Thein M.-W.L.,Center for Ocean Engineering |
Celikkol B.,Center for Ocean Engineering |
Pe'Eri S.,Center for Coastal and Ocean Mapping |
Decew J.,Center for Ocean Engineering
OCEANS 2012 MTS/IEEE: Harnessing the Power of the Ocean | Year: 2012
This paper proposes an optical detection system between a leader and a follower Unmanned Underwater Vehicle, specifically Remotely Operated Vehicles (ROVs). Cost efficient photodetectors and a single LED light source are used to develop distance detection algorithms to detect translational motion in x-and y-axis directions. Analytical simulations are performed where light is modeled as a first order Gaussian function and integrated into the nonlinear ROV dynamics. The stability of a proportional derivative (PD) controller is shown via Lyapunov stability, as in Fossen . Both leader and follower ROV motions are simulated and experimental results from the distance detection algorithm are shown for proof of concept. In this stage of research, all experiments are performed out of water. Initial results indicate that the proposed detection system shows promise as a precursor stage to underwater testing. © 2012 IEEE.
Lin Y.-T.,Woods Hole Oceanographic Institution |
Duda T.F.,Woods Hole Oceanographic Institution |
Emerson C.,Ocean Acoustical Services and Instrumentation Systems |
Gawarkiewicz G.,Woods Hole Oceanographic Institution |
And 7 more authors.
IEEE Journal of Oceanic Engineering | Year: 2015
A study of sound propagation over a submarine canyon northeast of Taiwan was made using mobile acoustic sources during a joint ocean acoustic and physical oceanographic experiment in 2009. The acoustic signal levels (equivalently, transmission losses) are reported here, and numerical models of 3-D sound propagation are employed to explain the underlying physics. The data show a significant decrease in sound intensity as the source crossed over the canyon, and the numerical model provides a physical insight into this effect. In addition, the model also suggests that reflection from the canyon seabed causes 3-D sound focusing when the direction of propagation is along the canyon axis, which remains to be validated in a future experiment. Environmental uncertainties of water sound speed, bottom geoacoustic properties, and bathymetry are addressed, and the implications for sound propagation prediction in a complex submarine canyon environment are also discussed. © 1976-2012 IEEE.
Michael Jech J.,National Oceanic and Atmospheric Administration |
Price V.,Center for Coastal and Ocean Mapping |
Chavez-Rosales S.,Integrated Statistics |
Michaels W.,National Oceanic and Atmospheric Administration
Journal of Northwest Atlantic Fishery Science | Year: 2015
Atlantic herring (Clupea harengus) in the Georges Bank, Gulf of Maine, and southern New England regions were sampled from early September into mid-November by the Northeast Fisheries Science Center during their annual randomly-stratified bottom trawl and systematic acoustic/midwater trawl surveys. Atlantic herring were randomly selected for length distributions and systematically subsampled for biological metrics (e.g., weight, age, maturity, and sex). Broad similarities in Atlantic herring biological metrics between midwater and bottom trawl catches suggest both gear types provide comparable sampling of herring demographics in the Gulf of Maine and Georges Bank regions during autumn. Annual mean lengths and weights and temporal patterns of herring size were consistently similar between gear types. Similarity in age structure between Georges Bank and the Gulf of Maine suggest a similar response to intrinsic and extrinsic factors between herring stocks in these regions, but apparent asynchrony in spawning timing suggests some level of independence between these stocks. Overall similarities can mask interesting distinctions such as midwater trawls seem to sample younger, smaller, but heavier fish than do bottom trawls. Sampling of historical spawning sites appears to characterize the biological state of Atlantic herring in the Georges Bank region and could be utilized to design an efficient sampling scheme for Atlantic herring in the Gulf of Maine. © 2015, Northwest Atlantic Fisheries Organization. All rights reserved.
Masetti G.,Center for Coastal and Ocean Mapping |
Calder B.,Center for Coastal and Ocean Mapping
Environment Systems and Decisions | Year: 2014
An increasing availability of geospatial marine data provides an opportunity for hydrographic agencies to contribute to the identification of potentially polluting marine sites (PPMS). This new acronym has been created not only to refer to shipwrecks of modern vessels, but also for other types of marine sites such as dumping areas, pipelines, etc. Independent of the specific type, a PPMS represents a potential source of pollution for the marine environment. Although several type-specific databases are available worldwide (from local to global scale), there is an evident lack of uniformity (e.g., different aims of data collection). A common approach description of these sites at local single-site level may permit aggregation for multi-scale decisions, e.g., for remediation and incident response. To adequately manage these sites, a standardized PPMS geospatial database (GeoDB) application has been designed to collect relevant information suitable for site inventory and geo-spatial analysis. In particular, benefits in structuring the data in conformance with the Universal Hydrographic Data Model (IHO S-100) and encoding using the Geographic Markup Language (GML) are presented. A possible practical storage solution is proposed using a GML-enabled spatial relational database management system. Finally, a Web GIS deployment is illustrated, being the simplest way to communicate to the public the collected information, with the related possibility of using the data as a Web Map Service in almost any GIS, allowing for better development and integration with other available datasets. The adoption of the PPMS GeoDB product specification as part of the IHO S-100 series would represent an innovative and important contribution from the hydrographic community to reduce, or at least better manage, environmental and economic risks related to PPMSs. © 2013 Springer Science+Business Media New York.