What is the term for the main horizontal plane of reference onboard a vessel?

The term "Ships Base Plane" refers to the main horizontal plane of reference onboard a vessel. It serves as an essential reference point for various measurements and operations related to the ship's structure, stability, and equipment placement. The Ships Base Plane is typically established at the waterline when the ship is at rest in calm water, serving to standardize vertical measurements and ensuring consistency throughout the vessel for tasks such as weight distribution analysis and stability calculations.

This reference plane is crucial in various naval architecture and marine engineering applications, allowing crews and engineers to ensure the vessel maintains appropriate stability and efficiency. Knowing where the Ships Base Plane is located helps in understanding how the ship will behave in different conditions and how to manage loads and ballast effectively.