Which of the following statements about the Horizontal Plane is true?

The Horizontal Plane is defined as a plane that runs parallel to the surface of the Earth or the ocean's surface. This characteristic allows it to represent a level surface from which measurements and navigational calculations can be made. Understanding this plane is crucial for tasks related to navigation, alignment of onboard systems, and overall stability assessments of a vessel.

In contrast to the Horizontal Plane, the relationships between it and other planes such as the Deck Plane or its center of mass are also vital, but they do not define the Horizontal Plane as accurately as the connection to the Earth's surface. Furthermore, the statement that it is fixed and does not change overlooks the fact that variations such as tides or ship movement can affect how we perceive and measure this plane in relation to real-world applications. Therefore, the true nature of the Horizontal Plane is best captured by its parallel alignment with the Earth's surface.