Today
Ships and boats commonly use electronic aids to navigation, mostly the Global Navigation Satellite Systems. However celestial navigation, which requires the use of a precise chronometer, is still a requirement for certain international mariner certifications such as Officer in Charge of Navigational Watch, and Master and Chief Mate deck officers, and supplements offshore yachtmasters on long-distance private cruising yachts. Modern marine chronometers can be based on quartz clocks that are corrected periodically by GPS signals or radio time signals (see radio clock). These quartz chronometers are not always the most accurate quartz clocks when no signal is received, and their signals can be lost or blocked. However, there are quartz movements, even in wrist watches, that are accurate to within 5 or 20 seconds per year. At least one quartz chronometer made for advanced navigation utilizes multiple quartz crystals which are corrected by a computer using an average value, in addition to GPS time signal corrections.
Read more about this topic: Marine Chronometer
Famous quotes containing the word today:
“In communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, fish in the afternoon, rear cattle in the evening, criticize after dinner, just as I have a mind, without ever becoming hunter, fisherman, shepherd or critic.”
—Karl Marx (1818–1883)
“At times it seems that the media have become the mainstream culture in children’s lives. Parents have become the alternative. Americans once expected parents to raise their children in accordance with the dominant cultural messages. Today they are expected to raise their children in opposition to it.”
—Ellen Goodman (20th century)
“The 19-year-old Diana ... decided to make her career that of wife. Today that can be a very, very iffy line of work.... And what sometimes happens to the women who pursue it is the best argument imaginable for teaching girls that they should always be able to take care of themselves.”
—Anna Quindlen (b. 1952)