Researchers Ponder Navigation Beyond GPS

By Stew Magnuson
Way back in 1966, a pair of Aerospace Corporation researchers prepared a report for the commander of the Air Force’s Space System Division on how a satellite navigation system might work.

That report, and other efforts, would eventually lead to the Global Positioning System, which became fully operational in 1995.

To say technology has changed radically since the 1960s is a huge understatement. And the same can even be said of 1995.

More than 20 years after GPS’ deployment, the El Segundo, California-based nonprofit is taking a second look at precision navigation and timing (PNT) and if it could be made more robust. 

David J. Gorney, Aerospace Corporation’s executive vice president, challenged a team of researchers to see if the system could be improved upon “in the broadest possible context” and dubbed the effort Project SEXTANT.

“We are not looking for a replacement or substitute for GPS. But really how to take GPS and the other sources of PNT and find a way to improve that capability — and most importantly — the resiliency,” Gorney said in an interview on the sidelines of the Space Symposium in Colorado Springs, Colorado.

Gorney and the project lead, Randy M. Villahermosa, came to the symposium as part of a tour to present its findings to the navigation and timing community. That includes the operators, customers and technology developers.

First and foremost in its report was the acknowledgment that there isn’t anything better than GPS. “It is really a gold standard,” he said.

Yet, there has been a lot of concern about disrupted environments, particularly radio frequency and GPS jamming. Are there ways to be more resilient? he asked.

The answer is “yes,” but one must look beyond GPS. There are many more methods to do precision navigation and timing — some date back to before the space-based system — others are newly emerging.

The report concluded that PNT is an “ecosystem,” and GPS is only one part of the equation.
Inertial sensors, terrain mapping, machine learning and optical sensors are among the methods used for navigation and timing. They all have their strengths and weaknesses, Villahermosa pointed out. While GPS might be the gold standard, it may not work well in natural or urban canyons, tunnels and so forth, he said.

A consumer may assume that when he looks at a navigation application on his smartphone in a city, that it’s employing GPS, but it may actually be using triangulation between cell phone towers to locate itself.

With terrain mapping, there is a database of maps in which the device places itself. Optical sensors take pictures 100 times per second and compares them to what it sees on a map. Smart cars are beginning to use this method.

“With GPS being so powerful in its ability to deliver such great performance, it really drives you to a monolithic model for how that business works — and it works really well — but the
question is what if we want to go beyond that. What would that look like?” Villahermosa asked.

The report foresees a time when all or some of the methods for collecting PNT data could stream into one device.

GPS is a vertically integrated system, but the precision navigation and timing world is growing ever more “horizontal” with new technologies being developed, the report said.

Vertically integrated systems tend to be more robust, Gorney pointed out. The original phone system developed by Bell Labs is an example. It can be argued that the quality of the signal hasn’t been beat. When cell phones came along, consumers sacrificed clear signals for flexibility, Gorney said.

GPS “is very vertically integrated, and vertically integrated systems give you high performance and give you high reliability but sometimes that can be a challenge for resiliency,” Villahermosa said.

GPS can’t, and shouldn’t be required to do everything. Working in tunnels and canyons is one example of niche applications, Gorney said.

A device should be able to take in different data streams depending on the user’s needs. A crop duster may have different needs than a taxi driver in a city with large buildings. Military users operating underwater have different needs than those in a truck or airplane.

GPS can be augmented with these other PNT methods. But there are currently no standards to make that happen dynamically in one device, the project found.

“As long as the provider meets the standard, they should be able to bring their inputs into our system, into our platform and be able to process it,” Gorney said.

“But we have to have a way to bring that all together,” Villahermosa added.

“We have been getting this idea out there [on the briefing tour], particularly talking to product developers. This concept has been well received so far. And I think the customers see the value in multiplying the capability of any particular technology,” he added.

Gorney said PNT needs to grow beyond the GPS architecture and into the broader “ecosystem.” It’s not a race to see what navigation method is best. The user should have access to variety of data depending on need. Work needs to be done to create the capability for these methodologies to integrate.

The Aerospace Corporation is not a technology developer, but since it runs a federally funded research and development center, it is well positioned as a neutral player to create the standards needed to make this vision happen, Gorney said.

Then “anybody who comes up with new techniques for providing a PNT source can have a way of plugging in with the other providers,” he said.

Topics: Science and Engineering Technology, Space, Technical Information

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