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Oceanic Engineering, IEEE Journal of

Issue 2  Part 1 • Date Apr 1991

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Displaying Results 1 - 7 of 7
  • Detection and localization of weak targets by space-time integration

    Publication Year: 1991 , Page(s): 189 - 194
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    A novel method of target motion analysis (TMA) is presented. In contrast to conventional TMA techniques, which use sequences of bearing and/or frequency estimates as their inputs, the method works directly with beam spectra to estimate the target track. Problems that arise in deriving bearing and frequency estimates from the beam spectra are consequently eliminated; the algorithm can handle fading or weak signals that give rise to large outliers or cause automatic signal followers to fail. Besides providing robust estimates of the target track, this algorithm, because of its long-term integration of the beam spectra, also has enhanced detection characteristics. The performance of the algorithm is illustrated with simulated data for a towed line array View full abstract»

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  • The simultaneous measurement of infrasonic acoustic particle velocity and acoustic pressure in the ocean by freely drifting Swallow floats

    Publication Year: 1991 , Page(s): 195 - 207
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1192 KB)  

    The Marine Physical Lab's Swallow floats, which are capable of simultaneously measuring the ocean's infrasonic (1-20 Hz) acoustic particle velocity and infrasonic acoustic pressure, are described. The floats are independent, freely drifting, neutrally buoyant sensor systems that can be ballasted to any desired depth (within ±100 m) in the ocean. Calibration measurements of the infrasonic sensors and electronics agree to within ±1 dB in amplitude and ±3° in phase with the theoretically predicted response curves. Electronic self-noise, quantization noise, and effects of signal clipping are significantly below ambient ocean noise levels, except in unusual circumstances. Rotational resonances, primarily float rocking below 0.5 Hz, contaminate the geophone data at the lowest end of the infrasonic band. From data collected in a deep-ocean deployment, the equivalent pressure autospectrum calculated from the particle velocity data agrees to within 1 dB of the actual pressure autospectrum in the frequency band from 1-20 Hz, thereby verifying the high quality of the infrasonic acoustic data View full abstract»

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  • Equivalence of MMSE and CCMP methods for broadband and robust array design

    Publication Year: 1991 , Page(s): 223 - 224
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    It is shown that the quadratic constraint established by M.H. Er and A. Canton: (see IEEE J. Oceanic Eng., vol.OE-10, p.231-40), can be approximated using linear and quadratic constraints. Based on the latter set of constraints, the equivalence between the MMSE (minimum mean square error) and CCMP (correlation-constrained minimization of power) methods for broadband and robust antenna-array design is further established. The relationship provides several insights into the CCMP and its improved methods View full abstract»

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  • Ocean-clutter model for high-frequency radar

    Publication Year: 1991 , Page(s): 181 - 188
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The time-varying behavior of ocean-clutter signals is investigated with the objective of clutter suppression for target detection. It is shown that the ocean clutter may be adequately modeled with two narrowband Bragg signals with time-varying frequencies. Low-order adaptive-prediction filters can thus be used to suppress the ocean clutter. Simple adaptive filters can also be designed to improve the signal-to-clutter ratio for low Doppler target signals. It is postulated that the time variations of the Bragg frequencies are related to the ocean wave-height spectrum. Initial results along these lines suggest that this may lead to an alternate, more robust method of estimating the sea state from HF radar data View full abstract»

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  • Towfish altitude computation using multipath acoustic ranging

    Publication Year: 1991 , Page(s): 212 - 216
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A technique that uses an acoustic ranging method to estimate towfish altitude, i.e., the height of the towfish above the seafloor, is presented. The ranging algorithm is an implementation of path-length calculation for acoustic signals generated at the towfish and received by a hydrophone located at the towing ship. The time delay between the direct and bottom-reflected signals is measured. By knowing the towfish depth and layback distance, the time delay can be used to compute the towfish altitude View full abstract»

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  • Effective vertical beam patterns for ocean acoustic reverberation calculations

    Publication Year: 1991 , Page(s): 208 - 211
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    A description is given of a concept for using effective vertical beam patterns to perform reverberation calculations in underwater acoustics when the source or receiver has both horizontal and vertical directivity. The concept involves integrating the 3-D beam pattern B (θ, φ) over azimuthal angles φ to obtain an effective vertical beam pattern that depends only on the vertical angle θ and gives the same reverberation response as the 3-D beam pattern. These effective vertical beam patterns have both computational and conceptual advantages. By precomputing the effective beam patterns, sonar models that normally handle only vertical directivity can be readily extended to handle general beam patterns. The concept is also very useful to the sonar engineer. The effective beam patterns are essentially equivalent to the gain against reverberation as a function of vertical angle; alternatively, they are a measure of the horizontal beamwidth of the array, as a function of vertical angle. To illustrate the concept, effective vertical beam patterns are calculated for several steering directions of a horizontal line array receiver, and bottom reverberation calculations are interpreted using these effective beam patterns View full abstract»

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  • Optimal estimation of layback distance for marine towed cables

    Publication Year: 1991 , Page(s): 217 - 222
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The estimation of towfish layback distance is usually performed with computer programs that implement numerical integration of system differential equations. The system dynamic model usually includes an estimate of coefficients of drag and velocities of the towfish and cable. Often these quantities are unknown or estimated with a great deal of uncertainty. The technique reported uses an optimization approach to circumvent the estimates of critical parameters and instead uses accurate measurements of towfish depth and length of cable paid out. A criterion is formulated and minimized using a simple gradient-optimization method. The simulation results indicate that the method works well and can be implemented in a real-time data-acquisition system 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