediments, mud, sand, and rock) in a highly heterogeneous area of the south-western continental shelf of the United Kingdom. Five different supervised classification methods were employed, and their accuracy estimated with a set of samples that were withheld. We found that all methods achieved overall accuracies of around 50%. Errors of commission and omission were acceptable for rocky substrates, but high for all sediment types. We predominantly attribute the low map accuracy regardless of mapping approach to inadequacies of the selected classification system, which is required to fit gradually changing substrate types into a rigid scheme, low discriminatory power of the available predictors, and high spatial complexity of the site relative to the positioning accuracy of the groundtruth equipment. Some of these issues might be alleviated by creating an ensemble map that aggregates the individual outputs into one map showing the modal substrate class and its associated confidence or by adopting a quantitative approach that models the spatial distribution of sediment fractions. We conclude that further incremental improvements to the collection, processing and analysis of remote sensing and sample data are required to improve map accuracy. To assess the progress in benthic habitat mapping we propose the creation of benchmark datasets.

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“…It allowed them to compare average backscatter values from one survey to another. The recent study of Gaida et al [13] showed a promising application of unsupervised Bayesian classification to time-series of MBES measurements. For comparison, OBIA was not designed to perform typical unsupervised classification, based on backscatter intensity values.…”

Section: Suggestions For Future Researchmentioning

confidence: 99%

“…Despite the recent rapid development of hydroacoustic devices and tools for geomorphometric analysis, detection of spatial and temporal changes of benthic habitats over time was only recently investigated [10][11][12][13][14][15]. The main measuring device used for high-resolution spatial mapping of the seafloor is the multibeam echosounder (MBES) [16].…”

Section: Introductionmentioning

confidence: 99%

Spatial and Temporal Changes of Tidal Inlet Using Object-Based Image Analysis of Multibeam Echosounder Measurements: A Case from the Lagoon of Venice, Italy

et al. 2020

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Scientific exploration of seabed substrata has significantly progressed in the last few years. Hydroacoustic methods of seafloor investigation, including multibeam echosounder measurements, allow us to map large areas of the seabed with unprecedented precision. Through time-series of hydroacoustic measurements, it was possible to determine areas with distinct characteristics in the inlets of the Lagoon of Venice, Italy. Their temporal variability was investigated. Monitoring the changes was particularly relevant, considering the presence at the channel inlets of mobile barriers of the Experimental Electromechanical Module (MoSE) project installed to protect the historical city of Venice from flooding. The detection of temporal and spatial changes was performed by comparing seafloor maps created using object-based image analysis and supervised classifiers. The analysis included extraction of 25 multibeam echosounder bathymetry and backscatter features. Their importance was estimated using an objective approach with two feature selection methods. Moreover, the study investigated how the accuracy of classification could be affected by the scale of object-based segmentation. The application of the classification method at the proper scale allowed us to observe habitat changes in the tidal inlet of the Venice Lagoon, showing that the sediment substrates located in the Chioggia inlet were subjected to very dynamic changes. In general, during the study period, the area was enriched in mixed and muddy sediments and was depleted in sandy deposits. This study presents a unique methodological approach to predictive seabed sediment composition mapping and change detection in a very shallow marine environment. A consistent, repeatable, logical site-specific workflow was designed, whose main assumptions could be applied to other seabed mapping case studies in both shallow and deep marine environments, all over the world.

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Monitoring underwater nourishments using multibeam bathymetric and backscatter time series

Cited by 15 publications

References 43 publications

From acoustics to underwater archaeology: Deep investigation of a shallow lake using high‐resolution hydroacoustics—The case of Lake Lednica, Poland

From acoustics to underwater archaeology: Deep investigation of a shallow lake using high‐resolution hydroacoustics—The case of Lake Lednica, Poland

Limitations of Predicting Substrate Classes on a Sedimentary Complex but Morphologically Simple Seabed

Spatial and Temporal Changes of Tidal Inlet Using Object-Based Image Analysis of Multibeam Echosounder Measurements: A Case from the Lagoon of Venice, Italy

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