单项选择题
A.adjust the barometer B.indicate any change in the reading of the barometer C.provide a correction for height above sea level D.provide a correction for temperature changes
The error in the measurement of the altitude of a celes...
单项选择题The error in the measurement of the altitude of a celestial body，caused by refraction，increases as the（）.
A.horizontal parallax decreases B.observer's height above sea level increases C.humidity of the atmosphere decreases D.altitude of the body decreases
The boom stops on a pedestal crane prevent the boom fro...
单项选择题The boom stops on a pedestal crane prevent the boom from（）.
A.being raised too high B.swinging at sea C.overloading when not in use D.being lowered too low
The average height of the surface of the sea for all st...
单项选择题The average height of the surface of the sea for all stages of the tide over a 19 year period is called（）.
A.mean high water B.mean low water C.half-tide level D.mean sea level
