What is considered a significant course change according to navigational rules?

A significant course change is defined within the context of navigational rules as a shift in direction that is likely to affect the navigation or safety of a vessel. A course change of 30 degrees or more is widely recognized as the threshold where navigational adjustments may require increased attention from bridge personnel and may have implications for the vessel's interaction with other traffic. Such a change can greatly influence the vessel’s path, necessitating reevaluation of the vessel's current navigation plans and potentially affecting the movements of other vessels in the vicinity.

In contrast, smaller angular adjustments—such as 5, 15, or even 45 degrees—do not typically invoke the same level of concern and management attention in navigational practices. A 5-degree change is often seen as negligible, while changes of 15 degrees may not substantially alter the vessel's course relative to other navigational factors. A 45-degree change, while significant, exceeds the common definition used in typical navigational operations, which recognizes 30 degrees as the more standard reference point. Therefore, defining a significant course change at 30 degrees strikes a balance among operational safety, communication clarity, and navigational efficiency.