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Dolphin echolocation research: VRML virtual replay capabilities

Stephen Martin
SPAWAR Systems Center San Diego

Wednesday, October 30, 2002
3:00 p.m. – Pacific Forum

SPAWAR Systems Center San Diego develops marine mammal systems used by the U.S. Navy in mine hunting applications. Dolphins are trained to locate and mark bottom mines to support the U.S. Navy Mine Counter Measures Mission. Dolphins are currently able to conduct much more effective mine hunting than existing manmade sonar systems. I will describe a research project sponsored by the Office of Naval Research. This project, which uses free-swimming dolphins to perform mine hunting tasks, provides levels of instrumentation never before available.

The dolphin is trained to carry a bite-plate-mounted instrumentation package while searching for inert mine-like shapes on the seafloor. The instrumentation package records the dolphin’s underwater navigational data (heading, pitch, roll, depth, speed), as well as a wealth of dolphin echolocation data (e.g., outgoing echolocation clicks, high gain binaural receiver data streams modeled after the dolphin’s hearing capabilities). A sixty-second search by the dolphin results in a data set of over 100 MB.

Virtual Reality Modeling Language (VRML) is used as a research tool to virtually replay the dolphin’s underwater search for two purposes. The first purpose is to provide researchers much more insight into what the dolphin does when it conducts its echolocation search (i.e., better situational understanding of the dolphin’s search strategies). The second purpose is to allow researchers to target selected sections of the large data set for more detailed signal processing analysis, such as testing signal processing algorithms to automatically detect the mine-like object’s echoes within the binaural echo stream. Samples of the VRML replay capabilities will be demonstrated in the seminar.

Next: The S.S. Central America Project