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Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating Shallow Water

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Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating Shallow Water University of New Orleans ScholarWorks@UNO University of New Orleans Theses and Dissertations Dissertations and Theses Fall 12-15-2012 Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating Shallow Water Patricia E. Giardina University of New Orleans, [email protected] Follow this and additional works at: https://scholarworks.uno.edu/td Part of the Physics Commons Recommended Citation Giardina, Patricia E., "Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating Shallow Water" (2012). University of New Orleans Theses and Dissertations. 1553. https://scholarworks.uno.edu/td/1553 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]. Interferometric Synthetic Aperture Sonar Signal Processing for Autonomous Underwater Vehicles Operating in Shallow Water A Dissertation Submitted to the Graduate Faculty of the University of New Orleans in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Science Underwater Acoustics by Patricia E. Giardina B.S. Old Dominion University, 1995 M.S. University of Southern Mississippi, 2001 M.S. University of New Orleans, 2012 December, 2012 © 2012, Patricia E. Giardina ii Dedication To My daughter Jodi Ellen Stiede and My Son Kevin Scott Stiede for taking this long journey with me and for all the love, support, encouragement, and all the special moments along the way. The family torch has been passed to them to lead the way as I will in great delight watch as they create their own paths on their magical journey. To My husband Kurt Alexander Giardina for the unconditional love and support and mostly his calming intellect that helps me see the right path clearly. iii Acknowledgements I wish to express my sincere appreciation and gratitude to my Dissertation Committee at the University of New Orleans, especially my dissertation advisor Dr. Juliette W. Ioup for having the patience and perseverance to guide me with her infinite wisdom on this enduring journey to obtain true knowledge of the natural universe. It is through her love and devotion to teaching science she imparts her knowledge that transcends the academic environment and permeates the mind body and soul so that one can attain an ethereal scholarly posture, and for this I am extremely grateful. I am extremely thankful to my co-chair Dr. Maria T. Kalcic for introducing me to the world of adaptive filter theory and the eloquent matrix inversion lemma. Dr. Stanley Chin-Bing who has nurtured my ability to unravel seemingly insurmountable physics and mathematics problems that I am indebted and grateful. I am thankful to Dr. George E. Ioup for encouraging me to pursue a higher academic posture, and I am thankful to Dr. Gregory Seab for encouraging me to keep going. A special thank you to Zella Huaracha for over a decade handled all the administrative work for my Masters and Doctoral degrees at the University of New Orleans. I would especially like to thank Dr. Dan D. Sternlicht for mentoring me throughout this process, for giving my research direction, for bringing my research to the forefront, and for connecting me with international experts. It is through him I am now part of the international community in this very specialized field of Interferometric Synthetic Aperture Sonars (InSAS). I would also like to thank Dr. Kerry Commander, at the Naval Surface Warfare Center (NSWC-PCD) for providing the funding and opportunity to continue my dissertation research. I would especially like to thank my colleague Dr. Gary Sammelmann who developed and provided the InSAS simulations for my research. I am very fortunate to have the expert technical guidance of Dr. Christophe Sintes and Dr. Gerard Llort-Pujol from Telecom Bretagne in Brest France, whose interferometric research is the current state of the art. I am forever grateful to Dr. Christophe Sintes for his extraordinary efforts in assisting me with my dissertation. Mon cher ami Christophe, je vous remercie beaucoup! Dr. Peter Gough from the University of Canterbury at Christchurch, New Zealand for sharing his unsurpassed knowledge of InSAS. He has provided me with the technical details and background knowledge necessary to conduct this research. I will always hold a special place in my heart for the Naval Oceanographic Office (NAVO) for affording me the time, and opportunity to master the art of oceanography and hydrography, and for this I am grateful. It was my work at the Naval Oceanographic Office that inspired me to conduct research in InSAS. It was the friendships at NAVO that made it all worthwhile. iv Most importantly I would like to thank my family. Especially my daughter Jodi and my son Kevin to whom I owe everything, they have been with me since my undergrad days and have seen me through to my doctoral days. It is their continuous love and support that made it possible. To my husband Kurt Giardina for his calming intellect and voice of reason that kept me on the right path. v Preface Original copy Software: Microsoft Office Word 2007 Mathworks Matlab R2012a PC SWAT Version 10 by Gary Sammelman As synthetic aperture sonar (SAS) systems are transitioned into operational naval applications, there is developing interest in enhancing SAS designs with additional capabilities, including interferometric bottom height determination. Bathymetry, gathered in a single pass with SAS, has the potential to improve mine countermeasure efforts by adding constraints to object dimensions, assisting with seabed characterization, improving SAS imagery through enhanced motion compensation, and improving navigation through enhanced motion estimates found using displaced phase center methods. With the addition of one or two receiver elements, coarse bathymetric solutions can be derived, and with the addition of a second SAS array, full interferometric SAS surveying may be conducted, allowing fine scale seafloor bathymetry and improved resolution of mine-like targets. While the interferometric technique is relatively mature within the synthetic aperture radar (SAR) community, the transition to sonar poses various technical issues which may require somewhat different approaches in the marine environment. Items of concern include approaches to data filtering and co-registration needed to resolve fine-scale height variations, the mitigation of errors due to sensor motion and medium variations, and the choice of phase unwrapping algorithms which are both effective and efficient for seafloor terrain typically mapped from altitudes of a few dozen meters. To address these topics, we will conduct comparative performance analyses for several interferometric processors using simulated SAS data, allowing direct quantitative comparisons between input depth values and bathymetric solutions. Improvements over existing inter-stave signal co-registration, filtering, phase unwrapping, and height estimation techniques for bathymetry mapping and small object shape identification will be the thrust of this research. My goal is to present a summary of basic ocean physics to lay the foundation for Interferometric synthetic aperture sonar (InSAS) processing in the shallow water acoustic environment. Ocean acoustic models derived from the previously mentioned physics will be used to predict the acoustic response of the sonar in a large set of ocean environments. Beamforming signal processing techniques are presented to give a basic understanding of what is involved in converting the changes in ocean pressures at the sonar face into meaningful digital electronic data to form images of the ocean bottom. The details of standard practices for synthetic aperture sonar will be presented to build the framework for three dimensional bathymetric imaging. The thrust of this investigation will be to benchmark the methods of InSAS bathymetric height and phase unwrapping techniques. The eloquence of the Matrix Inversion Lemma, the Principle of Stationary Phase and the Principle of Orthogonality are revealed and their usefulness in signal processing is extremely valuable. vi History Synthetic aperture Sonar (SAS) technology originates from the Synthetic Aperture Radar (SAR) community. Walsh ’69 was awarded a patent on high resolution seafloor imaging, which was the beginning of SAS. Cutrona ’75 ported SAR technology to SAS. He pointed out that sensor motion and the ocean media would be limiting factors to SAS capabilities. Spiess & Anderson ’83 were awarded a patent on InSAS. Griffiths ‘94 proposed using three vertically spaced receivers for interferometric bathymetry. Hawkins ’96 and Gough ‘98 provide a historical review of the development of SAR and SAS technologies. Wen Xu ’98 developed a direction of arrival amplitude estimation for multiple row bathymetric side scans. Chatillon ’99 produced bathymetric voxels of 1m 3 at 2.5 km. Lurton ’00 investigated
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