DOCSLIB.ORG

Signal Processing for Synthetic Aperture Sonar Image Enhancement

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Signal Processing for Synthetic Aperture Sonar Image Enhancement Signal Processing for Synthetic Aperture Sonar Image Enhancement Hayden J. Callow B.E. (Hons I) A thesis presented for the degree of Doctor of Philosophy in Electrical and Electronic Engineering at the University of Canterbury, Christchurch, New Zealand. April 2003 Abstract This thesis contains a description of SAS processing algorithms, offering improvements in Fourier-based reconstruction, motion-compensation, and autofocus. Fourier-based image reconstruction is reviewed and improvements shown as the result of improved system modelling. A number of new algorithms based on the wavenumber algorithm for correcting second order effects are proposed. In addition, a new framework for describing multiple-receiver reconstruction in terms of the bistatic geometry is presented and is a useful aid to understanding. Motion-compensation techniques for allowing Fourier-based reconstruction in wide- beam geometries suffering large-motion errors are discussed. A motion-compensation algorithm exploiting multiple receiver geometries is suggested and shown to provide substantial improvement in image quality. New motion compensation techniques for yaw correction using the wavenumber algorithm are discussed. A common framework for describing phase estimation is presented and techniques from a number of fields are reviewed within this framework. In addition a new proof is provided outlining the relationship between eigenvector-based autofocus phase esti- mation kernels and the phase-closure techniques used astronomical imaging. Micron- avigation techniques are reviewed and extensions to the shear average single-receiver micronavigation technique result in a 3{4 fold performance improvement when operat- ing on high-contrast images. The stripmap phase gradient autofocus (SPGA) algorithm is developed and extends spotlight SAR PGA to the wide-beam, wide-band stripmap geometries common in SAS imaging. SPGA supersedes traditional PGA-based stripmap autofocus algorithms such as mPGA and PCA|the relationships between SPGA and these algorithms is discussed. SPGA's operation is verified on simulated and field-collected data where it provides significant image improvement. SPGA with phase-curvature based estimation is shown and found to perform poorly compared with phase-gradient techniques. The operation of SPGA on data collected from Sydney Harbour is shown with SPGA able to improve resolution to near the diffraction-limit. Additional analysis of practical stripmap autofocus operation in presence of under- sampling and space-invariant blurring is presented with significant comment regarding iv Abstract the difficulties inherent in autofocusing field-collected data. Field-collected data from trials in Sydney Harbour is presented along with associated autofocus results from a number of algorithms. Acknowledgements First and foremost I acknowledge the support and guidance of my supervisors Dr. Michael Hayes and Professor Peter Gough; they have provided much needed perspective at times|\Sure it works on simulated data. what about real data?". The broad wealth of knowledge these men possess and their skills in intuitive explanation have helped me a great deal. Mike, Peter, it has been a real pleasure working with you. Many thanks to the other SAS lads: Philip Barclay, Steve Fortune, Edward Pil- brow, Alan Hunter, and L´oicSibeud for giving me someone to bounce ideas off and to complain to while debugging simulations. Steve, Al and Phil deserve special men- tion for wading through this and other documents on proof reading duties|let me know when its my turn guys. Thanks also to Mike Cusdin, Peter Lambert and Phil for the work on the KiwiSAS-II hardware and to Dave Wilkinson (a past member of the Acoustics Research Group) for all the help back in the early days (and providing us light relief by occasionally logging onto the linux server with a three-finger-salute). Working in R9 has been memorable; thanks to all those past and present who have made it so|I will particularly miss the cricket matches and the evening-shift \phat beats". A big thank-you to my family (my parents Clive and Doreen, brothers Kyle and Logan, sister Lauren, and fianc´eTanya) for their love and support|I would not be writing this today without you! Thanks too to all of those who decided to take pity on Tanya and I and invite us to dinner at different times. Paul Ryan and the Ellesmere Concert Band get a mention too for giving me necessary breaks from thinking about thesis work. Thanks to the Defence, Science and Technology Organisation, Australia for their assistance with data collection in Sydney Harbour and also to the Defence Technol- ogy Organisation, New Zealand for their assistance with data collection in Auckland Harbour. Many thanks to the Norwegian Defence Research Establishment (FFI) for allowing me to visit them at Kjeller and to Dr. Roy Hansen for describing their im- plementation of DPCA/RPC and SAS plans providing me with another perspective on SAS processing. Thanks also to Kongsberg-Simrad for letting me tag along as a \tourist" at the sea-trials of the HUGIN-3000 AUV. For the financial support I re- ceived I would like to thank the University of Canterbury for granting me a University vi Acknowledgements of Canterbury Doctoral Scholarship (1999), and the Foundation for Research, Science, and Technology for a Bright Futures Scholarship (2000-2002). Last but not least, thanks to my thesis examiners, Prof. Hugh Griffiths, Dr. Reinhard Holtkamp, and Dr. Philip Bones; it is a lot a work to examine a thesis and I am grateful they gave their time to do so. Mike and Peter get mention here too|their in-depth examination, proofing, and the big stick used to repeatedly beat this thesis (the almighty red pen) have made your job easier. My pen is at the bottom of a page, Which, being finished, here the story ends; 'Tis to be wished it had been sooner done, But stories somehow lengthen when begun. | Byron Preface This thesis is written in eleven chapters. Chapters 2{6 describe the deterministic as- pects of SAS imaging: governing SAS principles, reconstruction and compensation for known path-deviations. The later chapters (7{10) detail aspects of micronavigation and autofocus needed to overcome random path-deviations and medium fluctuations. Chapter 7 covers fundamentals of autofocus and chapter 8 summarises a number of spot- light autofocus techniques. Techniques for micronavigation and autofocus of stripmap systems are presented in chapters 9 and 10. The last chapter summarises the work in the thesis and presents recommendations for future research. Papers prepared during the course of this thesis are listed in order of presentation: P. T. Gough, M. P. Hayes, and H. J. Callow. Strip-map path correction using phase matching autofocus. In Proceedings of the fifth European Conference on Under- water Acoustics (ECUA) 2000, pages 412{418, July 2000. H. J. Callow, P. T. Gough, and M. P. Hayes. Not quite 20,000 leagues under the sea, sonar autofocus in a shallow water reverberant environment. In Image and Vision Computing New Zealand 2000, pages 304{309. IVCNZ, November 2000. H. J. Callow, M. P. Hayes, and P. T. Gough. Autofocus of multi-band, shallow-water, synthetic aperture sonar imagery using shear-averaging. In Proceedings of In- ternational Geoscience And Remote Sensing Symposium (IGARSS) 2001, pages 1601{1603. IEEE, July 2001a. P. T. Gough, M. P. Hayes, S. A. Fortune, and H. J. Callow. Autofocussing procedures for high-quality acoustic images generated by a synthetic aperture sonar. In Proceedings of the 17th International Congress on Acoustics. ICA, September 2001. H. J. Callow, M. P. Hayes, and P. T. Gough. Noncoherent autofocus of single receiver, broad-band synthetic aperture sonar imagery. In OCEANS 2001, volume 1, pages 157{162. IEEE, November 2001b. viii Preface M. P. Hayes, P. J. Barclay, P. T. Gough, and H. J. Callow. Test results of a bathymetric synthetic aperture sonar. In OCEANS 2001, volume 3, pages 1682{1687. IEEE, November 2001. H. J. Callow, M. P. Hayes, and P. T. Gough. Advanced wavenumber domain processing for reconstruction of broad-beam multiple-receiver synthetic aperture imagery. In Image and Vision Computing New Zealand 2001, pages 51{56. IVCNZ, November 2001c. H. J. Callow, M. P. Hayes, and P. T. Gough. A wavefront sensing method for synthetic aperture sonar autofocus. In Proceedings of the sixth European Conference on Underwater Acoustics (ECUA) 2002, pages 231{234, Gdansk, Poland, 2002a. H. J. Callow, M. P. Hayes, and P. T. Gough. Wavenumber domain reconstruction of SAR/SAS imagery using single transmitter and multiple-receiver geometry. Electronics Letters, 38(7):336{337, March 2002b. M. P. Hayes, H. J. Callow, and P. T. Gough. Strip-map phase gradient autofocus. In David Kenwright, editor, Image and vision computing New Zealand 2002, pages 71{76, Auckland, December 2002. H. J. Callow, M. P. Hayes, and P. T. Gough. Motion compensation improvement for wide-beam, multiple-receiver SAS systems. Accepted for publication in the IEEE Journal of Oceanic Engineering, 2003a. H. J. Callow, M. P. Hayes, and P. T. Gough. Stripmap phase gradient autofocus. In Oceans 2003, San Diego, USA, September 2003b. IEEE/MTS. CDROM. H. J. Callow, M. P. Hayes, and P. T. Gough. Autofocus of stripmap SAS data using the range variant SPGA algorithm. In Oceans 2003, San Diego, USA, September 2003c. IEEE/MTS. CDROM. Nomenclature This section defines the notation used in the thesis|a variant on the notation of Gough and Hawkins [1997] and Hawkins [1996]. In particular, the Fourier dual of a variable uses a subscript notation|i.e., kx is the radial Fourier frequency (wavenumber) cor- responding to the along-track variable x (kx = 2πfx). The 2-D Fourier transform for example is defined as 1 E(!; ku) = e(t; u) exp ( j(!t + kuu)) dt du: (1) −∞ − ZZ The double letter notation of Gough and Hawkins [1997] does not scale well to 3+ dimensions and has been replaced in favour of a single letter notation.
Load more

Recommended publications
  • The 10Th EAA International Symposium on Hydroacoustics Jastrzębia Góra, Poland, May 17 – 20, 2016
    ARCHIVES OF ACOUSTICS Copyright c 2016 by PAN – IPPT Vol. 41, No. 2, pp. 355–373 (2016) DOI: 10.1515/aoa-2016-0038 The 10th EAA International Symposium on Hydroacoustics Jastrzębia Góra, Poland, May 17 – 20, 2016 The 10th EAA International Symposium on Hy- Dr. Christopher Jenkins: Backscatter from In- droacoustics, which is also the 33rd Symposium on • tensely Biological Seabeds – Benthos Simulation Hydroacoustics in memory of Prof. Leif Børnø orga- Approaches; nized in Poland, will take place from May 17 to 20, Prof. Eugeniusz Kozaczka: Technical Support for 2016, in Jastrzębia Góra. It will be a forum for re- • National Border Protection on Vistula Lagoon and searchers, who are developing hydroacoustics and re- Vistula Spit; lated issues. The Symposium is organized by the Prof. Andrzej Nowicki et al.: Estimation of Ra- Gdańsk University of Technology and the Polish Naval • dial Artery Reactive Response using 20 MHz Ul- Academy. trasound; The Scientific Committee comprises of the world – Prof. Jerzy Wiciak: Advances in Structural Noise class experts in this field, coming from, among others, • Germany, UK, USA, Taiwan, Norway, Greece, Russia, Reduction in Fluid. Turkey and Poland. The chairman of Scientific Com- All accepted papers will be published in the periodical mittee is Prof. Eugeniusz Kozaczka, who is the Pres- “Hydroacoustics”. ident of Committee on Acoustics Polish Academy of Sciences and Chairman of Technical Committee Hy- droacoustics of European Acoustics Association. Abstracts The Symposium will include invited lectures, struc-
    [Show full text]
  • Acoustic Seabed and Target Classification Using Fractional
    University of New Orleans ScholarWorks@UNO University of New Orleans Theses and Dissertations Dissertations and Theses 12-15-2006 Acoustic Seabed and Target Classification using rF actional Fourier Transform and Time-Frequency Transform Techniques Madalina Barbu University of New Orleans Follow this and additional works at: https://scholarworks.uno.edu/td Recommended Citation Barbu, Madalina, "Acoustic Seabed and Target Classification using rF actional Fourier Transform and Time-Frequency Transform Techniques" (2006). University of New Orleans Theses and Dissertations. 480. https://scholarworks.uno.edu/td/480 This Dissertation is protected by copyright and/or related rights. It has been brought to you by ScholarWorks@UNO with permission from the rights-holder(s). You are free to use this Dissertation in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Dissertation has been accepted for inclusion in University of New Orleans Theses and Dissertations by an authorized administrator of ScholarWorks@UNO. For more information, please contact [email protected]. Acoustic Seabed and Target Classication using Fractional Fourier Transform and Time-Frequency Transform Techniques A Dissertation Submitted to the Graduate Faculty of the University of New Orleans in partial fulllment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Sciences by Madalina Barbu B.S./MS, Physics, University of Bucharest, Romania, 1993 MS, Electrical Engineering, University of New Orleans, 2001 December, 2006 c 2006, Madalina Barbu ii To my family iii Acknowledgments I would like to express my appreciation to Dr.
    [Show full text]
  • Matteo Bernasconi Phd Thesis
    THE USE OF ACTIVE SONAR TO STUDY CETACEANS Matteo Bernasconi A Thesis Submitted for the Degree of PhD at the University of St Andrews 2012 Full metadata for this item is available in Research@StAndrews:FullText at: http://research-repository.st-andrews.ac.uk/ Please use this identifier to cite or link to this item: http://hdl.handle.net/10023/2580 This item is protected by original copyright This item is licensed under a Creative Commons Licence The use of active sonar to study cetaceans Matteo Bernasconi Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy University of St Andrews July 2011 The use of active sonar to study cetaceans Matteo Bernasconi TABLE OF CONTENTS DECLARATIONS V ACKNOWLEDGMENTS VII ABSTRACT IX 1. INTRODUCTION 1 2. UNDERWATER ACTIVE ACOUSTIC 13 2.1 Historical notes 15 2.2 Sound: basic concepts 17 2.2.1 Sound propagation 18 2.2.2 Sound pressure and intensity 20 2.2.3 The decibel 21 2.2.4 Transmission Loss 22 2.2.5 Sound Speed 25 2.3 Transducers and beams 26 2.3.1 The beam pattern 28 2.3.2 The equivalent beam angle 29 2.3.3 Pulse and Ranging 30 2.4 Acoustic scattering 31 2.4.1 Target Strength 32 2.4.2 Target shape and orientation 33 2.4.3 Volume/area scattering coefficient 34 2.5 The sonar equation 35 3. CALIBRATION 39 3.1 The on‐axis sensitivity 41 3.2 Nearfield and Farfield 42 3.3 The TVG function 43 3.4 Standard experimental procedure 44 3.5 Calibration spheres 46 3.6 Calibration test of omnidirectional Sonar 47 3.6.1 Introduction 48 3.6.2 Method 49 3.6.3 Results & Discussion 51 3.6.4 Conclusion 57 4.
    [Show full text]
  • A Review on Deep Learning-Based Approaches for Automatic Sonar Target Recognition
    electronics Review A Review on Deep Learning-Based Approaches for Automatic Sonar Target Recognition Dhiraj Neupane and Jongwon Seok * Department of Information and Communication Engineering, Changwon National University, Changwon-si, Gyeongsangnam-do 51140, Korea; [email protected] * Correspondence: [email protected] Received: 13 October 2020; Accepted: 19 November 2020; Published: 22 November 2020 Abstract: Underwater acoustics has been implemented mostly in the field of sound navigation and ranging (SONAR) procedures for submarine communication, the examination of maritime assets and environment surveying, target and object recognition, and measurement and study of acoustic sources in the underwater atmosphere. With the rapid development in science and technology, the advancement in sonar systems has increased, resulting in a decrement in underwater casualties. The sonar signal processing and automatic target recognition using sonar signals or imagery is itself a challenging process. Meanwhile, highly advanced data-driven machine-learning and deep learning-based methods are being implemented for acquiring several types of information from underwater sound data. This paper reviews the recent sonar automatic target recognition, tracking, or detection works using deep learning algorithms. A thorough study of the available works is done, and the operating procedure, results, and other necessary details regarding the data acquisition process, the dataset used, and the information regarding hyper-parameters is presented in
    [Show full text]
  • Implementation of Adaptive and Synthetic-Aperture Processing Schemes in Integrated Active–Passive Sonar Systems
    Implementation of Adaptive and Synthetic-Aperture Processing Schemes in Integrated Active–Passive Sonar Systems STERGIOS STERGIOPOULOS, SENIOR MEMBER, IEEE Progress in the implementation of state-of-the-art signal- NOMENCLATURE processing schemes in sonar systems is limited mainly by the moderate advancements made in sonar computing architectures Complex conjugate transpose operator. and the lack of operational evaluation of the advanced processing Power spectral density of signal . schemes. Until recently, matrix-based processing techniques, such as adaptive and synthetic-aperture processing, could not AG Array gain. be efficiently implemented in the current type of sonar systems, Small positive number designed to main- even though it is widely believed that they have advantages that can address the requirements associated with the difficult tain stability in normalized least mean operational problems that next-generation sonars will have to square adaptive algorithm. solve. Interestingly, adaptive and synthetic-aperture techniques Narrow-band beam-power pattern of may be viewed by other disciplines as conventional schemes. For a line array expressed by the sonar technology discipline, however, they are considered as advanced schemes because of the very limited progress that has . been made in their implementation in sonar systems. Broad-band beam-power pattern of a line This paper is intended to address issues of implementation of array steered at direction . advanced processing schemes in sonar systems and also to serve as a brief overview to the principles and applications of advanced Beams for conventional or adaptive sonar signal processing. The main development reported in beam formers or plane wave this paper deals with the definition of a generic beam-forming response of a line array steered structure that allows the implementation of nonconventional at direction and expressed by signal-processing techniques in integrated active–passive sonar .
    [Show full text]
  • Wednesday Morning, 12 November 2008 Legends 9, 8:00 A.M
    WEDNESDAY MORNING, 12 NOVEMBER 2008 LEGENDS 9, 8:00 A.M. TO 12:00 NOON Session 3aAA Architectural Acoustics: Special Session Celebrating the Work of Russell Johnson Damian J. Doria, Cochair Artec Consultants, 114 W. 26th St., New York, NY 10001 William J. Cavanaugh, Cochair Cavanaugh Tocci Assoc., Inc., 327F Boston Post Rd., Sudbury, MA 01776-3027 Chair’s Introduction—8:00 Invited Papers 8:05 3aAA1. Russell Johnson: The Bolt Beranek and Newman years. William J. Cavanaugh ͑Cavanaugh Tocci Assoc. Inc., 327F Boston Post Rd., Sudbury, MA 01776, [email protected]͒ In 1954, the author and Russell Johnson both joined the architectural acoustics staff of the pioneering research and consulting firm, Bolt Beranek and Newman ͑BBN͒, in Cambridge, MA. Just over 16 years later, in 1970, after exposure to some of the brightest talents in the relatively new discipline of applied acoustics, both left BBN to form their own independent consulting firms: Cavanaugh, a general consulting practice, and Johnson, which was to become an internationally renowned firm, providing comprehensive services on all phases of performance facility design including acoustics. In the mid-1990s, the author began the process of nominating his long time friend and colleague for the Acoustical Society’s prestigious Wallace Clement Sabine Medal which was awarded in 1997 with the citation “for contributions to the understanding of the acoustics of performance spaces and the design of concert halls, theaters and opera houses throughout the world.” This paper traces Russell Johnson’s developing performance facility design interests from his early pre- WWII days, his US Army wartime service, his postwar studies at Carnegie Tech ͑now Carnegie Mellon University͒, and at Yale as well 3a WED.
    [Show full text]
  • Defense Applications of Acoustic Signal Processing
    Defense Applications of Acoustic Signal Processing Brian G. Ferguson Acoustic signal processing for enhanced situational awareness during Address: military operations on land and under the sea. Defence Science and Technology (DST) Introduction and Context Group – Sydney Warfighters use a variety of sensing technologies for reconnaissance, intelligence, Department of Defence and surveillance of the battle space. The sensor outputs are processed to extract Locked Bag 7005 tactical information on sources of military interest. The processing reveals the Liverpool, New South Wales 1871 presence of sources (detection process) in the area of operations, their identities Australia (classification or recognition), locations (localization), and their movement histo- Email: ries through the battle space (tracking). This information is used to compile the [email protected] common operating picture for input to the intelligence and command decision processes. Survival during conflict favors the side with the knowledge edge and superior technological capability. This article reflects on some contributions to the research and development of acoustic signal-processing methods that benefit warf- ighters of the submarine force, the land force, and the sea mine countermeasures force. Examples are provided of the application of the principles and practice of acoustic system science and engineering to provide the warfighter with enhanced situational awareness. Acoustic systems are either passive, in that they exploit the acoustic noise radiated
    [Show full text]
  • Compressive Underwater Sonar Imaging with Synthetic Aperture Processing
    remote sensing Article Compressive Underwater Sonar Imaging with Synthetic Aperture Processing Ha-min Choi 1 , Hae-sang Yang 1 and Woo-jae Seong 1,2,* 1 Department of Naval Architecture and Ocean Engineering, Seoul National University, Seoul 08826, Korea; [email protected] (H.-m.C.); [email protected] (H.-s.Y.) 2 Research Institute of Marine Systems Engineering, Seoul National University, Seoul 08826, Korea * Correspondence: [email protected]; Tel.: +82-2-880-7332 Abstract: Synthetic aperture sonar (SAS) is a technique that acquires an underwater image by synthesizing the signal received by the sonar as it moves. By forming a synthetic aperture, the sonar overcomes physical limitations and shows superior resolution when compared with use of a side-scan sonar, which is another technique for obtaining underwater images. Conventional SAS algorithms require a high concentration of sampling in the time and space domains according to Nyquist theory. Because conventional SAS algorithms go through matched filtering, side lobes are generated, resulting in deterioration of imaging performance. To overcome the shortcomings of conventional SAS algorithms, such as the low imaging performance and the requirement for high-level sampling, this paper proposes SAS algorithms applying compressive sensing (CS). SAS imaging algorithms applying CS were formulated for a single sensor and uniform line array and were verified through simulation and experimental data. The simulation showed better resolution than the !-k algorithms, one of the representative conventional SAS algorithms, with minimal performance degradation by side lobes. The experimental data confirmed that the proposed method is superior and robust with respect to sensor loss.
    [Show full text]
  • Acoustic Sampling Volume Kenneth G
    Acoustic sampling volume Kenneth G. Foote Instituteof Marine Research,5024 Bergen, Norway (Received5 April 1990;accepted for publication10 April 1991) Knowledgeof the acousticsampling volume is necessaryin many quantitativeapplications of acoustics.In general,the samplingvolume is not merelya characteristicof the transmitting and receivingtransducers, but alsodepends on the concentrationand scatteringproperties of the target, the kind of signalprocessing performed on the echo,and the detectionthreshold. Thesedependences are statedexplicitly in formulasfor the samplingvolume and a differential measure,the effectiveequivalent beam angle. Numerical examplesare givenfor dispersedor denseconcentrations of both point scatterersand directionalfish scatterers. Application of theory to optical and other remotesensing techniques is mentioned. PACS numbers: 43.30.Ft, 43.30. Gv, 43.30.Xm INTRODUCTION range 30-200 kHz. Consequently,a scattererthat gives a A numberofpractical uses of acoustics require knowl- strongecho when in oneorientation may givea very weak or edgeof the samplingvolume. In fluid-processingapplica- unobservableecho when in another, despitebeing in the tions these include determinations of the concentration of same position in the beam. Differencesin backscattering monodispersedscatterers and the sizedistribution and con- crosssections due to ordinary changesin tilt anglewill more- centration of polydispersedscatterers, e.g., of human red overbe slightfor smallsize-wavelength ratios and potential- bloodcells ] and othersmall particles, 2-5 such as contami- ly large for big ratios,thus nearly spanningthe rangeof ef- nants of industrial fluids. In oceanographicapplications fects intrinsic to the scatterer itself. theseinclude analogous determinations of scattererconcen- The dependenceof the samplingvolume on the back- trationand size distribution, e.g., of bubbles,6fish, 7-9 plank- scatteringcharacteristics of observedfish, in addition to ton,]ø-]3 and suspended sediment. ]4-]7 Some of thecited ap- transducerproperties, has alreadybeen recognized.
    [Show full text]
  • Acoustic Signal Processing for Ocean Exploration Kindle
    ACOUSTIC SIGNAL PROCESSING FOR OCEAN EXPLORATION PDF, EPUB, EBOOK J.M.F Moura | 676 pages | 14 Oct 2012 | Springer | 9789401046992 | English | Dordrecht, Netherlands Acoustic Signal Processing for Ocean Exploration PDF Book Several choices of starting fields are provided, including a Gaussian source beam of varying width and tilt with respect to the horizontal. Underwater acoustic communication is also finding increasing adoption as pre-warning system for underwater earthquakes or tsunamis and to monitor underwater pollution and habitat. Log in here. Keller and J. McLaren, M. View at: Google Scholar F. Read this book on SpringerLink. Download image jpg, 98 KB. Coherent ray clusters were observed in which large fans of rays with close initial conditions preserved close current dynamical characteristics over long distances. Prior and A. Sign up here as a reviewer to help fast-track new submissions. Paul C. Karasalo, and J. The tabu search begins by marching to a local minimum. Measuring currents is a fundamental practice of physical oceanographers. A year baseline inventory of modeling techniques was updated with the latest developments, including basic mathematics and references to the key literature, to guide soundscape practitioners to the most efficient modeling techniques for any given application. The bottom structure is modeled as a fluid sediment layer over a solid half-space. He has conducted more than 60 scientific expeditions in the Arctic, Atlantic, Pacific, and Indian Oceans. Ocean acidification, which occurs when CO 2 in the atmosphere reacts with water to create carbonic acid H 2 CO 3 , has increased. Most traditional active sonars are configured in what is termed a monostatic geometry, meaning that the source and receiver are at the same position.
    [Show full text]
  • Signal Processing Methods for Active Synthetic Aperture Sonar
    FOI-R--0528--SE SWEDISH DEFENCE RESEARCH AGENCY FOI-R--0528--SE Systems Technology June 2002 SE-172 90 Stockholm ISSN 1650-1942 Sweden Technical Report Signal Processing Methods for Active Synthetic Aperture Sonar Mattias Jönsson Elias Parastates Geoffrey Shippey Jörgen Pihl Peter Karlsson Eva Dalberg Bernt Nilsson 1 FOI-R--0528--SE FOI-R--0528--SE Issuing organization Report number, ISRN Report type FOI-R--0528--SE Technical Report FOI - Swedish Defence Research Agency Systems Technology Research area code SE-172 90 Stockholm 4. C4ISR Sweden Month year Project number June 2002 E6053 Customers code 5. Commissioned Research Sub area code 43 Underwater Sensors Author/s (editor/s) Project manager Mattias Jönsson, Elias Parastates, Jörgen Pihl Geoffrey Shippey, Jörgen Pihl, Approved by Peter Karlsson, Eva Dalberg, Bernt Nilsson Sponsoring agency Swedish Armed Forces Scientifically and technically responsible Mattias Jönsson Report title Signal Processing Methods for Active Synthetic Aperture Sonar Abstract In the autumn 2001 FOI carried out a field experiment at the Älvsnabben test site in the southern Stockholm archipelago. The aim of the experiment was to test Synthetic Aperture Sonar (SAS) algorithms developed at FOI during the last two years. These algorithms had previously been used to analyse data from an earlier experiment at the Djupviken test site with good results. The same equipment was used in both experiments, but with minor modifications to the transmitter. Studies of the recorded data revealed several shortcomings in the experimental equipment and experimental mistakes which made the analysis very complicated. Most problems stemmed from the lack of a proper naviga- tion instrument on the Remotely Operated Vehicle (ROV) carrying the sonar.
    [Show full text]
  • A Comparison of Two Techniques for Estimating the Travel Time of an Acoustic Wavefront Between Two Receiving Sensors
    University of Central Florida STARS Retrospective Theses and Dissertations 1984 A Comparison of Two Techniques for Estimating the Travel Time of an Acoustic Wavefront Between Two Receiving Sensors Frank J. Montalbano University of Central Florida Part of the Engineering Commons Find similar works at: https://stars.library.ucf.edu/rtd University of Central Florida Libraries http://library.ucf.edu This Masters Thesis (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Montalbano, Frank J., "A Comparison of Two Techniques for Estimating the Travel Time of an Acoustic Wavefront Between Two Receiving Sensors" (1984). Retrospective Theses and Dissertations. 4694. https://stars.library.ucf.edu/rtd/4694 A COMPARISON OF TWO TECHNIQUES FOR ESTIMATING THE TRAVEL TIME OF AN ACOUSTIC ~AVEFRONT BETWEEN TWO RECEIVING SENSORS BY FRANK J. MONTALBANO B.S.E.E., Florida Atlantic University, 1979 RESEARCH REPORT Submitted in partial "fulfillment of the requirements for the degree of Master of Science in Engineering in the Graduate Studies Program of the College of Engineering University of Central Florida Orlando, Florida Spring Tenn 1984 ABSTRACT In recent years the United States Navy has concentrated most of its Anti-Submarine Warfare (ASW) research and development efforts toward passive sonar. Its ability to locate enemy targets without being detected gives the passive sonar system a supreme strategic advantage over its active counterpart. One aspect of passive sonar signal processing is the time delay estimation of an underwater acoustic wavefront.
    [Show full text]