Reference Levels Preferences

You can define optional Reference Levels that will help you position elements. This is done at Levels Preferences (Options > Project Preferences > Reference Levels).
Select a level’s name and modify it as you like, then type the value you need in the Elevation field. In this example, we defined the top of the property, at 400 meters.
The Sea Level takes its value from the Altitude, which is set at Options > Project Preferences > Project Location.
Note: You cannot rename the Project Zero or Sea Level reference levels.
Note: Reference Levels are display and input aids only. Changing their value has no effect on placed elements, whose actual elevation is always calculated from Project Zero. The exception is Grid lines in Section view, whose position changes with the Reference Level.