U.S. 'Master Clock' Keepers Test Terrestrial Alternative to GPS

The U.S. Naval Observatory tests a ground-based GPS alternative that could work in crowded cities and indoors

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U.S. 'Master Clock' Keepers Test Terrestrial Alternative to GPS
Photo: Locata

GPS technology can do much more than guide drivers and smartphone users on unfamiliar streets. The Global Positioning System’s satellites carry expensive atomic clocks that also provide synchronized timekeeping for cell phone networks, major financial institutions, and power grids across the world. But a report by the U.S. government’s “master clock” keepers finds that a ground-based “TimeLoc” technology can provide even better timekeeping accuracy within crowded cities and indoor spaces—places where GPS signals have trouble reaching.

The TimeLoc technology made by the Locata Corp. represents a wireless synchronization procedure based on radio signals sent between “LocataLite” transceivers on the ground. Recent testing by the U.S. Naval Observatory (USNO), a scientific agency that controls the U.S. master clock” used for coordinating the GPS satellites, found that the LocataLite transceivers could synchronize across kilometers of Washington, D.C.’s urban environment with timing differences of less than 200 trillionths of a second. By comparison, GPS typically is less accurate, with synchronicity on the order of about 100 billionths of a second difference. Still, the ground- and space-based technologies could work together to deliver GPS-style location and timekeeping almost anywhere imaginable.

“We want to give world a seamless GPS experience, so they’ll never know when they’re transitioning from GPS to Locata,” said Nunzio Gambale, cofounder and CEO of the Locata Corporation. “Our next-gen chips will have a combination of incumbent GPS technology and ours which is based on terrestrial transmitters.”

Gambale and fellow cofounder, David Small, spent almost 20 years working with their team of engineers to realize their vision of “GPS everywhere.” Their TimeLoc technology’s timekeeping does not need to coordinate with an expensive “master clock” such as the USNO’s dozens of atomic clocks that are worth billions of dollars. Instead, the LocataLite transceivers can synchronize by each sending and receiving their own unique signals and analyzing the signal differences.  

“When we looked at the GPS constellation with its master clock on ground and atomic clocks in the sky, in our minds we a saw conductor with a band,” Gambale explained. “In our analogy, our Locata transmitters had to play like a band that could function without a conductor.”

The ability to accurately synchronize “like a rock band” without an atomic clock acting as the master timekeeper raised plenty of eyebrows among industry experts early on. But a central time reference is not so important to Locata’s system as its transceivers being able to synchronize with one another. Gambale compared Locata’s system to a group of grandfather clocks with swinging pendulums. 

“Even if all of the clock faces are covered (i.e. you can no longer see the time) you can still be sure the clocks are synchronized by looking at the pendulums swinging together,” Gambale explained.

The recent USNO report made special note of TimeLoc’s ability to function without atomic clocks.

As TimeLoc is accomplished without the use of atomic clocks, this coverage represents a completely new league in precision network synchronization of this scale. It could conceivably serve as a potential GPS augmentation or back-up solution over wide areas for critical applications that depend on precise time.

Locata’s system can synchronize as long as each transceiver receives signals from at least one other transceiver. That cascading concept has already been proven by a number of operational “LocataNets,” including a huge network configured by the U.S. Air Force to cover 6,500 square kilometers of the White Stands Missile Range in New Mexico—an area almost 80 times the size of Manhattan. In a 2011 test demonstration, that Locata system showed it could provide precise positioning information, accurate within centimeters, to an aircraft flying more than 7.6 kilometers above the ground and at speeds of up to 650 kilometers per hour.

The U.S. military has obvious reasons to want a highly accurate, reliable backup for GPS at a time when its most advanced vehicles and weaponry depend on accurate positioning and timekeeping information. But everyone living in modern society could potentially benefit from widespread deployment of Locata’s technology.

For example, cell phone towers and data networks often use GPS timekeeping to synchronize their many base stations. Better synchronization means a more efficient exchange of radio signals and digital data, which in turn could allow for more efficient use of the limited radio spectrum set aside for such technologies. A LocataNet’s ability to synchronize within picoseconds (billionths of a second) is about one million times as good as the current microsecond-level industry standard for 4G cell networks.

Locata’s precise positioning and timekeeping could also benefit the testing of new robots before they appear in U.S. skies and on the road. Before the end of 2015, NASA’s Langley Research Center plans to set up its first LocataNet to provide positioning data for its testing of flying drones. Locata’s technology has also found use at the Insurance Institute for Highway Safety’s Vehicle Research Center during safety tests of self-driving cars.

One of Locata’s partners, Leica Geosystems Mining, has created the first receiver that can use both GPS and “LocataLite” transmitter signals. That system has already been providing positioning data to robotic trucks and bulldozers working in an open-cut gold mine located in Western Australia. (The technology is also deployed at mines in Chile, Sweden and the U.S.) Gambale envisions such a combination of positioning technology guiding many more robots in the future, whether they are self-driving cars backed by Google or Amazon’s delivery drones.

The biggest opportunities for Locata’s technology may still lie ahead. The USNO report observed that the future “Internet of Everything,” also known as the Internet of Things, will need stability in its wireless links to ensure smooth coordination between household appliances, mobile devices and vehicles that all talk with one another in the future. The USNO testing found that a two-node LocataNet had a one-day frequency stability with a drift of just one part per quadrillion; more than adequate for future applications.

Gambale also anticipates the day when LocataLite transceivers become small enough to fit inside mobile devices. That opens the door for the technology to effectively provide location data for firefighters to pinpoint and rescue people inside buildings. Or it could simply guide shoppers to the exact store shelf where the product they want to buy is located.

“Today’s transmitters are 10 inches long, five inches wide, and one inch high,” Gambale said. “Eventually they’ll just be a sliver of silicon that can fit into your phone.”

Editor’s Note: This story has been corrected to reflect the fact that Locata’s technology does not work underground and only works in open-cut mines. The original story said that the White Sands Missile Range test configuration covered an area 200 times the size of Manhattan; it has been corrected to 80 times the size of Manhattan. The original story also said that the aircraft involved in the Air Force testing flew at a maximum speed of 885 kilometers per hour; that has been corrected to 650 kilometers per hour.

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