Collaborative Research: Improving the DSL-120A Sonar Mapping System

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P.I. Rognstad, Mark Proposal: 0222468 Bowen, Andrew 0222432The PIs propose to upgrade the DSL-120 sonar mapping system and resolve problems related to the integration of DSL-120A sensors and capabilities. Primary tasks to be completed as part of this work are: 1) Improvement of the signal to noise ratio of the system to enhance the ability to extract useful phase-bathymetry data from the basic sonar system. 2) The PIs will resolve the acoustic interference between the sidescan sonar and the Doppler velocity log (DVL), which has prevented the simultaneous operation of both systems. The inability to use the DVL results in sonar surveys with degraded navigation data, particularly for surveys covering areas too large for continuous transponder navigation. Attempts to synchronize the two sonars during the upgrade were unsuccessful, due to long and variable length latency in the response of the DVL to external triggering. 3) Bathymetric sonar capabilities of the DSL-120A system will be improved to enhance resolution of small-scale features closer to the resolving capabilities of the backscatter imagery. Phase bathymetric sonars like the DSL-120A cannot distinguish acoustic reflections from different parts of the seafloor that arrive at the sonar transducers at the same time - that is, that are the same distance from the tow vehicle. Over a flat bottom, this will be the case for that part of the seafloor closest to the vehicle; in areas with high relief, this can happen in any part of the mapped swath. Multibeam sonar, which combines signals from dozens of hydrophones, can synthesize narrow beams that reject adjacent reflections, giving greatly improved bathymetry in these situations. The capability to operate the SM2000 with the DSL-120A sonar system will be added. The multi-beam system will be synchronized with both DVL and sidescan/swath bathymetry sonars, so all three acoustic sensors may be used simultaneously. The proposed improvements will complete the full integration of all the requisite sensors and capabilities of the DSL-120A sonar system. These improvements will improve signal quality of the backscatter and phase-bathymetric sonar, improve navigation through the use of the DVL, and offer the potential for collection of SM2000 near-bottom multibeam data to improve the quality of bathymetric data acquired using the DSL-120A sonar.