Sea-bed characterisation and classification from the power spectra of side-scan sonar data

1993 ◽  
Vol 15 (1) ◽  
pp. 43-64 ◽  
Author(s):  
Duncan Tamsett
Keyword(s):  
Power Spectra ◽  
Side Scan Sonar ◽  
Sea Bed

scholarly journals Plough Marks in the Weddell Sea

1979 ◽  
Vol 23 (89) ◽  
pp. 402
Author(s):  
Olav Orheim
Keyword(s):  
Continental Shelf ◽  
Weddell Sea ◽  
Side Scan Sonar ◽  
Bed Morphology ◽  
Sea Bed ◽  
Abrupt Changes ◽  
Antarctic Research

Abstract The 1976/77 Norwegian Antarctic Research Expedition carried out studies of the sea bed by side-scan sonar. The equipment was operated from the expedition vessel down to about 350 m depth by personnel from the Continental Shelf Institute, Trondheim. Various types of plough marks mostly ranging from 10 to 100 m in width were observed. These included several generations of crossing plough marks as well as plough marks with abrupt changes in trend reflecting changing iceberg motion. The investigations will be expanded during the 1978/79 expedition to include towing at greater depths, and mapping of sea-bed morphology by mosaic towing patterns.

Recent Surveys

1983 ◽  
Vol 36 (1) ◽  
pp. 96-99
Author(s):  
R. de F. Browne
Keyword(s):  
Continental Shelf ◽  
New Technology ◽  
Regular Pattern ◽  
Side Scan Sonar ◽  
Safe Navigation ◽  
Line Searches ◽  
Sea Bed ◽  
The Uk ◽  
Modern Standard ◽  
Echo Sounder

Figure 1 shows the present state of surveys over the UK continental shelf. Out of an area of some 173 000 square miles contained within the British Fishery limits, 36 per cent has been surveyed by echo sounder, but not necessarily to a scale suitable for modern standards, and only surveys to full modern standards are sufficient to ensure safe navigation within r m of the seabed; a modern standard survey must be carried out using a modern echo-sounder and include a thorough sonar sweep. All hips of the Survey Flotilla are now fitted with a Kelvin Hughes MS48 echo sounder and an OAL side-scan sonar.New technology, such as the towed side-scan system, has enabled the surveyor to examine the whole of the sea bed between a regular pattern of sounding lines, spaced to ensure that the sonar beam from one line searches at least 50 m beyond the adjacent lines either side. This ensures that all wrecks, rocks and other obstructions on the sea bed which could be a danger to navigation are located, and subsequently closely examined for the least depth over them. Side-scan sonar is best operated at a speed of 5 or 6 knots, which means that the time taken to carry out a survey to full modern standards is far longer than twenty years ago, but during the last five years almost 8 per cent of the UK continental shelf has been fully surveyed to modern standards.Our Survey Flotilla comprises eleven vessels, four Ocean Survey Ships – Heda, Hecate, Herald and Hydra; four Coastal Survey Vessels – Bulldog, Beagle, Fox and Fawn; and three Inshore Survey Craft – Egeria, Enterprise and Echo.

scholarly journals Plough Marks in the Weddell Sea

1979 ◽  
Vol 23 (89) ◽  
pp. 402-402
Author(s):  
Olav Orheim
Keyword(s):  
Continental Shelf ◽  
Weddell Sea ◽  
Side Scan Sonar ◽  
Bed Morphology ◽  
Sea Bed ◽  
Abrupt Changes ◽  
Antarctic Research

AbstractThe 1976/77 Norwegian Antarctic Research Expedition carried out studies of the sea bed by side-scan sonar. The equipment was operated from the expedition vessel down to about 350 m depth by personnel from the Continental Shelf Institute, Trondheim. Various types of plough marks mostly ranging from 10 to 100 m in width were observed. These included several generations of crossing plough marks as well as plough marks with abrupt changes in trend reflecting changing iceberg motion. The investigations will be expanded during the 1978/79 expedition to include towing at greater depths, and mapping of sea-bed morphology by mosaic towing patterns.

scholarly journals Occurrence of Gas Charged Sediments and Pock Marks in “Semob” Fields Offshore Western Niger Delta: Implications for Offshore Operations

2018 ◽  
pp. 1-12
Author(s):  
Chuku, Chibuzor H. ◽  
Odigi, Minapuye I. ◽  
Ideozu, Richmond U. ◽  
Ibe, Chidi A.
Keyword(s):  
Niger Delta ◽  
High Fidelity ◽  
Gulf Of Guinea ◽  
Sedimentary Processes ◽  
Side Scan Sonar ◽  
Sea Floor ◽  
Safe Delivery ◽  
M 10 ◽  
Sea Bed ◽  
Offshore Operations

The safe delivery of operations in offshore province is dependent on the availability of high fidelity information of the geological state of the sea floor. Sediments and sedimentary processes determine the sea bed composition and bathymetry. The study was done in the inner shelf environment of Gulf of Guinea, in Niger Delta. The acoustic equipment used is side scan sonar and sub-bottom profiler and they work with geophysical principles of sea floor sediments acoustic reflectivity and refraction. The acquisition, processing and interpretation of data reveal the existence of gas charged sediments between the sea bed and the lithified layer(strong seismo stratigraphic layer) and the existence of genetically related depressions with surrounding rings of sand called pock marks which vary between 3 m-10 m in diameter on the sea floor. The gas charged sediments thickness ranges from 20 m-25 m. The areas of the ‘Semob’ fields that have gas charged sediments and pock marks are liable to endanger the installation and safety of subsea facilities, offshore operations and sea going vessels. Therefore, are geohazards areas and should be avoided.

scholarly journals Ice-Gouging Topography of the Exposed Aral Sea Bed

2019 ◽  
Vol 11 (2) ◽  
pp. 113 ◽  
Author(s):  
Stepan Maznev ◽  
Stanislav Ogorodov ◽  
Alisa Baranskaya ◽  
Aleksey Vergun ◽  
Vasiliy Arkhipov ◽  
...  
Keyword(s):  
Aral Sea ◽  
Motion Processing ◽  
Remotely Sensed Data ◽  
Large Lakes ◽  
Side Scan Sonar ◽  
Sea Bottom ◽  
Sea Bed ◽  
Aerial Vehicle ◽  
Remote Sensing Techniques

Ice gouging, or scouring, i.e., ice impact on the seabed, is a well-studied phenomenon in high-latitude seas. In the mid-latitudes, it remains one of the major geomorphic processes in freezing seas and large lakes. Research efforts concerning its patterns, drivers and intensity are scarce, and include aerial and geophysical studies of ice scours in the Northern Caspian Sea. This study aims to explain the origin of the recently discovered linear landforms on the exposed former Aral Sea bottom using remotely sensed data. We suggest that they are relict ice gouges, analogous to the modern ice scours of the Northern Caspian, Kara and other seas and lakes, previously studied by side scan sonar (SSS) surveys. Their average dimensions, from 3 to 90 m in width and from hundreds to thousands of meters in length, and spatial distribution were derived from satellite imagery interpretation and structure from motion-processing of UAV (unmanned aerial vehicle) images. Ice scouring features are virtually omnipresent at certain seabed sections, evidencing high ice gouging intensity in mid-latitude climates. Their greatest density is observed in the central part of the former East Aral Sea. The majority of contemporary ice gouges appeared during the rapid Aral Sea level fall between 1980 and the mid-1990s. Since then, the lake has almost completely drained, providing a unique opportunity for direct studies of exposed ice gouges using both in situ and remote-sensing techniques. These data could add to our current understanding of the scales and drivers of ice impact on the bottom of shallow seas and lakes.

scholarly journals Marine geophysical methods for archaeological investigation of volcanic and bradyseismic areas

1995 ◽  
Vol 38 (5-6) ◽  
Author(s):  
F. Giordano
Keyword(s):  
Geophysical Methods ◽  
Thin Layers ◽  
Archaeological Sites ◽  
Visible Radiation ◽  
Vertical Movements ◽  
Archaeological Investigation ◽  
Side Scan Sonar ◽  
The Past ◽  
Sea Bed ◽  
Different Levels

The aim of this work was to test several geophysical methods for the identification and study of submerged prehistorical coastlines and archaeological sites. This research program was carried out in collaboration with the <<Osservatorio Vesuviano>> in the Gulf of Pozzuoli and dealt in particular with the bathymetric strips extending from - 5 m to - 50 m Within these strips we identified the coastline dating from the Rornan period. former beach boundaries associated with the vertical movements of the earth's surface caused by seismic-volcanic activity, and the variations in sea level following the climactic changes throughout the last 15000 years. The UNIBOOM system was used for this part of the programme, perinittiilg the identification of several coastlines and submerged beaches lying at different levels. The use of a modern Side Scan Sonar - for the morphological invesdgation of the sea bed - in a zone which had been the object of numerous archaeological surveys in the past, permitted previously unknown structures near the Lacuus Baianus to be identified. Other features worth pointing out include the operating speed of the system (15000 m'lfirst minute approx) and its observation capacity in cloudy waters compared to visible radiation, as well as its ability to penetrate thin layers of mud which generally impede direct underwater observation.

scholarly journals Geology of outer Horns Rev, Danish North Sea

2008 ◽  
Vol 15 ◽  
pp. 41-44
Author(s):  
Jørn Bo Jensen ◽  
Peter Gravesen ◽  
Steen Lomholt
Keyword(s):  
North Sea ◽  
Wind Farm ◽  
Offshore Wind ◽  
Side Scan Sonar ◽  
Cone Penetration Tests ◽  
The North ◽  
Complex Information ◽  
Sea Bottom ◽  
Sea Bed ◽  
The North Sea

In 2006, Dong Energy initiated the development of the Horns Rev II offshore wind farm in the North Sea (Fig. 1). In order to evaluate and map the characteristics of the surface features of the sea bed and to characterise the subsurface in the wind farm area, the Geological Survey of Denmark and Greenland (GEUS) conducted a geophysical survey of the area. The survey utilised a variety of instruments: sparker, side-scan sonar, marine caesium magnetometer and a multibeam echo-sounder. In addition, information on the subsurface sediments was obtained by cone penetration tests (CPT) and by drilling to 30–50 m below the sea bottom. Geological correlation of the CPT results with the other survey results was extremely complicated but was required in order to understand the architecture of the ice marginal glaciotectonic complex. Information on the geology is crucial for evaluation of the geotechnical problems of the region.

Image formation analysis of thick biological specimens using three-dimensional power-spectra of through focus series

1994 ◽  
Vol 52 ◽  
pp. 124-125
Author(s):  
Karen F. Han
Keyword(s):  
Inelastic Scattering ◽  
Imaging Techniques ◽  
Mass Density ◽  
Relative Proportion ◽  
Three Dimensional ◽  
Power Spectra ◽  
Image Formation ◽  
Energy Filtering ◽  
Ewald Sphere ◽  
Nonlinear Imaging

The primary focus in our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the deconstruction of an object by combining multiple projection views of the object at different tilt angles, image intensities are not always accurate representations of the projected object mass density, due to the effects of electron-specimen interactions and microscope lens aberrations. Therefore, an understanding of the mechanism of image formation is important for interpreting the images. The image formation for thick biological specimens has been analyzed by using both energy filtering and Ewald sphere constructions. Surprisingly, there is a significant amount of coherent transfer for our thick specimens. The relative amount of coherent transfer is correlated with the relative proportion of elastically scattered electrons using electron energy loss spectoscopy and imaging techniques.Electron-specimen interactions include single and multiple, elastic and inelastic scattering. Multiple and inelastic scattering events give rise to nonlinear imaging effects which complicates the interpretation of collected images.

Log-log scale roughness spectroscopy of surfaces

1993 ◽  
Vol 51 ◽  
pp. 224-225
Author(s):  
P. Fraundorf ◽  
B. Armbruster
Keyword(s):  
Power Spectrum ◽  
Autocorrelation Function ◽  
Power Spectra ◽  
Scanning Force Microscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Scanning Force ◽  
Lateral Structure ◽  
Scale Roughness

Optical interferometry, confocal light microscopy, stereopair scanning electron microscopy, scanning tunneling microscopy, and scanning force microscopy, can produce topographic images of surfaces on size scales reaching from centimeters to Angstroms. Second moment (height variance) statistics of surface topography can be very helpful in quantifying “visually suggested” differences from one surface to the next. The two most common methods for displaying this information are the Fourier power spectrum and its direct space transform, the autocorrelation function or interferogram. Unfortunately, for a surface exhibiting lateral structure over several orders of magnitude in size, both the power spectrum and the autocorrelation function will find most of the information they contain pressed into the plot’s origin. This suggests that we plot power in units of LOG(frequency)≡-LOG(period), but rather than add this logarithmic constraint as another element of abstraction to the analysis of power spectra, we further recommend a shift in paradigm.

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