| 摘要 |
PURPOSE:To obtain the approximately accurate position of a ship, by computing a plurality of dead-reckoned present positions, computing the present position group by assuming the speed of a tidal current, making the mean value as a true present position, and determining the assumed tidal current speed as a true tidal current speed. CONSTITUTION:A position reckoning device 1 comprises a navigation signal receiver 11 and a coordinate converter 12 and outputs a reckoned position signal Sp as a digital signal. A moving distance measuring device 3 comprises a log indicator 21, an azimuth meter 22, and a vector converting circuit 23, and outputs a speed signal Sv. The reckoned position signal Sp and the speed signal Sv are stored in a memory circuit 3, and computed in a computing circuit 4. The computing circuit 4 obtains the moving distnce of the ship with repect to the water by multiplying the log speed Sv and the time at first, then obtains a plurality of the dead-reckoned positions, further obtains the present position group, and computes the deviation of the present position group. The present position whose deviation value is the smallest is made to be the true present position, and the corresponding assumed tidal current speed is determined to be the true tidal current speed. |
