National Library Bibliothèque nationale I*m ofCanada du Canada Acquisitions and Acquisitions et Bibliographie Services seMces bibliographiques 395 Wellingtoii Street 395. me Wdiington OîtawaON K1AW OtÉawaON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothéque nationale du Canada de reproduce, loan, distriibute or sell reproduire, prêter, distribuer ou copies of this thesis in microfonn, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/^ de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or othenvise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Abstract Efforts to extract information regarding the surficial composition of the ocean bottom have increased in the last decade as increases in the availability of computing power have corre- sponded with advances in signal processing techniques. The ability to extract information from acoustic echosounders is especially desirable due to the relatively low cost and ease of deployment of such systems. Products already exist for the acquisition and logging of echosounder retums. An acoustic remis comprked of the incoherent backscatter from individual scat- terers within the annulus of insonification that occurs when a spherically-spreading trans- mit pulse intersects with the ocean floor. The return is a convolution of the source ping, and the impulse response modeled by the backscatter profile. Most echosounders generate an envelope of the received signal. The bottom impulse response undergoes a dilation lin- ear with depth due to simple geometry which cm be corrected with tirne-scale normaliza- tion. Under certain circumstances it may be necessary to deconvolve the source ping from the envelope of the retum prior to time-scale normalization. It is shown that this cm be done by modelling the envelope generation function with a finite sum discrete convolution and the Hilbert transform of the source signal. A second-order Volterra kernel cm be denved using a standard predictor network with constrained optimization. Other factors which contribute to the quality of the return include off-vertical transducer angles which in fact improve the classification by elirninating the nulls that occur in the bonom impulse response due to transducer beam pattern. Spatial averaging can have the effect of beam widening if the transducer angle varies. Contents Abstract Contents List of Tables List of Figures xiii xvii 1 Introduction 1 1.1 Motivation .................................................................................................1 1.2 Constraints .. .. ... .. .. .. .. .. .. .. .- -..- -.. .. ... ... -... -. .. -. .. .. ... -.-. -. .. .. .. - -3 1.3 Support .. .. ..... .. ... ........................ .... ........................--......-. ...... .. ...-.--.......-.... .............. 3 1.4 Thesis Outiine .. .. .. .. .. .. .... .... .. .... .. .. .. .. ... ......-.... ... ... ... .. .. .. --...-... .. .. ... .. ... .. ..-... ... .. .... ..4 1.5 Contributions to the FieId .....................................................-..........................-.......5 1.6 Typographie conventions .. .. .. .. .. .. ... .. - -... -. .. .. .. -6 1-7 Trademarks and Copyrights .. ... .. .. .. .. .. ... .-. .. .. .. .. .. - -... -. .. -. .. .. .. .. .. ... .-6 2 Technical Background 7 2.1 Seabed Classification Overview ............................................................................... 7 2.1.1 hterpretation ...................................................................................................7 2.1.1.1 Sub-bottom profiling ........................................................................... 8 2.1.1.2 Surficial classification .........................................................................8 2.2 Echo-sounder Rems......*...................*.*....*~~....................................... .... ....... 10 2.2.1 Beam pattern ........................................ ......................................................... 11 2.2.2 Water column attenuation ............................................................................. 11 2.2.3 Spherical spreading ....................................................................................... 12 2.2.4 Water column reflectors ................................................................................ 13 2.2.5 Bottom impulse response .............................................................................. 13 2.2.5.1 Backscatter ................................ .. ............................................ 13 2.2.5.2 Volume reverberation ................................................................... -20 2.2.6 Source signai ............................................................................................... --33 2.2.7 Transducer time-varying gain ...................................................................... -23 7-28Envelope generation ................................................................................... 23 2.3 Surnmary ................................................................................................................ 24 3 Literature Survey 3.1 Historical Developrnent ......................................................................................... 25 3.1.1 The coherence era ....................................................................................... -25 3.1.1.1 Milligan et al, ( 1978) ........................................................................ 25 3.1.1.2 Dunsiger, Cochrane and Vetter, ( 198 1) ............................................. 27 3.1.1.3 Pace and Ceen, (1982) ...................................................................... 28 3.1.1.4 Cochrane and Dunsiger, ( 1983) ........................................................ 29 3.1.1.5 Orlowski, ( 1984) ..................................................... 30 3.1.2 The recent era ................................................................................................30 3.1.2.1 Reut, Pace and Keaton, ( 1985) .........................................................30 3.1.2.2 Jackson and Nesbitt. (1988) .............................................................. 31 3.1.2.3 Chivers. Emerson and Burns. ( 1990)................... .. ....................... 31 3.1 .2.4 Poulinquen and Lurton. ( 1992)........................................................ -33 3.1.2.5 LeBlanc et al, ( 1992) ........................................................................ 34 3 -2 Current Research ................................................................................................... -35 3.2.1 Parametric modelling .................................................................................... 35 3.2.1.1 Kavli. Carlin and Madsen. ( 1993)............................ .. .................... 35 3 .2.2 Scale- and frequency-based methods ...................................................... 36 3.2.2.1 Milvang et al. ( 1993) ... .................................................................... -36 3.3.2.3 Caughey et al. ( 1994)........................................................................ 36 3.2.3 Neural networks ............................................................................................ 37 3.2.3.1 McCleave. Owens and Ingles. ( 1992)............................................... 38 3.2.3.2 Kavli. Carlin and ~Madsen.( 1993)..................................................... 38 3.2.3.3 AIexandrou and Pantzartzis. ( 1993).................................................. 38 3.2.3.4 Zerr. Maillard and Gueriot. ( 1994) ................................................... 39 3.2.4 S hape analysis ............................................................................................... 39 3.2.4.1 Mayer. Clarke and Wells. ( 1993) ...................................................... 39 3.2.4.2 Milvang et al. ( 1993) ........................................................................ 40 3.2.4.3 Caughey et al. ( 1994)........................................................................ 40 3.2.4.4 Tan and Mayer. (in prep.) .................................................................. 40 3.2.5 Classification methods ............................................................................ 41 3.2.5.1 Kavli. Carlin and Madsen. ( 1993)..................................................... 41 vii 3.2.5.2 Tan and Mayer. (in prep.)............. ... ............................................ 1 3 -2-6 Sub-boîtom profiling ........... .... ............................................................. -42 3 .2.6 .1 Lambert, 1993 .................... .. ......................................................... 42 3.2.6.2 Caulfield ........................................................................................... -42 3.3 Summary ............................................................................................................ 43 4 Initial Processing 4.1 Generai procedures ................................................................................................ 44 4.1 -1 Run-time ....................................