Search results
Results from the WOW.Com Content Network
Nautical time divides the globe into 24 nautical time zones with hourly clock offsets, spaced at 15 degrees by longitudinal coordinate, with no political deviation. Nautical timekeeping dates back to the early 20th century as a standard way to keep time at sea, although it largely only applied to military fleets pre–World War 2.
Using the Equation of time correction along with the time averaged ascending/descending noon sights can result in accuracies of 1 nautical mile (1.9 km) or less. Without time averaging, the difficulties in determining the exact moment of local noon due to the flattening of the Sun’s arc across the sky reduce the accuracy of calculation.
A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation.It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.
Time zones of the world. A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.
If present, a dagger (†) indicates the usage of a nautical time zone letter outside of the standard geographic definition of that time zone. Some zones that are north/south of each other in the mid-Pacific differ by 24 hours in time – they have the same time of day but dates that are one day apart. The two extreme time zones on Earth (both ...
The 15° gore that is offset from GMT or UT1 (not UTC) by twelve hours is bisected by the nautical date line into two 7.5° gores that differ from GMT by ±12 hours. In reality nautical time zones are used only for radio communication etc. Internally on the ship, e.g. for work and meal hours, the ship may use a suitable time of its own choosing.
Such designations can be ambiguous; for example, "CST" can mean China Standard Time (UTC+08:00), Cuba Standard Time (UTC−05:00), and (North American) Central Standard Time (UTC−06:00), and it is also a widely used variant of ACST (Australian Central Standard Time, UTC+9:30). Such designations predate both ISO 8601 and the internet era; in ...
Royal Observatory, Greenwich, London.Installed in 1833, a time ball sits atop the Octagon Room. A time ball or timeball is a time-signalling device. It consists of a large, painted wooden or metal ball that is dropped at a predetermined time, principally to enable navigators aboard ships offshore to verify the setting of their marine chronometers.