Title: THE PREDICTION OF TIME OF CLOSEST APPROACH
Author(s): A. C. Rawling
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 17, Number 2
Pages: 186 - 189
Cite this article: Rawling, A. C., "THE PREDICTION OF TIME OF CLOSEST APPROACH", NAVIGATION, Journal of The Institute of Navigation, Vol. 17, No. 2, Summer 1970, pp. 186-189.
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Abstract: A basic procedure used in obtaining a running fix of position involves taking two non-simultaneous bearing on the same stationary object and measuring either the intervening run of time interval. The identical technique may also be used to determine the predicted distance at which the object should be passed abeam (provided the vessel maintains its course and speed) as shown in Fig. 1. The various methods used to predict the distance abeam include graphical construction, arithmetical calculations (e.g. numerical evaluation of trigonometrical formulas, use of precomputed tables, simple rules of thumb for special cases) and even analog computation (reference 1). All the preceding obtain the predicted distance abeam first, followed by the calculation of the time of closest approach, if the latter is desired. In some instances it may be simpler to predict the time of closest approach first and then calculate the minimum distance of passing. This paper presents two such cases amendable to a simple mnemonic rule.