Abort Point
The Abort Point is a position on the marked course where the ship may abandon her passage and be able to return (or hold position safely).
Point of No-Return
Point of no return is the position after which the ship is committed to proceed on voyage. It will be the position where the ship enters water so narrow that there is no room to return or where it is not possible to retrace the track due to a falling tide and insufficient UKC.
It is to note that both these are calculated during passage planning and are dependent on the manoeuvring characteristics of the vessel, particularly the turning radius. Point of no return is generally taken to be the point after which the vessel cannot turn back as there is insufficient room to turn. Hence, this point is dependant on the tides at the port. Considering the lowest tide on the arrival day, point of no return is market on the route.
