| 摘要 |
PROBLEM TO BE SOLVED: To easily calculate the position of an object drifting on the ocean. SOLUTION: A database part 3 storing data, obtained by making an ocean current speed vector at each spot on the ocean correspond to its position coordinates, is provided. The on-the-water landing position coordinates (P0)s and landing time t0 of a dropping object are calculated based on its speed over a ground <VG>, a speed over the air <VA>, an altitude (h) and a wind speed (VW), at the time of dropping the object. An ocean current speed vector (VT0) corresponding to (P0) is read out of the database part 3, and a position after the elapse of time t1 from the landing is found as <P1>=<P 0>-<VT0>×t1. Similarly, an ocean current speed vector <VTn-1> at a position <Pn-1> is read out of the data base part 3, and a position <Pn> at an optional elapsed time tn is found one by one by a general formula <Pn>=<Pn-1>+<VTn-1>×(tn-tn-1).
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