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Oceanic Engineering, IEEE Journal of

Issue 2 • Date Apr 1988

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Displaying Results 1 - 9 of 9
  • A least sensitive multichannel optimum filter for sensor arrays

    Page(s): 64 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    A family of multichannel filters that can provide complete suppression of coherent interference for almost all frequencies is characterized. The authors then determine the particular member in this family that yields an output that is least sensitive to estimation errors in the parameters which characterize the coherent interference. This filter, called the absolutely optimum array filter (AOAF), is described. This robustness property of the AOAF filter is considered particularly important in applications where imperfect estimates of the parameters are used in the filter design. An example illustrating the results is presented View full abstract»

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  • Swathe seabed classification

    Page(s): 83 - 90
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The degree to which different seabed types may be discriminated using features of the power spectrum of the signals backscattered from the seabed, in a side-scan mode, is evaluated. The statistics derived from the data samples considered suggest that the probability of correctly classifying the six seabed types (sand, mud, clay, gravel, stones, rock) is in excess of 97% using the spectral features that are defined View full abstract»

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  • Wind-wave generation of ocean current: on model identification

    Page(s): 43 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    It is shown how stochastic models based on inertial fluctuations, forced by Stokes drift and wind stress, give apparently accurate predictions of sea surface current. A parameter estimation procedure that gives subjectively reasonable results may therefore also be found. However, objective model identification turns out to be difficult and an estimation model capable of following large-scale model errors is necessary for reasonably accurate parameter estimates. Such a model is proposed and simulation results are presented and discussed. In this mode the inertial oscillation damping, is easily overestimated and the Stokes drift effect is seen to be smaller than the wind stress effect. The latter appears to be uncertain View full abstract»

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  • Onboard correction of mispointing errors in satellite altimeter returns [oceanographic measurement]

    Page(s): 77 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    An investigation to determine whether useful onboard mispointing corrections to satellite altimeter measurements for errors in antenna mispointing can be made with the European Research Satellite (ERS-1) altimeter is reported. An analytic model of the nonlinear mispointing control loop is developed and the step response and signal-to-noise ratio (SNR) behavior of the loop in isolation are derived. The ERS-1 altimeter is expected to have a maximum static mispointing error of 0.2° and a maximum harmonic error of 0.1°. Taking these values as typical, it is concluded that with a loop time response of about one minute, it is not possible to correct the biased estimate of backscattering coefficient without decreasing its SNR. However, it is possible to achieve an unbiased estimate with a noise level significantly less than the uncorrected bias, but a successful implementation would require very accurately calibrated range gate samplers View full abstract»

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  • A deep-ocean penetrator telemetry system

    Page(s): 55 - 63
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    The use of seabed penetrators-streamlined free-fall projectiles of up to 20 metric tons-is a possible method of disposing of high-level nuclear waste by embedment in deep-ocean sediments. In order to determine the feasibility of such a technique, penetrator simulation studies have been conducted. Approaches to transmitting data from measuring instruments carried onboard a model penetrator are briefly reviewed. A description is then given of the super-Doppler penetrator telemetry system that uses a 12-kHz frequency-shift-keyed acoustic link to effect telemetry from within seafloor sediments and then vertically upwards through the ocean. A consideration of system performance is presented, in the light of trial results obtained during cruises in the Atlantic Ocean and Mediterranean Sea View full abstract»

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  • Modeling of the sea surface for daylight imagery studies

    Page(s): 81 - 83
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    Plastic-coated paper is shown to possess reflectivity characteristics quite similar to those of the surface of water. This correspondence has been used with a conversion factor to model a sea surface by means of plastic-coated paper. Such a paper model is then suitably illuminated and photographed, yielding physically simulated daylight imagery of the sea surface under controlled conditions. A simple example of sinusoidal surface simulation is described View full abstract»

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  • Artificial intelligence-definition and practice

    Page(s): 14 - 42
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    A class of computer systems has emerged that makes extensive use of the capability of computers to operate equally well in processing either numbers or symbols. The best known such systems are the expert systems. The research from which these systems are derived is called artificial intelligence. An overview of the field is presented with definitions, recommendations, and an example. Following the definition of terms and a brief history, potential roles which a symbolic processing system might play are discussed, with a brief summary of those which have been most successfully used. The various methodologies in use and their respective strengths are reported. Arguments about the best language to use (such as the choice between LISP and PROLOG) are addressed. A practical example is described in some detail. The strengths and potential of parallel architectures and neural-net machines are briefly noted View full abstract»

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  • Adaptive noise canceling applied to Sea Beam sidelobe interference rejection

    Page(s): 70 - 76
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    An adaptive noise cancelling (ANC) technique involving a joint-process deterministic least-squares lattice filter was applied to the Sea Beam bathymetric survey system data. The filtering scheme used in Sea Beam adversely affects the underlying acoustic return and may also lead to bathymetric artifacts. The authors investigate a possible remedy for this sidelobe interference problem offered by ANC coupled with signal preservation, provided both amplitude and phase information. The joint-process deterministic least-squares lattice is the adaptive filter of choice because of its superior transit response in the presence of power discontinuities. A REVGEN (reverberation generator) simulation (R.P. Goddard, 1985) of the Sea Beam system provided support for the proposed filtering technique. A complex data acquisition system was designed and built to record the in-phase and quadrature component of Sea Beam returns. Initial ANC processing of these recorded Sea Beam data provided satisfactory sidelobe interference cancellation with no noticeable degradation of the actual bottom returns View full abstract»

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  • Reconstruction of the vertical structure of time-dependent flow from current-meter data by means of the observer technique

    Page(s): 50 - 54
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    It is demonstrated that, in the framework of control system theory, an observer equation can be defined from mathematical properties of the partial differential equation that describes the time evolution of the horizontal sea current as a function of depth. An example is presented that applies the observer equation to reconstruct the vertical current profiles at a given location based on field data from meters at fixed depths View full abstract»

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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