Underwater acoustic surveillance of harbor and channel areas

摘要

1. A catacoustic system for detecting the intrusion of a body in an object field under a water surface at a harbor entrance or the like comprising a high resolution sonar apparatus including a submerged transducer having a vertically oriented fan shape directivity pattern directed at an object field athwart the harbor entrance and having its principal axis slanted towards the water surface, means for periodically pulsing said transducer to radiate pulses, a display medium, and means for receiving flutter echoes of each pulse returned from the water surface and for producing markings at points along a line on said medium varying in position in accord with the range from which said echoes are received, the markings for echoes from successive pulses being produced in line by line correlation, whereby a significant change in the display with time indicates the position of a body intruding in said object field.