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oceanS

作者： C. Roman H. Singh MIT/WHOI Joint Program in Applied Ocean Science and Engineering Massachusetts Institute of Technology Cambridge MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA

This work focuses on the creation of high resolution micro-bathymetric maps using a high frequency pencil beam sonar. These maps typically cover areas of 10's to 100's of square meters. Data is collected using a sonar mounted to an underwater vehicle that can be positioned at discrete locations on the sea floor or flown in a survey pattern above the bottom. Specifically, we are focused on improving the accuracy of these terrain maps by merging sonar pings taken from multiple vantage points over the same location. This requires the adaption of data registration techniques to handle errors related to the sonar sensor. The registration can also be modified to incorporate the navigation data available from an instrumented underwater vehicle. A two axis scanning sonar was used to gather data in the form of densely sampled range images. The data registration works on the 3D projection of these range images in a scan-matching manner. Through this process regions occluded in a single scan are filled with data available from other scans and individual pings which show a poor return are removed. Refined estimates of the scan vantage points are also generated during the registration. The initial estimates of these locations are provided by navigation data. The practical application of this work complements photographic mapping when visibility is limited. It also provides additional measurements which can be used to improve vehicle navigation.

关键词： Sonar navigation Sonar measurements Remotely operated vehicles Underwater vehicles Sea floor Underwater acoustics Layout oceans Acoustical engineering Acoustic beams

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The abundance and localization of environmental microplastics in gastrointestinal tract and muscle of Atlantic killifish (Fundulus heteroclitus): a pilot study

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Microplastics and Nanoplastics 2024年第1期4卷 23页

作者： Pitt, Jordan A. Gallager, Scott M. Youngs, Sarah Michel, Anna P. M. Hahn, Mark E. Aluru, Neelakanteswar Biology Department Woods Hole Oceanographic Institution Woods Hole 02543 MA United States Massachusetts Institute of Technology (MIT) – Woods Hole Oceanographic Institution (WHOI) Joint Graduate Program in Oceanography and Oceanographic Engineering Woods Hole 02543 MA United States CoastalOceanVision Inc 10 Edgerton Drive North Falmouth 02556 MA United States Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole 02543 MA United States

Microplastics (MPs) have been found in a diverse range of organisms across trophic levels. While a majority of the information on organismal exposure to plastics in the environment comes from gastrointestinal (GI) data, the prevalence of MP particles in other tissues is not well understood. Additionally, many studies have not been able to detect the smallest, most prevalent, MPs (1 µm – 5 mm) that are the most likely to distribute to tissues in the body. To address these knowledge gaps, MPs in the GI tract and muscle of Atlantic killifish (Fundulus heteroclitus) collected from two sites (Falmouth and Bourne) on Buzzards Bay, Cape Cod, MA were quantified down to 2 µm in size. Eight fish from Falmouth and 10 fish Bourne site were analyzed. Fourier-transform infrared spectroscopy and Raman spectroscopy were used to identify all particles. The mean concentrations of MPs in the GI tract and muscle from fish collected from Falmouth was 85.5 ± 70.2 and 11 ± 12.5 particles per gram wet weight, respectively. Fish collected from Bourne site had mean particle concentrations of 12.2 ± 18.1 and 1.69 ± 5.36 particles per gram wet weight. Of the 2,008 particles analyzed in various fish tissue samples, only 3.4% (69 particles) were identified as plastic;polymers included nylon, polyethylene, polypropylene, and polyurethane. MPs detected in the GI tract samples also tended to be more diverse in both size and polymer type than those found in the muscle. We found that MPs < 50 µm, which are often not analyzed in the literature, were the most common in both the GI tract and muscle samples. There was not a significant correlation between the MP content in the muscle compared to the GI tract, indicating that GI tract MP abundance cannot be used to predict non-GI tract tissue MP content;however, MP abundance in muscle correlated with fish total length, suggesting potential bioaccumulation of these small MPs. © The Author(s) 2024.

关键词： Bioaccumulation Fish Fourier-transform infrared spectroscopy Microplastics Raman spectroscopy Translocation

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Tunable Diode Laser Absorption Spectroscopy Instrument for Flow-Through Measurement of Dissolved Carbon Dioxide in the ocean

Tunable Diode Laser Absorption Spectroscopy Instrument for F...

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Conference on Lasers and Electro-Optics (CLEO)

作者： Beckett Colson Anna P. M. Michel Woods Hole Oceanographic Institution Woods Hole MA USA Massachusetts Institute of Technology Cambridge MA USA MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge and Woods Hole MA USA

The measurement of dissolved carbon dioxide is important for understanding many ocean processes. Here we present the design and field deployment of a TDLAS sensor for the measurement of dissolved carbon dioxide.

ISBN: (纸本)9781943580910

关键词： Spectroscopy Semiconductor lasers oceans Instruments Sea measurements Measurement by laser beam Carbon dioxide

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Adaptive multi-altitude search and sampling of sparsely distributed natural phenomena

Adaptive multi-altitude search and sampling of sparsely dist...

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IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)

作者： Jessica E. Todd Seth McCammon Yogesh Girdhar Nicholas Roy Dana Yoerger Department of Aeronautics and Astronautics MIT-WHOI Joint Program in Applied Ocean Science and Engineering at the Woods Hole Oceanographic Institution (WHOI) Massachusetts Institute of Technology (MIT) Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution Woods Hole MA USA Department of Aeronautics and Astronautics Massachusetts Institute of Technology

ISBN: (数字)9798350377705

ISBN: (纸本)9798350377712

In this paper, we propose a novel method for autonomously seeking out sparsely distributed targets in an unknown underwater environment. Our Sparse Adaptive Search and Sample (SASS) algorithm mixes low-altitude observations of discrete targets with high-altitude observations of the surrounding substrates. By using prior information about the distribution of targets across substrate types in combination with belief modelling over these substrates in the environment, high-altitude observations provide information that allows SASS to quickly guide the robot to areas with high target densities. A maximally informative path is autonomously constructed online using Monte Carlo Tree Search with a novel acquisition function to guide the search to maximise observations of unique targets. We demonstrate our approach in a set of simulated trials using a novel generative species model. SASS consistently outperforms the canonical boustrophedon planner by up to 36% in seeking out unique targets in the first 75-90% of time it takes for a boustrophedon survey. Additionally, we verify the performance of SASS on two real world coral reef datasets.

关键词： Surveys Adaptation models Monte Carlo methods Adaptive systems Marine vegetation Substrates Intelligent robots

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Coherent source direction estimation for three-row bathymetric sidescan sonars

Coherent source direction estimation for three-row bathymetr...

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oceanS

作者： Wen Xu W.K. Stewart MIT/WHOI Joint Program in Applied Ocean Physics and Engineering Cambridge MA USA Virtual Marine Associates Inc. Fort Pierce FL USA

In practical applications with bathymetric sidescan sonar, the multipath reflection and other directional interferences are the key limiting factors for a better performance. To deal with this problem, a multiple-row system can be used to resolve the multipath reflections from the direct signal instead of smoothing the measurements over some time and/or angle intervals as previously widely investigated. However, most current algorithms for signal direction-of-arrival estimation fail when the sources from different directions are coherent, which often occurs in a shallow water multipath environment. In the context of three-row bathymetric sidescan sonars, this paper proposes a coherent source direction estimator (CSDE) to resolve two sources from different directions. This method is compared with the ESPRIT-based approach using different sonar data models. The simulations show that CSDE works very well for highly coherent sources at the angular separation of 10/spl deg/ between two sources and at the signal-to-noise ratio above 10 dB while the ESPRIT-based method is quite robust for the incoherent source signal model. In addition, CSDE gives the source time series estimation on the basis of the direction estimation as well. Analyses to the interference field associated with the sidescan sonar show that a model with two or three simultaneously received signals describes even some shallow water fields very well. These preliminary results suggest that the combination of above two approaches could replace the currently used differential phase technique to get a better performance in shallow water without significant increase of the system cost.

关键词： Sonar measurements Reflection Interference Signal resolution Sonar applications Smoothing methods Time measurement Direction of arrival estimation Water resources Data models

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Dead reckoning through the water column with an acoustic Doppler current profiler: Field experiences

Dead reckoning through the water column with an acoustic Dop...

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oceanS

作者： M Jordan Stanway Joint Program in Oceanography Massachusetts Institute of Technology USA Applied Ocean Science and Engineering Woods Hole Oceanographic Institution USA

Underwater vehicles currently rely on external acoustic tracking systems to estimate position when away from the surface or the seafloor. Many vehicles dead reckon near the seafloor using a Doppler velocity log. This paper presents a method for dead reckoning through the water column using over-lapping water profiles measured by a vehicle-mounted acoustic Doppler current profiler. Under mild assumptions, the vehicle can simultaneously estimate its own global velocity at the same time as identifying the ocean current profile. The estimation problem is solved using batch least squares, recursive least squares, or a simple online depth bin averaging scheme. We discuss challenges encountered in implementing the approach during three field deployments of the autonomous underwater vehicle Sentry, and provide estimates of the ocean current, the vehicle velocity, and integrated position.

关键词： Vehicles Sea measurements Current measurement oceans Navigation Velocity measurement Instruments

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Exactly Sparse Delayed-State Filters

Exactly Sparse Delayed-State Filters

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IEEE International Conference on Robotics and Automation (ICRA)

作者： R.M. Eustice H. Singh J.J. Leonard MIT/WHOI Joint Program in Applied Ocean Science and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole MA USA Department of Ocean Engineering Massachusetts Institute of Technology Cambridge MA USA

This paper presents the novel insight that the SLAM information matrix is exactly sparse in a delayed-state framework. Such a framework is used in view-based representations of the environment which rely upon scan-matching raw sensor data. Scan-matching raw data results in virtual observations of robot motion with respect to a place its previously been. The exact sparseness of the delayed-state information matrix is in contrast to other recent feature based SLAM information algorithms like Sparse Extended Information Filters or Thin Junction Tree Filters. These methods have to make approximations in order to force the feature-based SLAM information matrix to be sparse. The benefit of the exact sparseness of the delayed-state framework is that it allows one to take advantage of the information space parameterization without having to make any approximations. Therefore, it can produce equivalent results to the “full-covariance” solution.

关键词： Delay Simultaneous localization and mapping Navigation Cameras oceans Information filters Sparse matrices Information filtering Remotely operated vehicles Robot vision systems

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Temporal and spatial variability in vessel noise on tropical coral reefs 4

Temporal and spatial variability in vessel noise on tropical...

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4th International Conference on the Effects of Noise on Aquatic Life 2016

作者： Kaplan, Maxwell B. Mooney, T. Aran Lammers, Marc O. Zang, Eden Massachusetts Institute of Technology Woods Hole Oceanographic Institution Joint Program in Oceanography Applied Ocean Science and Engineering CambridgeMA United States Biology Department Woods Hole Oceanographic Institution Woods HoleMA United States Hawaii Institute of Marine Biology KaneoheHI United States Oceanwide Science Institute HonoluluHI United States

Coral reef soundscapes are dynamic, demonstrating amplitude and spectral variability across timescales from seconds to seasons. Some of this variability can result from spatiotemporally heterogeneous patterns of human activity. To characterize this variability and the extent to which anthropogenic sound can modify the biological soundscape, seven Hawaiian reefs were equipped with acoustic recorders operating on a 10% duty cycle for 16 months. Spatially, vessel activity was acoustically detected unevenly across reefs;for example, vessels were acoustically present almost every day at a popular snorkeling reef but were rare in a protected area closed to boats, which indicates that exposure of reef fauna to vessel noise will vary by reef. Temporally, vessel activity was most likely to occur during daylight hours, which is consistent with patterns of human activity. This heterogeneity in exposure could have implications for physiology and behavior and underscores the need for long-term acoustic monitoring alongside more targeted studies investigating the potential for effects of noise on aquatic organisms. © 2016 Acoustical Society of America.

关键词： Reefs

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Enabling Under-Ice Geochemical Observations with a Size, Weight, and Power-Constrained Robot

arXiv

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arXiv 2022年

作者： Horowitz, Jess Preston, Victoria Michel, Anna P.M. Mechanical Engineering Massachusetts Institute of Technology Cambridge United States MIT-WHOI Joint Program Massachussetts Institute of Technology Cambridge United States Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution Woods Hole United States

Estimates of greenhouse gas emissions from Arctic estuarine environments are dominated by in situ summer-time ice-free dissolved gas measurements due to the logistical ease of performing field observations in these conditions. Recent evidence in coastal Arctic environments, however, has demonstrated that dissolved methane (CH4) and carbon dioxide (CO2) are strongly seasonally variable, and at least one significant gas ventilation event occurs during the spring freshet. Whether the Arctic serves as a source or sink of greenhouse emissions has significant implications on modeling climate change and its feedback mechanisms. To enable higher resolution spatiotemporal measurements of dissolved gases in typically undersampled conditions, remotely operated vehicles (ROVs) can be used to extract near continuous water samples below ice before and during the spring freshet. Here, we present a size, weight, and power-constrained (SWAP) underwater vehicle (UV) and novel geochemical sampling system suitable for taking under-ice geochemical observations and demonstrate the proposed system in a field-analog setting for Arctic estuarine studies. Copyright © 2022, The Authors. All rights reserved.

关键词： Carbon dioxide

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Tracking Sargassum in the Caribbean: The Deployment and Validation of a Low-Cost Surface Drifter

SSRN

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SSRN 2023年

作者： Pixa, Chase Manganini, Kevin Myers, Alyson Michel, Anna P.M. Department of Applied Ocean Physics and Engineering Woods Hole Oceanographic Institution 266 Woods Hole Road Woods HoleMA02543 United States Department of Mechanical Engineering Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering Cambridge and Woods Hole MA United States Fearless Fund 3029 Woodland Drive NW WashingtonDC20008 United States

Sargassum blooms have been causing significant ecological and economic damage to coastal regions in the Northern Equatorial Atlantic since 2011. To better understand the movement and effects of this macroalgae, there is a need to track its transport. In this study, a low-cost drifter was deployed, designed to entangle with Sargassum and aid in its tracking. The design was based on the results of twenty-seven drifter designs and five days of field trials. The tracking data was validated using gridded wind and current products, as well as high resolution satellite imagery. The successful entanglement and tracking with the Sargassum demonstrated in this study can provide in situ movement data to ground-truth models and supplement gaps in satellite imaging. The results can guide future studies and further our understanding of its movement in the great Atlantic Sargassum belt (GASB). © 2023, The Authors. All rights reserved.

关键词： Costs

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