The previous reports discussed the fundamental idea of this system and the accuracies of distances and fixes estimated by this system on fixed points. This paper provides some findings about the acuracy of this system in motion. The transponder was hung from the boat. At the first, the boat was anchored and the examination ship "Kakusui" sailed near the boat and measured the distances and the angles, then the boat sailed slowly at about 1～2 knots and "Kakusui" tracked it and measured necessary items. When the boat was anchored the measured fixes scattered in the range of 0.01 NM (about 20 m)from calculated fixes. In the other case, the values of displacement of fixes were less than 0.02 NM (about 37 m) and the mean value was 0.015 NM (about 27 m). These values are equal to the variable error of Decca navigation system that is used as the senser of the ship's positioning and the results show that this system measure up to our expectation.
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