Marine chronometers are precise, portable timekeeping instruments used to determine a ship's position at sea. This particular clock was used on U.S. Coast and Geodetic Survey ships in the 1940s.
The face of a Ulysses Nardin marine chronometer used by the Coast and Geodetic Survey in the 1940s. (Image credit: NOAA Heritage)
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The development of marine chronometers in the 18th century revolutionized navigation. Sailors could now determine their longitude by comparing a known time set on the clock — usually Greenwich Mean Time (GMT) — to the time at their current location, found using observations of celestial bodies.
Nowadays, NOAA ships determine their position using the Electronic Chart Display & Information System (ECDIS) which integrates and overlays Global Positioning System (GPS) data, electronic charts, vessel course and speed, and other information into a single unified display. Of course, like traditional chronometers, ECDIS also tells the time.
Ulysses Nardin of Le Locle, Switzerland started manufacturing marine chronometers in 1856. Their marine deck chronometers were some of the most accurate of the time and can still be tuned to a precision of only a 0-0.5 second difference in 48 hours. This particular marine chronometer is set in a Hamilton Watch Co. case, probably due to damage to the original case.
Have an idea for an artifact, photo, or document from NOAA’s history that you think we should feature in “Friday Finds!”? Send an email with a description and, if possible, a photo to heritage.program@noaa.gov.
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