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Evora slideshare

  1. 1. Post- processing Pouliquen echo correction for• Daniel Rodríguez Pérez, UNED• Noela Sánchez Carnero, UDC bottom• Juan Freire Botana, UDC classification
  2. 2. The problem…• Sea bottom classification • Muddy • Sandy • Rocky (Folk classification of sediments)• Single beam echosounder • Cheap and simple • Transect based• Coastal areas • Fast bottom type changes • Large depth differences
  3. 3. Our goal…• Use single-beam echosounder• Correct echoes in coastal areas• Get a sound classification • In a coastal area
  4. 4. Study area• Ría de Cedeira• Acoustic survey CORERS• Diving transects• Fishermen map • Interview based • Consensus map
  5. 5. The correction and the idea…• Power correction • Pouliquen ECAS 2004 • +30 log ( R/Rref ) • Change pulse duration online• Time correction • Our approach • Time stretching • Change pulse duration offline • How? • Convolution
  6. 6. The correction and the idea…
  7. 7. The correction and the idea…• Time correction • Pouliquen ECAS 2004 • Time stretching • Change pulse duration online• Power correction • Our approach • +30 log ( R/Rref ) • Change pulse duration offline • How? • Convolution Time adjustment Power adjustment
  8. 8. The correction and the idea…• Time correction • Pouliquen ECAS 2004 • Time stretching • Change pulse duration online• Power correction • Our approach • +30 log ( R/Rref ) • Change pulse duration offline • How? • Convolution
  9. 9. The correction and the idea…• Time correction • Pouliquen ECAS 2004 • Time stretching • Change pulse duration online• Power correction • Our approach • +30 log ( R/Rref ) • Change pulse duration offline • How? • Convolution CONVOLUTION
  10. 10. First results• Pings over sand in the study area • Different depths• Pings over rock in the study area • Different depths • Larger variations
  11. 11. Classification• Ping average 38 kHz • 20 ping averages • 50 m segments• Nearby ping grouping • Spatial coherence • Transect classification• Global ping grouping • Global classification 200 kHz• Class representatives• Ping classification
  12. 12. Classification• Ping average • 20 ping averages • 50 m segments• Nearby ping grouping • Spatial coherence • Transect classification• Global ping grouping • Global classification• Class representatives• Ping classification
  13. 13. Classification• Ping average • 20 ping averages • 50 m segments• Nearby ping grouping • Spatial coherence • Transect classification• Global ping grouping • Global classification• Class representatives• Ping classification
  14. 14. Validation…• Fishermen map validation • qualitative• Diving transect validation
  15. 15. Validation…• Fishermen map validation • qualitative• Diving transect validation FS&M CS R CL1-3 259 8 10 CL2 5 2 40 CL4-5 6 1 157 κ=0.73
  16. 16. Discussion• Ping averaging • (forced) Spatial coherence • Physically (intensity) motivated • What about rocky bottoms?• Classification based on templates • (implied) Spatial coherence • Transducer (and frequency) dependent• Accuracy and kappa? Not too good • Ground-truthing samples • Only one frequency (and one echo per ping) used
  17. 17. Conclusions• PLP correction • Effectively corrects the shape of the echoes to a shallow water reference • … at the cost of losing some details• Aggregative method classification • Ping averaging taken to its most • Echo template based classification • … relative success• Further research needed for rocky bottom correction
  18. 18. Acknowledgements• The authors wish to acknowledge Prof. M. Mozynsky for enlightening discusion about the ideas in this paper• ... and the organization of the ACUSTICA 2012 for the opportunity to present this work here.
  19. 19. Acknowledgements• The authors wish to acknowledge Prof. M. Mozynsky for enlightening discusion about the ideas in this paper• ... and the organization of the ACUSTICA 2012 for the opportunity to present this work here.

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