| 摘要 |
PURPOSE:To prevent errors due to the pitching of a vessel and to simplify the structure of a measuring device by determining the ground speed of an underwater object on the basis of the difference between the ground speed of the vessel and the speed thereof to the underwater object. CONSTITUTION:The transmission 7 and reception 8 of an ultrasonic wave are made, with a depression respectively, in the forward direction and the backward directin at an angle of 180 deg. thereto in relation to the cource VG of a vessel, and echoes fGF and fGA from the bottom of the water and echoes fWF and fWA from an object under water are received. Then, a value proportional to (1/fGA-1/fGF) is found from fGF and fGA, and based on this value, the ground speed VG of the vessel or a value proportional to VG is calculated 12. Meanwhile, a value proportional to (1/fWA-1/fWF) is found from fWF and fWA, and based on this value, the speed VW of the vessel to the underwater object or a value proportional to VW is calculated 11. Furthermore, the ground speed VS of the underwater object is calculated 13 from the difference between the speed VG or the value proportional to VG, and the speed VW or the value proportional to VW. |
