ABSTRACT
In Chapter 2, it is explained that many of the actions performed onboard are techniques for achieving safe navigation. Thus, many onboard actions correspond to certain necessary techniques, and these techniques were categorized into nine groups according to the intended functions. Because these nine basic techniques are mutually independent from each other in function, they are termed elemental techniques. The various situations encountered during navigation can be adequately addressed by combining the necessary elemental techniques for achieving safe navigation. The significance of the categorization is now discussed.
Safe navigation achievement and necessary techniques
The requirements for realizing safe ship navigation are explained in Section 1.4 of Chapter 1 “Conditions Necessary for Safe Navigation”. Figure I.1.8 from that section is reprinted here as Figure I.4.1.
The vertical axis in the figure indicates the achievable competency level of seafarers. The horizontal axis indicates the necessary competency level required by the navigational environment. The relationship between the two can be interpreted as follows. Let us imagine a condition of navigational environment, such as a coastal navigation by a very large crude carrier (VLCC). If we also consider the tide in this water area, adequate measures need to be taken against grounding accidents. In such an environmental condition, ship position needs to be frequently measured and shallow water area perceived prior to approach. A necessary condition is the frequent high-precision measurement of ship position. This water area can be considered to be one requiring measurements every 5 minutes within an error of 0.5 cables. This refers to the situation shown on the horizontal axis. When it is possible to measure ship position every 5 minutes within an error of 0.5 cables, the achievable technical level demonstrated by the seafarers navigating this ocean area is equal to the level required by the 98environment, and ship position measurements for safe navigation are satisfied. On the figure, this situation appears as a point on a 45° line. This 45° line represents the situation in which the respective competency levels shown by the vertical and horizontal axes are equal.
In this situation, ship position measurements can also be made with a seafarer technical level that is within an error of 0.5 cables every 3 minutes. In this case, the achievable seafarer competency level is higher than the level required by the environment. This state is represented by a point within the area above the 45° straight line on the figure. Since the achievable competency level of seafarers is higher than the level required by the environment, ship position measurements necessary for safe navigation are satisfied, and so are the conditions for safe navigation.
By contrast, in cases where the achievable competency level of seafarers is low and ship position measurements are not possible every 5 minutes within an error of 0.5 cables, the conditions of safe navigation are not satisfied, resulting in a dangerous state. On the figure, this state is represented as a point within the area under the 45° straight line, which indicates dangerous navigational conditions.
Thus, for safe navigation to be realized, realizing the necessary techniques to the level determined by the environmental conditions is an indispensable requirement. The environment in the example only required position fixing, but typically, the environmental conditions usually require various and multiple techniques. Even in such cases, conditions on the horizontal axis are decided by what elemental techniques are required and to what level. Thus, navigational safety can be estimated by estimating the achievable level of competency versus the level required by the environment. Ship navigational safety can be estimated by balancing these parameters.
Clarification of necessary techniques in target situations
What action seafarers must take to achieve safe navigation in the various situations faced onboard is important.99
For example, consider the situation in which another traffic vessel is encountered during navigation. The following actions must be performed by the seafarers to avoid colliding with the vessel:
Detection of the other vessel
Estimation of risks to the ship being handled (hereafter, “the ship”) from the other vessel
Determination of means of avoiding collisions
Execution of collision-avoiding actions
Verification of the effects of the avoidance action
The collision-avoiding action discussed here corresponds to the elemental techniques required at each stage. First, the traffic vessels must be detected. The relevant technique at this stage is lookout, and the instrument operation technique is also required depending on the lookout method. Next, future impending risks to the ship must be estimated. This is achieved through continuous lookout; RADAR/ Automatic Radar Plotting Aids (ARPA) and other instruments may also be used. When lookout and instrument operation competency are inadequate at this stage, predictions may be late or mistaken, and dangerous conditions may arise. If accurate predictions cannot be obtained, then very high frequency (VHF) or other communication instruments may be used to contact the target ship and verify her intentions. This is a situation in which the communication technique is applicable. When a future collision risk is verified, then preparations are made for collision-avoiding action. Collision-avoidance methods are determined by observing the traffic laws and in accordance with a plan based on understanding the maneuverability of the ship and lookout for the surrounding ships. After a collision-avoidance plan is finalized, the changes in the situation are monitored through the lookout technique, and the starting time for collision-avoiding action is decided through technical management. Subsequently, the plans are executed through the maneuvering technique. As collision-avoiding action proceeds, its effects are verified by lookout, by monitoring the change in the closest approach distance and the encountering situation, and by monitoring whether safe passing is ensured. Since collision-avoiding action results in deviation from the planned course, ship position must be verified through position fixing.
Thus, the eight elemental techniques are applied at the appropriate times, even when it is only a matter of following collision-avoidance procedures. In addition, to simplify the discussion, only a sampling of the applicable techniques has been mentioned here; a more detailed analysis would reveal the further involvement of the technical management, communication, and instrument operation techniques at each stage. Furthermore, in the abovementioned situation, the occurrence of an emergency condition between the ship and another ship has not been assumed, so no additional emergency treatment technique situations are discussed.100
Actual navigation situations (for example, navigating congested water areas under low-visibility conditions, harbor navigation, and docking) can entail the synthesizing of all nine elemental techniques. Thus, necessary elemental techniques can be clarified for each maneuvering situation.
Key factors of Section 4.1: Significance of Elemental Technique DevelopmentThe following are made possible by developing elemental techniques for ship handling:
By analyzing safety in ship navigation based upon necessary techniques, it becomes clear that the attainment of necessary techniques determined by environmental conditions is a necessary condition for realizing safe navigation.
The techniques necessary for safe navigation in any situation can be organized into nine technical elements, and safe navigation can be achieved by synthesizing these nine elemental techniques.
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