Next wave of GPS promises stronger signals
By DAN ELLIOTT Associated Press December 18, 2011 4:52PM
Jim Keyser, manager of Lockheed Martin's GPS Processing Facility, stands next to a prototype of the propulsion core for a Block III statellite. The new generation of satellites will improve the accuracy of military and civilian GPS receivers. | AP Photo
DENVER — The future of the U.S. Global Positioning System is taking shape in a vast white room south of Denver, where workers are piecing together the first of more than 30 satellites touted as the most powerful, reliable and versatile yet.
The new generation of satellites, known as Block III, will improve the accuracy of military and civilian GPS receivers to within three feet, compared with 10 feet now, according to the Congressional Budget Office.
Block III will also have additional signals for civilian use — one brand new, others already in the first stages of deployment — offering more precision and making more navigation satellites available to civilian receivers.
“It’s a really big jump,” said Col. Harold “Stormy” Martin of the Air Force Space Command. “With these additional signals, the additional power it’s going to bring, it’s quite a leap from the other systems.”
Block III may not be a bigger advance than previous generations of GPS satellites were, said Glen Gibbons, editor of the website and magazine Inside GNSS, which tracks global navigation satellite systems.
“But I’m completely comfortable saying that it will be a very substantive advance,” Gibbons said in an email to The Associated Press.
GPS has spread into nearly every corner of civilian and military life. Farmers use it for precision mapping and banks use it to record the precise time of transactions. It has found wide use in transportation, guided weapons, emergency response and disaster relief.
Block III satellites, which will begin replacing older orbiting GPS satellites in 2014, offer a new, internationally agreed-upon civilian signal that other nations’ navigation satellites will also use.
That would allow civilian receivers to tap into Europe’s budding Galileo navigation system and others.
“So all of a sudden you’ve got 70, 80, 90 satellites up in orbit,” compared with 30 operational satellites in the U.S. system today, Gibbons said in an interview. “It’s giving you a much greater number of satellites to be receiving.”
GPS receivers need signals from at least four satellites to establish their position, so having more satellites to tune into would improve accuracy. It also makes it easier for a receiver to find enough satellites.
Military receivers could also use the international signal, as well as the other civilian signals and the encrypted, military-only signals the satellites transmit, the Air Force said.
Block III will add to the number of satellites transmitting two other relatively new civilian signals. One will likely be used for such high-precision activities as surveying, Gibbons said.
The Federal Aviation Administration’s GPS-based NextGen air traffic control system, which is still under development, could benefit from at least one of the new signals. But the system could also work with the older, existing civil systems, said Hans Weber, president of TECOP International Inc., an aviation technology management firm.
It’s not yet clear when enough satellites will be transmitting the international signal and the other new civilian signals to make them usable. It typically takes 18 satellites transmitting a signal to reach initial operation and 24 to reach full capability, Gibbons said.