短時間内に於ける推定船位誤差の一例について(日本航海学会第26回講演会)

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  • On the Error of Estimated Ship's Position When Sailing Time has been short
  • 短時間内に於ける推定船位誤差の一例について
  • タンジカン ナイ ニ オケル スイテイセンイ ゴサ ノ イチレイ ニ ツイテ

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抄録

As the error of estimated ship's positon varies according to tract of sea, sea-route, style, size, speed and draft of ship, capacity of navigational instruments, etc., one can not determine the quantity of error uniformally ; but the writer attempted to find the general tendency of relationship between duration of sailing time and decline in accuracy of estimated ship's position. In that case, everybody acknowledges that if the sailing time is long the error of estimated position does not increase in proportion to the time, but in the case of a short time of sailing a few questions remain. Of course, from the point of view of how to estimate the error boundary of ship's position toward the expiration of the given sailing period, the relation is more important if the time is longer ; but a study was made of the relation between the sailing time and decline of accuracy in short time from the standpoint of determination of a ship's position, use being made of the data gotten by the training ship "Oshoro-maru (616T, 9.45kt)" of Hokkaido University off the east and south coasts of Japan and Eastern China Sca. In general, as the elements of error due to estimation of a ship's position are classified as elements proportional to sailing time and errors proportional to square root of sailing time, the synthetic error is expressed by √<at+bt^2>. (a, b: coefficient, t: sailing time) The error of before and behied estimated position is expressed by equations (1) & (2) by least square method from the data shown in Fig.1 (A) & (B) and the error of right and left is expressed by equations (1') & (2') from the data shown in Fig.2 (A) & (B) and the average values of two tracts of sea are shown in equations (3) & (3'). As above mentioned no large difference can be found between those errors, accordingly the relation between the sailing time and the error of estimated ship's position is expressed simply, approximately and practically by σ='.74√<t>.

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