Sea Technology

JUN 2017

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Page 14 of 72

14 st / June 2017 Acknowledgments Special thanks to personnel from both Woods Hole Oceanographic Institution (Andrew Girard, Roger Stokey and Mike Purcell) and Pennsylvania State University Ap- plied Research Laboratory (Dr. Thomas Montgomery and Chad Smith) for their assistance in the development of the AUV spiral scan trajectories and field test plans for the Buz- zards Bay, Massachusetts, field tests. In addition, special thanks to the NSWC PCD Rapid Pro- totype Laboratory (Chuck Self) in the generation of the 3D prints from the CSAS imagery. References For a list of references, contact Jermaine Kennedy at jer ST form operating in a new spiral scan mode. An advantage of the spiral scan pattern is that it enables the system to gener- ate a multipass array having the same vertical extent as in the previous experiments but in only one-third the time. The water depth was approximately 13 m, and a large sound speed gradient was encountered within a few meters of the seabed. Targets were deployed on a variety of bottom types, which consisted of either mud or fine- to medium-grained quartz sand. The spiral trials were extremely successful, and future tests are planned in more challenging environments affected by strong currents. Conclusion Until recently, true volumetric imaging has not been a capability of synthetic aperture sonar systems. Significant challenges that were overcome in its development included compensating for spatial and temporal sound propagation speed variations, the complexity of the local seafloor, and the 3D positioning uncertainties inherent to underwater navigation that complicate multiple-pass synthetic aperture processing. Overall, the recent field trial results have been successful in a wide variety of environments. By using relatively low frequencies, the technique generates volume images that have enabled us to remotely and nondestructively evaluate both the external and internal structure of many interesting targets. We foresee many additional uses for the technology, ranging from model development for 3D printing to rapid acquisition of training data for automatic target recognition, oceanography and physical acoustics. Dr. Jermaine L. Kennedy is a physicist at the NSWC PCD. He received two different B.S. degrees in phys- ics and physics education from State University of New York at Buffalo. He received an M.S. and Ph.D. in applied physics from University of South Florida in 2001 and 2006, respectively. Dr. Timothy M. Marston is a senior engineer in the Acoustics Department at Applied Physics Labora- tory University of Washington. He received his B.S. in electrical engineering from Seattle Pacific Univer- sity in 2004 and his M.S. and Ph.D. in acoustics from Pennsylvania State University in 2006 and 2009, re- spectively. Identify a target "under" the ocean floor - Easy operation - Boat towable for deep water - Pole mountable for shallow search - Displays data on laptop - Commercial grade - Shows density disturbance within different strata layers JW Fishers Mfg., Inc. 1953 County Street East Taunton MA 02718 USA (800)822-4744 or (508)822-7330 Email: with the SBP-1 Sub Bottom Profiler

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