In the context of navigation, what is referred to as a "horizon"?

In navigation, the term "horizon" refers to where the earth meets the sky, which is fundamental for various navigational practices. This line indicates the limit of one's sight and plays a critical role in determining positional fixes at sea. The visual horizon is especially important for mariners who rely on visual cues to navigate, taking into account the curvature of the Earth and the observer's eye level.

While options related to visibility on a water body and celestial navigation touch on aspects of navigation, they do not capture the broader and more universal definition of the horizon itself. The height of the sun pertains to solar navigation but is a specific aspect rather than a definition of what constitutes the horizon in navigation. Understanding the concept of the horizon is essential for navigators as it aids in recognizing landmarks, utilizing instruments effectively, and conducting celestial observations.