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Oceanic Engineering, IEEE Journal of

Issue 1 • Date Jan. 2011

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Displaying Results 1 - 18 of 18
  • Table of contents

    Publication Year: 2011 , Page(s): C1
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  • IEEE Journal of Oceanic Engineering publication information

    Publication Year: 2011 , Page(s): C2
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  • Bayesian Inversion of Interface-Wave Dispersion for Seabed Shear-Wave Speed Profiles

    Publication Year: 2011 , Page(s): 1 - 11
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (952 KB) |  | HTML iconHTML  

    This paper applies Bayesian inversion to estimate seabed shear-wave speed profiles and their uncertainties from interface-wave dispersion data. A nonlinear formulation is developed to estimate the most probable profile together with marginal probability distributions and credibility intervals from the posterior probability density (PPD) using adaptive hybrid optimization and Metropolis-Hastings sampling (MHS). To address correlated data errors, a full error covariance matrix is estimated from residual analysis, and rigorous a posteriori statistical tests are applied to validate the covariance estimate and the assumption of a multivariate Gaussian error distribution. The most appropriate parameterization for the shear-wave speed profile is determined using the Bayesian information criterion (BIC), which provides the simplest model consistent with the resolving power of the data. Parameterizations considered vary in the number and type of layers, and include layers with uniform speed, and with linear and power-law shear-speed gradients. For the data considered here, a power-law parameterization is indicated, which is consistent with theoretical expectations for uniform, unconsolidated sediments under overburden pressure. The maximum depth to which the dispersion data constrain the shear-speed profile is investigated using an approximate analytic formula for power-law profiles and repeated inversions in which the maximum depth to an underlying half-space is systematically increased. View full abstract»

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  • Volumetric Reconstruction of Oceanographic Fields Estimated From Remote Sensing and In Situ Observations From Autonomous Underwater Vehicles of Opportunity

    Publication Year: 2011 , Page(s): 12 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1995 KB) |  | HTML iconHTML  

    A main challenge of military oceanography (MILOC) is to assess the oceanographic conditions of denied/high-risk marine regions. Monitoring technologies are limited to those that can provide access to these regions. Remote sensing and autonomous underwater vehicles (AUVs) can support MILOC requirements. Unfortunately, the environmental information gathered by these technologies is not complete: remote sensing provides information about some surface conditions and water-column integrated variables, whereas operational priorities often constrain AUVs use during real crisis situations to missions with higher priority than environmental assessment. Under this scenario, data fusion techniques to maximize the information of the collected data are essential. This paper attempts to reconstruct thermal fields fusing data gathered by remote sensing platforms and AUVs performing missions not specifically designed for environmental data collection. The technique estimates the state that maximizes the posterior probability subjected to some smoothing constraints. A variational methodology allows remote sensing information to serve as boundary constraints. The approach uses 3-D finite elements to solve the maximization problem. The procedure investigated has been tested with different smoothing constraints in a simulated environment and in a real field experiment conducted by the Muscle AUV in the Gulf of Riga (Baltic Sea) on April 19, 2008. Results highlight the relevance of incorporating the surface information provided by remote sensors into the estimation. View full abstract»

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  • Experimental Results of Passive Imaging of Moving Continuous Broadband Sound Sources Within a Sensor Field

    Publication Year: 2011 , Page(s): 25 - 36
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4008 KB) |  | HTML iconHTML  

    Sparsely distributed sensors or sparse arrays can be associated with high positional accuracy and capability for large area surveillance. This paper shows, both through simulations and with real measurement data, that sparse sensor systems can be used to accomplish high-performance underwater surveillance. The paper focuses on measurement setups with several passive single hydrophones placed hundreds of meters apart in a water depth of dozen of meters. By such a setup, a sound source is more likely to move inside the array, and thus near-field processing can be considered. The sensor pairs will also be located in different directions in relation to the sound source. These two prerequisites give the possibilities to high spatial resolution. Images of the coherent sound activity for different sensor pairs are formed, and every sensor pair map is summarized into a resulting map. In this way, an arbitrary number of sound sources of a target can be resolved. Good correlation results are shown even when the sound sources are at the same distance as the baseline of the sensor pairs. This is achieved by Doppler compensating for target movement and also by whitening of the cross spectra. The analyses of the measurements also show that baseline-dependent bandwidth can improve the results. In this paper, it is indicated from experimental data that two propeller sound sources could be resolved, and in another measurement setup, the engine could be separated from the propellers. View full abstract»

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  • Coherence-Based Underwater Target Detection From Multiple Disparate Sonar Platforms

    Publication Year: 2011 , Page(s): 37 - 51
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1124 KB) |  | HTML iconHTML  

    This paper explores the use of multichannel coherence as a tool for detection of underwater targets from imagery captured from multiple disparate sonar systems. The use of multiple disparate sonars allows one to exploit a high-resolution sonar with good target definition while taking advantage of the clutter suppression abilities of a low-resolution broadband (BB) sonar coregistered over the same region to provide much better detection performance comparing to those of the single-sonar cases. In this paper, the standard Neyman-Pearson detector is extended to the dual disparate sonar case allowing target detection across two sensory channels simultaneously. A novel distributed detection system is also developed that exploits the use of multiple dual-sonar detectors for multiplatform target detection. Test results of the proposed detection methods are also presented on an underwater synthetic aperture sonar (SAS) imagery database containing data from three different imaging sonars operating at three different frequencies and resolutions. Test results illustrating the effectiveness of different coherent-based detection systems will be presented and benchmarked against those of two other detection methods in terms of probability of detection, false alarm rate, and the receiver operating characteristic (ROC) curve. Performance gains of about 23% in probability of detection were achieved over the benchmarked methods. View full abstract»

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  • False-Alarm Reduction for Low-Frequency Active Sonar With BPSK Pulses: Experimental Results

    Publication Year: 2011 , Page(s): 52 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (989 KB) |  | HTML iconHTML  

    In the last two decades, low-frequency active sonar (LFAS) emerged as one of the most efficient tools for shallow-water antisubmarine warfare (ASW). Like any long-range active sonar system, LFAS produces a large amount of unwanted sea bottom echoes or clutter. These echoes give way to false alarms that increase the computational load of target trackers and delay the correct classification of each echo. The number of false alarms due to clutter can be reduced either through echo classification techniques or through Doppler filtering provided the targets of interest have a nonzero radial velocity. Much research has been carried out on waveform investigation for the efficient use of bandwidth capabilities of modern sonar transmitters. Among the quantity of waveforms, binary phase-shift keyed (BPSK) pulses have emerged as exhibiting cross-correlation properties relevant to Doppler filtering while maintaining a range resolution comparable to frequency-modulated (FM) pulses. In this paper, we have successfully applied a false-alarm reduction technique using contacts obtained with an FM pulse subsequently processed by Doppler filtering with a BPSK pulse. The Doppler filtering performance for this pulse is evaluated on an experimental data set and a few limitations of BPSK are identified. View full abstract»

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  • Time-Reversal Detection of Multidimensional Signals in Underwater Acoustics

    Publication Year: 2011 , Page(s): 60 - 70
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1938 KB) |  | HTML iconHTML  

    Time-reversal processing (TRP) has been intensively studied for underwater object detection, however, most of the current research focuses on demonstration of the concept and development of the methods. This paper concerns the application of TRP to improving detection performance of multidimensional signals from the statistical signal processing perspective. Two commonly used time-reversal (TR) methods, the iterative time-reversal (ITR) and the decomposition of the time-reversal operator (DORT), are considered, and the detection probability given the false-alarm probability is used as the performance measure. The optimal detectors in the Neyman-Pearson sense are first derived given that the signal transfer function is known; then the corresponding generalized likelihood ratio tests (GLRTs) are developed when the transfer function is unknown. Analyses and example simulations demonstrate the following: 1) due to choosing the right wavefront at the transmitter to compensate for distortions introduced by propagation through medium, TR detectors provide performance improvements over the conventional plane wave beam-steering approach, whether the signal transfer function is known or not; 2) while they perform equally well with a known transfer function, with an unknown transfer function, the DORT detector can be superior to the ITR detector; 3) by trying to match the waveguide transfer function at both the transmitter and the receiver, performance of the TR detectors degrades more compared to the conventional approach when the transfer function is unknown. View full abstract»

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  • An Overview of Sequential Bayesian Filtering in Ocean Acoustics

    Publication Year: 2011 , Page(s): 71 - 89
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2566 KB) |  | HTML iconHTML  

    Sequential filtering provides a suitable framework for estimating and updating the unknown parameters of a system as data become available. The foundations of sequential Bayesian filtering with emphasis on practical issues are first reviewed covering both Kalman and particle filter approaches. Filtering is demonstrated to be a powerful estimation tool, employing prediction from previous estimates and updates stemming from physical and statistical models that relate acoustic measurements to the unknown parameters. Ocean acoustic applications are then reviewed focusing on source tracking, estimation of environmental parameters evolving in time or space, and frequency tracking. Spatial arrival time tracking is illustrated with 2006 Shallow Water Experiment data. View full abstract»

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  • Multiview, Broadband Acoustic Classification of Marine Fish: A Machine Learning Framework and Comparative Analysis

    Publication Year: 2011 , Page(s): 90 - 104
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2496 KB) |  | HTML iconHTML  

    Multiview, broadband, acoustic classification of individual fish was investigated using a recently developed laboratory scattering system. Scattering data from nine different species of saltwater fish were collected. Using custom software, these data were processed and filtered to yield a data set of 36 individuals, and between 200 and 500 echoes per individual. These data were sampled uniformly randomly in fish orientation. Feature-, decision-, and collaborative-fusion algorithms were then developed and tested using support vector machines (SVMs) as the underlying classifiers. Decision fusion was implemented by cascading two levels of support vectors machines. Collaborative fusion was implemented by using SVM outputs to estimate confidence levels and performing weighted averaging of probabilities computed from each view with feedback from other views. Collaborative fusion performed as well or better than the others, and did so without requiring assumptions about view geometry. In addition to a comparison between classification algorithms and feature transformations, two data collection geometries were explored, including random observation geometries. In all cases, combining multiple, broadband views yielded significant reductions in classification error (>;50%) over single-view methods, for uniformly random fish orientation. View full abstract»

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  • A Normal Mode Solution for Low-Frequency Bottom-Refracted Wave Propagation

    Publication Year: 2011 , Page(s): 105 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB) |  | HTML iconHTML  

    A normal mode solution for low-frequency bottom-sediment-refracted wave propagation is formulated for use with a normal mode method of solving the Helmholtz wave equation to describe the underwater sound field for a fixed point source in a plane multilayered medium. The approach utilizes a factorization of the Wronskian of Green's function which enables sediment reflecting and refracting modes to be summed independently. The sensitivity of propagation loss to the nature of mode interaction with the bottom is investigated for multiple frequencies in a sample environment, and results are compared to measurements of 100-Hz bottom returns in the Caribbean Basin. View full abstract»

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  • Experimental Study of Sound Propagation Through Bubbly Water: Comparison With Optical Measurements

    Publication Year: 2011 , Page(s): 114 - 125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2406 KB) |  | HTML iconHTML  

    The study of the acoustical properties of bubbly flows remains a challenge for scientists. Classical theoretical results provide the expression of a complex effective wave number characterizing sound propagation through such a medium. Theoretical attenuation and phase-speed changes of sound can be obtained from this effective wave number and are specifically observable around characteristic frequencies related to the size of the bubbles. With the aim to contribute to the ongoing research, this paper presents experimental work conducted in a large laboratory tank, to study sound propagation through bubbly water. An original bubble generation technique and the characterization of the generated bubbles by both acoustical and optical methods are reported. In the experiments of this work, air bubbles are injected, using a high-pressure washer, into a large water-filled tank through which sound signals are propagated. The characteristic frequencies and the bubble sizes are determined from the measurements of the sound attenuation and the sound phase speed. These measurements are complemented by concurrent acquisitions of acoustic signals and optical images. A comparative study is conducted between the bubble size distributions deduced from the optical and those deduced from the acoustical measurements. View full abstract»

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  • Optimal Resampling of OFDM Signals for Multiscale–Multilag Underwater Acoustic Channels

    Publication Year: 2011 , Page(s): 126 - 138
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1139 KB) |  | HTML iconHTML  

    Underwater acoustic channels (UACs) have a large fractional bandwidth and are well modeled by a multiscale-multilag model, which is a generalization of the commonly employed single time-scale model. The path-dependent time scaling introduces significant channel variation, destroying carrier orthogonality and yielding intercarrier interference (ICI) in an orthogonal frequency division multiplexing (OFDM) system. Typical front-end processing at the receiver for a channel with common time scaling on every path involves resampling the received signal to compensate for this scaling. This work examines the choice of resampling parameter for the multiscale scenario. Bounds are derived for the performance and hard and soft data detection schemes using the Hammersley-Chapman-Robbins bound (HCRB) and the Cramér-Rao bound (CRB), respectively, which when optimized yield the optimal resampling parameter. It is shown that resampling is equivalent to matched filtering the incoming signal with an approximated channel having a common time scale on each path. A second criterion for optimizing the resampling parameter then minimizes the aggregate error between the multiscale channel and its single-scale approximation. Analysis of special cases suggests that the optimal resampling parameter is close to the time-scaling parameter of the dominant path. The scenarios under which using the time-scaling factor on the dominant path for resampling are suboptimal are also investigated. Blind and pilot-aided estimators for the optimal resampling parameter, which are a generalization of the estimators for the common time-scale model, are derived building on the channel approximation model for resampling. Numerical simulations show the advantages of the derived estimators over a classical packet-length-based time-scale estimator. View full abstract»

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  • A Markov Chain State Transition Approach to Establishing Critical Phases for AUV Reliability

    Publication Year: 2011 , Page(s): 139 - 149
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (897 KB) |  | HTML iconHTML  

    The deployment of complex autonomous underwater platforms for marine science comprises sequential steps each of which is critical to mission success. Here we present a state transition approach, in the form of a Markov chain, which models step sequence from prelaunch to operation to recovery. The aim is to identify states and state transitions presenting high risk to the vehicle and hence to the mission, based on evidence and judgment. Developing a Markov chain consists of two separate tasks. The first defines the structure that encodes event sequence. The second assigns probabilities to each possible transition. Our model comprises 11 discrete states, and includes distance-dependent underway survival statistics. Integration of the Markov model with underway survival statistics allows us to quantify success likelihood during each state and state transition, and consequently the likelihood of achieving desired mission goals. To illustrate this generic process, the fault history of the Autosub3 autonomous underwater vehicle (AUV) provides the information for different operation phases. In our proposed method, faults are discriminated according to the mission phase in which they took place. View full abstract»

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  • Why we joined

    Publication Year: 2011 , Page(s): 150
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  • 2011 IEEE membership form

    Publication Year: 2011 , Page(s): 151 - 152
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  • IEEE Oceanic Engineering Society Information

    Publication Year: 2011 , Page(s): C3
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    Publication Year: 2011 , Page(s): C4
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Aims & Scope

The IEEE Journal of Oceanic Engineering (ISSN 0364-9059) is published quarterly by the IEEE Oceanic Engineering Society (IEEE OES). The scope of the Journal is the field of interest of the IEEE OES, which encompasses all aspects of science, engineering, and technology that address research, development, and operations pertaining to all bodies of water. This includes the creation of new capabilities and technologies from concept design through prototypes, testing, and operational systems to sense, explore, understand, develop, use, and responsibly manage natural resources.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
N. Ross Chapman
School of Earth & Ocean Sciences
University of Victoria
3800 Finnerty Road
Victoria, BC V8P 5C2 Canada
chapman@uvic.ca