Bathymetric Images Research Articles

3D bathymetric images of the Truong Sa Archipelago (Spratly Islands)

This article centers on the creation of three-dimensional (3D) bathymetric images of the Truong Sa Archipelago, utilizing gridded bathymetric data from the General Bathymetric Chart of the Oceans (GEBCO) to unveil the submerged topography of this archipelago. The study's outcomes provide a comprehensive understanding of 3D bathymetric imaging of the Truong Sa Archipelago, underscoring the research's significance in unraveling the complex underwater landscape.The importance of this study extends to geopolitical considerations, emphasizing the strategic value of precise bathymetric mapping in resolving territorial disputes. The global interest in the bathymetric and environmental exploration of the Truong Sa Archipelago is highlighted, emphasizing the potential applications of GEBCO bathymetric data at both regional and global scales. The study also reveals prospects in the future for fostering collaboration among sovereign nations within the Truong Sa Archipelago to enhance bathymetric data resolution, thereby creating maps for safe international shipping routes through the archipelago. Consequently, these 3D bathymetric images not only advance scientific understanding but also bear practical implications for maritime navigation, environmental conservation, and geopolitical assessments of this unique maritime region.

Rip Current: A Potential Hazard Zones Detection in Saint Martin’s Island using Machine Learning Approach

Beach hazards would be any occurrences potentially endanger individuals aswell as their activity. Rip current, or reverse current of the sea, is a typeof wave that pushes against the shore and moves in the opposite direction,that is, towards the deep sea. The management of access to the beach sometimes accidentally push unwary beachgoers forward into rip-prone regions,increasing the probability of a drowning on that beach. The research suggestsan approach for something like the automatic detection of rip currents withwaves crashing based on convolutional neural networks (CNN) and machinelearning algorithms (MLAs) for classification. Several individuals are unableto identify rip currents in order to prevent them. In addition, the absenceof evidence to aid in training and validating hazardous systems hinders attempts to predict rip currents. Security cameras and mobile phones have stillimages of something like the shore pervasive and represent a possible causeof rip current measurements and management to handle this hazards accordingly. This work deals with developing detection systems from still beachimages, bathymetric images, and beach parameters using CNN and MLAs.The detection model based on CNN for the input features of beach imagesand bathymetric images has been implemented. MLAs have been applied todetect rip currents based on beach parameters. When compared to other detection models, bathymetric image-based detection models have significantlyhigher accuracy and precision. The VGG16 model of CNN shows maximumaccuracy of 91.13% (Recall = 0.94, F1-score = 0.87) for beach images. Forthe bathymetric images, the highest performance has been found with anaccuracy of 96.89% (Recall= 0.97, F1-score=0.92) for the DenseNet model of CNN. The MLA-based model shows an accuracy of 86.98% (Recall=0.89,F1-score= 0.90) for random forest classifier. Once we know about the potential zone of rip current continuosly generating rip current, then the coastalregion can be managed accordingly to prevent the accidents occured due tothis coastal hazards.

Building consistent time series night-time light data from average DMSP/OLS images for indicating human activities in a large-scale oceanic area

• Random Forest algorithm and a stepwise intercalibration approach were combined. • Multi-filter and bathymetric images were composited to improve intercalibration. • Noise impact on the intercalibration was greatly eliminated. • Consistent time series night-time light data specialized for large-scale oceanic area was build. • Total light index was implied as an effective indicator of ocean fishery activities. Human activities in the ocean have never been chronically and continuously investigated on a large scale. Night-time light (NTL) images collected by the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) have been used as a proxy for monitoring the distribution and intensity of some human activities in the ocean from 1992 to 2013. However, systematic radiometric biases exist among the average visible-light DMSP/OLS NTL images (DMSP avg ) derived from different satellites. Moreover, the high randomness of fishing vessel locations and the large amount of noise impede the intercalibration of DMSP avg . To address these issues, this study has developed a method for generating a series of consistent NTL images from 1992 to 2013 for a large-scale oceanic area. A composite image was first constructed by combining the original DMSP avg , median, and standard deviation filter images derived from the DMSP avg , and a bathymetry image. Thereafter, Random Forest (RF) algorithm was employed to classify the composite image into effective and noisy pixels. Finally, a stepwise intercalibration method was adopted to reduce the systematic radiometric biases in the denoised images. The experimental results showed that RF had an overall accuracy of 96% and a Kappa coefficient of 0.775. Furthermore, the intercalibration was shown to significantly reduce the systematic radiometric biases owing to the noises being effectively discarded by the RF. Specifically, the Sum Normalized Different Index (SNDI) of the images intercalibrated by the proposed method can reach 0.61, which is 68.2% less than that of the original DMSP avg . In addition, the correlation coefficients between the intercalibrated DMSP avg and fishery catches in the exclusive economic zones (EEZs) of Japan and Malaysia can reach 0.949 and 0.901, respectively, which are higher than other values, such as the one intercalibrated using the Pseudo-Invariant Features (PIFs) method. In summary, the proposed method has been proven to be effective and feasible for generating consistent time-series NTL data for a large-scale oceanic area, and the derived Total Light Index (TLI) is an effective indicator of ocean fishery activities for ocean ecosystem research and related applications.

Late Pleistocene iceberg scouring in the north-eastern Baltic Sea, west of Estonia

During the last glacial period, the western sea area of Estonia in the northern Baltic Sea was covered by the Fennoscandian continental ice sheet. High-resolution multibeam bathymetric images of the seafloor reveal widespread linear and curved depressions, interpreted as iceberg scours (ploughmarks) that were produced by ploughing and grounding icebergs during and soon after the final ice retreat from the area. Two main populations (A and B) of scours are identified, formed either on top of the acoustic substratum (bedrock or coarse-grained glacial deposits) or on top of the superimposed glaciolacustrine and post-glacial sediments that are exposed on the seafloor. Both populations have similar characteristics, being on average 780 m long, 54 m wide and 1.6 m deep. Most of the scours are linear, with an average NE-SW orientation for Population A, and an average ENE-WSW orientation for Population B. The scour patterns indicate a partially grounded ice sheet in the shallower parts of the study area. We suggest that the period of most intensive iceberg calving and scouring lasted for approximately 1100 years, from 13.2 to 12.3 kyr BP.

Scale‐Dependent Bedform Migration and Deformation in the Physical and Spectral Domains

AbstractMulti‐scale bathymetries observed in laboratory channels and natural rivers have posed several challenges to the description of bedform geometry and kinematics. To better quantify scale‐dependent migration velocity, high resolution spatio‐temporal bed evolution data are analyzed using three independent methods: (i) a bedform tracking method that identifies individual bedforms in longitudinal bed elevation profiles, (ii) a cross‐correlation based, image matching technique in consecutive bathymetry scans similar to Particle Image Velocimetry, and (iii) two‐dimensional frequency‐wavenumber spectra marking a dispersion relation between bedform period and length, allowing estimation of Fourier‐based, scale‐dependent migration velocities. The comparative studies show that the spectral and bedform tracking methods present small differences in the migration velocity of medium‐large bedforms. However, significant deviations occur in the small bedforms, mostly due to bedform sheltering or amplified exposure to the flow, which also contribute to their enhanced scale‐dependent deformation. The analysis also shows that some form of scale separation is needed to extract the large and slowly migrating bedforms as they are masked by secondary features when several bedform orders coexist. Bathymetric Image Velocimetry reasonably estimates the averaged migration velocity and exhibits potential to study relations between spanwise bed surface velocity and local bedform kinematics.

High-resolution bathymetry by deep-learning-based image superresolution.

Seafloor mapping to create bathymetric charts of the oceans is important for various applications. However, making high-resolution bathymetric charts requires measuring underwater depths at many points in sea areas, and thus, is time-consuming and costly. In this work, treating gridded bathymetric data as digital images, we employ the image-processing technique known as superresolution to enhance the resolution of bathymetric charts by estimating high-resolution images from low-resolution ones. Specifically, we use the recently-developed deep-learning methodology to automatically learn the geometric features of ocean floors and recover their details. Through an experiment using bathymetric data around Japan, we confirmed that the proposed method outperforms naive interpolation both qualitatively and quantitatively, observing an eight-dB average improvement in peak signal-to-noise ratio. Deep-learning-based bathymetric image superresolution can significantly reduce the number of sea areas or points that must be measured, thereby accelerating the detailed mapping of the seafloor and the creation of high-resolution bathymetric charts around the globe.

Morpho-stratigraphic features of the northern shelf of the Strait of Gibraltar: Tectonic and sedimentary processes acting at different temporal scales

The northern shelf of the Strait of Gibraltar adjacent to Camarinal Sill, defined here as the Cape Paloma continental shelf, has been investigated by analyzing a set of geophysical data including multibeam bathymetric images, a side-scan sonar mosaic and high-resolution seismic profiles, and the simulation of water-mass circulation patterns along the northern coastal margin. The aim of the study was to establish the significance of factors determining the evolution of this shallow margin at different temporal scales and to assess the implications for bedform generation in strait settings, taking into account the complex tectonic evolution and the energetic hydrodynamic regime of the strait.Deformed basement rocks are part of the Betic-Rif thrust wedge, western Gibraltar Arc, mainly formed by the materials of the Flysch Complex units and covered by Pliocene to Quaternary post-orogenic deposits. A central high (Bajo de los Cabezos High) is delimited by lateral depressions, that nucleated two major depocentres with distinctive filling histories. The eastern depocentre is controlled by WNW-ESE faults cutting the Cretaceous-Miocene basement rocks; these faults generate horsts and grabens that could have contributed to the opening of the Strait of Gibraltar during the Pliocene. The largest and westernmost depocentre is related to the complete infilling of a shelf palaeovalley. The sediment cover is molded by different fields of submarine dunes and comet marks that indicate the influence of hydrodynamic processes on sediment transport at the coastal margin.The observations in the study area regarding bedform development must be placed into a wider context of strait sediment dynamics. The Cape Paloma continental shelf exhibits both erosional and depositional forms, due to its intermediate location between the strait, mostly dominated by erosional processes, and the Barbate Platform (northwest of the study area), mostly characterized by depositional forms. The long-term evolution of the sediment depocentres in the study area appears to be mainly influenced by the morpho-tectonic configuration of the margin, which in turn was established to a large extent by differential uplifting along the coast. In the shelf east of the central high, the basement horst and graben structure trapped sediments in the physiographic lows and fostered the formation of large-scale sediment banks. In the shelf west of the central high, the occurrence of a major infilled palaeovalley is in agreement with a gentle subsidence trend.The physiographic configuration is also thought to play a major role in defining short-term processes, particularly in confining a cyclonic eddy to the east of the Bajo de los Cabezos High during specific conditions of the tidal cycle. This eddy favors the recirculation of sediments in the coastal margin, as evidenced by small bedform fields that apparently show a wider distribution that the larger-scale, confined sediment banks, due to the instauration of the modern sediment dynamics after the complete shelf flooding. The sediment transport pattern established in the study area seems to be eventually captured by a submarine channel that provide an efficient mechanism for sediment export toward deep-water settings, where an extensive contourite depositional system has been documented.

Seafloor pockmarks and gas seepages, northwestern Bay of Fundy, New Brunswick, Canada

Bathymetric images of linear and circular pockmark depressions on the Bay of Fundy seafloor, offshore eastern Canada, are interpreted to have been caused by escaping gas from underlying sediment or bedrock. Shallow interstitial gas within marine sediments restricts seismic reflection imaging (acoustic masking) of sub-bottom units resulting in obscured reflections within seismic profiles, confirming that interstitial gas is present in the underlying units. Pockmark fields are frequent in several bays and shallow coastal areas along the northern coast of the Bay of Fundy. The largest field containing over 10 000 pockmarks occurs in Passamaquoddy Bay, an estuary underlain by igneous and metamorphic bedrock. These features are interpreted to be caused by generation of biogenic methane from the microbial breakdown of organic matter buried within Holocene-age sediments and along the underlying Pleistocene/Holocene unconformity. The unconformity is recorded as a distinctive horizon that represents a time when glacier recession resulted in exposure of parts of the bay to sub-aerial erosion and growth of terrestrial vegetation at locations subsequently submerged by post-glacial transgression. Three areas of potential thermogenic gas occurrence were identified in seismic profiles collected south and east of The Wolves islands, New Brunswick. The underlying bedrock has not yet been precisely mapped, although outliers of Carboniferous-age bedrock that is the major petroleum source in New Brunswick may extend into this area of the Bay of Fundy.

Lateral shear-moraines and lateral marginal-moraines of palaeo-ice streams

Abstract An understanding of the nature of sedimentation at ice-stream lateral margins is important in reconstructing the dynamics of former ice sheets and modelling the mechanisms by which sediment is transported beneath contemporary ice streams. Theories of the formation of ice-stream lateral moraines (ISLMs) have hitherto been based on a relatively limited number of terrestrial and marine examples. Here, an inventory of ISLMs is compiled from available studies, together with independent analysis of seismic-reflection and bathymetric datasets. The locations and dimensions of 70 ISLMs, alongside a synthesis of their key architectural and geomorphic characteristics, are presented. Two different types of ISLMs are identified. Type 1 ISLMs are up to 3.5 km wide and 60 m thick. They maintain a constant width, thickness and cross-sectional shape along their length. Type 1 ISLMs are interpreted and referred to as ice-stream lateral shear-moraines that form subglacially in the shear zone between ice streams and slower-flowing regions of an ice sheet. In contrast, Type 2 ISLMs are up to 50 km wide and 300 m thick. They are only identified close to the shelf break in the marine environment. Type 2 ISLMs exhibit an increase in width and thickness along their length and their distal slopes become steeper in a seaward direction. They contain internal dipping reflections that indicate sediment progradation away from the former ice stream. Type 2 ISLMs are interpreted and referred to as ice-stream lateral marginal-moraines that were formed at the lateral boundary between ice streams and seafloor terrain that was free of grounded ice. We suggest that, using bathymetric images and acoustic profiles, it is possible to differentiate between ice-stream lateral shear-moraines and lateral marginal-moraines in the geological record. This distinction is important for understanding the mechanisms of sediment transfer beneath ice streams and for making inferences about the conditions that existed beyond the lateral ice-stream margin at the time of lateral-moraine formation: slow-moving ice beyond lateral shear-moraines, and ocean water rather than ice beyond lateral marginal-moraines.

Bouldery debris mantle deposited by cold-based ice offshore of the Vestfold Hills, East Antarctica

Streamlined subglacial sediments are common in seafloor bathymetric images from many glaciated margins. Less common are seafloor features left by cold-based ice. The shallow waters around the now largely ice-free Vestfold Hills in East Antarctica (Fig. 1a, e) show few streamlined sedimentary features, even though the area has clearly been glaciated as implied by striated bedrock, moraine ridges and abundant erratic boulders on adjacent exposed land. A likely explanation for the absence of streamlined subglacial landforms is that the area was glaciated by ice frozen to its bed. Fig. 1. Multibeam swath bathymetry, outcrop photo and topographic profiles of boulder-rich debris mantle and sand ribbons from the Vestfold Hills coastal zone, East Antarctica. ( a ) Sun-illuminated bathymetric image of Airport Beach Embayment showing the debris mantle. Ice-keel ploughmarks are shown outside the embayment. Acquisition system Kongsberg EM3002. Frequency 300 kHz. Grid-cell size 2 m. ( b ) Close-up of debris mantle showing individual boulders. ( c ) Photograph of bouldery debris mantle above sea level. Large boulder is 4 m in diameter. ( d ) Multibeam image of sand ribbons and boulders. ( e ) Location of study area (red …

Assemblages of submarine landforms in the glacial troughs of the northern Barents Sea, east of Svalbard

The Barents Sea is a wide, relatively deep epicontinental sea consisting of shallower banks ( c. 50–100 m depth) separated by broad, flat-bottomed troughs ( c. 200–400 m depth) that radiate out towards its western and northern margins (Fig. 1a). These troughs have been excavated by grounded ice during multiple glaciations through the Plio-Pleistocene (Jakobsson et al. 2014). During the Last Glacial Maximum (LGM) the Barents Sea Ice Sheet (BSIS) extended across the entire northern Barents Sea to the shelf break (Svendsen et al. 2004; Jakobsson et al. 2014). Fast-flowing ice drained the ice sheet through these troughs and produced a suite of seafloor landforms that preserves both a record of former ice-flow patterns and of how the ice sheet retreated during deglaciation (Dowdeswell et al. 2010; Hogan et al. 2010 a ). Fig. 1. Bathymetric images and sub-bottom profiles of landforms in glacial troughs east of Svalbard. Acquisition system Kongsberg EM120. Frequency 12 kHz. Grid-cell size 10–20 m. Acquisition system for profiles Kongsberg TOPAS PS018 parametric sub-bottom profiler (secondary beam frequency 0.5–6 kHz). ( a ) Location of study area (red boxes; map from IBCAO v. 3.0). KT, Kvitoya Trough; OT, Olga Trough; E, eastern Erik Eriksen Trough; W, western Erik Eriksen Trough; KKL, Kong Karls Land; No, Nordaustlandet; FVT, Franz Victoria Trough. ( b ) Glacial lineations (long dashes) overprinted in part by a debris-flow deposit (dotted) in western Erik Eriksen Trough; recessional moraine orientations shown by solid lines. Large black arrow indicates former ice-flow direction. ( c ) Saw-tooth-shaped recessional moraines in Olga Trough. ( d ) Hill–hole pairs and glacial lineations in eastern Olga Trough; same depth scale as (c). ( e ) Streamlined crag-and-tail landforms in Kvitoya Trough. ( f ) Sub-bottom profile over the till sheet and recessional moraines shown in (c). ( g ) Acoustic facies on the upper slope north of Kvitoya Trough. ( h ) Subglacial meltwater channels …

Landforms in Hvítárvatn, central Iceland, produced by recent advances of surging and non-surging glaciers

Hvitarvatn is a proglacial lake adjacent to Langjokull, the second largest ice cap in Iceland. The lake is 422 m a.s.l. and 36 km2 with a maximum depth of 85 m (Fig. 1). Langjokull feeds two outlet glaciers, Suðurjokull and Norðurjokull, which both terminated in the lake during the Little Ice Age (LIA; AD 1300–1900). The LIA extent of both outlet glaciers is clearly defined by moraines visible on land and in high-frequency multibeam sonar bathymetric images of the lake bottom (Geirsdottir et al. 2008). The multibeam sonar bathymetry, chirp bottom profiles and numerous sediment cores contain information on the sedimentary history of the lake and indicate that, following regional deglaciation 10 ka ago, glaciers entered the lake only during the LIA (Larsen et al. 2011, 2012). Suðurjokull remained in the lake until the mid-twentieth century, whereas Norðurjokull retreated from the lake in the summer of 2009. The multibeam sonar bathymetric data show large differences in the behaviour of Norðurjokull and Suðurjokull during the LIA that can be explained by both glacial processes and variations in the stability of the catchment. Fig. 1. Langjokull and Hvitarvatn glacier geological setting. ( a ) Topographic map of field site showing location of Hvitarvatn (HVT) adjacent to Langjokull's eastern margin (map gridlines are spaced 1 km). Lake surface is overlain with bathymetric map; maximum LIA extent (dashed lines) of outlet glaciers Norðurjokull (NJ) and Suðurjokull (SJ) are visible in lake bathymetry. Inset map highlights position of Langjokull in Iceland's central highlands. Other geographical features mentioned in text are Skriðufell (SK), Leggjarbrjotur (LB) and the Hvitarnes delta (HV). ( b ) Multibeam bathymetric map of Hvitarvatn's main basin showing detailed view of lake-floor morphology and position of seismic profile (dashed line) presented in (c). Multibeam acquisition system Seabat 8101. Frequency 240 kHz. ( c ) Chirp seismic profile (dashed line …

Gebra Slide: glacial and tectonic controls on recurrent submarine landsliding off the northern tip of the Antarctic Peninsula

Late Quaternary–Holocene submarine landslides occurring in high-latitude, glacial-influenced continental margins have been increasingly investigated during the last three decades. Both relatively small and large landslides have been identified in these settings (e.g. Canals et al. 2004; Vanneste et al. 2006). However, much more evidence on submarine instabilities is available from the Arctic than the Antarctic. Bransfield Basin (BB) is a 450 km long, SW–NE-orientated, marginal rift basin opening between the South Shetland archipelago and the northern tip of the Antarctic Peninsula (AP) (Fig. 1a, b). The middle part of BB is occupied by the 215 km long and 120 km wide Central Bransfield Basin (CBB), bounded at its ends by transverse ridges forming the volcanoes of Deception (not shown) and Bridgeman islands. CBB is asymmetrical, with a narrow and steep South Shetland margin and a broader and gentler AP margin, where the continental shelf is about 70 km wide (Fig. 1a). Fig. 1. ( a ) Shaded-relief bathymetric image of the Central Bransfield Basin. Acquisition system Simrad EM12-S. Frequency 12.5 kHz. Grid-cell size 200 m (colour image) and GEBCO_08 Grid (grey image). Land area is from the Landsat Image Mosaic of Antarctica (US Geological Survey). ( b ) Location of study area (red box; map from IBCSO v. 1.0). SSI and BB refer to South Shetland …

A glacial landform assemblage in Placentia Bay, Newfoundland, eastern Canada

Placentia Bay, located on the south coast of the island of Newfoundland, is bounded to the west by Burin Peninsula and to the east by Avalon Peninsula (Fig. 1a). At the Last Glacial Maximum (LGM) the Laurentide Ice Sheet extended south of the bay, reaching the edge of the continental shelf (Shaw et al. 2006). Placentia Bay was an onset region for fast-flowing ice in Halibut Channel, a cross-shelf trough beyond the bay. The bay became ice free at c. 14 ka, by which time retreat of Laurentide ice had isolated a Newfoundland ice cap. Placentia Bay has been mapped with multibeam sonar and surveyed with sub-bottom profilers. Results from these activities are contained in 1:50 000 scale shaded-relief maps, backscatter strength maps, a ‘seascape’ map (Shaw et al. 2011) and in various papers (e.g. Brushett et al. 2007; Shaw et al. 2009). The landform assemblage includes: (1) glacially overdeepened troughs; (2) streamlined sedimentary landforms; (3) rock drumlins; (4) flutes overprinting sedimentary drumlins; (5) De Geer moraines superimposed on streamlined landforms; (6) a complex landform suite comprising coast-parallel moraines, drumlins and megaflutes, eskers and hummocky moraine; (7) transverse moraines; (8) submarine slides; and (9) paraglacially modified terrain. Fig. 1. Multibeam sonar bathymetry from Placentia Bay, Newfoundland, eastern Canada (Fig. 2g). ( a ) Sun-illuminated multibeam sonar bathymetric image, with a cross-section across the bay. Acquisition systems Kongsberg EM1002 and EM300. Frequency 12 kHz. Grid-cell size 5 m. ( b ) Backscatter strength. White line indicates area of seafloor erosion (megaflutes). ( c ) Streamlined glacial-sedimentary landforms. ( d ) Rock drumlins. ( e ) Drumlins (top) overprinted by flutes (bottom), illustrating a readvance from the SW. The inner bay includes three narrow channels (Fig. 1a): Western Channel (maximum depth 450 m), Central Channel (265 m), and Eastern Channel (333 m). The outer bay has lower relief and encompasses …

Geomorphology of the huge Hinlopen–Yermak landslide on the northern Svalbard margin

Submarine landslide scars, including the huge Hinlopen–Yermak slide-scar north of Svalbard (Fig. 1) (Vanneste et al. 2006; Winkelmann et al. 2006), are relatively common geomorphological features on glaciated continental margins. However, landslide characteristics, for example scar area, run-out and displaced volume, vary significantly (Hogan et al. 2013). A key pre-condition for failure is rapid deposition of mainly diamictic glacier-derived sediment on the slope during full-glacials, alternating with fine-grained interglacial deposition. This layered architecture, and the varying geotechnical properties of the debris, facilitate downslope mass-movements with a variety of possible triggers. Fig. 1. Marine geophysical data over Hinlopen–Yermak landslide scar, northern Svalbard. ( a ) Multibeam image showing slide scar. PR, arcuate pressure ridges. DR, detached sediment ridges. Acquisition systems Kongsberg EM300. Frequency 30 kHz (RV Jan Mayen ). Hydrosweep DS2. Frequency 15.5 kHz (RV Polarstern ). Kongsberg EM120. Frequency 12 kHz (RSS James Clark Ross ). Grid-cell size 100 m. ( b ) Seismic-reflection profile of slide headwall and post-slide sediment fill. Acquisition system two 40 cubic inch airguns. VE×6. ( c ) Bathymetric image of the complex eastern headwall area showing detached sediment ridges (DR and inset; VE×7) and blocky debris (BD) on slip planes. ( d ) Bathymetric image of rafted mega-blocks within slide debris. Ridges of material pushed up …

Three cross-shelf troughs on the continental shelf of SW Greenland from Olex data

Glacial cross-shelf troughs, often hundreds of metres deep and tens to hundreds of kilometres long, are characteristic components of most high-latitude continental shelves (e.g. Anderson 1999). Most Arctic shelves are dissected by large cross-shelf troughs, separated by shallower sedimentary banks (Batchelor & Dowdeswell 2014). The geomorphology of these troughs provides information about the extent and dynamics of ice flow on polar continental margins during Quaternary glacial periods. This study uses Olex data (www.olex.no), consisting of multiple single-beam echo-sounder lines, to describe and interpret three large, though relatively poorly known, cross-shelf troughs on the continental shelf of SW Greenland between about 62° and 65° N (Fig. 1a–d). Fig. 1. Olex bathymetry of three cross-shelf troughs off SW Greenland. The horizontal resolution of Olex data is dependent on the density of single-beam track lines. It is about 50 m at best and usually more than a few hundred metres in areas that are less densely covered by track lines. ( a ) Location of study area (red boxes; map from IBCAO v. 3.0). ( b ) Olex bathymetric image of Sukkertop …

Glacially eroded cross-shelf troughs surrounding Iceland from Olex data

Iceland is surrounded by a continental shelf of around 100 km in width, sloping gently towards a shelf break at 250–400 m below sea level. Incised into the shelf are numerous cross-shelf troughs positioned radially and mostly reaching the shelf-edge. The troughs are typically about 100 km long and 20 km wide. They vary in depth between 15 and 350 m and are interpreted to have formed by glacial erosion beneath fast-flowing ice streams or outlet glaciers of former Icelandic ice sheets that extended to the shelf-break (Ingolfsson & Norddahl 1994). Bathymetric images combining interpolated depth-soundings from Olex (multiple single-beam echo-sounder lines; http://www.olex.no/index_e.html) and IBCAO v. 3.0 (Jakobsson et al. 2012) databases show that the Icelandic continental shelf is incised by numerous linear to curvilinear depressions, positioned radially (Fig. 1a). These troughs are generally relatively short, narrow and straight in the eastern and southern areas of the continental shelf, large and long on the western shelf, and deep, long, sinuous and distributive on the northern shelf (Fig. 1). Their locations and geometries are shown in Figure 1a and their dimensions recorded in the table. Cross-profiles of the troughs vary from symmetrical and flat-bottomed to asymmetrical and U- or V-shaped (Fig. 1e). Prominent breaks …

Underwater terrain-aided navigation based on multibeam bathymetric sonar images

Underwater terrain-aided navigation is used to complement traditional inertial navigation employed by autonomous underwater vehicles during lengthy missions. It can provide fixed estimations by matching real-time depth data with a digital terrain map. This study presents the concept of using image processing techniques in the underwater terrain matching process. A traditional gray-scale histogram of an image is enriched by incorporation with spatial information in pixels. Edge corner pixels are then defined and used to construct an edge corner histogram, which it employs as a template to scan the digital terrain map and estimate the fixes of the vehicle by searching the correlation peak. Simulations are performed to investigate the robustness of the proposed method, particularly in relation to its sensitivity to background noise, the scale of real-time images, and the travel direction of the vehicle. At an image resolution of 1 m2/pixel, the accuracy of localization is more than 10 meters.

Improving bathymetric images exploration: A data mining approach

Bathymetry is the science of measuring and charting the depths to determine the topography of the seafloor and other bodies of water. It has several important practical and academic applications. For this reason, having computational tools capable of analyzing bathymetric charts would be useful for domain experts studying the various problems related to water depth. Data mining is a well known technique for extracting information from large datasets, but cannot be directly applied to images. The contribution of this work is an approach for using data mining in bathymetry images. We propose a method for processing input images, in order to extract records and their features, which can be processed by classic data mining algorithms. Additionally, we also propose techniques to visualize both data mining results and map characteristics. For evaluation purposes, the proposed approach was applied to a cold-water corals dataset, in order to predict where corals are likely to be found, under a domain expert supervision.

The Research of Mutlibeam Data Registration Algorithm Basing on False Grey Scale Double-Zone Matching

Combined with the characteristics of multibeam bathymetric data and grey scale image, this paper proposed an algorithm of mutlibeam data registration based on false grey scale double-zone matching. By analyzing the original grey normalized matching algorithm, this paper improved the original algorithm by adding another matching zone, and then deals the mutlibeam data with the algorithm of false grey scale and the new method this paper proposed. Finally, verified the new algorithm both on theory and simulation, and evaluated the running speed of the algorithm. The simulation results showed that the algorithm did improve the speed of program, which meets the requirement of real-time in multibeam data matching better.