scholarly journals Limitations of Boulder Detection in Shallow Water Habitats Using High-Resolution Sidescan Sonar Images

Geosciences ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 390 ◽  
Author(s):  
Rönn ◽  
Schwarzer ◽  
Reimers ◽  
Winter
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Distribution Patterns ◽  
Sidescan Sonar ◽  
Shallow Waters ◽  
Benthic Species ◽  
Pixel Resolution ◽  
Form Complex ◽  
Sonar Images ◽  
Different Levels

Stones and boulders in shallow waters (0–10 m water depth) form complex geo-habitats, serving as a hardground for many benthic species, and are important contributors to coastal biodiversity and high benthic production. This study focuses on limitations in stone and boulder detection using high-resolution sidescan sonar images in shallow water environments of the southwestern Baltic Sea. Observations were carried out using sidescan sonars operating with frequencies from 450 kHz up to 1 MHz to identify individual stones and boulders within different levels of resolution. In addition, sidescan sonar images were generated using varying survey directions for an assessment of range effects. The comparison of images of different resolutions reveals considerable discrepancies in the numbers of detectable stones and boulders, and in their distribution patterns. Results on the detection of individual stones and boulders at approximately 0.04 m/pixel resolution were compared to common discretizations: it was shown that image resolutions of 0.2 m/pixel may underestimate available hard-ground settlement space by up to 42%. If methodological constraints are known and considered, detailed information about individual stones and boulders, and potential settlement space for marine organisms, can be derived.

High-resolution sidescan-sonar imagery of the Manchas Interiores-Manchas Exteriores coral reef complex, Mayaguez, Puerto Rico

1992 ◽  
Author(s):  
William C. Schwab ◽  
R.M. Webb ◽  
W.W. Danforth ◽  
T.F. O'Brien ◽  
B.J. Irwin
Keyword(s):  
Puerto Rico ◽  
Coral Reef ◽  
High Resolution ◽  
Sidescan Sonar ◽  
Reef Complex

Experimental Study of a Tanker Ship Squat in Shallow Water

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
Mohammadreza Fathi Kazerooni ◽  
Mohammad Saeed Seif
Keyword(s):  
Experimental Study ◽  
Shallow Water ◽  
Experimental Approach ◽  
Model Tests ◽  
Ship Hull ◽  
Experimental Results ◽  
Shallow Waters ◽  
Towing Tank ◽  
Ship Model

One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained.

scholarly journals Shallow water seagrass observed by high resolution full waveform bathymetric LiDAR

2014 ◽  
Author(s):  
Zhigang Pan ◽  
Juan Carlos Fernandez-Diaz ◽  
Craig L. Glennie ◽  
Michael Starek
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Full Waveform

High-resolution 3D marine seismic acquisition and imaging in shallow waters: Application to shallow fault detection, Beppu-Bay, Japan

2021 ◽  
Author(s):  
Yosuke Teranishi ◽  
Fumitoshi Murakami ◽  
Shinji Kawasaki ◽  
Motonori Higashinaka ◽  
Kei Konno ◽  
...  
Keyword(s):  
High Resolution ◽  
Fault Detection ◽  
Shallow Waters ◽  
Seismic Acquisition ◽  
Marine Seismic

scholarly journals AN INTEGRATED PHOTOGRAMMETRIC AND PHOTOCLINOMETRIC APPROACH FOR PIXEL-RESOLUTION 3D MODELLING OF LUNAR SURFACE

2018 ◽  
Vol XLII-3 ◽  
pp. 1117-1122
Author(s):  
W. C. Liu ◽  
B. Wu
Keyword(s):  
High Resolution ◽  
Lunar Surface ◽  
Image Matching ◽  
Point Cloud ◽  
3D Modelling ◽  
Conjugate Points ◽  
Stereo Pair ◽  
Pixel Resolution ◽  
Dense Image ◽  
Lunar Reconnaissance Orbiter

High-resolution 3D modelling of lunar surface is important for lunar scientific research and exploration missions. Photogrammetry is known for 3D mapping and modelling from a pair of stereo images based on dense image matching. However dense matching may fail in poorly textured areas and in situations when the image pair has large illumination differences. As a result, the actual achievable spatial resolution of the 3D model from photogrammetry is limited by the performance of dense image matching. On the other hand, photoclinometry (i.e., shape from shading) is characterised by its ability to recover pixel-wise surface shapes based on image intensity and imaging conditions such as illumination and viewing directions. More robust shape reconstruction through photoclinometry can be achieved by incorporating images acquired under different illumination conditions (i.e., photometric stereo). Introducing photoclinometry into photogrammetric processing can therefore effectively increase the achievable resolution of the mapping result while maintaining its overall accuracy. This research presents an integrated photogrammetric and photoclinometric approach for pixel-resolution 3D modelling of the lunar surface. First, photoclinometry is interacted with stereo image matching to create robust and spatially well distributed dense conjugate points. Then, based on the 3D point cloud derived from photogrammetric processing of the dense conjugate points, photoclinometry is further introduced to derive the 3D positions of the unmatched points and to refine the final point cloud. The approach is able to produce one 3D point for each image pixel within the overlapping area of the stereo pair so that to obtain pixel-resolution 3D models. Experiments using the Lunar Reconnaissance Orbiter Camera - Narrow Angle Camera (LROC NAC) images show the superior performances of the approach compared with traditional photogrammetric technique. The results and findings from this research contribute to optimal exploitation of image information for high-resolution 3D modelling of the lunar surface, which is of significance for the advancement of lunar and planetary mapping.

MODELING MOVING BOUNDARY IN SHALLOW WATER BY LBM

2013 ◽  
Vol 24 (01) ◽  
pp. 1250094 ◽  
Author(s):  
Y. PENG ◽  
J. G. ZHOU ◽  
J. M. ZHANG ◽  
R. BURROWS
Keyword(s):  
Shallow Water ◽  
Present Model ◽  
Moving Boundary ◽  
Lattice Boltzmann Model ◽  
Shallow Waters ◽  
Shallow Water Flows ◽  
Moving Body ◽  
Body Boundary ◽  
Multiple Relaxation Time ◽  
Boltzmann Model

A lattice Boltzmann model (LBM) for a moving body in shallow waters is developed. Three different schemes, FH's, Guo's and MMP's schemes, for a curved boundary condition at second-order accuracy are used in the study and compared in detail. The multiple-relaxation-time (MRT) is adopted for better stability. In order to deal with the moving body boundary, a certain momentum is added to reflect the interaction between the fluid and the solid; and a refill method for new wetted nodes moving out from solid nodes has been proposed. The described method is applied to simulate static and moving cylinders in shallow waters. The corresponding experiments are further performed for validation of the present model. It is found that all of the three schemes produce similar results that agree well with the experimental data for the static cylinder. However, for the moving boundary, MMP's scheme performs best. Overall, the proposed modeling approach is able to simulate both, static and moving cylinders in shallow water flows at acceptable accuracy.

Quantification of Bioerosion by Sphaerechinus Granularis on ‘Coralugène’ Concretions of the Western Mediterranean

1997 ◽  
Vol 77 (2) ◽  
pp. 565-568 ◽  
Author(s):  
Stephane Sartoretto ◽  
Patrice Francour
Keyword(s):  
Shallow Water ◽  
Small Diameter ◽  
Western Mediterranean ◽  
Biological Agent ◽  
High Abundance ◽  
Shallow Waters ◽  
Mean Diameter ◽  
The Mean ◽  
The Mediterranean

Sphaerechinus granularis (Echinodermata: Echinidea) is involved in the erosion of ‘coralligène’ concretions in the Mediterranean. In shallow water (10 m), a high abundance of this species (>20 ind 25 m−2) is associated with small diameter individuals (56·7 ±7·7 mm). In deep clean waters (>40 m), the abundance is lower (<1 ind 25 m−2) and the mean diameter is higher (86·0±9·3 mm). Daily erosion of Corallinaceae by this species is related to the urchin diameter (r=0.87). Local variations in urchin abundance and diameter influence the amount of CaCO3 eroded annually. In shallow waters, the eroded CaCO3 mass reaches 210 g m−2 y−1 vs 16 g m−2 y−1 in coralligène concretions in deep clean waters. Sphaerechinus granularis is an important biological agent which substantially erodes the Mediterranean coralligène concretions.

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