抄録
In the radar navigation, the plotting is necessary for judging the motion of the target and the risk of collision or avoiding the target. In that case, the motion of the target on the radar scope is usually quite small; the interval of the observational time is every six or three minutes. Because we have to plot on the basis of such a small relative movement, we feel uneasy about the result of the plotting. From this viewpoint, the aim of this paper is to find the error included in the C.P.A. distance, after taking the step of avoiding the target, in case of the error being found in observing the target.
