What does 'innage' refer to in the context of cargo measurement?

In the context of cargo measurement, 'innage' specifically refers to the measured distance from the surface of the liquid to the bottom of the tank. This measurement is crucial for determining the amount of liquid cargo contained within a tank, as it helps in assessing the volume of cargo present. The innage is commonly used during loading and unloading operations to ensure that the correct quantities are managed and documented.

This measurement is essential for accurate inventory control, as it can be converted into volume using the tank's specific calibration curves or tables. Understanding innage is critical for tankerman assistants because it aids in monitoring the safety and efficiency of cargo operations.

In contrast, the other options address different concepts that do not align with the definition of innage. The amount of cargo removed from the tank relates to measurements during unloading (not the distance from the liquid to the tank bottom), while the volume of gas inside the tank and the total cargo volume before loading pertain to other aspects of cargo management rather than the specific measurement termed 'innage.'