What is a "navigational aide"?

A navigational aide refers specifically to a structure or device designed to assist mariners in navigating safely. This includes various tools such as buoys, lighthouses, and markers that provide important visual cues about safe routes, hazards, and other critical navigation information. These aides are essential for helping vessels determine their position and course, particularly in coastal and restricted waters.

While the other options involve elements related to navigation, they do not capture the precise definition of a navigational aide. For instance, a person assisting with maritime navigation provides support but is not a physical aid in the same context. Similarly, a type of nautical chart is a crucial tool for navigation but does not fit the definition of a physical structure or device. Lastly, while a system for tracking ship movements is valuable for navigation and safety, it refers more to tracking technology rather than the physical aids used directly in guiding vessels. Thus, the correct answer encompasses the tangible tools and structures critical for the navigation process itself.