Category: Opinions

Flawed spectrum proposal could cause disruption and risks to public safety
On March 27, 2025, the Federal Communications Commission (FCC) launched a proceeding on commercial technologies that would complement GPS. “Although GPS is indispensable to America’s economic and national security, it represents a single point of failure that can be vulnerable to disruption or manipulation by our adversaries,” said the FCC’s announcement, highlighting the federal government’s bipartisan call to develop complementary systems that provide positioning, navigation and timing (PNT) data to to better achieve PNT resilience nationwide and protect America’s economic and national security.

The Security Industry Association (SIA) commends the FCC’s commitment to protecting America’s economic and national security and exploring available PNT options. We believe the docket will show that there is a wide array of PNT technologies that can complement to GPS, and we look forward to providing information to the Commission about tradeoffs among these emerging PNT offerings and encouraging the Commission to avoid taking action that could disproportionately disrupt valuable public safety technologies.

One company, the for-profit entity NextNav, has petitioned the FCC to reconfigure the 902-928 MHz band (the Lower 900 MHz frequency) and grant it a nationwide license for 15 MHz of spectrum so it can establish a 5G terrestrial-based PNT network. NextNav also seeks the removal of the current requirement that it not cause unacceptable levels of interference to Part 15 devices. These devices include low-power, radio frequency (RF) devices ranging from consumer electronics and appliances to wireless alarm systems, smart home equipment, electronic access control devices and a wide range of devices used to increase economic productivity and efficiency, bolster safety, deliver innovation and provide other important benefits to consumers. This proposal has a dangerous likelihood of causing significant interference in the band that would be adverse to the public interest and threaten public safety.

The Lower 900 MHz band is vital for millions of security cameras, including popular models used in homes and small businesses. These devices are essential for protecting homes, preventing package theft and home intrusions, ensuring children’s safety and aiding law enforcement by capturing criminal activity. The changes proposed by NextNav would likely force these incumbent users into a shared portion of spectrum that is almost 60% smaller than the current Lower 900 MHz band — crowding that will cause many devices to stop operating reliably, compromising Americans’ safety and the security of our facilities and communities, and will be exacerbated by the growing concentration of devices using new technologies that require more spectrum bandwidth.

Another important service likely to be disrupted by the proposed band restructuring would be Z-Wave technologies. Z-Wave technology enables comprehensive home automation and security solutions —such as smart locks, thermostats and security systems — to integrate seamlessly with various smart home devices, while preserving advanced security features such as encrypted communication and secure inclusion. Z-Wave devices are not designed to withstand interference from fixed and/or mobile devices operating at commercial macro power limits and out-of-band emission limits, such as those in NextNav’s proposed high-power operations.

Additionally, millions of electronic access control and other wireless connected devices that are now in use in residential, institutional, commercial and government buildings across the United States would be impacted. The interference generated from NextNav’s higher-power communications would significantly impact the reliability of these important safety and security products and ecosystems, effectively making them unusable in the same spectrum.

In addition to these public safety and security uses, more critical systems that could be disrupted include:
- Municipal infrastructure, including such systems as traffic control, street lighting, weather monitors and flood warning systems that are deployed in this band to make communities safer and more energy efficient.
- Critical infrastructure, including utilities’ use of the band for remote monitoring and management of power, gas and water distribution networks.
- Railroad operations and safety, including the Automatic Equipment Identification network that enables tracking of rail cars and equipment, as well as essential traffic control, sensors and other devices necessary for operational safety and efficiency.
- Highway infrastructure and tolling, including the operation of electronic tolling systems, such as E-ZPass and other similar toll collection systems.
- Retail, manufacturing and supply chain operations, including building control systems, tank and leak monitoring system and inventory control systems.
- Agriculture solutions used for connecting modern farms’ Internet of Things devices and equipment to keep our farms connected.
As other concerned parties have pointed out, there are a number of existing backup GPS options available to establish a terrestrial PNT without any reallocation of spectrum. While a backup GPS system is ultimately necessary, the other solutions that would be much less disruptive. The tradeoffs required by implementing the NextNav proposal are simply not worth the risk to our nation’s security and safety.
April 7, 2025
First fix: Our varied routes to GNSS/PNT

We each arrived at our current involvement with the GNSS/PNT industry by a different path. For many, it was through engineering, perhaps initially thinking of focusing on completely different challenges than those posed by extremely weak RF satellite signals, intentional interference, or ionospheric scintillation. For others, it was through surveying, which they might have entered to make a living traipsing through open fields — well, traversing them — while working independently and in nature.

For others still, it was through one of the myriad applications of GNSS — from mapping the geographic distribution of the few remaining Amur leopards to guiding a tractor in the field, from commercial fishing in Alaska to conducting search and rescue missions, to training for military raids. Yet for others, it was through business, perhaps because they were tasked to route delivery trucks more efficiently or to track each vehicle in a rental fleet. Professor Richard Langley started out as an applied physicist and a radio tinkerer, building his first radio at the age of 14. My colleagues at North Coast Media got here via a career in journalism, with the steep subject-matter learning curve following their training in writing and editing.

I got here mostly through my passion for maps, charts and navigation. I first became interested in maps as a child — after twice getting lost. The first time, I was 5 years old and lost track of my mother as she entered a store in Berkeley, California, and I kept walking down the street. The next time, I was 7 and had insisted on walking home alone from school in Milan, Italy. I was determined not to let it happen again. So, when I was 11, I was the only kid I knew who walked around Pisa studying a map and a compass.

Next came the topographic maps I used for hiking. In my 20s, sailing around the Boston Harbor islands and off the coast of Maine, I learned to use nautical charts, sextants, radio direction-finders, sonar, radar, Loran C, and, finally, hand-held GPS receivers. I read my first technical article on GPS in 1985, when I was a graduate student in international security at MIT and Harvard, and the U.S. military was building the system. I studied its technical specifications and dreamt about its many possible future applications.

In 2000, when looking for a career change and a job in journalism, I saw a posting for the position of managing editor of this magazine. I applied and 25 years later I am still in the business.

Throughout, I always have been impressed by the deep expertise of the scientists and engineers who created this fantastic GNSS that billions of people use multiple times a day yet take for granted. Those who discount, belittle or even mock the expertise of people who have spent decades studying complex subjects — from climate change to economics, from foreign policy to epidemiology, from education to urban planning — are profoundly unaware and misguided, when not hypocritical. We need experts.

March 25, 2025
Tips to combat cyberattacks on GNSS/PNT systems

For our March 2025 issue, Professor Washington Ochieng proposed the following question to members of our editorial advisory board: When we discuss the security of GNSS/PNT systems, we nearly always focus on interference — i.e., meaconing, intrusion, jamming or spoofing. However, GNSS/PNT systems are embedded in systems of systems that also offer many other opportunities for cyberattacks. What should we do about it?

Miguel Armor

“As a GNSS receiver manufacturer and correction service provider, cyber attacks are a risk we must consider seriously that arises from our customers’ integration of our solutions into complex systems. At the receiver level, it is important to make risk assessments to identify vulnerabilities across all components and implement a robust, multi-layered security strategy that includes physical, network and software components. At the core, our strategy incorporates cybersecurity considerations into our product/service development processes. We utilize the ASPICE framework for our engineering processes and we layer into that process the ISO21434 standard to ensure that we take steps all along the development path to consider cybersecurity. We selected this standard from the automotive industry due to the connected car use case, which is now in the front of cybersecurity development. ISO21434 covers the entire development life cycle — from system, to hardware and software, to verification and validation — in a way that many other standards do not. As a correction service provider, we ensure our data streams are secure and reliable, maintaining the highest standards of accuracy and availability. We also use ISO27001 as an IT framework for our correction network infrastructure. Continuous monitoring and iterative improvements are crucial to maintaining a secure and resilient GNSS/PNT infrastructure. It is key also to prioritize redundancy and backup systems to ensure continuity and resilience, to develop a comprehensive incident response plan that allows for rapid action in case of a breach and to conduct regular employee training to promote cybersecurity awareness across all products and platforms.” – Miguel Amor, Hexagon Positioning Intelligence

Alison Brown

“Cyberattacks are a credible threat to all existing GNSS systems and certainly need to be taken into account when considering alternative resilient PNT solutions. In fact, Goal 3 of the recently released U.S. Department of Transportation PNT Strategic Plan identifies PNT cybersecurity as a critical element of PNT resilience. The National Institute of Standards and Technology (NIST) provided a report titled Foundational PNT Profile: Applying the Cybersecurity Framework for the Responsible Use of Positioning, Navigation, and Timing (PNT) Services. This cybersecurity framework was created for both users of PNT services to manage risks when using PNT signals or data, and for operators of alternative PNT services to leverage when providing PNT signals or services. It was created by applying the NIST Cybersecurity Framework (CSF) and provides approaches for cybersecurity for PNT by continuously monitoring for attacks (e.g., denial of service, jamming), false data, and other malicious behavior within the systems and across the PNT services, using data-driven methods and solutions. This Cybersecurity Framework should be routinely adopted by both users and providers of PNT services.” – Alison Brown, NAVSYS Corp.

March 18, 2025
More on EUSPA’s first ever GNSS and Secure SATCOM User Technology Report
In case you missed it, the European Union Agency for the Space Program (EUSPA) recently issued its first ever User Technology Report addressing both GNSS and Secure SATCOM. Though they seem to be different and distinct topics, EUSPA does a reasonable job of drawing them together with an “Editor’s Special — Synergies from Space” at the end of the document.

The first half of the report deals with GNSS and is an exploration and celebration of how far we have come with GNSS. While the report is aimed at “users” and is designed to be “technical,” it is written to be accessible by most who are generally familiar with the topic.

Also, a careful reading reveals several messages for policymakers.

Protecting Frequencies

The report opens with a celebration of what has now become a multi-constellation, multi-frequency, open positioning, navigation and timing (PNT) system with 110 satellites, two regional augmentation systems (Japan’s QZSS and India’s NavIC), and Satellite Based Augmentation Systems (SBAS). All of this depends, of course, on clear and uninterrupted signals.

One of the first cautions policy makers should note is a subheading in the section that reads “Frequencies: a scarce resource to be protected.” This is the first of many mentions of the need to protect signals and users from accidental and malicious interference.

From 2016 to 2019, the European Union’s STRIKE3 project deployed equipment to monitor L1/E1 signals in 23 countries across the globe. They found more than 450,000 signals that could interfere with GNSS, 59,000 of which were assessed to be intentional jamming or spoofing.

This was well before the current wars in Ukraine and the Middle East and before Russia’s malicious ongoing electronic warfare in the Baltic. So, even in the absence of aggressive nation-state actions, which could flare up at any time, STRIKE3 showed that GNSS interference was a significant problem threatening users’ reliance on GNSS.

Both the European Union and the United States have undertaken projects in response to widespread jamming and spoofing.

In Europe, EUSPA has begun the EGIPRON project, or European Global Interference PROtection Network. It aims to develop and deploy “…an interference monitoring system covering all European territories and worldwide areas of European interest” working with contractors Qascom and Leonardo.

The U.S. Department of Transportation (DOT) announced the “GNSS Situational Awareness Common Operational Picture GovCloud Environment” at the December 2024 National PNT Advisory Board meeting. The government version was described as operational, with a public version to be available in mid-2025.

These detection — and hopefully geolocation — systems will be great tools. Policy makers must remember, though, that better understanding the scope of the problem will not solve it.

Better laws and regulations to empower enforcement, along with improved enforcement capability, will both be needed if even a dent is to be made in the problem. Getting these in place will be significant legislative and budgetary challenges. Even then, the problem of accidental and malicious GNSS interference will not be solved. Authorities will just be able to manage it a bit better.

Toughen Receivers

A great majority of the GNSS portion of the document is appropriately devoted to receivers. They are, after all, the only part of the GNSS system over which users have any discretion and control.

Receiver design, signal processing, antennas and PNT processing are all discussed. The most attention is paid to describing the characteristics and appropriate uses of five different families of GNSS receivers:
- Mass Market Entry-Level
- Mass Market Premium
- Professional Non-Regulated
- Professional Regulated
- Special Applications
Using the right kind of GNSS receiver for a given application is essential for safety and effectiveness.

The question for policymakers, though, is not whether the right technology exists to mitigate risks — it does. Rather, the issue is whether that technology is being used appropriately.

Most GNSS users are uninformed about GNSS issues and tend to purchase equipment based upon price rather than resilience. Policymakers must consider how to motivate users, especially in critical applications, to purchase and use more expensive equipment. Government leaders have many levers of influence at their disposal, from education to regulation and requirements. As of yet, however, we have seen few in use.

Alternative & Complementary PNT

The booklet devotes a page to “Complementary PNT Technologies” with the subhead “Complementary PNT technologies are redefining navigation solutions.” Saying “one size does not fit all” — which can also be said for GNSS — includes a graphic from the most recent European Radionavigation Plan of a conceptual, system of systems PNT architecture.

Perhaps more significantly, other pages have mentions of the desirability of “diversifying” PNT sources and “hybridizing” PNT sources.

Safety-Critical Applications

Overall, the GNSS section of the User Technical Report is an excellent general overview and reference document.

Its description of SBAS, however, might give a misimpression to the uninformed reader.

The title on page 12 reads “SBAS enhance GNSS performance and enable safety critical operations.”

SBAS improves GNSS accuracy with corrections and ionospheric models and helps with integrity. However, it does little to prevent service disruptions due to interference.

The title for SBAS conflict on page 12, with a comment on page 17, discusses “GNSS Vulnerabilities and Mitigation Measures.” The very last note on the page and in the tiniest type reads, “For critical applications, implement alternative (non-GNSS) technologies as a backup to ensure continuous PNT information.”

This latter statement is very much in keeping with the most current, 2023 version of the European Radionavigation Plan, which says:

“Thus, for critical applications or critical infrastructure protection, it is broadly accepted that GNSS, even in a multi-constellation and multi-frequency environment, should not be the unique source of PNT information. For those applications, an alternative PNT solution (back-up but also complementary) should be developed and maintained, not necessarily based on radio frequency technologies.”

To a certain extent, this has been echoed in the United States as well.

In 2020, a Presidential Executive Order warned against over-reliance on GPS/GNSS, saying the government “must ensure critical infrastructure can withstand disruption or manipulation of PNT services.”

Following this, in its January 2021 report on a PNT demonstration project, the DOT said:

“Promoting critical infrastructure owner/operator use of those technologies that show strong performance, operational diversity, operational readiness, and cost-effectiveness is worthwhile. Based on this demonstration, those technologies are LF and UHF terrestrial and L-band satellite broadcasts for PNT functions with supporting fiber optic time services to transmitters/control segments.”

Additionally, a 2023 presentation to an international group by the Office of the Assistant Secretary of the Air Force was titled “Alt. PNT — the Pathway to Resilience.”

GNSS are great systems, but we cannot let our understandable enthusiasm for what are truly miracles of technology unintentionally mislead others. Policymakers must be constantly on the lookout for such missteps and help us all maintain a broader, user-focused perspective.
March 10, 2025
Why OPUS Projects’ hub processing strategy is not a radial survey

On Jan. 16, 2025, as part of the OPUS User Forum, the National Geodetic Survey (NGS) Northeast Regional Geodetic Advisor, Dan Martin, gave a webinar titled “Why OPUS Projects’ Hub Processing Strategy is not a Radial Survey.” The presentation can be downloaded here.

First, let’s define a GNSS radial survey.

A “GNSS radial survey” is a surveying technique where a central control mark is established within an area, and vectors are measured from the central control mark to various other marks of interest surrounding the central control mark, essentially creating a “spoke-like” network design.

Plot of OPUS Projects network diagram. Hub is Addicks CORS, all marks are simultaneously observed during the session. (Photo: Dave Zilkoski)

Why not use a GNSS radial survey when establishing geodetic control networks?

Basically, you cannot directly calculate a “relative accuracy” between two marks if no observations are taken between them. That said, a direct measurement such as a GNSS vector allows error propagation between two marks. Therefore, using the “spoke-like” concept, you know the relative accuracy between the central control mark and a single mark at the end of a single spoke. Still, you don’t know the relative accuracy between marks on the different spokes.

Anyone who has used OPUS Projects or seen presentations on OPUS would think, based on the OPUS Project’s HUB processing strategy, that OPUS Projects was performing a radial survey.

When using OPUS Projects, NGS recommends that users select one CORS as a HUB while processing GNSS session data. In the example here, the Addicks CORS (ADKS) was used as the HUB in data processing. So, why is this not considered a radial survey? It may look like a GNSS radial survey but there’s a lot that goes on behind the scenes.

The bottom line is that OPUS Projects is denoted as a simultaneous (session) processor. This means the vector solution is computed from simultaneous processing of all independent vectors with mathematical correlations between all simultaneously observed vectors. OPUS Projects processing includes all independent vectors along with mathematical correlations to provide the relative connection to marks that are simultaneously observed. In the example above, when processed by OPUS Projects, all the marks occupied (indicated by the lines connecting to the Addicks CORS HUB) will have correlations computed between each other. These correlations are included in the data that is used in the least squares adjustments that are performed during the OPUS Projects workflow (NGS uses a file denoted as the gfile to document the correlations.)

The image below provides a sample of mathematical correlations between marks simultaneously observed during the session. The gfile can be a large file when the survey includes a lot of simultaneously observed marks because there will be correlations between all marks. There were 13 marks simultaneously observed during the sample session, so the “spoke-like” diagram includes imaginary lines between every mark because of the mathematical correlations between these marks.

Excerpt from an output from simultaneous (session) processing.
(Gfile contains baseline information with mathematical correlations.)

Dan’s presentation included a slide that described the file’s format. The file provides information on the vectors (delta X, delta Y, delta Z and their standard deviations) between the HUB and the individual marks, plus the mathematical correlations between all marks simultaneously observed during the session. I have highlighted a vector’s components and standard deviations and a set of mathematical correlations.

The image below, from Dan’s presentations, describes the format of NGS’s gfile.

Photo: NGS

Some software programs perform what is called sequential (baseline) processing, which involves processing one vector at a time and ignoring the mathematical correlation between baselines observed in the same session. So, what does this mean, and why is it important?

A couple of definitions are necessary to understand the concept. Independent baselines are baselines where no other baseline is a linear combination of another baseline. Linearly dependent (trivial) baselines are baselines that are linear combinations of another baseline. Basically, once you have used a particular set of data to compute a vector, you can’t use the same data to compute a different vector.

Dan did a nice job during his webinar explaining what baselines are considered trivial and what baselines are non-trivial. This is very important because if your software is a sequential (baseline) processor, you must ensure that trivial vectors are not included with the non-trivial vectors. As Dan highlights in his webinar, dependent vectors are not additional observations. But they do offer useful information if treated properly.

Photo: NGS

There was a 1992 study performed by Michael Craymer and Norm Beck, “Session Versus Baseline GPS Processing,” that explained the differences between sequential baseline processing and simultaneous (session) processing, and what the user needed to do to use sequential baseline processing. Basically, when all the trivial vectors are added to the adjustment, they are treated like additional independent observations, resulting in an inflating degree of freedom and overly optimistic error estimates. If all possible vectors are processed, then resulting coordinates may essentially be the same as in simultaneous (session) processing, but statistics will be overly optimistic and misleading. The 1992 paper does state that the two different processing techniques can produce the same results.

“It is shown that using all possible baseline solutions (with the covariance matrix scaled by n/2, where n is the number of simultaneously observing receivers) is mathematically equivalent to session processing with all correlations only under certain conditions. This equivalence is verified empirically using simulated and real data. However, the conditions under which this equivalence holds are difficult to achieve in practice.”

Users who process data using a sequential processor should read the 1992 study by Craymer and Beck to understand the conditions under which the two processes generate the same results.

I would encourage all individuals that process GNSS data, regardless of which software you use, to download the NGS OPUS User Forum webinar. NGS also has a website that provides training material on the use of OPUS Projects. The more you know about the software you use, the better you will be prepared to address issues associated with your survey results.

OPUS Projects’ training material. (Photo: NGS)

March 5, 2025
Editorial Advisory Board Q&A: The hidden cyber threats to GNSS/PNT systems

When we discuss the security of GNSS/PNT systems, we nearly always focus on interference — i.e., meaconing, intrusion, jamming or spoofing. However, GNSS/PNT systems are embedded in systems of systems that also offer many other opportunities for cyberattacks.

What should we do about it?

Ellen Hall

“The key is platform architecture, specifically ensuring robust spatial and temporal partitioning between safety-critical and non-safety-critical functions. Safety-critical functions, such as navigation and autopilot, must be isolated from non-safety-critical functions, such as mission compute, where artificial intelligence typically operates. This partitioning minimizes the scope and effort required to produce design assurance artifacts for airworthiness certification. Additionally, it enhances security by reducing potential attack vectors through the isolation of safety-critical and mission-critical capabilities.”

— Ellen Hall
Imminent Federal

Mitch Narins

“An old mariner’s proverb is: ‘The prudent mariner never relies solely on any single aid to navigation.’ A more recent statement offers: ‘With so many pieces of sophisticated electronic equipment at our beck and call it would seem some are lulled into complacency and are ignoring basic seamanship.’ In September 2018, the U.S. Naval Institute published an article titled, ‘Professional Mariners Cannot Rely on Electronics Alone.’ The recent news that the U.S. ITAR restrictions on multi-element antenna arrays will be lifted (thanks to many in our community who have lobbied hard for this for many, many years) is excellent news. It will help and was a necessary change — but it is not sufficient. It certainly does not remove the need to pursue complementary, PNT solutions that will ensure the safety, security, and economic well-being of PNT users and their PNT-dependent systems worldwide. From a basic systems engineering perspective, incorporating multiple solutions with independent failure mechanisms is ultimately the end product that we in the PNT community should all be seeking. We must not forget, however, a key element of many of these systems: the human in the loop, who, if continually provided the opportunity to train in PNT-challenged environments, often can be the ultimate system safety element. This will require the design of our PNT services to ensure that the human factors designed into these systems include sufficient information for the human component to understand an off-normal situation and have the training and skills to take the appropriate corrective actions.”

— Mitch Narins
Strategic Synergies

February 27, 2025
UAS updates: Advancements in integration, new UAV approvals and more

Unmanned Traffic Management (UTM) is an air traffic management system for UAVs and other unmanned air taxis or similar aircraft. In the United States, this is in airspace below 400 ft, avoiding other airborne traffic — including other UAVs — and informing authorities of your intended flight plan and how you execute it versus the posted plan.

Where are we on getting such a system? Well, there is an entire directory of nearly 80 UTM suppliers, mostly commercial outfits that offer UAV traffic control of some description for some application – typically like surveying a limited area for construction or maybe a related military application. Few companies possess “full function” UTM capabilities, along with extensive expertise and experience. Each commercial flight needs the approval of the FAA, so software packages include an FAA application to fly and feedback of authorization for the flight plan, as well as approval of operator certification and UAV type. There are complex packages from third-party sources, including NASA-developed UTM, as well as independent commercial systems.

So, how would that work across a major geographical area, such as the entire United States? The FAA and NASA have been working to establish how it could work, at least at a test site in Dallas, Texas.

First, the industry participants in this trial who wanted to operate in the same area had to accede to cooperate. Agreements were signed and means were established for data to flow between the participants, their drones and the FAA (the North Texas Shared Airspace Implementation). The limits of the area near Dallas/Fort Worth for the trial were established as the boundaries in which the parties would fly and, in this case, complete deliveries. The players are Walmart, Amazon, Wing, Manna and ANRA, with FAA and NASA watching carefully.

One of the principal actors in Air Traffic Management (ATM) is ANRA in Washington D.C., with offices in London, UK, and New Delhi, India. With more than 100 customers in 15 countries and more than 200 projects, their UTM/ATM systems are gaining wider experience in several different airspaces and differing traffic compositions. The system is evolving with wider applications as installations worldwide meet new requirements. AAM for eVTOL passenger-carrying aircraft provides mission planning, traffic deconfliction, vehicle tracking, constraints management, route authorization and vehicle registration. EVTOL aircraft will likely fly not only in and out of existing airports but also from new Vertiports specially built for short-hop eVTOL flights across cities. ANRA has already engineered a Vertiport Management System (VMS) to control unmanned and autonomous access to airports and Vertiports alike.

Another unrelated development in the world of UAVs is the phenomenon of high-altitude platform station (HAPS) UAVs and their ground infrastructure. Although flying at altitudes on the edge of space, it is likely special provisions would be required within its associated UTM system to keep track and warn other high-altitude flyers. Nevertheless, the highest-flying commercial aircraft would probably be at an altitude nearly 30,000 ft below HAPS remote Stratospheric perch.

Airbus Zephyr HAPS. (Photo: Aalto)

Airbus company Aalto Haps, based in Farnborough, UK, is now responsible for the manufacture, operation and commercialization of the Airbus Zephyr HAPS vehicle line. Designed to fly for months at a time, with wings covered in solar cells for power, Zephyr has established a world record of 64 days on station in the Stratosphere, and aalot has a target to fly for 200 days regularly.

So, what do you do with such a high-altitude, long-persistence platform? Well, it is like having your own satellite, which you can hang payloads on for tasks such as surveillance, disaster assessment and relief, border control, and numerous precision GNSS applications. With an apparent footprint of close to 3,000 square miles and an appropriate communications relay capability, you have a cell-phone tower in the sky. Perhaps even a partial equivalent to the Space-X Starlink space-based satellite communication service for provision of voice and internet, but seemingly far less infrastructure than the conventional 250 ground cell-towers needed for such an area.

Places starved of phone and internet service — such as Africa — could greatly benefit from flying their kite and gaining wide area coverage. To demonstrate how this capability would work, Aalto recently established a presence in Laikipia, Kenya, building an AALTOPORT ground facility and working with the Kenyan civil aviation authority to qualify Zephyr and its communications role for operations in Kenyan airspace. It is, of course, opportune that Kenya’s location on the equator provides access to one of the most sunny days available to power Zephyr at altitude. Laikipia County is also on a raised plateau, providing Zephyr with an altitude advantage for initial launch. Incidentally, Aalto flew Zephyr for 13 days over Kenya to prove the point.

With the facility in the UK able to build Zephyr-like UAVs every three months or so, Aalto aims to establish a number of hubs (such as the one in Kenya) around the world and operate a number of HAPS aircraft continuously, providing communications and all sorts of services commercially.

A new startup is investigating the concept of putting a tethered drone in the air with specially designed propellers driven by electric motors. This combination then turns into electricity generators for a particular flight pattern.

Windlift power generation cycle. (Photo Windlift)

Transportable power generation. (Photo Windlift)

Initially focused on propeller design, Windlift was established in 2006 and is still based in Durham, North Carolina. Its approach is to use UAVs as a power source — flying repeatedly in a figure of eight, potential energy is converted to electricity in several non-powered phases of flight. The specially designed rotors turn to capture energy in those phases and their prop motors become generators of electric current, which is passed to the ground through the tether wire, to be ultimately supplied to the grid.

However, this setup could be portable, making it suitable for a small military or research team in the field needing power. This portability could be related to a $30 million contract Windlift has received from the U.S. Naval Research Laboratory, which is interested in technologies that the Navy and Marine Corp could use. Under the contract, the building and testing of a working prototype and demonstration to the Department of Defense is required. According to Windlift, this is a successful result of several earlier, smaller Small Business Innovation Research contracts to helped develop the necessary technological elements of today’s system.

Commercially, the UAV power generation approach appears to be extremely cost-effective versus the costs associated with today’s wind farms of huge wind turbines. Not only is the construction cost of each tower, its generator, and the huge blades very high, but the wear and tear of operations over time require expensive maintenance. Meanwhile, the UAV, while still in its infancy with lots of reliability and weatherproofing to be accomplished, has the potential to reduce power generation costs by up to 80%, Windlift said.

This month’s UAS news indicates how UTM is well along the path towards managing UAV integration into the National Airspace System, HAPS high-altitude aircraft may be back in the news as Aalto moves forward with commercialization plans, and yet another application for UAVs appears to involve a new potential approach for power generation. A pretty wide range of unmanned requirements and applications.

February 19, 2025
GNSS disruption at sea level: An interference study in the Baltic Sea
For years, aviation safety organizations and maritime authorities have relied on ADS-B-based reports to assess GNSS interference. Services such as gpsjam.org, spoofing.skai-data-services.com and flightradar24 have provided valuable insights into interference patterns at high altitudes. However, this data tells only part of the story. Ground-based infrastructure — ports, telecommunications networks, and precision navigation systems — operate in a vastly different signal environment. High-altitude detections cannot reliably indicate the presence or impact of interference at sea level.

To address this critical knowledge gap, GPSPATRON and Gdynia Maritime University have conducted a six-month study on GNSS interference in the Baltic Sea. Using terrestrial GNSS monitoring technology, the project examined the frequency, duration and characteristics of interference events affecting maritime navigation and other critical applications.

Data collection and analysis

At the core of this study is a terrestrial GNSS monitoring system developed by GPSPATRON, designed to capture and analyze signal disruptions in real-time. Installed at the Faculty of Navigation at Gdynia Maritime University, this system continuously recorded GNSS signal integrity and transmitted the collected data to a cloud-based analytics platform. This platform facilitated the automated detection, classification and visualization of GNSS interference events, providing a comprehensive understanding of interference patterns and their potential impact on maritime navigation. The results paint a stark picture of persistent and evolving interference patterns in the Baltic region. More than 84 hours of GNSS interference were recorded, with October exhibiting the highest activity. Two primary interference types were identified: multi-constellation jamming, prevalent in the summer months, and multi-tone interference, which emerged in October.

Key findings
- Persistent GNSS Interference: A total of 84 hours of GNSS interference was detected, indicating continuous disruptions in the region. Most incidents were caused by jamming rather than spoofing.
- October saw peak interference levels: The month recorded six major jamming events totaling 29 hours, showing an escalation in disruption frequency and severity.
- Maritime sources of interference suspected: Signal pattern analysis confirms that the source was mobile, reinforcing the likelihood of a single ship or multiple vessels operating the same advanced jamming technology.
- High-Precision Jamming Signatures: The interference signals detected exhibit structured modulation patterns and frequency agility, suggesting the use of highly sophisticated jamming techniques. These characteristics indicate high-grade equipment, potentially of military origin, with capabilities far exceeding those of common commercial jammers. The consistency and precision of these disruptions highlight the need for further investigation into the source and intent behind these operations.
- No link to ADS-B reports: Despite extensive ground-level interference, ADS-B-based monitoring systems failed to register corresponding events, highlighting their limitations in assessing terrestrial threats.
- Long-duration disruptions: Some interference events lasted more than seven hours, significantly affecting GNSS-dependent operations in maritime navigation and port activities.
Implications for maritime and critical infrastructure

The findings of this study expose a critical gap in current GNSS monitoring methods. High-altitude interference reports, primarily based on ADS-B data, fail to capture the real impact of jamming and spoofing at ground level. Maritime operations, port logistics, and other critical infrastructure remain vulnerable due to this oversight.

Ports, telecommunications providers, and emergency services rely heavily on GNSS for navigation, timing synchronization, and security. Without precise ground-level monitoring, disruptions can go unnoticed, leading to cascading failures across multiple sectors.

A major concern is the false sense of security created by ADS-B-based detection systems. While these services report daily interference incidents, they do not reflect the full extent of ground-based GNSS disruptions. As a result, infrastructure operators may underestimate the risk, assuming that existing monitoring solutions provide adequate coverage. This misconception is dangerous, as it masks the severity of interference threats that remain undetected in high-altitude datasets.

To mitigate these risks, there is an urgent need for a dedicated GNSS interference monitoring network along the Baltic Sea coast. Such a network would provide real-time, localized data to accurately assess threats, detect interference sources, and enhance infrastructure resilience against GNSS disruptions.

Conclusion

This study confirms that GNSS interference is a persistent issue at sea level, posing a serious threat to critical infrastructure, which predominantly operates at ground level. Prolonged interference events were recorded, some lasting several hours, leading to significant degradation in positioning and timing accuracy. This disruption directly impacts maritime operations, telecommunications, emergency response, and other sectors reliant on GNSS services.

High-altitude interference detection alone is insufficient, as it fails to capture threats affecting ground-level operations. Relying solely on ADS-B-based reports creates a false sense of security, leaving critical systems vulnerable to undetected risks.

To mitigate these risks, there is a clear need for a dedicated ground-based GNSS interference monitoring network. Such a system would provide real-time detection, precise geolocation of interference sources, and timely countermeasures to protect infrastructure.

GPSPATRON and Gdynia Maritime University urge regulatory bodies to take proactive steps toward enhancing GNSS interference detection and mitigation. Without coordinated action, vulnerabilities in national infrastructure will continue to escalate, leading to potentially severe operational and security consequences.

The full report can be downloaded from the GPSPATRON website.
February 18, 2025
First Fix: Freeing CRPAs

Illustrative beam patterns of a CRPA antenna in the presence of jamming (Figure: Michael Jones)

Controlled Reception Pattern Antennas (CRPAs, pronounced “serpers”) are still the single most effective counter to the threat to GNSS from jamming and spoofing — a growing problem in and near conflict areas, such as Ukraine and the Middle East. CRPAs, which make use of the fact that the desired satellite signals and the unwanted jamming signals generally arrive from different directions, reduce the effective range of jammers by up to five orders of magnitude. They are attractive because they replace existing antennas on GNSS receivers without requiring any other changes — though they are generally larger than typical GPS antennas because they contain several antenna elements and some associated electronics.

Beginning on Sept. 15, 2025, CRPAs will no longer be covered by the International Traffic in Arms Regulations (ITAR), which prohibit the sale outside of the United States of defense articles, services and technical data and impose very large penalties for violators. ITAR is managed by the Directorate of Defense Trade Controls (DDTC) in the Bureau of Political-Military Affairs at the U.S. Department of State, which announced the rule change in mid-January. It removes items that “no longer warrant inclusion” from the U.S. Munitions List (USML), which defines the “defense articles” that fall under ITAR jurisdiction. CRPAs for PNT will instead be classified as dual-use commercial items and fall under the Export Administration Regulations list managed by the Department of Commerce. The Directorate removed CRPAs for PNT from the USML because they “no longer provide a critical military advantage, with increasing commercial utilization applicable to civil GPS resiliency” and because the department “intends to facilitate civil global navigation system resiliency.”

This is a seismic shift that many in the GNSS/PNT community — including the National Space-Based Positioning, Navigation and Timing Advisory Board (PNTAB) — have been advocating for years. While U.S. manufacturers have been prohibited from exporting CRPAs, TUALCOM, a Turkish company based in Ankara, has been selling 4- and 8-element CRPAs for GNSS applications, as have some Canadian companies.

Airlines and manufacturers of autonomous vehicles will be among the early beneficiaries of this policy change, as will many safety-of-life applications. Presumably, the vast expansion in the market for CRPAs also will quickly lead to a sharp drop in their cost.

In a November 2022 presentation to the PNTAB, Brad Parkinson listed the use of CRPAs among the major techniques that can make GPS receivers “virtually immune” to jamming and spoofing, recalling that they were first tested in 1978. However, he pointed out, they had been neglected because they were perceived as too expensive and large for many applications, because of delays in implementing the L5 signal, and because ITAR prohibited beam-steering antennas with more than three elements. He argued that restrictions on GNSS CRPAs were no longer effective at preventing potential enemies of the United States from using them.

Barring a reversal from the new administration, U.S. CRPA manufacturers can now help protect GNSS worldwide from jamming and spoofing.

February 14, 2025
The GPS High Accuracy and Robustness Service
From Dec. 4-5, 2024, the National Space-Based Positioning, Navigation and Timing (PNT) Advisory Board met to discuss GPS-related topics. The PNT Advisory Board provides independent advice to the U.S. government on GPS-related policy, planning, program management and funding profiles in relation to the current state of national and international satellite navigation services. A March 28, 2024, GPS World article by Dana Goward highlighted that the PNT Advisory Board has been providing the government with independent expert advice about GPS and PNT for 20 years. He highlighted that the Board is chaired by retired Admiral Thad Allen and has six subcommittees.

This newsletter will highlight a topic that the emerging capabilities, applications and sectors subcommittee discussed at the final PNT Advisory Board meeting of 2024. The presentation title is “GPS High Accuracy and Robustness Service (HARS).” A white paper on the topic and the Dec. 4, 2024, presentation by Shachak Pe’eri, Ph.D., NOAA/NOS/National Geodetic Survey (NGS), can be found on the PNT Advisory Board website.

According to the document, the board prepared the white paper to support recommendation number PNT27-04-ECAS, which is to develop and implement a GPS HARS delivered to users via the Internet. The HARS concept was approved at the PNTAB-27 meeting (Nov. 16-17, 2022) and formally submitted to the National Space-Based PNT EXCOM co-chairs via Memorandum on Jan. 27, 2023.

Recommendation PNT27-04. (Photo: Presentation by John W. Betz, PhD Member, National Space‐Based PNT Advisory Board on May 29, 2024)

The November and December Advisory Board meetings are recorded, and individuals can listen to the entire meeting. The Board’s website provides links to the meeting agenda and presentations. Pe’eri’s presentation on HARS started at 10:30 am on Dec. 4 (2:04 on the recording).

Day 1 can be found here.

During the meeting, the PNT Advisory Board officially stated that it supports the HARS Concept described by NOAA. Of course, the Board also stated that it has no money, but the Board’s stamp of approval of the concept is very important. Now, it is up to NOAA’s NGS to work with other federal agencies, such as NASA’s Jet Propulsion Laboratory (JPL), to work out the details and resources. By leveraging NASA’s real-time Global Differential GPS (GDGPS) System infrastructure and NOAA’s service delivery platforms, a high-accuracy, resilient service that ensures delivery of precise, reliable and secure GNSS corrections for a wide range of scientific and commercial applications can be built for the nation.

So, what exactly is the GPS High Accuracy and Robustness Service (HARS)? The following is a statement from a Jan. 27, 2023, PNT Memo:

“Implementing a GPS High Accuracy and Robustness Service: To augment GPS and overcome some inherent limitations of space-based PNT, the USG should provide a service comparable to the European Union’s Galileo HAS that provides signal corrections than enable better than one-meter level accuracy, as well as cryptographically-protected satellite navigation message data bits for integrity processing. The U.S. should develop and implement GPS HARS, based on the capabilities developed by the JPL for GDGPS, to be made available to users over the Internet.”

The white paper describes the problem and the solution as the following:

“The problem: GPS is falling behind other Global Navigation Satellite Systems (GNSSs) such as Europe’s Galileo and China’s Beidou. GPS has adopted an approach of allowing augmentation by third-party systems (such as Assisted-GNSS in mobile phones, WAAS for aviation accuracy and integrity, and commercial RTK for precision users), rather than providing specialized advanced services itself. Also, the data message modulated on the GPS signals is fragile. Environmental effects or malicious actions can prevent a receiver from reading the information or manipulate what is read, limiting the robustness of the GPS signals. Currently, GPS is the primary system in almost all GNSS chips, even chips made in Europe or Asia. That is: chips are designed to acquire GPS signals first, then signals from other systems. But Galileo and BeiDou are deploying high accuracy services that provide sub-meter position accuracy, enhancing satnav use in many civil applications. The absence of any plan for GPS to offer a similarly high accuracy service could cause GNSS chips to begin using Galileo or BeiDou, rather than GPS, as the primary system. A switch away from GPS as the primary PNT system is a problem for the US Government because it will lose its strategic advantage. Existing commercial chips are used in many strategically important US assets, such as airlines, ships, and organizations that support the US military. Once these chips change their architecture to Galileo-first or BeiDou-first, these strategic use cases depend on these services. It is one step in the direction of not having a GNSS system at all and borrowing the system of another power, exactly the situation that Europe and China were in before they built their own systems. GPS would no longer be the “pre-eminent space-based PNT service” called for in Space Policy Directive 7.”

“The Solution: A high accuracy and robustness service (HARS) provides information to user receivers, reducing errors and enhancing the ability to operate in challenging conditions. The PNT Advisory Board has identified a solution that the U.S. government can provide a HARS without adding cost and complexity to GPS itself; instead, the needed information from government or government-sponsored organizations can be obtained and provided over the Internet to properly equipped receivers. The result would be a world-class HARS at a small fraction of the cost or time, compared to implementing it on new GPS satellites. The HARS would provide cryptographically-protected robust (resistant to jamming and spoofing) GPS for critical infrastructure and would enable new applications (such as lane-dependent route guidance in automobile navigation and emergency vehicle guidance, GPS-only precision positioning of drones) that extend the societal benefits of GPS. HARS would be secure and less sensitive to radio noise and disruptions, including spoofing.”

The following are a few slides from Pe’eri’s presentation highlighting the need for HARS. He mentioned that there are six regional high accuracy systems and one global service that is already operational or in development.

Six regional HAS and one global HAS are operational or in development at this time. (Photo: NOAA/NGS)

NOAA’s presentation by Pe’eri was in response to a request by the Advisory Board. The Board was interested in learning more about the funding and operating a public service that can provide robust real-time GPS corrections. Summarized in three bullets:
- High-Accuracy: Real-time corrections to GPS orbit parameters and clocks to enable more accurate positioning solutions.
- Robustness: Nav Data (ephemeris) can be cryptographically signed and delivered on the same channel.
- Service: Delivered over the Internet and is free to all users.
The HARS could be accomplished by employing the expertise, knowledge, and capabilities of NASA’s JPL and NOAA’s NGS.

NOAA has the authority to provide real-time operational services and regularly collaborates with other federal and state agencies and local communities. NGS manages and distributes the NOAA CORS Network (Foundation and Cooperative CORS). NASA JPL collects GNSS data and generates products with high accuracy.

NGS expertise and knowledge. (Photo: NGS/NOAA)

NASA’s GDGPS is a complete, highly accurate and extremely robust real-time GNSS monitoring and augmentation system. The CCDIS website states, “Employing a large ground network of real-time reference receivers, innovative network architecture, and real-time data processing software, the GDGPS System provides sub-decimeter (<10 cm) positioning accuracy and sub-nanosecond time transfer accuracy anywhere in the world, on the ground, in the air, and in space, independent of local infrastructure.”

JPL expertise and knowledge. (Photo: NASA)

By leveraging NASA’s real-time GDGPS System infrastructure and NOAA’s service delivery platforms, NGS and JPL can build a high-accuracy, resilient service that ensures delivery of precise, reliable and secure GNSS corrections for a wide range of scientific and commercial applications.

Pe’eri’s presentation highlighted HARS benefits to the daily operations of users of geospatial data.

HARS benefits for users. (Photo: NOAA/NGS)

The HARS concept is extremely important to the U.S. GPS user community, where the number of users is increasing every day. A 2019 Department of Commerce (NIST) study, “Economic Benefits of the Global Positioning System (GPS),” highlighted the economic damages a GPS outage would have on the agricultural industry.

The 2019 NIST study, “Economic Benefits of the Global Positioning System (GPS),” determined that $1.4 trillion in U.S. economic benefits from GPS. The study stated that a 30-day widespread outage could erode less than $1 billion in economic value per day. The study also highlighted the impact a GPS outage would have on Agriculture, stating that during planting season, economic damages in the agriculture sector could increase 30-day losses to $15 billion due to lower yields.

Table ES-1 and figure ES-1 from the 2019 report highlight the economic benefits of GPS for private sector use.

Table ES-1: Summary of economic benefits of GPS for private-sector use, 1984 to 2017. (Photo: NIST)

Figure ES-1: Time series of GPS’s economic benefits for the private sector. (Photo: NIST)

I would encourage others to look at the PNT website, especially the Advisory Board website, to obtain information about space-based PNT. Other recommendations and letters from the Advisory Board to the Executive Committee (EXCOM) can be found on the PNT and Advisory Board websites. The webpage provides the Advisory Board’s recommendations on ways to improve GPS and national GPS management. The recommendations are published in the interest of public transparency.
February 5, 2025
A special welcome to the GPS World Editorial Advisory Board

I am very pleased to announce that professor Washington Yotto Ochieng has agreed to join our Editorial Advisory Board.

He is the current head of the department of civil and environmental engineering and chair professor in positioning and navigation systems at Imperial College London, where he has been on the faculty since 1997. He is also the interim director of the college’s Institute for Security Science and Technology. Among his several other current roles, he is the president of the Royal Institute of Navigation, formed in 1947 following the example of the U.S. Institute of Navigation; a member of the board of trustees of the Science Museum Group appointed by the UK prime minister; and chair of the advisory board of the Science Museum in London.

For a much longer bio of Ochieng, including his full list of titles and honors, visit here.

GPS World featured Ochieng in its May 2009 issue, in a special section on “GNSS Leaders to Watch.” We wrote that he was “excited by the potential benefits of the new signals from modernized and new signals, and their integration with novel terrestrial systems/sensors.”

He has proposed the following question for EAB discussion:

When we discuss the security of GNSS/PNT systems, we nearly always focus on interference — i.e., meaconing, intrusion, jamming or spoofing. However, GNSS/PNT systems are embedded in systems of systems that also offer many other opportunities for cyberattacks. What should we do about it?
We will publish responses from other EAB members in the next issue.

Finally, our heartfelt thanks to Terry Moore and Jean-Marie Sleewaegen, who resigned from the EAB, for their many contributions over the years, and a special thanks to Jules McNeff, who has served on the EAB since the magazine’s inception 35 years ago!

January 27, 2025
First Fix: War, collaboration and elections

(Photo: Jirapong Manustrong/iStock / Getty Images Plus/Getty Images)

In February 1991, two Russians joined this magazine’s Editorial Advisory Board: Nocolay Ivanov, Ph.D., research and development director of the USSR’s Institute for Space Device Engineering, and Gennady Gromov, Ph.D., chief designer general for the Leningrad-based All-Union Scientific Research Institute for Radio Equipment. Both were leading experts in GLONASS.

In October 1982, 4 1/2 years after the launch of the first GPS satellite, the Soviet Union had launched the first test satellite for its new constellation. It peaked in 1996, with more than two dozen operating satellites in orbit, then declined, hitting a nadir of just seven operational satellites in 2001.

Additionally, early GLONASS satellites were plagued by orbital failures and short lifetimes. Many observers wrote the system off as another victim of the economic and political disarray following the collapse of the Soviet Union. Then, the new Russian government reversed the trend by substantially increasing its funding for the program. By October 2011, the full orbital constellation of 24 satellites was restored. Next year, Russia plans to launch Glonass K-2, the latest generation of GLONASS satellites.

Following Russia’s invasion of Ukraine, however, much international scientific and technical cooperation with the country has been on hold. On April 8, 2022, the European Commission declared: “Following the Russian invasion against Ukraine and in solidarity with the people of Ukraine, the Commission has decided to suspend the cooperation with Russian entities in research, science and innovation.” Two months later, on June 11, 2022, the White House followed suit: “Consistent with U.S. domestic and international law, we will wind down institutional, administrative, funding, and personnel relationships and research collaborations in the fields of science and technology with Russian government-affiliated research institutions.”

By contrast, cooperation between the U.S. and European space agencies continues apace, as evidenced by a recent successful test of the interoperability of GPS and Galileo receivers.

Meanwhile, in 2024, China reached a total of 45 operational BeiDou satellites in orbit. It is also conducting research on BDS technology upgrades and technological trials for integration with low-Earth orbit PNT systems. It touts this, together with its active participation in the work of relevant United Nations bodies, as enhancing international collaboration.

At the latest two-day meeting of the National Space-Based Positioning, Navigation and Timing Advisory Board, in early December, much of the agenda was devoted to updates on international GNSS capabilities — including Japan’s QZSS and Korea’s KPS — and discussion of how GPS compares with the other global and regional navigation satellite system constellations.

Future GPS policies and budgets will depend largely on the choices made by the next U.S. administration.

War, international collaboration and the periodic changes in national perspectives and priorities brought about by elections contribute as much as scientific and technical research to the prospects of GNSS — this fantastic global utility that enables us, among other things, to track the movement of containers from Shanghai to Los Angeles, fly safely from New York to Paris and coordinate universal time across our planet.

January 21, 2025