(a) Every vesselThe word 'vessel includes every description of water craft, including non-displacement craft, WIG craft and seaplanes, used or capable of being used as a means of transportation on water'. shall use all available means appropriate to the prevailing circumstances and conditionsThis phrase is used in Rules 5,6,7 & 19. It indicates to the reader that the rule must be considered within the context that it is being applied. Although this type of 'catch-all phrase' makes the rules challenging to interpret it allows mariners to respond to the variety of events that can occur at sea. More to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.
(b) Proper use shall be made of radar equipment if fitted and operational, including long-range scanning to obtain early warning of risk of collision and radar plottingRadar plotting is a process used for measuring the movement of other vessels or objects. This process often involves the use of a plotting tool or form which allows for the tracking of true or relative movement. Learn more about radar plotting. More or equivalent systematic observation of detected objects.
(c) Assumptions shall not be made on the basis of scantyThe word scanty means 'small' or 'insufficient'. This part of the rule warns against making decisions based on a small number of observations. More information, especially scanty radar information.
(d) In determining if risk of collisionThe term risk of collision is described in Rule 7. 'Every vessel shall use all available means appropriate to the prevailing circumstances and conditions to determine if risk of collision exists. If there is any doubt such risk shall be deemed to exist.' More exists the following considerations shall be among those taken into account:
(i) Such risk shall be deemed to exist if the compass bearing of an approaching vessel does not appreciably change;
(ii) such risk may sometimes exist even when an appreciable bearing change is evident, particularly when approaching a very large vessel or a tow or when approaching a vessel at close range.