Jules S. Jaffe
Marine Phys. Lab., Univ. of California at San Diego, San Diego, CA 92093-0238
As part of a National Science Foundation initiative in Global Ecology (GLOBEC) our group in acoustic imaging in the Marine Physical Laboratory, Scripps Institution of Oceanography, U.C.S.D., has been operating a multibeam acoustic imaging system whose purpose is to track small animals (zooplankton) in the water column in three dimensions. The system has been constructed to operate at a frequency of 420 kHz and consists of a set of side-scan sonarlike transducers. Together, the eight transmitters and eight receivers allow imaging of an 8x8 image. Lateral resolution is 2x2 deg and the range resolution of the system is on the order of centimeters. The system produces frames (3-D images) at a rate of approximately 1 frame per second. To date, the system has been used to image the trajectories of small fish and test targets in a test tank environment. Animated movies, derived from the data have been fabricated which clearly show the animal's movements. Quantitative analysis of the systems's performance has confirmed the three-dimensional locations of the animals that are produced from the data.