A wide angle shallow water observing sonar

Initial results, briefly presented here, from a single-beam sounder installation support the presence in marine reserve of snapper spawning behaviour seen in captivity. A design for a split-beam adaptation of a commercial swath sounder to allow further investigation of this behaviour is presented here. Custom elements & transducer arrays to enlarge the swatch field of view have been designed, modelled, fabricated & tested. Design issues are introduced, calculated & measured polar patterns are presented. Signal processing additions to the swath processing are outlined to enable split-beam operation to locate individual fish targets.