G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
G01C9/00—Measuring inclination, e.g. by clinometers, by levels
G01C9/18—Measuring inclination, e.g. by clinometers, by levels by using liquids
G01C9/20—Measuring inclination, e.g. by clinometers, by levels by using liquids the indication being based on the inclination of the surface of a liquid relative to its container
G01C9/22—Measuring inclination, e.g. by clinometers, by levels by using liquids the indication being based on the inclination of the surface of a liquid relative to its container with interconnected containers in fixed relation to each other