Acoustic seabed classification

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Acoustic seabed classification is the partitioning of a

interferometric systems and sub-bottom profilers. Seabed classification based on acoustic properties can be divided into two main categories; surficial seabed classification and sub-surface seabed classification. Sub-surface imaging technologies use lower frequency sound
to provide higher penetration, whereas surficial imaging technologies provide higher resolution imagery by utilizing higher frequencies (especially in shallow water).

Surficial seabed classification

Classification methods

Surficial seabed classification is concerned primarily with distinguishing marine

LiDAR systems.[1]
Nevertheless, acoustics remain the preferred method of imaging the seafloor because data can be acquired over a much larger area (than in-situ sampling) from almost any depth.

Multibeam systems acquire both bathymetry (depth) and backscatter (intensity) data. Multibeam backscatter was previously considered to be a by-product of a multibeam survey, with bathymetry being the primary information. Recent advances in multibeam backscatter acquisition, processing and analysis methods have increased the range of applications for which multibeam systems can be used and now allow the collection of spatially and temporally coincident multispectral multibeam backscatter.[2][3][4] New methods of analyzing backscatter data, have increased its potential for seabed characterization. Backscatter data resolution has also increased significantly with the introduction of snippet data. Snippet data is raw backscatter time-series data for each beam footprint and each ping (Lockhart et al., 2007). These advances have allowed some multibeam backscatter data to achieve a quality comparable to that of sidescan sonar imagery.

Different classification approaches and algorithms can yield different results. These approaches include image-based seabed classification methods such as

accuracy of classification results (e.g. confusion matrix
).

Seabed characterization

Classification maps are subject to ground-verification in order to identify the compositions and bottom type that characterize each class. The functionality of

Geographic Information Systems (GIS) can be used to integrate data from different sources, including ground truth data. Such data may come from in-situ sediment grab sampling, the use of a dredge, trawl net, visual imagery or surveys using Remotely Operated Vehicles
(ROVs). The seabed classification map can be combined with other information about the area, such as fish distribution and abundance or vegetation characteristics, to establish habitat groups based on associations. This process allows classification maps derived from multibeam data to help characterize the seabed and more effectively manage its use.

Sub-surface seabed classification

Sub-surface seabed classification is commonly referred to as sub-bottom profiling and is generally used for geological assessment of the sub-surface characteristics. Sub-bottom profiling can return information from tens to hundreds of meters below the seafloor, and is often used to complement reflection seismology. From sub-surface classifications, scientists and engineers can characterize rock and sediment types, as well as pore fluids. This information is used for many applications, such as slope failure analysis and hydrocarbon exploration.

References

  1. ^ Radiometric Calibration of Airborne LIDAR Intensity Data for Land Cover Classification, by Wai Yeung Yan & Ahmed Shaker
  2. ^ 2. Anderson, J.T.; Van Holliday, D.; Kloser, R.; Reid, D.G., and Simard, Y., 2008. Acoustic seabed classification: current practice and future directions. ICES Journal of Marine Science, 65(6)
  3. ^ 3. Hughes-Clarke, J., 2015. Multispectral acoustic backscatter from multibeam, improved classification potential. Proceedings of United States Hydrographic Conference (National Harbor, Maryland)
  4. ^ 4. Brown, C.J.; Beaudoin, J.; Brissette, M., and Gazzola, V., 2019, Multispectral multibeam echo sounder backscatter as a tool for improved seafloor characterization. Geosciences, 9(3)

External links

  1. What is habitat mapping? (www.searchmesh.net)
  2. Lawrence & Bates, 2001, Acoustic ground discrimination systems (AGDS)
  3. Lockhart et al., 2007
  4. Hughes-Clarke et al., 1997, Ocean Mapping Group, UNB
  5. Applied Acoustics- Special Issue:The Application of Underwater Acoustics for Seabed Habitat Mapping
  6. Acoustic seabed classification: current practice and future directions
  7. Sediment Classification Software (2009)
  8. Acoustic Seabed Classification Systems (2001)
  9. Bottom Classification
  10. Acoustic Seabed Classification – Applications in Fisheries Science and Ecosystem Studies
  11. Seabed classification

Resources - seabed surface:

  1. Acoustic Seabed Classification Bibliography
  2. Maritime Way Scientific
  3. Mapping European Seabed Habitats (MESH) Project
  4. RoxAnn Seabed Classification System
  5. ICES Study Group on Acoustic Seabed Classification
  6. Case Studies and References for Lakes, Rivers & Marine
  7. BioSonics VBT Seabed Classification Software
  8. ECHOplus seabed discrimination
  9. GEOHAB - Marine Geological and Biological Habitat Mapping - Conferences
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