Which of the following best describes Geographic Position (GP)?

Geographic Position (GP) refers specifically to the theoretical point on the Earth's surface directly underneath a celestial body, such as a star or planet, when it is observed from the surface of the Earth. This concept is fundamental in celestial navigation as it allows navigators to establish their position relative to celestial bodies. By determining the GP of a celestial body, navigators can then use their observations to triangulate their own location on the Earth's surface.

The other options do not accurately capture the definition of Geographic Position. For instance, the location of a ship at a specific time is generally referred to as the ship's position, which is distinct from the GP. Coordinates of a destination port pertain to the known location of a specific place rather than the theoretical point associated with a celestial body. The point of observation used in celestial navigation would refer to the vantage point or specific location where observations are made, rather than the GP itself.