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J M Woodside - One of the best experts on this subject based on the ideXlab platform.
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geology of mud volcanoes in the eastern mediterranean from combined Sidescan Sonar and submersible surveys
Deep Sea Research Part I: Oceanographic Research Papers, 2005Co-Authors: T A C Zitte, C Hugue, J M WoodsideAbstract:Abstract Submersible observations and seafloor mapping over areas of mud volcanism in the eastern Mediterranean Sea reveal an abundance of methane-rich fluid emissions, as well as specific seep-associated fauna (e.g. tubeworms, bivalves and chemosynthetic bacteria) and diagenetic deposits (i.e. carbonates crusts). Cold seeps characterized by abundant chemosynthetic bivalves, bacterial mats, and reduced sediments are the surface manifestations of present-day expulsion of methane-rich fluids, whereas massive carbonate crusts with clusters of tubeworms indicate long-term seeping that might be dormant at present. The surface characteristics of the mud flows (roughness of the surface, gas escape features, presence of hemipelagic dust, colonization by benthic fauna, development of carbonate crusts) present a high variability related to the intensity and age of seepage, and can be correlated to the observed backscatter variations. The repartition of the mud flows and active seeps is organized concentrically around the centre of the mud volcanoes and potential parasitic cones. Sidescan Sonar backscatter patterns are thus indirectly related to spatial and temporal variation of mud volcanic activity.
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Sidescan Sonar images of mud volcanoes from the mediterranean ridge possible causes of variations in backscatter intensity
Marine Geology, 1996Co-Authors: Alexande V Volgi, J M WoodsideAbstract:Abstract A survey of a large field of mud diapirs on the Mediterranean Ridge south of Crete was carried out using both OKEAN (9.5 kHz) and MAK-1M (30 kHz) Sidescan Sonar systems during Leg-2 of the Third Training Through Research cruise of R/V Gelendzhik in June and July, 1993. High backscatter intensities were recorded by both systems to different degrees over the mud diapirs and their immediate surroundings. Causes of variations in the backscatter intensity are considered to be the spatial distribution of mud breccia associated with the mud domes (both the burial depth of the mud breccia beneath hemipelagic drape and its areal extent) and its physical properties, along with contributions from seafloor roughness and the topography of the mud domes. Significant sources of volume scattering of the Sidescan Sonar sound signal are considered to be mud breccia inhomogeneities represented by millimetric/centimetric clasts of various lithologies and free gas bubbles distributed through the mud matrix. A good general relationship is established between these sources and the observed backscatter variations through analysis of ground truth data from core samples, with 5 kHz deep-tow subbottom profiler records and seafloor video observations as well as the Sidescan Sonar records; but a fully quantitative assessment of this relationship would require acoustic modelling and additional ground truth data.
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brine pools associated with mediterranean ridge mud diapirs an interpretation of echo free patches in deep tow Sidescan Sonar data
Marine Geology, 1996Co-Authors: J M Woodside, Alexande V VolgiAbstract:Abstract MAK-1M deep tow Sidescan Sonar surveys have revealed two echo-free patches in an area of mud diapirs on the Mediterranean Ridge. The unusual shape of these patches and absence of returned signal can be explained more easily by the presence of brine pools rather than as a topography effect. The high acoustic impedance contrast at the interface between brine and seawater, a result of the salinity contrast there causing a relatively high contrast in sound velocity and water density, acts as a screen preventing Sidescan Sonar sound signal at low grazing angles from reaching the seafloor. Sound is reflected and refracted away from the Sonar towfish without any backscatter. The inferred brine pools appear to be associated with faults recognized on sonographs and subbottom profiler records. This first observation of brine pools related to mud volcanoes and mud diapirs suggests that salt is present in areas of mud diapirism, possibly playing a role in that process, or at least that the brines and mud may share flow paths within the Mediterranean Ridge.
Shrikanth S Narayana - One of the best experts on this subject based on the ideXlab platform.
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robust object classification in underwater Sidescan Sonar images by using reliability aware fusion of shadow features
IEEE Journal of Oceanic Engineering, 2015Co-Authors: Navee Kuma, Urbashi Mitra, Shrikanth S NarayanaAbstract:Detecting and classifying objects in Sidescan Sonar images is an important underwater application with relevance to naval transportation and defense. Properties of the imaging modality, in this case, often introduce large intraclass variabilities reducing the discriminative power of any classification algorithm and limiting the possibilities of improving classification accuracy by advances in pattern recognition only. In this work, we investigate the role of an ancillary feature set computed on object shadows and propose a scheme for exploiting this useful, but variedly reliable information for object classification. A mean-shift-clustering-based segmentation technique is used for isolating highlight and shadow segments from the images. We show the results of reliability-aware fusion of features computed on highlight and shadows on three different data sets of Sidescan Sonar images, to illustrate under what conditions such information might be useful.
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object classification in Sidescan Sonar images with sparse representation techniques
International Conference on Acoustics Speech and Signal Processing, 2012Co-Authors: Navee Kuma, Shrikanth S NarayanaAbstract:Most supervised classification approaches try to learn patterns in inter class variabilities using training samples. However in the real world, their discriminative power is often diminished, because data is seldom free from irregularities within a class. Apriori modeling of these intra class variabilities poses a challenge even in underwater Sidescan Sonar images that we consider for object classification in this work. Sparse representation techniques prove particularly useful in this regard because of their data driven approach to model these variabilities. Results on the NSWC Sidescan Sonar database suggest that sparse representation classifier with zernike magnitude features is significantly robust in the presence of these non-idealities.
Hans Tore Rapp - One of the best experts on this subject based on the ideXlab platform.
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roxann bottom classification system Sidescan Sonar and video sledge spatial resolution and their use in assessing trawling impacts
Ices Journal of Marine Science, 2004Co-Authors: Oddborre Humborstad, Leif Nottestad, Svei Lokkeborg, Hans Tore RappAbstract:Three complementary seabed characterization tools with different spatial resolution were used to locate a research site and to assess physical effects of experimental otter trawling in the Barents Sea: an acoustic seabed classification system (RoxAnn), Sidescan Sonar and a video-sledge. The marine protected area (MPA) around Bear Island was chosen as it offered unfished reference sites. The area was topographically complex which resulted in certain challenges for choice of the experimental site due to the requirements of representativity and homogeneity and suitable sampling substrate. Systematic waylines with RoxAnn gave broad-scale patterns of bottom conditions, the more informative Sidescan revealed topographic reliefs, whilst detailed information on sediment composition and small-scale seabed features was provided by the video-sledge. Accurate positioning of towed gears (trawl, Sidescan and video-sledge) ensured unbiased data acquisition. Trawl doors and rockhopper gear created furrows that were visible by Sidescan Sonar and video. Intensive trawling also caused changes in the acoustic properties by increasing roughness and decreasing hardness. Results are consistent with a possible resuspension of the sediment and a homogenizing effect from the trawl doors and ground gear ploughing the area. The suitability and advantages of using spatially overlapping tools in trawl impact studies are discussed.
Neil Golding - One of the best experts on this subject based on the ideXlab platform.
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mapping seabed habitats in the firth of lorn off the west coast of scotland evaluation and comparison of habitat maps produced using the acoustic ground discrimination system roxann and Sidescan Sonar
Ices Journal of Marine Science, 2005Co-Authors: Craig J Brown, David S Limpenny, Annika Mitchell, Mike Robertson, Neil GoldingAbstract:In September 2003 a national workshop took place in the United Kingdom with the aim of assessing the accuracy of the acoustic ground-discrimination system (AGDS), RoxAnn ,a s a tool for mapping seabed habitats in Special Areas of Conservation (SACs). A heterogeneous area of seabed, approximately 1 km 2 in size, was selected for the study. The area was first surveyed using a Sidescan-Sonar system and a mosaic of the output was produced covering 100% of the survey area. Interpretation of the mosaic identified three acoustically distinct seabed types, the spatial distributions of which were mapped. Four RoxAnn data sets were then collected over the same area of seabed applying different survey parameters (e.g. different survey grids, track spacing, survey vessels, survey speeds, and RoxAnn systems). Extensive ground-truthing was carried out involving 26 drop-down video stations, and from these data six benthic classes (seabed habitats) were identified. Following interpolation of the RoxAnn track-point data to produce full spatial-coverage data, these sixseabed habitat categories were used to conduct supervised classification of the RoxAnn data to produce full-coverage habitat maps of the area for each of the four RoxAnn data sets. Comparisons were then made between the four RoxAnn maps and the Sidescan-Sonar interpreted map. The accuracy of each map was assessed and the application of this mapping approach for mapping seabed habitats in SACs is discussed.
Veerle A I Huvenne - One of the best experts on this subject based on the ideXlab platform.
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detailed mapping of shallow water environments using image texture analysis on Sidescan Sonar data and multibeam backscatter imagery
Underwater Acoustic Measurements 2007, 2005Co-Authors: Veerle A I Huvenne, Philippe Londel, V Huehnerbach, O GomezsichiAbstract:Multibeam backscatter (240 kHz) and Sidescan Sonar data (325 kHz) of the West Solent (Southern UK) were analysed with automated image classification techniques based on Grey Level Co-occurrence Matrices (GLCM?s) to assist the mapping of different seabed facies in this dynamic, tide-influenced area. After processing and ortho-rectification with PRISM, the GLCM entropy and homogeneity indices were calculated with TexAn. Those image texture indices quantify the lack of organisation and the amount of local similarities in a chosen neighbourhood around each pixel. Used together with the original images, they help the human eye to distinguish different patterns and hence to increase the understanding of the morphology and dynamic processes at the seabed. The fact that the multibeam and Sidescan Sonar data were collected simultaneously allowed a comparison between the two survey methodologies and allowed to test the performance of the GLCM analysis for the two types of imagery. The Sidescan Sonar gives a much wider range and hence a much better coverage than the multibeam, which is also affected by high levels of speckle noise and lesser quality imagery in the far ranges. In addition, due to the different geometry and beam-forming patterns of the 2 methods, similar features may yield different textural complexities, which makes comparison between the two classification results not so straightforward.
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the seabed appearance of different coral bank provinces in the porcupine seabight ne atlantic results from Sidescan Sonar and rov seabed mapping
EPIC3Cold-water corals and ecosystems : with 104 tables André Freiwald ... (eds.) Berlin [u.a.] : Springer 535-569. (Erlangen Earth Conference series), 2005Co-Authors: Veerle A I Huvenne, A Eye, H De Haas, K Dekind, J P Henrie, M Kozachenko, Olule K Roy, A J WheeleAbstract:Carbonate mounds, identified as deep-water coral banks, have been reported recently from three provinces in the Porcupine Seabight, SW of Ireland. As yet, the mechanisms behind their formation and development are only partly understood. This contribution discusses their seabed appearance and present-day sedimentary environment, based on a large-scale TOBI Sidescan Sonar mapping carried out in 2002, and on detailed ROV video records from specific sites within the three mound provinces, collected in 2001. The study of the present-day characteristics and variability of these mounds can help to understand their development history in the past.
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textural analyses of Sidescan Sonar imagery from two mound provinces in the porcupine seabight
Marine Geology, 2002Co-Authors: Veerle A I Huvenne, Philippe Londel, J P HenrieAbstract:Large mound structures have been discovered in the Porcupine Seabight (Northeast Atlantic) at a depth of 500–1200 m, associated with the growth of cold-water deep-sea coral species such as Lophelia pertusa (L.) or Madrepora oculata (L.). During the Training Through Research cruise in 1997, high-resolution OREtech Sidescan Sonar data were acquired over two provinces of these structures. This article focuses on the presentation and quantitative interpretation of representative sections of these Sidescan data from areas around the Belgica and Hovland mounds. Several image analysis tools were used, but texture analysis, based on grey level co-occurrence matrices, gave the best results. Entropy and homogeneity indices were calculated, and the resulting images made it possible to discriminate between different seabed features on a quantitative basis. Mounds, moats and background sediments could be delineated accurately, and the image textures could be linked to the actual seafloor appearance through core descriptions and deep-towed video data. A major difference was found in the acoustic returns from the two provinces studied: the Belgica province shows much rougher textures. This is due to an actual difference in seabed roughness, caused by a difference in bottom currents and sediment dynamics in the two areas. The combined effect of the northward-directed North Atlantic slope current and superimposed internal waves and tides appears to be much stronger in the Belgica province. The reported difference in current strength might well influence the growth of the deep-water coral species in both areas.