NOAA will lead an international effort to pinpoint the locations of more than 40 global positioning satellites in Earth orbit, which is vital to ensuring the accuracy of GPS data that millions worldwide rely upon every day for safe navigation and commerce.

NOAA personnel will compile and analyze satellite orbit data from 10 analysis centers worldwide to ensure the accuracy of GPS information. For the next four years NOAA's National Geodetic Survey will serve as the Analysis Center Coordinator for the International Global Navigation Satellite Systems Service, a voluntary federation
of more than 200 organizations that provide continuous global satellite-tracking data.

"For GPS receivers to provide accurate information, the precise location of positioning satellites as they orbit the Earth must first be determined," said David Zilkoski, director of NOAA's National Geodetic Survey. "NOAA looks forward to leading this international partnership to produce the highest quality satellite position data possible."

The Global Navigation Satellite Systems, which include the U.S. based Global Positioning System, the Russian GLONASS system, and the upcoming European Galileo system, are used for accurately determining the geographic position of any point on Earth.

A GPS receiver calculates its position by measuring the time it takes a signal to travel from the satellite to the receiver. Because the signal travels at a known rate and the time is precisely measured using an atomic clock, the receiver can calculate its distance from the satellite. By repeating this process from four or more GPS satellites whose orbits are precisely known, the GPS receiver can determine its position.

About NOAA
NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of our nation's coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, more than 70 countries and the European Commission to develop a global monitoring network that is as integrated as the planet it observes, predicts and protects.

On the Web: NOAA: http://www.noaa.gov NOAA's National Geodetic Survey: http://www.ngs.noaa.gov