Question 716Navigation General
70% to passA mercurial barometer at sea is subject to rapid variations in height ("pumping") due to the pitch and roll of the vessel. To avoid this error, measurements of atmospheric pressure at sea are usually measured with a(n) _______________.
A) aneroid barometer is the correct answer. Aneroid barometers are preferred for measuring atmospheric pressure at sea because they are not subject to the rapid fluctuations or "pumping" that can occur with a mercurial (mercury) barometer due to the pitch and roll of the vessel. Aneroid barometers use a flexible metal diaphragm to measure changes in atmospheric pressure, which is not affected by the motion of the ship the way a column of mercury would be. The other options (syphon, fortin, and cistern barometers) are less suitable for use at sea because they rely on a column of liquid, which would be susceptible to the same "pumping" error as a mercurial barometer.
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