A new image analysis system for a motion measurement of a free-running model ship is developed. In the present system, a target is traced through template matching procedure, and error identification is distinguished by using some characteristic parameters. The tracking procedure by a human judgment is supported in the system. The change in the mutual correlation coefficient of the image and the contrast of the image are used as characteristic parameters. The characteristic parameters are projected on a characteristic vector field and the error identification is judged on the characteristic vector field. For the verification of the present system, a target on a rotating disk with a constant speed was traced. The error of the rotating radius remained less than 2% and the mean tangential velocity remained less than 0.5% respectively. The measurement of a free running model ship succeeded with satisfactory results. Moreover, it was confirmed that the judging error identification of the present system was very effective.