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The evaluated accuracy u B reports of various primary frequency and time standards are published online by the International Bureau of Weights and Measures (BIPM). In May 2013 the NIST-F1 cesium fountain clock reported a u B of 3.1 × 10 −16. However, that BIPM report and the other recent reports are based on an evaluation that dates to 2005. [4]
Modern marine chronometers can be based on quartz clocks that are corrected periodically by satellite time 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, it uses math to adjust the timing chain for accuracy: time = time + rate. When the "time" variable exceeds a constant, usually a power of two, the nominal, calculated clock time (say, for 1/50 of a second) is subtracted from "time", and the clock's timing-chain software is invoked to count fractions of seconds, seconds, etc.
The most accurate pendulum clocks were controlled electrically. [166] The Shortt–Synchronome clock, an electrical driven pendulum clock designed in 1921, was the first clock to be a more accurate timekeeper than the Earth itself. [167] A succession of innovations and discoveries led to the invention of the modern quartz timer.
The most accurate pendulum clock was the Shortt-Synchronome clock, a complicated electromechanical clock with two pendulums developed in 1923 by W.H. Shortt and Frank Hope-Jones, which was accurate to better than one second per year. A slave pendulum in a separate clock was linked by an electric circuit and electromagnets to a master pendulum ...
Calling a clock the most accurate ever may sound like hyperbole, but physicists at the National Institute of Standards and Technology in Boulder, Colorado have built a pair of devices that can ...
A common misconception is that a digital clock is more accurate than an analog wall clock, but the indicator type is separate and apart from the accuracy of the timing source. Talking clocks and the speaking clock services provided by telephone companies speak the time audibly, using either recorded or digitally synthesized voices.
It is impossible to determine longitude with an accuracy better than 10 nautical miles (19 km) by means of a noon sight without averaging techniques. A noon sight is called a Meridian Altitude. [ 2 ] While it is very easy to determine the observer's latitude at noon without knowing the exact time, longitude cannot accurately be measured at noon.