What is the difference between the terms "close quarter situation", "risk of collision" and "Impeding the safe passage" ?
May I contribute some of my opinion sirs.
Close quarter situation mean
A situation at which vessels are dangerously approaching each other and the action of one vessel alone may not be enough to avoid Risk of collision. The distance may vary case by case, however, the following factors may take into account.
(1) Approaching rate and directions.
(2) The speed of both vessels.
(3) Manoeuvribilities of both vessels.
(4) Weather, visibility and traffic condition etc.
The distance between the vessels may assume that there is a close quarter situation if one vessel entering into the turning circle of the other.
The risk of collision is that the bearing between the vessels is not changing enough so if these vessels are kept going that course and speed they will meet (collide or almost collide) at a point.However, as per Rule 7 (a), we should assume that there is a risk of a collision even if we have any doubt.
Impeding the safe passage.
Its concern with ( rule 9 b,c,d rule 10 i,j and rule 18 d,e,f)
Above mentioned vessel suppose to take early action to allow sufficient sea room for the safe passage of the vessel not to be impeded.( rule 8 f i).
That means the vessel not to impede should take action early without waiting to determine the risk of collision exit or not.