抄録
Assembling the data of Crash-Stop Astern by courtesy of the Institute for Sea Training, the authors recomputed the tracks for each trial. The training ships have performed the trials at least once a year in their curriculums using various methods, namely ; (1) The Dumb-Card Method which calculates a ship's relative positions against a target afloat by observing the relative azimuths with fore and aft cards repeatedly. (2) The Sextant Method which calculates her relative positions against a drifting life boat, from which one of the ship's fixed points is measured by observing vertical angles with sextants, and of which the bearing is simultaneously observed from the ship repeatedly. (3) The Radar Method which calculates her relative positions against an appropriate floating target by measuring the distance with a radar and the bearing by a compass repeatedly. (4) The Numerical-Integration Method which calculates her track by summing up distances run during a short interval with respect to x and y directions. The above comparison shows that the Numerical-Integration Method fairly fits with the Sextant Method, which is highly evaluated by training ship officers, and from start of astern revolution the speed of the ship decreases almost linearly. The authors have arrived at the conclusion that the Numerical-Method is likely to be most suitable for merchant vessels if the trial is to be performed by the ship's crew only. This is because this method can be carried out only by 2 or 3 personnel. It is to be remembered, however, that the speedmeter precheck is vital.
