結氷湖における氷上よりの水深測量とワカサギ探知の実験

概要

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In echo sounding of a lake, an artificial lake of an hydroelectric power station, for example, the accurate determination of positions is important. When using an echo sounder installed on a boat it is difficult to determine positions accurately because of shift due to wind or current; and so, the error due to inaccuracy of position is large and great efforts are needed to achieve even approximate accuracy. However, when the lake is frozen, it is easy to determine the positions with accuracy from the surface of the ice and if it were possible to sound from its surface then sounding work would be made much easier. But unfortunately, transmission loss of ultrasonic waves in ice and the existence of air between the ice and the surface of the water had to be taken into account. Hence experiments on sounding from the surface of the ice were made on frozen Lake Haruna in Gumma Prefecture in January and February 1962 and in February 1963. The measured transmission loss in ice of Lake Haruna was 0. 40dB/cm for 200kc and 400kc, and 0. 25dB/cm for 28kc. The echo trace of the bottom was obtained from the surface of ice of the frozen lake by scraping away the snow on the surface with shoes, putting the transducers on it and then pouring over a little amount of water. The sounding was carried out rapidly and accurately. Pond-smelt swimming beneath the ice were also detected from the surface.
1964-05-30