Advance: When a ship is turning the distance traveled by centre of gravity along the original course.
Transfer: Distance traveled by COG measured from the original track to the point where the vessel has altered her course by 90 degrees.
Tactical diameter: It is the transfer for 180 degrees.
Stopping distance: It is the minimum distance that a vessel requires to come to rest over the ground.
Head reach: Distance along the direction of the course that it covers from the moment the full astern command is given until ahead speed changes sign.
Turning circle: The roughly circular path followed by a vessel when it alters course under helm through 360 degrees.
Drift angle: Angle between ship's fore and aft line and the tangent to the turning circle.