JPS57151878A - Fish detector for dragnet - Google Patents

Abstract

PURPOSE:To ensure stable recording with sea level as a reference, by writing upper echo data into a memory in an address sequence which is arranged in the reverse order, and writing only necessary data into a second memory, with the stable sea level wave that is read out at first as the reference. CONSTITUTION:The echo from an ultrasonic wave device attached to the dragnet is received by a wave receiver 1. The upper echo data is written into the first memory 6 in the address sequence which is arranged in the reverse order through a control signal generator 5 and the like. The contents are sequentially read out. The signal corresponding to the first stable sea level wave in the range of a predetermined sea level wave signal is determined by the correlation by a stable signal detecting circuit 7, a sea level wave detecting circuit 8, and the like. With said signal as a reference, only the necessary data such as the sea level echo wave is recorded in the second memory 10 from the memory 6 through a writing control circuit 9. Therefore, the signal corresponding to the sea level wave is detected by the recording of the sea level reference without the effect to the reflected wave from the school of fish and the like. Thus the fish detector for the dragnet which can ensure stable recording in the relatively simple constitution is obtained.