NIST method improves reliability of GPS clocks

Oct 07, 2005

The average user may not notice, but the Global Positioning System (GPS) is more reliable today than it was several years ago.

Widely used by the military, first responders, surveyors and even consumers, GPS is a navigation and positioning system consisting of ground-based monitors and a constellation of satellites that rely on atomic clocks. A statistical method, developed by the National Institute of Standards and Technology (NIST) and tested and implemented with the help of several collaborators, has made the job of analyzing the accuracy and reliability of these satellite-borne time signals significantly faster and easier. The method will help ensure that GPS clocks produce accurate location and distance measurements and remain closely synchronized with official world time.

The NIST method, described in a recent paper,* has been incorporated over the past few years into the GPS clock analysis software system managed by the Naval Research Laboratory (NRL). The satellite clocks--commercial devices based in part on research originally done at NIST--use the natural oscillations of rubidium atoms as "ticks," or frequency standards. The algorithm helps detect and correct GPS time and frequency anomalies. The algorithm also can be used to improve the control of other types of atomic clocks and has been incorporated into commercial software and instruments for various timing applications, according to NIST electronics engineer David Howe, lead author of the paper.

A GPS receiver pinpoints its location based on the distance to three or more GPS satellites at known locations in space. The distance is calculated from the time it takes for satellite radio signals to travel to the receiver. Thus, timing accuracy affects distance measurements. The NIST method makes a series of mathematical calculations to account for numerous measures of random "noise" fluctuations in clock operation simultaneously.

This makes it easier to estimate many sources of error and identify the onset of instabilities in the clocks in minutes or hours rather than days. Adjustments then can be made promptly. The technique also could accelerate the evaluation of clocks during the process of building GPS satellites, where test time is at a premium. "Ultimately, it should improve reliability, stability and accuracy for many people who use GPS for time and navigation,"said Howe.

Co-authors of the paper include scientists from NRL, the Jet Propulsion Laboratory at the California Institute of Technology, the Observatoire de Besancon in France, and Hamilton Technical Services in South Carolina.

* D.A. Howe, R.L. Beard, C.A. Greenhall, F. Vernotte, W.J. Riley, T.K. Peppler. Enhancements to GPS operations and clock evaluations using a "total" hadamard deviation. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. August 2005.

Source: NIST

Explore further: Robot scouts rooms people can't enter

add to favorites email to friend print save as pdf

Related Stories

Portable frequency comb rolls out of the lab

Mar 21, 2014

A PML team is hitting the road with a fine-tooth comb. Scientists in the Quantum Electronics and Photonics Division have devised a portable optical frequency comb that is capable of laboratory-grade measurements ...

A new era for atomic clocks

Feb 05, 2014

A revolution is under way in timekeeping. Precision timekeeping based on atomic clocks already underpins much of our modern technology—telecommunications, computer networks and satellite-based positioning ...

The ultimate accuracy machine

Oct 04, 2013

A clock being developed by a physicist at The University of Western Australia is the first of its kind in Australia - and will be the only southern hemisphere-based clock in the international Atomic Clock ...

Recommended for you

FCC to propose pay-for-priority Internet standards

2 hours ago

The Federal Communications Commission is set to propose new open Internet rules that would allow content companies to pay for faster delivery over the so-called "last mile" connection to people's homes.

SK Hynix posts Q1 surge in net profit

2 hours ago

South Korea's SK Hynix Inc said Thursday its first-quarter net profit surged nearly 350 percent from the previous year on a spike in sales of PC memory chips.

Brazil enacts Internet 'Bill of Rights'

2 hours ago

Brazil's president signed into law on Wednesday a "Bill of Rights" for the digital age that aims to protect online privacy and promote the Internet as a public utility by barring telecommunications companies ...

Zynga founder Pincus leaving operations role

13 hours ago

Online game maker Zynga says company founder Mark Pincus is stepping down as chief product officer, less than a year after he was replaced as the company's CEO.

User comments : 0

More news stories

SK Hynix posts Q1 surge in net profit

South Korea's SK Hynix Inc said Thursday its first-quarter net profit surged nearly 350 percent from the previous year on a spike in sales of PC memory chips.

FCC to propose pay-for-priority Internet standards

The Federal Communications Commission is set to propose new open Internet rules that would allow content companies to pay for faster delivery over the so-called "last mile" connection to people's homes.

Brazil enacts Internet 'Bill of Rights'

Brazil's president signed into law on Wednesday a "Bill of Rights" for the digital age that aims to protect online privacy and promote the Internet as a public utility by barring telecommunications companies ...

Phase transiting to a new quantum universe

(Phys.org) —Recent insight and discovery of a new class of quantum transition opens the way for a whole new subfield of materials physics and quantum technologies.

Imaging turns a corner

(Phys.org) —Scientists have developed a new microscope which enables a dramatically improved view of biological cells.

Fresh hope for preventing pneumonia in the elderly

There are calls for the frail and elderly not be be overlooked for vaccines against pneumonia this winter, with UNSW research challenging conventional wisdom on immunisation effectiveness in older patients.