Abstract
Lengths and positions of medium-sized ships on the Uraga Suido were measured by the "Camera Locator" in search for the dimension of the offective area of the ships. The result shows the dimension of the area to be about 250m in the course direction and about 100m in the direction perpendicular to the course. The investigation of the result together with those 1964 and 1965 gives the dimension of the effective area to be about 8L in the course direction and about 3.2L in the direction perpendicular to the course where L is the total length of ship.
