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The United Kingdom has issued a summary of input it requested on positioning, navigation and timing (PNT) technologies. The UK deems PNT resilience critical for the UK’s economy.
After a call for evidence, the UK Department for Science, Innovation & Technology received 128 responses from business, industry, academics and the public. These views on opportunities and challenges for the UK’s PNT industry are gathered in a document available online.
Key themes identified
A viable market exists for GNSS-independent PNT, with respondents citing applications in defense and critical infrastructure.
Awareness of GNSS vulnerabilities in end users and critical infrastructure sectors is low.
Potential opportunities in GNSS-independent PNT and other technologies include eLoran, LEO-PNT, 5G, quantum PNT, inertial systems, and applications for GNSS-denied environments.
Short-term challenges include funding constraints and a lack of legislation and standards.
Long-term challenges include scalability, lack of sovereign manufacturing capability, and insufficient planning .
The industry is experiencing a skills shortage, especially in engineering, with a limited talent pipeline and lack of dedicated training opportunities.
In all, 128 responses were received from businesses (sellers and users of PNT), academics, industry bodies and the public. Respondents could select multiple sectors when describing their background; the defense sector was selected most frequently (39 responses), followed by space (35 responses), aviation and drones (28 responses), maritime (28 responses) and communications (27 responses).
Responses will be used, along with wider research, to inform future government policy interventions to support the UK PNT sector.
1. Precision card High-accuracy positioning with the mosaic-X5
The M.2 card GW16160 is the first Septentrio-based product from Gateworks, a U.S.-based manufacturer of single-board computers. The GW16160 provides reliable high-accuracy positioning powered by the mosaic-X5 GNSS module, a high-quality positioning solution for autonomous robots, UAVs and industrial mission-critical applications. The GW16160 allows engineers to integrate high-accuracy GNSS into edge systems without bulky external receivers or complex RF design. This ultra-low power card features an M.2 A/E-Key interface with USB 2.0 connectivity for plug-and-play integration. Gateworks, gateworks.com; Septentrio, septentrio.com
2. SPOOFING MITIGATION Can protect GPS, BeiDou and Galileo signals
Photo: TRIMBLE
The Trimble RTX-NMA (Navigation Message Authentication) mitigates spoofing attacks on GPS and BeiDou signals. RTX-NMA leverages the Trimble RTX correction service and enhances the security and integrity of GNSS navigation messages for all Trimble ProPoint receivers. Used in conjunction with Galileo OSNMA, users now have three constellations protected from spoofing attacks. Trimble RTX-NMA seeks to detect both fake GNSS signals and faulty ephemeris data through real-time authentication that ensures navigation messages from multiple RTX reference station receivers are genuine and trustworthy. It also encompasses faulty ephemeris detection, preventing unreliable data from being included in the correction stream. Enhanced security through advanced cryptographic techniques like AES encryption, and stream authentication, take it a step further. Trimble RTX-NMA is compatible with various Trimble GNSS receivers using firmware version 6.40 or greater. Trimble, trimble.com
Achieving PNT resilience for critical infrastructure applications
GNSS are magic. They are. One dictionary defines magic as “a power that allows people (such as witches and wizards) to do impossible things by saying special words or performing special actions.” By this definition, we have all become witches and wizards, doing what previous generations would have deemed impossible.
This magic, however, can be affected by external forces that render it useless at best and, at worst, dangerous. Warnings about GNSS positioning, navigation and timing (PNT) service vulnerabilities have been raised for 25+ years. Numerous organizations have warned of the potential safety, security and economic impacts of GNSS interference. Still, like modern-day Cassandras, their warnings have been ignored, and sole use of PNT services that rely on space-based signals continues to expand.
“Magic services” are addictive and cannot be ignored. Yet, it is well past the time to merely admire the problem of GNSS interference — benefitting from magical GNSS services while ignoring existing and emerging threats and challenges. It is time to draw a line and implement resilient, complementary PNT solutions to support all critical infrastructure sectors and applications in the event of any GNSS disruption, due to jamming or spoofing or systemic causes. “Magic” is magical when it works. When it does not, first and foremost, it should “do no harm.”
Threats, Challenges and Needs
Presidential Policy Directive (PPD) 21, Critical Infrastructure Security and Resilience,issued in 2013, defines resilience as “the ability to prepare for and adapt to changing conditions and withstand and recover rapidly from disruptions.” It also notes that “resilience includes the ability to withstand and recover from deliberate attacks, accidents, or naturally occurring threats or incidents.”
In 2016, the UK Department of International Development noted that “Resilience covers both ‘physical and societal systems” through four “R” principles: robustness, redundancy, resourcefulness and rapidity (see Figure 1).
Figure 1. Infrastructure resilience properties. (Image: UK Department of International Development)
More recently, Andy Proctor (RethinkPNT) pointed out that “A resilient PNT system protects its critical capabilities (assets) from harm by using protective resilience techniques to passively resist or actively detect threats, respond to them, and recover from the harm they cause.”
Policies, processes, financial arrangements and incentives are also crucial to achieving resilience — and that has been, and remains, the problem. Lacking the emergence of strong leadership from our institutions, the ability to achieve actual resilience will continue to falter and admiration of the problem will continue.
Developing a resilient PNT system is always a balance of technical complexity and non-technical aspects, for example, costs. The key consideration for users must be the required performance metrics they need for their use-case(s) to ensure their resilience — including accuracy, availability, integrity, continuity and coverage. The one least understood and many times omitted is integrity — the level of trust a user/use-case needs to safely and securely use the PNT services. The ability to trust PNT services must always be a consideration for critical infrastructure applications.
Unfortunately, many users of critical infrastructure PNT do not know some of the PNT metrics they need to ensure safety and security. More troubling, there is no guidance as to what constitutes “significant economic impact” (see PPD 21) or acceptable economic loss — and over what period or range of use cases. This understanding will require analysis of their design, development and operational experiences, and working with PNT systems engineers to first derive these metrics and then drive the continuous improvements (see Figure 2) needed to achieve and retain truly complementary PNT capabilities. Without clear metrics and guidance, one cannot claim that any solution will meet any “required level of resilience.”
Figure 2. Resilient PNT lifecycle.
Supporting PNT Users
As with all systems engineering (SE) activities, PNT system resilience begins with identifying and documenting user needs based on their specific user stories/use cases. Figure 3 depicts different aspects of resilience that can be sought, depending on the unique use-case “demands.”
Figure 3. Resilience aspects. (Photo: UK Space Agency)
While the resilience needs of different use cases will differ, for any specific use case, a given “PNT solution” will either achieve the required/threshold level of resilience (based on the operational environment) or it will not. Some use cases may also require fail-safe or fail-soft capability and the ability to recover to known, trusted and usable states. Shouldn’t many, if not all critical sector use cases require this?
Equally important is the identification of risks and threats, as they are critical to understanding the challenges that the system must face while continuing to provide the necessary P, N and/or T service performance. It is also key to understand and document the system architecture and environment in which it must perform. With knowledge of a user’s needs, the threats, hazards and challenges they face, and the system architecture, the SE process can develop an understanding of the “gaps” that exist and of the levels of risk they impose on a critical infrastructure system’s functional, physical and operational performance. Understanding this, essential use-appropriate mitigations can be identified, or if need be, developed, and a resilient, solution-agnostic PNT requirement document created.
The Way Forward
The Critical Infrastructure Resilience Institute (CIRI), a U.S. Department of Homeland Security Center of Excellence, notes that “critical infrastructure systems are facing a myriad of challenges. Solutions must address the cyber, physical and human dimensions.” They keyed into four areas where critical infrastructure resilience activities should be directed: building the business case, information policy and regulation, developing new tools and technologies, fostering and educating the workforce.
These include the recognition that “policy and regulation have a powerful impact on market forces.” While the fact that “most U.S. infrastructure is owned and operated by the private sector” is a challenge, it should not be an excuse.
We must start immediately to re-establish strong SE practices, policies, and principles to help critical users understand their needs and determine the metrics required to ensure safety and “preclude significant economic impact.” Only then can we understand from a national perspective, the needed safety and security metrics and what constitutes significant economic impact, and then establish categories of solution-agnostic requirements. Lacking these clear resilience targets, detailed planning, and required resource commitments, the growing threats of PNT vulnerability will continue only to be admired, rather than be mitigated. Hope is not a strategy, but this systems engineer hopes that it does not take a truly catastrophic event to finally prompt much needed and long overdue actions.
Mitch Narins is the principal consultant/owner of Strategic Synergies LLC, a consultancy he formed following more than 40 years of U.S. government service. He is a Fellow of the Royal Institute of Navigation, a aenior member of the Institute of Electrical and Electronic Engineers, a member of the Institute of Navigation and head of its Washington, D.C., section, and a member of RTCA, RTCM, IEEE and SAE Standards Committees.
A roundup of recent products in the GNSS and inertial positioning industry from the November 2022 issue of GPS World magazine.
OEM
GNSS Module
For UAV, precision agriculture and autonomous machines
Photo: Unicore Communications
The UM982 GNSS module is a high-precision, dual-antenna real-time kinematic (RTK) positioning and heading module. It supports BeiDou B1I/B2I/B3I; GPS L1/L2/L5; GLONASS L1/L2; Galileo E1/E5a/E5b, QZSS L1/L2/L5; and SBAS in dual-antenna mode. The highly integrated, compact (16 mm × 21 mm × 2.6 mm) module can reduce the design area of an OEM board by 72% compared to previous modules. Power consumption is less than 0.6 W. The NebulasIV GNSS system-on-chip is a key part of the UM982’s navigation system. The NevulasIV integrates RF, baseband and high-precision algorithms on a single chip, with supporting functions built in. High-level performance indicators include raw observation accuracy, RTK positioning accuracy, precise point positioning accuracy, and time to first fix. The two antennas can independently participate in deriving an RTK solution and outputting the positioning results.
Alternative to ceramic patch provides omni-directional performance
Photo: Antenova
The Agosti (part number SR4G080) is a new miniature surface-mount-designed (SMD) antenna for GNSS applications. It measures 9.0 mm x 5.8 mm x 1.7 mm and operates with exceptional efficiency in a reduced space on a corner of a printed circuit board. It has a small ground-plane requirement of 40 mm x 20 mm, 70 mm x 25 mm and 80 mm x 30 mm, making it suitable for small form-factor designs such as wearable devices, trackers and onboard diagnostics.
Housed Dual-Band antenna with Accutenna technology
Photo: Tallysman
The dual-band TW3885T antenna supports GPS/QZSS L1/L5; Galileo E1/ E5a/b; BeiDou B1/B2/B2a; GLONASS G1/G3; and satellite-based augmentation systems in the region of operation: WAAS (North America), EGNOS (Europe), MSAS (Japan) or GAGAN (India). It is housed in a through-hole mount, weatherproof (IP69K) enclosure. It mitigates the effects on GNSS receivers of new signals or harmonic frequencies from adjacent LTE bands on the radio-frequency spectrum. For permanent installations, L-bracket (PN 23-0040-0) or pipe (23-0065-0) mounts are available. Tallysman provides an antenna installation guide that recommends a 100 mm –125 mm ground plane and provides antenna installation and cable connector waterproofing best practices.
Simplifies product development for high-precision applications
Photo: Taoglas
The TFM.110A is the first in a new series of high-precision, multi-band GNSS front ends for autonomous vehicles, precision agriculture, automotive applications and robotics. It comes fully integrated with two cascaded low noise amplifiers (LNA) and pre-filters in a small, low-profile, shielded surface-mount package. When used between the device’s GNSS receiver and antenna, the two-stage amplifier solution eliminates the need for complex and challenging onboard filter and amplifier circuits. It supports L1, L2 and L5 bands and enables seamless signal transmission, signal purity and position accuracy in high-precision applications.
Provides interference, spoofing, encryption and authentication capability
Photo: IFEN GmbH
Version 2.8 of the NCS Nova RF signal simulator offers advanced capabilities. With integrated interference generation capability, the Nova can generate coherent interference signals with a signal power of up to –30 dBm. The ability to assign two users to one RF output enables integrated spoofing scenarios with a single RF output, meaning spoofing is available even with an entry-level single RF Nova. The new release has advanced navigation message authentication simulation capability compliant to User ICD 1.0 for the Galileo E1-B OSNMA, meaning specific OSNMA events can be simulated — key to ensuring compliant receiver behavior. Supported events include renewal and revocation of both a public key and a TESLA keychain. GPS cross-authentication and generation of Galileo E6-C encrypted codes are also supported.
Enables first responders to locate callers on floor levels
Photo: Polaris Wireless
Z-axis location service enables the pinpointing of a smartphone user within one floor level inside a multi-story building. The technology — demonstrated to meet the 3-meter vertical location accuracy requirement of the Federal Communications Commission (FCC) — is integrated into Schok Gear’s newly released flip phones. The Schok phones provide consumers with a simple, powerful device. Adding indoor and vertical location to these phones enables first responders to locate all wireless 911 callers with floor-level accuracy in multi-story buildings.
The new ACR Electronics GlobalFix V5 Emergency Position-Indicating Radio Beacon (EPIRB) and ResQLink AIS Personal Locator Beacon (PLB) have integrated the automatic identification system (AIS) to increase the speed of location and aid. They also are compatible with Return Link Service (RLS) alerting. The combination of services ensures faster rescue and increases chance of survival of both boat (EPIRB) and crew (PLB). The safety beacons deliver mobile connectivity to a cell phone with a free mobile app, made possible with the addition of near-field communication technology in the beacons. With the app, users can monitor their beacons, review self-test results, view GNSS test locations, and monitor beacon performance and maintenance by scanning the beacons with their mobile phones. Besides GNSS positioning, the lightweight beacons have 406-MHz Cospas-Sarsat distress signal with MEOSAR compatibility and 121.5-MHz local homing signal.
The Canvas Device Manager simplifies workflows for configuration and maintenance of internet of things (IoT) device deployments. It enables users to easily set up devices, monitor performance, and keep software up-to-date across the entire IoT device fleet. Device parameters can be remotely managed, and performance monitored. Canvas enables users to organize large numbers of devices to quickly build and maintain IoT solutions, and software updates can be remotely and rapidly deployed, thwarting security attacks.
The N2 Palm RTK GNSS receiver is suitable for surveying, mapping and construction. It has a highly integrated main board and a three-in-one antenna, yet weighs 0.72 kg with battery and measures 48 mm. Powered by ComNav’s SinoGNSS K8 high-precision module, the N2 can track 1,590 channels, including all existing and planned signals of GPS, BDS-2, BDS-3, GLONASS, Galileo, QZSS and SBAS. Its advanced satellite-tracking technology ensures it works well even in harsh environments, such as under heavy foliage or close to buildings. A third-generation inertial measurement unit (IMU) makes the N2 immune to magnetic disturbance, which greatly improves its reliability. Pole-tilt compensation of up to 60° allows surveyors to locate points within 2.5 cm. By using the company’s Quantum algorithm, the N2 achieves calibration-free operation — after 10 seconds of initialization, users can make tilt measurements with centimeter-level accuracy for an extended period, greatly improving efficiency.
Airbus has added 30-cm Pléiades Neo imagery to its OneAtlas Living Library service. The new data source will complement the service which already allows users to instantly access a premium catalogue of Pléiades 50 cm and SPOT 1.5 m data via streaming, download and API. The Living Library provides frequent updates over urban areas, airports, harbors and military sites to name a few. Imagery is updated every day and processed in the cloud, with flexible options for integration into GIS workflows. With the OneAtlas Living Library, Airbus offers a pay-per-order option but also a subscription-based service that allows users to access premium content quickly available into their account, as well as a deeper archive of more than 10 years of imagery by Pléiades and SPOT satellites at a higher incidence angle and cloud coverage threshold, which will be available in just a few hours. OneAtlas also provides access to several other data services, such as reactive tasking, that allows users to task a full suite of optical and radar satellites, including Pléiades Neo, or access more than 15 years of global radar data, as well as the ability to download the WorldDEM product suite among others.
Free, user-friendly tool shows the Earth’s changes
Photo: Kermap
The Nimbo Maps platform provides monthly 10 m-resolution images of changes on Earth in a user-friendly format. The images are chronological, seamless and free of clouds, and include intuitive comparison timelapse features. The platform, developed by French startup Kermap, relies on innovative artificial intelligence methods to process satellite images supplied by the European Union’s Copernicus program through its Sentinel missions. APIs automatically retrieve data extracted from satellite imagery, providing Kermap customers with real-time, strategic, value-added information in the fields of agriculture, land planning and environmental transitions. Current coverage includes Europe, the Middle East and the United States, with plans to provide global coverage by early 2023.
The TrueView 655/660 3D imaging system uses the Riegl miniVUX-3UAV laser scanner and three fully integrated mapping cameras (right, left and nadir) for high-accuracy mapping with excellent vegetation penetration and wire detection. Previous TrueView 3D systems carried dual oblique cameras to maximize mapping coverage. The TrueView 655/660 adds a third RGB camera, allowing for imagery directly below the sensor to be captured. The third camera provides a direct view of the ground below to maximize data collection for time flown, while improving the quality of photogrammetry and colorized point clouds.
Geometer International, a Ukrainian developer of GNSS/RTK instruments and applications for satellite positioning, has introduced the Walker RTK, a dual-frequency L1, L2 RTK receiver in the compact form factor of a portable RTK device.
The Walker RTK is a lightweight, small-sized, affordable and full-featured device for collecting, storing and processing geo-referenced data on the survey site. According to the developer, a GNSS receiver in a convenient and affordable format will significantly expand the use of RTK technology. The new technology will be suited to most tasks requiring centimeter precision positioning and measurements in a 3D coordinate system.
Compact and lightweight, Walker RTK is the ideal solution for field workers working away from the office. The new device can be operated with just one hand, significantly improving the productivity of service personnel.
Possible applications for GNSS Walker RTK include surveying, utilities, solar power plant engineering, trenching and pipeline installation, drilling, forestry and municipal infrastructure control.
What’s under the bonnet of Walker RTK?
The Walker RTK is built around a 2-frequency L1/L2 184 channel board and a sensitive Helix antenna, satisfying up to 90% of basic user requirements. The tube-shaped housing geometry allows it to fit with any universal mount. The receiver weight is only 0.25g (0.470 with smartphone holder) due to the aluminum alloy housing with a protective coating. The Walker RTK has a built-in Li-Ion battery with enough power for 24 hours of continuous operation without additional recharging. The new energy-efficient architecture of the unit achieves this.
The GNSS receiver has the minimum amount of leading interfaces, resulting in high IP67 dust and waterproof rating. The device can be paired with a smartphone or tablet via Bluetooth, while connection via Bluetooth low energy is also planned for a future release.
Compatible with satellite systems
Walker RTK can track and determine geo-position using signals from all known existing satellite systems. This feature makes it possible to achieve the centimeter-level accuracy of an RTK solution within seconds.
GNSS signals processed by the Walker RTK GNSS receiver:
Thanks to NMEA messaging, the Walker RTK GNSS receiver is fully compatible with any professional or freeware geolocation software, providing high accuracy and reliable RTK-corrected positioning.
In a world where GPS and other GNSS signals can be easily denied or, worse, spoofed, interest in other forms of navigation has rebounded.
Imagine being able to locate yourself within a couple of centimeters with just your cellphone – deep underground. Or inside a metal structure. Or underwater (assuming you can keep your equipment dry).
No satellite signals, no Wi-Fi ranging, no inertial system. Just the ambient magnetic flux that constantly surrounds us all. Everywhere.
Animals have used the Earth’s magnetic field to find their way for millions of years. People have been using magnetic compasses for over a thousand. Until the advent of GPS, magnetic compasses were foundational tools for aircraft and ship navigation, especially when out of sight of easily recognized landmarks.
Then GPS came along, and almost everyone’s eyes turned to space.
But in a world where GPS and other GNSS signals can be easily denied or, worse, spoofed, interest in other forms of navigation has rebounded. And because GPS helped demonstrate the efficiencies geospatial services provide, users also want those services to be more resilient and to work in places signals from space just can’t reach.
According to Neill, “Our solution builds upon inexpensive magnetometers, smartphones, machine learning, edge computing, and some incredibly complex math to convert raw magnetic data into a source of ultra-precise location data. These relatively recent tech developments allow us to bring things together for a major update to a centuries-old way of navigation and positioning.”
Describing AstraNav as a software tech company, Neill said that the company’s system is “hardware agnostic.” It can work on “just about anything that has a magnetometer. No additional hardware or external connectivity is required, and we can run on any existing operating system.”
The company has partners in retail, automotive and telecom validating the technology. They have also been working with a U.S. Department of Defense (DOD) combatant commander to demonstrate the product, as well as Virginia Tech and its National Security Institute (VTNSI.) “This is not a case of ‘here’s an idea that we hope will materialize,” said Neill. Describing two real-world trials and use cases to the board, he said, “This technology is a reality, and we’re doing it.”
Most previous magnetic navigation efforts relied upon relatively low-resolution maps. An airplane could find its way safely across the ocean using the maps that were available and likely end up within a mile or two of an airport. Much higher resolution maps built through surveys and artificial intelligence are critical to AstraNav’s centimeter-level accuracy with systems that continue to learn on their own.
Intellectual property is AstraNav’s biggest asset. “We have multiple patents filed and pending,” said Neill. “Our IP is what allows us to sense and analyze magnetic fields so finely, develop maps, and make use of very low-cost magnetometers, such as the ones in cell phones.”
Several people at the advisory board presentation expressed surprise that they had not heard of the company and this capability before. “We have been busy getting established as a company, supporting our first commercial clients, and doing demonstrations for various folks within DOD,” Neill explained. “This presentation is by way of our coming out party. We are very eager to become better known and are looking forward to explaining our capabilities one-on-one with potential users.”
Citing an abundance of proprietary material, Neill was unwilling to discuss a lot of technical detail at the public meeting. His short presentation, he said, was to raise awareness and stimulate interest.
The number of those in attendance who after the presentation said they were eager to learn more showed that he was successful.
Dana A. Goward is President of the Resilient Navigation and Timing Foundation
A PNT expert suggested that my piece titled “Opposite and Complementary: eLoran is part of the solution to GNSS vulnerability” in our November 2021 issue could be augmented with information not currently available on the proposed eLoran capability. This expert also questioned my statement that eLoran “does not have any common failure modes with GNSS” and pointed to potential common threats such as from cyberattacks, physical attacks, and space weather.
Matteo Luccio
I welcome such feedback on the contents of these pages — and agree that in this case some hard questions are warranted. So, in the interest of further exploring the use of eLoran, I pose some questions, hoping that its advocates will provide answers. I know that at least some of them will not shy away from this challenge.
Please note that I wish to keep the discussion on positioning, not the easier question of timing, because that was the primary focus of my article. I also wish to address long-term outages (weeks or months), which would have a greater impact on the United States.
Some of these questions have been addressed, at least in part, in various studies and proposals, most of them now more than a decade old. So, it would be helpful to update those answers and consolidate them in the pages of this magazine.
1. Accuracy specifics. While my November article stated that eLoran would have a two-dimensional accuracy of “better than 20 meters, and in many cases, better than 10 meters,” is that RMS, 95%, or some other statistic?
2. Performance standard. GPS provides a commitment to users in a published performance standard. What specific measures of positioning accuracy, integrity and continuity would you recommend the proposed eLoran system be committed to provide (using the architecture described in the answer to Question 6)?
3. Coverage. Would you recommend this eLoran positioning performance hold for the entire United States (including Alaska, Hawaii, Puerto Rico and other territories), only for the “lower 48” states, or only parts of these 48 states?
4. Current users. By number of users, the predominant common current civil uses of GNSS for positioning are consumer devices (mostly cellphones). By contribution to the U.S. economy, the predominant uses are high-precision applications. For what fraction of these uses would eLoran positioning be adequate? Could an eLoran receiver and antenna fit in today’s consumer devices?
5. Future uses. Emerging civil uses of GPS for positioning include autonomous ground and air vehicles, navigation to space and in space, and lane-accurate car navigation. Which of these could be served by eLoran?
6. Architecture. To maintain accuracy during a prolonged GPS outage, eLoran would require reference stations to calibrate time-varying propagation errors, as well as a certain number of transmitters for good nationwide geometry and for redundancy, ensuring service even if a transmitter is attacked or is taken off-line for maintenance. What architecture would you recommend to achieve this?
7. Infrastructure cost. What would be the cost of installing the required transmitters, power supplies, reference stations, communication links and control system for the architecture described in the answer to Question 6? Can you reference a recent and independent estimate? To a ballpark figure, what cost fixed-price contract would you accept to implement it? Similarly, what would be the annual costs for operating and maintaining this infrastructure?
8. Impact. eLoran transmitters are large and high-power. Providing positioning across the United States could require building some of them from scratch or significantly reconstructing old Loran sites. What issues — such as environmental, aviation safety and security — would this raise, and how would you recommend they be addressed?
9. Receivers. Assuming all the above were achieved, it would accomplish nothing unless eLoran receivers were widely purchased, installed and used. How much would that cost? Who would pay? Should we assume that “if we build it, they will come”?
10. Alternatives. Given the widespread development of other positioning technologies over the past decade, much has changed since the earlier recommendations for eLoran. How do we know that eLoran is the right investment — or even a needed part of the solution or needed system in a system of systems — for the future of U.S. PNT?
Common threats to GNSS and eLoran could include the following:
1. Cyber attacks. Given that GPS’s OCX is said to be the most cybersecure system built by the U.S. Department of Defense, how would eLoran’s control system be even more cybersecure than OCX, to avoid a common cyber-vulnerability?
2. Physical attacks. Given concerns about possible physical attacks on GPS satellites, which move at multiple km/sec 20,000 km from Earth, would it not be easier to physically attack eLoran transmitters, which are stationary, terrestrial, in remote locations, and hundreds of feet tall and require massive power sources?
3. Space weather. GPS is potentially vulnerable to severe space weather that could damage satellites or temporarily hinder signal propagation from space to Earth. However, severe space weather could also damage the power grid upon which megawatt eLoran transmitters rely. How would eLoran service be protected from the effects of severe space weather, such as a Carrington Event?
Send me your thoughts at the e-mail address below, with “eLoran” in the subject line.
Though marvelous, GNSS are also highly vulnerable. eLoran, which has no common failure modes with GNSS, could provide continuity of essential timing and navigation services in a crisis.
GPS fits Arthur C. Clarke’s famous third law: “Any sufficiently advanced technology is indistinguishable from magic.” Yet, it also has several well-known vulnerabilities — including unintentional and intentional RF interference (the latter known as jamming), spoofing, solar flares, the accidental destruction of satellites by space debris and their intentional destruction in an act of war, system anomalies and failures, and problems with satellite launches and the ground segment.
Over the past two decades, many reports have been written on these vulnerabilities, and calls have been made to fund and develop complementary positioning, navigation and timing (PNT) systems. In recent years, as vast sectors of our economy and many of our daily activities have become dependent on GNSS, these calls have intensified.
A key component of any continent-wide complementary PNT would be a low-frequency, very high power, ground-based system, because it does not have any common failure modes with GNSS, which are high-frequency, very low power and space-based. Such a system already exists, in principle: it is Loran, which was the international PNT gold standard for almost 50 years prior to GPS becoming operational in 1995. At that point, Loran-C was scheduled for termination at the end of 2000.
However, beginning in 1997, Congress provided more than $160M to convert the U.S. portion of the North American Loran-C service to enhanced Loran (eLoran). In 2010, when the U.S. Loran-C service ended, its modernized and upgraded successor was almost completely built out in the continental United States and Alaska. During the following five years, Canada, Japan, and European countries followed the United States’ lead in terminating their Loran-C programs.
Today, however, eLoran is one of several PNT systems proposed as a backup for GPS.
The National Timing Resilience and Security Act of 2018 required the Secretary of the U.S. Department of Transportation (DOT) to “provide for the establishment, sustainment, and operation of a land-based, resilient, and reliable alternative timing system” as a backup to GPS. In January 2020, the DOT awarded contracts to 11 companies to demonstrate their technologies’ ability to act as a backup for GPS. Of these companies, two were working on eLoran projects.
Technical advisers to the federal PNT Executive Committee have been advocating and recommending that the government implement eLoran for the past 11 years. Yet, while the U.S. government announced in 2008, and again in 2015, its intention to build an eLoran system, it has not done so yet.
Not Your Grandfather’s Loran
In the 1980s, I used Loran-C to navigate on sailing trips off the U.S. East Coast. It had an accuracy of a few hundred feet and required interpreting blue, magenta, black and green lines that were overprinted on nautical charts. The system was a modernized version, launched in 1958, of a radio navigation system first deployed for U.S. ship convoys crossing the Atlantic during World War II. Its repeatability was greater than its accuracy: lobster trappers could rely on it to return to the same spots where they had been successful before, though they may have had some offset from the actual latitude and longitude.
By contrast, eLoran has an accuracy of better than 20 meters, and in many cases, better than 10 meters. It was developed by the U.S. and British governments, in collaboration with various industry and academic groups, to provide coverage over extremely wide areas using a part of the RF spectrum protected worldwide. Unlike GNSS, eLoran can penetrate to some degree indoors, under very thick canopy, underwater and underground, and it is exceptionally hard to disrupt, jam or spoof.
Unlike Loran-C, eLoran is synchronized to UTC and includes one or more data channels for low-rate data messaging, added integrity, differential corrections, navigation messages, and other communications. Additionally, modern Loran receivers allow users to mix and match signals from all eLoran transmitters and GNSS satellites in view.
Finally, eLoran can be used for integrity monitoring of GPS — and vice versa. “Think of a resiliency triad, consisting of GNSS (global), eLoran (continental), and an inertial measurement unit, a precise clock, or a fiber connection,” said Charles A. Schue, CEO of UrsaNav. “It is extremely difficult to jam or spoof all three sources at the same time, in the same direction, and to the same amount.”
For the eLoran system to cover the contiguous United States, between four and six transmission sites could provide overlapping timing coverage, and 18 transmission sites could provide overlapping positioning and navigation.
U.S. Developments
The INVEST in America Act authorizes $157 million for the Department of Homeland Security to conduct research in five separate areas, one of which is positioning, navigation and timing resiliency; however, none of this money is for eLoran per se. The regular DOT appropriation for next year has $17 million for PNT-related research, $10 million of which is for “GPS Backup/Complementary PNT Technologies Research.” However, neither of these bills has yet been finalized, let alone passed into law, so they may change.
“These are very complex systems, with five- to seven-year sales cycles,” pointed out Schue, “and the process is even slower now due to the pandemic. With adequate funding, eLoran signals could start becoming available in the contiguous United States within a year of a service contract being signed. We should recall that GPS — as, indeed all of the GNSS — was brought online gradually as satellites were developed and launched into space. There should be no expectation that any other nationwide system would be available at the flip of a switch instead of through gradual implementation.”
the former Loran-C transmission antenna at Værlandet, Norway. (Photo: UrsaNav)
International Developments
Loran-C and eLoran operate internationally. Saudi Arabia, China and Russia continue to operate Loran-C or Chayka systems. In October 2020, a Chinese paper described how the nation is expanding Loran to its west to cover the whole country to protect itself from disruptions of space-based services. A previously published report made it clear that they are upgrading or have upgraded from Loran-C to eLoran. South Korea has an ongoing project to upgrade its Loran-C to eLoran. It also seems the project will ensure that the South Korean system will be useable on its own, even if the Russian and Chinese systems with which it normally cooperates are not available for some reason, according to Dana Goward, president of the Resilient Navigation and Timing Foundation.
The United Kingdom is still committed to eLoran, and operates one station that has been used as an alternative time reference to GNSS. “However, as the sole station still transmitting in that area of Europe it’s of no use for positioning,” said Nunzio Gambale, CEO of Locata Corporation. “Unfortunately, the EU’s shutdown of their old Loran sites seems to have been completed, and no EU-based Loran sites remain operational. Their actions leave scant hope for Loran’s resurrection any time soon as an alternative to GNSS positioning in Europe. That’s a shame, because eLoran has beneficial PNT characteristics that other alternate technologies will struggle to replicate.”
A deck officer on a ship takes a relative bearing using a pelorus. Loran-C was developed in large part for maritime navigation. (Photo: aytugaskin/iStock/Getty Images Plus/Getty Images)
Advocacy
“There is fairly good agreement across the PNT community that there is no sole solution [to GPS vulnerabilities],” Schue said. “It needs to be a system of systems.”
The PNT community, he said, is working with Congress and the administration “to move ahead with actual RFPs to start the contracting process — instead of continuing to admire the problem.” UrsaNav, NextNav, OPNT and other companies and organizations “are working together as best as we can to tell the federal government that we all believe in a system-of-systems approach and that there ought to be some tangible forward motion.”
While DOT has the lead on providing PNT resiliency, it and the departments of Defense and Homeland Security need to cooperate on this, Schue argued. “Many, if not all, of the other departments — such as Commerce, Energy, State, Interior and Agriculture — also have a stake.”
GNSS will remain for a reason. “Unless a new national terrestrial PNT system moves the game forward for many markets, it’s just far too easy to remain with the GNSS system, which is fundamentally free,” Gambale said. “That’s a really difficult price point to compete with, unless you’re delivering significant new value to the market.”
The time to act is now. “This issue has been studied to death for more than 20 years,” Goward said. “There are technologies ready to deploy. It is time for action. A failure of national PNT will be catastrophic.”
Admiral Lord Alan West of Spithead has served the United Kingdom as First Sea Lord and led the government’s efforts for counter terrorism and cybersecurity. He has been a member of the House of Lords since 2007 and has stayed engaged with defence and maritime issues. RNT Foundation President Dana A. Goward spoke with him in early September about the UK’s way forward for GPS-like services.
DG: The UK government has been talking for years about the nation’s vulnerability to disruption of space-based signals such as those from GPS and Galileo. What is being done about it?
LW: Unfortunately, the government is not being as transparent as we might like on this. I do know from comments made in the House of Lords that there is a group developing a strategy. Also, that the Cabinet Office — our equivalent of the National Security Council in the United States — is deciding who is to be in charge and how things will be run.
I have heard the strategy group will propose a mix of technologies such as has been discussed in the United States. The idea of having several different systems, I am sure, is so that something interfering with one won’t disrupt them all.
This is all supposed to published in November. But I am concerned that government distractions with COVID, Afghanistan and other issues will delay that.
DG: What about the OneWeb project? That doesn’t seem to be waiting for a November announcement. And there is talk it may provide GPS-like timing and navigation services.
LW: OneWeb is moving forward, but at present it is only about 5G and making it available more quickly and broadly. There may be a OneWeb Phase 2 that includes modified or additional satellites to provide positioning, navigation and timing (PNT), but that is to be decided.
Admiral Sir Alan West, then First Sea Lord, is pictured with the official chart of anchorages for the International Fleet Review. (Photo: DP Kilfeather’s book Trafalgar 200 Through the Lens, Queen Elizabeth II 80th Birthday Edition, CC BY-SA 2.5)
DG: How about the UK rejoining Galileo?
LW: Actually, that makes a lot of sense from a practical point of view for both the UK and Europe. Unfortunately, there were a lot of hurt feelings on the continent with Brexit, some EU leaders seemed to be in punishment mode, and expulsion from Galileo was part of the fallout. I think that in due course as tempers cool, we will fully re-engage with the European Space Agency.
DG: So, no UK project for a GPS equivalent?
LW: The government allocated £90 million to that, which enabled a thorough look at the idea but was woefully inadequate to even start a project. Doing a British version of GPS or Galileo would be hugely expensive and doesn’t make sense. There are better, cheaper ways of getting what we need.
DG: And what does the UK need? What is the goal?
LW: We need several things.
First, we need a global capability that is ours, or that we are closely partnered in, to support the UK’s worldwide military and economic interests.
We also need to have something in place so that, even if space is denied to us — and that is getting to be more and more of a threat each day — we can keep our industries, critical infrastructure and economy going at home.
And third, we need a resilient PNT capability as a foundation for current applications, and to build on for such things as autonomy, intelligent transportation, and the like.
DG: So how do you get there?
LW: For the global bit, the OneWeb, and perhaps an even closer partnership with the United States on GPS.
At home, we definitely need a sovereign capability for when space is denied by solar weather or our adversaries. Also to be a check on space signals because our adversaries and criminals are spoofing them more and more.
I have always thought eLoran was a good choice. The UK pioneered its development and had the world’s first operational system in 2015. It is really hard to interfere with the signal, and there are other features that could be added to it that would make it even more robust.
There was a very interesting report called MarRINav put out last year about what UK maritime needs to ensure it can navigate regardless of whether the satellites are working or not. They came up with a reasonably inexpensive combination of systems anchored by eLoran.
By the way, it is interesting that the MarRINav study was funded by the European Space Agency. They seem to understand that satellites are not the be all and end all for PNT services.
DG: That all seems pretty straightforward and the right thing to do. What’s standing in the way?
LW: Well, so few people understand the problem. The population as a whole is almost completely unaware. At some level government understands all 13 of our critical infrastructure sectors could be impacted, but the people senior enough to drive action have dozens of other issues to deal with that probably seem more urgent.
DG: I wonder what it will take to make it seem urgent enough.
LW: Let’s hope the wakeup call is something short of a national disaster.
Accurate and reliable positioning, timing and navigation (PNT) technologies, such as GPS, have become “invisible utilities” that enable many critical applications, including the electric grid, telecommunications, agriculture and port operations. These systems, however, are vulnerable to accident and attack, including cyber threats and jamming.
Therefore, the Science and Technology Directorate of the U.S. Department of Homeland Security and the National Risk Management Center of the Cybersecurity and Infrastructure Security Agency have been working in collaboration with industry and government stakeholders to develop the Resilient PNT Conformance Framework, which provides a common framework for defining resilient PNT systems and addresses strategic risks to U.S. national critical infrastructure. This work is now transitioning to the Institute of Electrical and Electronics Engineers (IEEE) as the Standards Working Group for Resilient PNT User Equipment (P1952) and will help serve as starting resources for the refinement and development of a standard.
By creating common definitions for different levels of resilient PNT systems, this new standard will enable vendors to differentiate their products from non-resilient PNT systems, as well as enable end-users to make deliberate, risk-informed decisions as to which systems are most appropriate for their applications and needs. The development of this voluntary standard will help influence the future design, acquisition and deployment of resilient PNT systems within our national critical infrastructure.
The IEEE standards process is an inclusive one, designed to gather many stakeholders interested in resilient PNT. If you would like to participate in the standards working group, just notify the group’s chair (Shelby Savage at [email protected]) or its secretary (Patricia Larkoski at [email protected]). Voting membership requires sufficient participation in work group meetings.
The development of this voluntary standard will help influence the future design, acquisition and deployment of resilient PNT systems.
After the standards working group votes to approve the draft standard, it will be submitted to the membership of the IEEE Standards Association (IEEE SA) for final approval. The IEEE Standards Balloting Center will then send an invitation to any SA members it knows to be interested in the subject matter of the proposed standard, and anyone answering the invitation affirmatively will have a right to vote on the final standard.
Compared to the early days of GPS, PNT systems have become highly sophisticated pieces of equipment with a multitude of components, both hardware and software, along with associated vulnerabilities. Additionally, with a wide array of stakeholders and a variety of ideas on what PNT resilience means, getting consensus and developing such a standard would be challenging without an established process.
To help address this challenge, DHS developed the Resilient PNT Conformance Framework with input from industry stakeholders to establish baseline concepts on the definition of resilience and necessary behaviors within resilient PNT systems. DHS designed this framework to be outcome-based and non-prescriptive, to encourage industry innovation.
“To address security and resilience, GPS and PNT receivers need to be treated more like computers rather than radios,” said Ernest Wong, technical manager for the Science and Technology Directorate. “The refinement of the Resilient PNT Conformance Framework into industry standards will help to ensure that future PNT receivers are resilient and designed to withstand and recover from threats.”
Editor’s Note: This article does not represent a formal position of P1952 Working Group, Communications Society Standards Committee, IEEE, or IEEE SA.
The trial for the U.S. Department of Homeland Security showcases the precise, resilient timing capabilities of NextNav’s TerraPoiNT service in the event GPS is unavailable.
NextNav has successfully demonstrated the timing precision and resilience of its terrestrial positioning, navigation and timing (PNT) system, TerraPoiNT, in a recent evaluation by the Science and Technology Directorate of the Department of Homeland Security (DHS S&T).
The trial tested the timing redundancy of the TerraPoiNT system in a number of scenarios, including instances of GPS outages, spoofing and jamming. It validates TerraPoiNT’s capabilities as a terrestrial, GPS-free network capable of powering critical national infrastructure in the event of GPS failure.
During a simulated 72-hour GPS outage, the TerraPoiNT service was able to deliver a timing accuracy better than 50 nanosecond in urban and semi-urban environments, successfully meeting timing requirements for various applications including 5G networks, the synchronization of the power grid, and more.
In addition, TerraPoiNT provided precise timing and redundancy utilizing two alternate absolute timing sources — atomic clock (Cesium/Rb) and LEO satellite (Satelles).
“GPS is critical infrastructure, but it has its limitations,” said Ganesh Pattabiraman, co-founder and CEO of NextNav. “In working with DHS S&T, we’ve validated that TerraPoiNT can serve as an important backup to GPS and ensure the resilience and continuity of our nation’s most critical systems, including next-generation telecommunications networks, financial services, and power grids.”
Satelles STL
STL from Satelles was one of two alternate absolute timing sources for the trial. Available today on a global basis, STL is a service that provides alternative PNT independent of GPS, supporting PNT-reliant applications such as 5G communications networks, high-frequency trading in financial markets, and electrical grids throughout the United States and around the world.
“Satelles applauds NextNav for conducting a successful field demonstration of its resilient PNT service, and we were delighted to have played an instrumental part in the exhibition,” said Christina Riley, vice president of Commercial PNT.
NextNav’s selection of STL to help demonstrate their own technology’s operation in the absence of GPS was a natural fit. That’s because earlier this year the U.S. National Institute of Standards and Technology (NIST) confirmed STL as an accurate and reliable source for the wide-area delivery of Coordinated Universal Time independent of GPS/GNSS.
Previous TerraPoiNT evaluations
The successful trial builds on recent evaluations of TerraPoiNT conducted by independent bodies. Earlier this year, the Department of Transportation (DOT) evaluated 11 alternate PNT solutions, in which each was rigorously tested across applications and scenarios. As a result of the evaluation, the DOT named TerraPoiNT the best and only performing solution across all PNT categories.
Spartacus. In June, NextNav entered into a definitive merger agreement with Spartacus Acquisition Corporation in a transaction that would result in NextNav being listed on the Nasdaq. The transaction is expected to close late in the third quarter of 2021 or early in the fourth quarter of 2021, subject to satisfaction of customary closing conditions.
