Broadband Synthetic Aperture Matched Field Geoacoustic Inversion

Transcription

1 Broadband Snthetic Aerture Matched Field Geoacoustic Inversion PhD Candidate: Bien Aik Tan htt:// PhD Coittee: Prof. Willia Hodgkiss Chair Prof. Peter Gerstoft Co-chair Prof. Willia Coles Prof. Barnab Rickett Prof. Willia Kueran Dr. Caglar Yardi

2 Overview Introduction, Motivation and Aroach Part Broadband Snthetic Aerture Geoacoustic Inversion [] Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics [2] Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion [3] Suar and Future Works Acknowledgeents [] B. A. Tan, et. al. Broadband snthetic aerture geoacoustic inversion, J. Acoust. Soc. A., vol. 34, no., , Jul [2] B. A. Tan, et. al., Recursive Baesian snthetic aerture geoacoustic inversion in the resence of otion dnaics, J. Acoust. Soc. A., in Press, 204. [3] B. A. Tan, et. al., Change-oint detection for recursive Baesian geoacoustic inversion, J. Acoust. Soc. A., to be subitted,

3 Introduction What is geoacoustic inversion? versus costl direct easureents: coring Measureent and rerocessing Measured signal, Cost / likelihood function Relica signal, b Forward odel Otiization to iniize cost / axiize likelihood Forward odel araeters, Paraeter estiates Alications Sonar erforance rediction Source localization Detection and classification of UW an-ade objects Broadband Snthetic Aerture Matched Field Geoacoustic Inversion 8/2/204 3

4 Motivation Tical inversion require owerful acoustic source for high Signal to Noise Ratio SNR Large aerture arra irove SNR and the satial diversit of easureents But deloing large arras can be tie consuing and colex. Powerful acoustic sources are big and heav. Dissertation aroach: Mobile single source-receiver/snthetic aerture inversion oerationall attractive, surve large area quickl. Oerate in low SNR condition less disturbance to arine aals, low or batter owered source. Broadband Snthetic Aerture Matched Field Geoacoustic Inversion 8/2/204 4

5 Motivation Well suited for raid environent assessent AUV-based inversion have been gaining interests Concetual drawing Batter owered Soe AUV- based inversion exales NATO-CMRE CLUTTER 2009 NATO-CMRE GLASS 202 Low wr db SL Frequenc 0.-3 khz Batter owered For AUV-based inversion SCEx 205 VERSUS J kg 80 db 0 x bigger 00x heavier 8/2/204 5

6 Aroach Four ain obile single source and receiver aroaches Disersion Curve Analsis [Gervaise 202] incoherent rocessing reresents ultilaered waveguide as two-laer waveguide- loss of resolution. Matched iulse resonse ethod [Josso 202] waveguide Doler itigation instead of odeling- residual errors. Snthetic aerture odal inversion [Rajan 2008] easure transission loss curve b traversing long distances- tie consuing. Matched field inversion does not have the above liitations [Carriere 202] high SNR/ower broadband source, slow-drifting coact arra. [Siderius 998] high SNR, static single source-receiver broadband frequenc coherent inversion ossible. siulation stud Thus, its ost roising to focus on atched field inversions ethods for obile, single source and receiver configurations in low SNR conditions. Broadband Snthetic Aerture Matched Field Geoacoustic Inversion 8/2/204 6

7 Overview Introduction, Motivation and Aroach Part Broadband Snthetic Aerture Geoacoustic Inversion Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion Suar and Future Works Acknowledgeents Part Broadband Snthetic Aerture Matched Field Geoacoustic Inversion 8/2/204 7

8 Broadband snthetic aerture geoacoustic inversion Features Horizontall obile single source and receiver Broadband frequenc coherent atched field rocessing Long coherent observation of ultile P LFM ulses to increase SNR but becoes Doler intolerant Waveguide Doler odel rearaeterizes tie-varing source range to initial source range and constant horizontal radial seeds Part Broadband Snthetic Aerture Geoacoustic Inversion - concet 8/2/204 8

9 Al. Coherentl exloiting ultile LFMs P Pulses Pulse width T Pulse reetition interval T r Periodic eaks at /T r Hz S t δ t nt r rect t PT r/2 PT r Peak salings and doubling P Signal eak increases 6 db Noise level increase 3 db 3 db gain Increasingl Doler intolerant st st st st S c f S c f = P =0 ex i2πft r S f FT tie FT Mag. 2 freq S f δ f j/t r PT r sinc fpt r Part Broadband Snthetic Aerture Geoacoustic Inversion - concet 8/2/204 9

10 Schidt and Kueran 994 Sectral/Modal Solution Non-recirocit Frequenc doain Waveguide Doler ω = ω s + k n v s Mode Mode N ω s v s ω r Receiver v R Each ode has a different Doler Source Proagation Receiver ω s ω = ω s + k n v s ωr k n = ωs + k n v s v r ω s k n = ωr k n v s v r ω = ω r + k n v r ω r Part Broadband Snthetic Aerture Geoacoustic Inversion - concet 8/2/204 0

11 SW06 Exerient JD UTC Source: J-5, 30, LFM Hz T= s T r = s, 2.5 /s Receiver: Hdrohone 8 of VLA, 44.6 Source receiver range ~ SNR ~ 6 db SHARK interolated sound seed rofile 2.5 /s Part Broadband Snthetic Aerture Geoacoustic Inversion 8/2/204

12 Otiizer: Genetic Algorith SW06 Siulation LFM Hz T= s T r = s Static source/receiver Coherentl exloit P LFMs Moving source & static receiver Waveguide Doler Enhanced frequenc saling Data Model = b + w where = easured field b = odeled/relica field = odel araeters w = Gaussian noise Part Broadband Snthetic Aerture Geoacoustic Inversion - Siulation 8/2/204 2

13 Static source / receiver Sensitivit lots Monte Carlo inversion versus P=[, 2, 4, 8, 6, 32, 64] 200 noise realizations SNR = 6 db Peak frequenc saling f = 5 Hz Part Broadband Snthetic Aerture Geoacoustic Inversion - Siulation 8/2/204 3

14 Moving source & static receiver Source radial seed is 2.5 /s Waveguide Doler odel Reduce uncertaint till P=6 Thereafter, uncertaint increases Different frequenc saling schee needed Part Broadband Snthetic Aerture Geoacoustic Inversion - Siulation 8/2/204 4

15 Waveguide Doler Peak ± Doler sread Hz saling 0.2 Hz Moving source & Static Receiver Source sectru Source radial seed is 2.5 /s Proagate For high P values, eak saling = loss of higher odes Received sectru Loss of higher order odes = loss of deeer botto enetration and resolution Part Broadband Snthetic Aerture Geoacoustic Inversion - Siulation 8/2/204 5

16 SW06 received sectru Section of SW06 received signal sectru with LFM ulses P = [, 4, 64] Part Broadband Snthetic Aerture Geoacoustic Inversion Exeriental Data 8/2/204 6

17 SW06 data inversion results P=64 Inversion results 0 src rad. vel. /s sed. thickness sed. densit g/c 3 to. sed vel. /s Part Broadband Snthetic Aerture Geoacoustic Inversion Exeriental Data 8/2/204 7

18 Part Conclusion Single hdrohone broadband atched field inversion in low SNR. Coherentl exloits ultile LFMs Waveguide Doler and increased frequenc saling is needed. Part Broadband Snthetic Aerture Geoacoustic Inversion 8/2/204 8

19 Overview Introduction, Motivation and Aroach Part Broadband Snthetic Aerture Geoacoustic Inversion Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion Suar and Future Works Acknowledgeents Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 9

20 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics Though successful, the all-ulses-at-once coherent aroach [] is iractical and liited to constant source/receiver radial velocities. Alternativel, a coherent ulse-b-ulse rocessing using the recursive Baesian aroach [2] will allow: An aroxiation to acceleration b assuing iecewise constant but linearl changing velocities ulse-to-ulse. Assessent of the teoral evolution of araeter uncertaint [] B. A. Tan, et. Al. Broadband snthetic aerture geoacoustic inversion, J. Acoust. Soc. A., vol. 34, no., , Jul [2] B. A. Tan, et. Al., Recursive Baesian snthetic aerture geoacoustic inversion in the resence of otion dnaics, J. Acoust. Soc. A., in Press, 204. Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 20

21 Recursive Baesian aroach Data odel of l th ulse easureent l = b l + w l where l = easured field b l = odeled/relica field = odel araeters w l = Gaussian noise 8/2/204 Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 2 :l l+ Posterior rob. densit PPD Current Likelihood Adative iortance saling new easureent Udate PPD odel araeters l = ot Generalizing for L easureents,,,,, Posterior Probabilit Densit PPD two easureent case Consider Baes rule : : :2 :2 L L L l l L

22 Recursive Baesian aroach Data odel of l th ulse easureent l = b l + w l where l = easured field b l = odeled/relica field = odel araeters w l = Gaussian noise 8/2/204 Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 22 :l l+ Posterior rob. densit PPD Current Likelihood Adative iortance saling new easureent Udate PPD odel araeters l = 2 ot Generalizing for L easureents,,,,, Posterior Probabilit Densit PPD two easureent case Consider Baes rule : : :2 :2 L L L l l L

23 Recursive Baesian aroach Data odel of l th ulse easureent l = b l + w l where l = easured field b l = odeled/relica field = odel araeters w l = Gaussian noise 8/2/204 Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 23 :l l+ Posterior rob. densit PPD Current Likelihood Adative iortance saling new easureent Udate PPD odel araeters l = 3 ot Generalizing for L easureents,,,,, Posterior Probabilit Densit PPD two easureent case Consider Baes rule : : :2 :2 L L L l l L

24 Recursive Baesian aroach Data odel of l th ulse easureent l = b l + w l where l = easured field b l = odeled/relica field = odel araeters w l = Gaussian noise 8/2/204 Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 24 Generalizing for L easureents,,,,, Posterior Probabilit Densit PPD two easureent case Consider Baes rule : : :2 :2 L L L l l L

25 Aroxiation to acceleration However, odeling acceleration is non-trivial Tie varing odal wavenubers and functions Walker 2007 Circuvent b aroxiating acceleration Assue radial velocities are iece-wise constant for each ulse CROSS SECTION VIEW TOP VIEW Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 25

26 SW06 Exerient JD UTC Moving Source: J-5, 30, LFM Hz T= s T r = s, Static Receiver: Hdrohone 8 of VLA, 44.6 Source receiver range ~600 Initial source radial velocit ~.9 /s with acceleration ~ /s 2 SNR ~ 0 db Static rcvr Moving source Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 26

27 Siulation SW06 environent Towed Source, static receiver Source-receiver range 600. True PPD L= ulses 24 4 exhaustive sales True PPD L=64 ulses 24 4 exhaustive sales Coutational savings will increase exonentiall with diensions AIS-based PPD L=64 ulses 8k AIS sales Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 27

28 Siulation True -D PPD evolution No acceleration in relica True -D PPD Acceleration in relica AIS based -D PPD Acceleration in relica AIS iortance distribution arginalized onto α sed Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 28

29 SW06 Inversion results one ulse Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 29

30 SW06 Inversion results 64 ulses Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 30

31 SW06 Inversion results 64 ulses no acceleration Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 3

32 SW06 Inversion results Aniation Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics 8/2/204 32

33 Part2 Conclusion Using the recursive Baesian ulse-b-ulse aroach, a broadband, frequenc coherent atched-field inversion rocedure for a oving source and receiver at low SNR is roosed. Real data analsis of the Shallow Water 2006 exerient deonstrated that Via online uncertaint analsis, araeter uncertaint reduces with increasing nuber of ulses When acceleration exist, odeling acceleration in the inversion reduce further araeter estiation biases and uncertainties. Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics

34 Overview Introduction, Motivation and Aroach Part Broadband Snthetic Aerture Geoacoustic Inversion Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion Suar and Future Works Acknowledgeents Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 34

35 Change-oint detection for recursive Baesian geoacoustic inversion A ke assution for ethods in Part and 2 constant underling odel araeters Long-tie coherent integration and source-receiver otion sace-tie environent changes Modeling the change araetricall is the best aroach but also adversel increase the inversion search diension. E.g. v s, a s A odel araeter change-oint detection ethod that detects abrut or gradual change in odel araeters is utilized. The robabilit distributions iortance sales and weights fro recursive Baesian inversion that are generated for odel araeters estiations can also be used for inferences about the ossible change-oints. Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 35

36 Change-oint detection Consider a sequence of easureents l Where there is a change-oint r Pre-change-oint easureents follow odel Post-change-oint easureents follow odel 2 ML estiate Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 36

37 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 37

38 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 2 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 38

39 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 3 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 39

40 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 4 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 40

41 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 5 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 4

42 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 6 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 42

43 Change-oint likelihood Change-oint detection exale For 8 easureents with true change-oint r true = r = 7 4 r Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 43

44 Siulation: Abrut change Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 44

45 Change-oint detected r = 64 L = 7 Siulation: Abrut change When a change-oint is detected, the current inversion concludes and a new inversion is started using ost change-oint easureents. Pre-change-oint iortance sales retained Post-change-oint iortance sales discarded Reconstructed PPD Onl 95% HPD lotted Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 45

46 Siulation: Gradual change Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 46

47 Siulation: Gradual change No significant bias due to constant odel aroxiation Gradual change segented into three constant odels Change-oint triggered r = 4 L = 7 Pre-change-oint iortance sales retained Post-change-oint iortance sales discarded Reconstructed PPD Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion 8/2/204 47

48 Part3 Conclusions Cobining change-oint detection and recursive Baesian inversion has enabled a data-driven verification of the constant odel araeter assution. Controlling the coherent integration tie in recursive Baesian inversion. Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics

49 Suar Part Broadband Snthetic Aerture Geoacoustic Inversion All-ulses-at-once aroach Waveguide Doler Part 2 Recursive Baesian Snthetic Aerture Geoacoustic Inversion in the Presence of Motion Dnaics Pulse b ulse aroach with uncertaint analsis Aroxiation to acceleration Part 3 Change-oint Detection for Recursive Baesian Geoacoustic Inversion Validate constant odel araeter odel assution with data Control the integration tie of recursive Baesian inversion. Suar Broadband Snthetic Aerture Matched Field Geoacoustic Inversion 8/2/204 49

50 Future work Cobining change-oint detection for recursive Baesian geoacoustic inversion and a range-deendent waveguide Doler noral ode odel will facilitate inversions being conducted in a sace-tie varing environent. The satial diversit gain b adding vertical otion to a oving source or receiver in a geoacoustic inversion context will be significant. Using a slow oving AUV glider in a snthetic aerture geoacoustic inversion is a otential extension to this research Develoing a change-oint ethod to also deterine which araeters have changed would be useful. Knowing the changed odel araeters is beneficial as it allows the osterior densit of the unchanged odel araeters fro the re-change-oint inversion to roagate as the rior densit in the ost-change-oint inversion when a changeoint is detected. 8/2/204 50

51 Advisors: Acknowledgeents Prof. Willia Hodgkiss, Prof. Peter Gerstoft, Dr. Caglar Yardi. Coittee ebers: Prof. Willia Coles, Prof. Willia Kueran, Prof. Barnarb Rickett. Everone at MPL ast and resent. Dr. Hee Chun Song, Mr. Dave Ensberg. M arents, wife, daughter, and sisters. Sonsors: DSO National Laboratories of Singaore ONR Grant No. N /2/204 5