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“The problem of GNSS disruptions will never be solved, but it can be much better managed”

May 2024 | No Comment

Dana A. Goward

President, Resilient Navigation & Timing Foundation

Tell us briefly about the mission and objectives of Resilient Navigation and Timing Foundation.

The foundation advocates for policies and system s to protect GNSS satellites, signals and users. We are a chartered scientific and educational charity. As such we have no interest in any commercial products or services and do our best to focus on benefits to the public.

Would you like to comment on GPS III and also on other existing and upcoming systems?

GPS is a great system and supports an uncountable number of technologies and applications. It is no wonder the U.S. government is so committed to maintaining and continually improving it for decades to come.

With four global navigation satellite systems (GNSS) that are interoperable, users have access to a lot of L-band signa ls from MEO. I think that is why many folks are looking to the future of space-based PNT as being in LEO and/or GEO, and perhaps using additional frequencies.

Terrestrial systems are also interesting. There are a wide variety of solutions for different applications. Some can be deployed across, even continental sized, areas.

And then there are autonomous systems that have the promise of determining location without external signals. Artificial intelligence will likely accelerate development of these.

The key going forward is combining all of these in a resilient architecture to ensure users always have the information they need.

With increasing dependence on GNSS, how do you perceive PNT vulnerability?

GPS and other GNSS are great. They provide highly precise and accurate signals to any receiver with a view of the sky, free of charge to the user. But no system or set of systems is perfect. I am sure most of your readers already know that GNSS signals are very weak and can be easily denied or imitated. And that both accidental and malicious interference happens all the time.

Should users be concerned? It depends.

If they are using GNSS-based PNT for their fitness watch or to find their way to someplace they have already been many times, probably not so much.

But if they are using solely GNSS for mission critical or safety of life applications, they should be concerned. They should plan what they will do in a GNSS-denied or compromised situation.

I am reminded of my grandmother’s caution “Don’t put all your eggs in the same basket!”

As the world is of multi-GNSS, don’t you think it is better equipped to deal with the PNT vulnerability issues?

Users receiving multiple GNSS are, of course, less vulnerable than those using just one. Yet all GNSS share many of the same vulnerabilities.

They are all in the same general frequency band. Most jammers interfere with the entire band and deny reception of all GNSS. – In fact, I understand it is more difficult and expensive to build a jammer that interferes with only one system.

And the specifications for all GNSS signals are public knowledge so they are all fairly easy to compromise or spoof. – In 2018 a pair of researchers published a paper outlining how they built a device with about $400 in parts that spoofed all four GNSS at the same time.

And of course, all GNSS are in space and subject to the same threats from debris, solar activity, and attack by adversaries’ militaries.

Using multiple GNSS is generally better than using just one. But to significantly reduce their PNT vulnerability users must integrate non-GNSS PNT sources in their solutions.

What is your take on the recent warning issued by the FAA dated Jan 25, 2024 recognizing and mitigating GPS/GNSS disruptions? Why it is so significant?

The FAA had issued warnings before, but I think this most recent is the most adamant and detailed so far. It was a significant step in the U.S. government’s formal recognition that disruptions are really getting to be a problem, especially in aviation.

The warning includes an impressive list of systems that can be impacted, including inertial systems that are supposed to “backup” GNSS-based navigation.

It is a good reminder about over-dependence on GNSS, and the importance of properly integrating alternative systems.

Do you think that there is enough awareness regarding the GNSS vulnerability? What policy initiatives do you think should be taken by the governments?

There is definitely NOT enough awareness of GNSS vulnerability, despite all the evidence we see every day in the Baltic, Ukraine, and Middle East.

If policy makers were sufficiently aware of the vulnerabilities and the risks posed, every nation would be implementing a plan to ensure they had a resilient national PNT infrastructure. One that included multiple diverse methods of delivering secure and authenticated PNT for all their applications and citizens.

Affordable, wide-area terrestrial solutions give every nation the ability to have their own, sovereign PNT capability, while still using and cooperating with multiple GNSS.

So, it isn’t a matter of technology or cost. It is a matter of decision makers not appreciating the need for action.

What has to be done technologically to handle these disruptions?

The problem of GNSS disruptions will never be solved, but it can be much better managed. The key is to make it more difficult to disrupt GNSS, and ensure users have alternatives when it is disrupted. This will make GNSS use safer by discouraging malicious interference. And it will make users safer by ensuring they can safely weather disruptions.

The presidential advisory board I am a member of advocates a holistic approach of Protect, Toughen, and Augment.

“Protect” means doing things to prevent interference, with GNSS signals, detect it when it occurs, and end the interference as quickly as possible. This requires the right laws and regulations, interference detection systems, and the ability to physically ensure an interfering signal is terminated.

“Toughen” is making receivers more robust with hardware and software that resist interference.

And “Augment” is ensuring users are able to access alternative PNT services when needed.

What’s your opinion on GNSS back-ups? Its pros and cons. How have different countries responded to its adoption and deployment?

Before discussing individual GNSS augmenting, complementary, or alternative systems, nations must resolve to focus on users.

Putting users first should result in a nation establishing a national resilient PNT architecture. One that leverages all the benefits of GNSS and includes other diverse methods of PNT delivery that can be easily accessed by as many users as possible.

Several nations are in the process of combining GNSS with space-based augmentation, terrestrial transmissions, and fiber and clock networks to ensure users always have needed PNT. Some leaders in this are China, South Korea, and the United Kingdom.

With GNSS becoming almost ubiquitous, what technology trends do you envision and innovative applications you anticipate around it in near future?

GNSS as a foundational technology has massively increased our appreciation of the importance of accurately knowing “where” and “when” with a high degree of precision.

The biggest improvements in GNSS use in the near term will likely be integrating it with other systems and sensors to make users safer and more resilient.

How do you think the GNSS positioning technology can leverage alternative positioning technologies like cell phones, A-GPS, Bluetooth, WiFi, etc?

GNSS technology is amazing. But we are often so fascinated by the technology that we lose sight of the user. Combining GNSS with other technologies to create resilient national PNT architectures is the next essential step in the evolution of GNSS.

Would you like to comment on autonomous navigation?

Navigation without external signals has a lot of promise. Magnetometers, LIDAR, gravimetrics, cameras, highly accurate maps, quantum sensors and the like could be intelligently integrated and produce highly reliable and accurate location information.

But, to paraphrase the poet, “no navigator is an island.” All users will need common references to initialize time and location and safely operate with each other. So rather than replacing other technologies, I see autonomous systems becoming part of larger, user-focused PNT architectures.

How do you see the impact of AI in positioning and navigation domain?

“A prudent mariner uses every means available to determine their position” has been the navigator’s motto since the days of sail. And it is surprising the number of things in a user’s environment that can be sensed and used to determine location. Artificial intelligence will make it much easier to incorporate more external signals and environmental sensing into navigators’ calculations to ensure safe and accurate precise navigation.

You had a long association with maritime navigation. How do see the evolution of navigation technology in general and marine navigation in particular?

I think all navigation tech is going to continue to evolve in two distinct ways.

First, it will continue to develop and benefit from increasing connectivity and the information that it makes available. For example, data to increase accuracy and authenticate signals will become more and more a matter of course rather than special services.

Users will also increasingly be able to navigate without external signals. Environmental sensing, map matching, internal and inertial sensors, and the like will enable relatively safe autonomous operation. And when the ship, aircraft or vehicle are connected, they will be ideal complements to the wealth of information available from other sources.

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