When a ship proceeds to the quay in a harbor, her captain will require the following data for ship-handling aid. 1. ship's speed underway, v1 2. wind and current effect, lee way, vn 3. proceeding angle to the quay. θ in degrees 4. differential value on the above data, dv1/dt, dvn/dt and dθ/dt 5. true course and speed of ship in view of wind and current effects In this paper, the measuring system of the proceeding angle to the quay by means of hydroacoustic apparatus and the digital indicator of its degrees are discribed. Thc proceeding angle is determined by measurning two minimum distances to the quay from two sound sources which obtained at the normal incident of ultrasound to the quay. The installation arrangment of these transducers is shown in Fig. 4 and the measuring systen in Fig. 5. The required proceeding angle to the quay can be obtained by the following equations sinθ=△d/1,△d=d1-d2 θ≒△d/0.017.1in degrees where, d1 and d2 are the two minimum distances and 1 is the distance between the two sound sources.
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