ION’s Pacific PNT Conference is a global cooperative development of Positioning, Navigation and Timing technology and applications where policy and technical leaders from around the world meet to discuss policy updates, receive program status updates and exchange technical information.
The 2022 conference will be hosted virtually April 11-13 PDT on a complimentary basis for ION members. The conference will include sessions on policy and status updates, performance schedules and plans, plus special challenges affecting Asia-Pacific presented by an elite list of experts representing BeiDou, COSMIC/ FORMOSAT, and QZSS.
A session will broadcast each day at 9:00 a.m. JST / 5:00 p.m. PDT. Live-stream attendees will have the opportunity to participate in virtual question and answer periods through the portal.
The Navigation Sensor Switching in Hostile Environments (NAV-SSHE) project aims to design, prototype and demonstrate new solutions for positioning, navigation and timing using 5G plus GNSS for critical applications in hostile environments. NAV-SSHE is supported by the European Space Agency (ESA).
Geolocation company M3 Systems Belgium is taking part in the project in collaboration with Telespazio Belgium. The project began in September 2021 and will last until January 2023.
In the context of NAV-SSHE, M3 Systems Belgium will implement both a GNSS and a 5G signal based on positioning engines. The output of both engines will be fused to provide a unique solution with increased robustness.
The complete system will be demonstrated on two real-use cases:
autonomous vehicles on an airport platform (specifically autonomous lawn mowers)
autonomous docking of vessels in port
The demonstrations will also be used to test potential use of these technologies for drone applications — specifically for the navigation system of the autonomous remotely piloted aircraft Boreal.
Register today to attend the ION’s co-located International Technical Meeting (ITM) and the Precise Time and Time Interval (PTTI) Systems and Applications Meeting, being held January 25–27, 2022, at the Hyatt Regency Long Beach in Long Beach, California, with technical presentations available for on-demand viewing at ion.org.
Plenary and Keynote Sessions
The ITM/PTTI 2022 keynote addresses, “Traffic Jams, Autonomy, and Lagrangian Control” and “The Future of Industrial Atomic Clocks,” taking place on Tuesday, January 25 will be recorded live and uploaded for on-demand viewing through the ITM/PTTI 2022 virtual meeting portal.
Technical Sessions
Individual technical presentations will be pre-recorded and uploaded with slides to the ITM/PTTI 2022 virtual meeting portal for viewing at a time of your choosing, and will remain available for 30 days. Attendees will have the option to submit questions to each presenter. View the full online Technical Program now!
Exhibit Experience
ITM/PTTI 2022 features industry partners with expanded exhibitor profiles, that allow attendees to review the latest PNT-related technologies, products, and product demonstration videos.
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.”
All four current GNSS and two regional systems have been built and are operated by public agencies. Many correction services and complementary PNT services are operated by private companies.
Going forward, what do you expect the division of labor to be between the public and private sectors in building and maintaining PNT capabilities? What should it be?
Ellen Hall
“The space race was championed by governments. Space travel, communications and other technologies were born from government exploration into space. Today we see many private companies engaged in space. Several are intent on supplementing GNSS navigation, and some envision competing. Private companies have a way to go if they plan to compete with systems like GPS, but competition is often at the center of innovation and may benefit everyone.” — Ellen Hall Spirent Federal Systems
Jules McNeff
“GNSS and regional systems are established and sustained to meet the needs of the governments and public agencies that operate them. They cover wide areas and provide services to extremely diverse user communities at levels of performance based on resources that are justified by user requirements and limited by technical affordability. When the global/regional service levels don’t meet the needs of a particular user group or require backup for security, the opportunity is opened for other agencies or private companies to create augmentations and complements to meet the additional needs. The mix is variable and will be determined by the user groups and the market.” — Jules McNeff Overlook Systems Technologies
F. Michael Swiek
“There is really no single ‘correct’ answer or specific division of labor between public- and private-sector entities in GNSS. The situation we see today is the result of decades of constructive and successful ad hoc evolution of roles among and between public- and private-sector entities. Public agencies are better suited to provide foundation technologies and infrastructure due to the large costs and long timelines associated with establishing the constellations and maintaining stable and consistent service. The private sector is better positioned to provide variety and timely flexibility in developing innovative solutions to the broad range of constantly emerging user requirements across all market segments. This unofficial and continually evolving division of labor has worked successfully and continues to adapt to the evolving world of PNT.” —Michael Swiek GPS Alliance
Spirent Federal has launched an alternative RF navigation simulator. As GPS jamming and spoofing continue to rise, interest in complementary sources of positioning, navigation and timing (PNT) data has likewise increased.
Recent government directives recommend a layered, multi-source approach, with much of the attention focused on non-GNSS radio frequency signals. These RF signals, coined alternative RF navigation, offer unique PNT capability in GPS-degraded or denied environments. The signals are secure and resilient and can act as an effective complement to GPS signals.
Spirent Federal’s product can simulate resilient alternative RF navigation signals on its own or concurrently with GNSS signals. Testing can be static or dynamic, with stationary, pedestrian and ground vehicle trajectories available.
“As a result of our extensive research and development incorporating a variety of assured PNT technologies, we’re pleased to be the first to provide this capability to our customers,” said Roger Hart, director of engineering. “Our product enables developers to test early and often, from the first stages of R&D to integration and field testing. Solutions can be tested with edge cases, hardened against interference, and deployed faster with greater confidence they will work for our warfighters.”
Spirent is actively engaged with several alternative RF navigation technologies and technology providers to incorporate signal simulation capability. To learn more, contact Spirent Federal to discuss fielded configurations.
A U.S. Marine Corps radio operator grounds an during long-range HF radio training in Kuwait Oct. 7, 2020. (Photo: U.S. Marine Corps/Capt. Joshua Hays)
Collaboration with Xona Space Systems
Spirent Federal Systems also announced that it is collaborating with Xona Space Systems to develop simulation and test capabilities for Xona signals produced by small satellites (smallsats) operating in low Earth orbit (LEO). Xona is a San Mateo-based startup developing a smallsat constellation for a dedicated PNT service.
Xona’s patent-pending approach using small satellites in LEO is intended to improve global PNT resilience and accuracy by both enhancing GNSS and operating as an independent system. Xona’s high-power signals utilize advanced signal structure and security techniques, improving jamming and spoofing resistance as well as multipath mitigation.
“We do all we can to protect, toughen, and augment PNT and are eager to work with emerging companies like Xona who are developing a next-gen navigation and timing architecture,” said Jennifer Smith, senior director of Business Development at Spirent Federal. “Our simulators provide critical support to developers and integrators by enabling testing and validation before the product deploys.”
The space and defense sectors also benefit from Spirent Federal’s expertise in generating high fidelity RF signals using quadrature (I/Q) data. Spirent test tools allow the full customization of I/Q data. Customers can generate unique I/Q data corresponding to experimental modulation schemes and use Spirent Federal’s signal generation capabilities to create the corresponding RF. Such rapid prototyping allows for quick turnaround times and shorter iteration cycles.
Alternatively, scenarios created using Spirent Federal’s proprietary SimGEN software can be saved as I/Q data which can be processed by software-implemented receivers.
“Building a new generation of satellite navigation and timing services goes far beyond just the satellites,” said Brian Manning, CEO of Xona Space Systems. “It requires building an entire ecosystem from ground stations to chipset manufacturers to end users and systems integrators. Having reliable and trusted simulation capabilities is critical to support all of these areas which is why we are thrilled to be working with Spirent to provide a robust solution to our partners.”
UNMANNED SOLUTION, a South-Korean company based in Seoul, develops autonomous vehicles, including driverless shuttles, autonomous agricultural equipment, robots, and educational platforms. (Image: SBG Systems)
What is complementary / alternative positioning, navigation, and timing (PNT)? In this month’s cover story, five of our marketing partners share their perspective on this question and explain how their products address it.
The four global navigation satellite systems (GNSS), two regional navigation satellite systems and public and private augmentation services continue to provide exceptional levels of accuracy and reliability for positioning, navigation and timing (PNT). Yet their well-known vulnerabilities also continue to fuel the need for alternative/complementary sources of PNT data, especially for new and rapidly expanding user segments such as autonomous vehicles.
What constitutes a complementary service to GNSS for PNT and what constitutes a true alternative is partly a matter of definition and opinion. In a January report, the U.S. Department of Transportation stated
…suitable and mature technologies are available to owners and operators of critical infrastructure to access complementary PNT services as a backup to GPS. To achieve the parallel objective of resilience, as described in Executive Order (EO) 13905, that path should involve a plurality of diverse PNT technologies. 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. (Andrew Hansen et al., Complementary PNT and GPS Backup Technologies Demonstration Report, prepared for the Office of the Assistant Secretary for Research and Technology, Department of Transportation, January 2021, p. 195.)
A portion of the former USCG Loran Support Unit in Wildwood, New Jersey, with its iconic Loran antenna. (Image: UrsaNav, Inc)
For this year’s Q&A on complementary / alternative PNT, I asked five companies in the GNSS/PNT space to tell us how they define the issue, what solutions they prioritize, what markets they target, and which of their products specifically address the need to make PNT more resilient.
Roger Hart: The deep adoption of the state-sponsored, space-based global navigation satellite systems (GNSS) defines them as the primary PNT source at this time. Inertial navigation, long predating GNSS, does provide an independent navigation solution but does not provide time. In today’s conversation, alternative PNT generally refers to deriving position and timing from existing signals not purposed for navigation, to ground-based location systems, and also to emerging satellite systems that operate at higher power — or out of the GNSS band — to provide a diversity of PNT sources.
David Sohn: Simply put, alternative PNT is usually anything that is not GNSS. So, this includes PNT derived from low Earth orbit (LEO) satellites; vision, radar, lidar combined with inertial measurement units (IMUs) and map matching; positioning off cellular WiFi, digital TV signals and other signals of opportunity; legacy nav aids like VORTAC, ILS, DME and eLoran; and new dedicated infrastructure positioning systems like Locata, NextNav or RFID.
Matthieu Noko: Here at SBG Systems, for 15 years we have been developing navigation systems based on smart coupling of GNSS technology and inertial sensors. From our perspective, inertial sensors as well as sensors such as odometers or DVL, combined with high-end algorithms and RAIM, build consistent alternatives to GNSS-only systems in the vast majority of outdoor applications. Inertial sensors dramatically enhance GNSS-only navigation systems, making it possible to provide navigational data during GNSS outages in urban environments or to reject false GNSS measurements due to multipath effects.
As its entry into the driverless category of the Formula Student Germany car race, AMZ modified the car it has used in competition since 2015 to be driverless. (Image: SBG Systems)
The hybridization of several technologies makes it possible to reach a sufficient reliability level for the majority of commercial applications. However, in some indoor applications or in case of intentional jamming or spoofing, a higher resiliency is required. Using visual odometry can then complement quite effectively the navigation system, although this technology is still at a research level. Compared to infrastructure-based alternative PNTs — such as WiFi, Bluetooth or ultra wideband (UWB) ranging — visual odometry has the great advantage of not requiring any infrastructure.
Jacob Amacker: GNSS remains the dominant method of PNT in terms of market applicability and performance, but there are many rival technologies that have great potential and will compete with GNSS going into the future. The most important changes in PNT will be methods of position localization that are able to replace GNSS, and we will likely see these technologies integrated into huge systems, making use of ubiquitous technologies such as lidar. Whereas GNSS still provides the most accurate timing, as systems get more complex, time synchronization becomes a bigger issue, so different methods of this need to be explored.
There are many ways of improving the navigation data overall. Most commonly an IMU and a Kalman filter will be employed to stabilize any errors in the position localization method. A Kalman filter is a method of processing data from a range of sources—say, GNSS, an IMU, and a wheel speed sensor—and using them in such a way as to arrive at the position with a greater accuracy and precision than either source alone would be able to achieve. This process, however, requires precise timing for each data stream. Therefore, one area in which alternative PNT has to compete with GNSS is timing precision. GNSS makes use of atomic clocks used on satellites that are as accurate as you will get. There are also several ways of synchronizing time. A timing system can only be as precise as the most precise clock on the network, but there have been developments, such as Precision Time Protocol (PTP) that can synchronize timings across a network of clocks over Ethernet connections. Traditionally, PPS has been used and whereas this is still very precise it is not able to compete with PTP on convenience or sophistication.
Charles Schue: The common definition these days for “alternative PNT” seems to be with respect to, or as compared to, GPS or GNSS. Even the U.S. DOT’s website speaks to PNT as related to GPS.
I used alternative, complementary and backup somewhat interchangeably during my entire career with the U.S. Coast Guard. In recent years, I injected “co-primary” into the conversation as well. Prior to GNSS becoming ubiquitous, alternative, complementary and backup were not technology-based terms, but were instead operationally based. For example, “the prudent mariner” or “the prudent aviator” should use all means at their disposal to safely navigate their platform. For the navigator, this would include visual, audible and electronic signals or aids. The solution of choice obviously was the one that provided the highest accuracy, availability, integrity and continuity. However, prudence required always checking the solution of choice against other readily available alternatives, preferably that complemented each other, to ensure safety and continuity of operations. At one time, shipboard navigators might have at their disposal Loran-C, OMEGA, GPS, INS, radar, sextant, visual bearings (such as lights and landmarks), beacons, and soundings. Similar alternatives were available on aircraft.
Although always in the mix, timing was often in the background until around 2000. Then it started to become as important as positioning and, in many areas, even more important than positioning. Today’s incredible dependence on technology, and interdependence between technologies, means that knowing your “when” has become as important as knowing your “where”.
Whatever the terminology, the definition of alternative PNT should include some key features. Firstly, we should accept that the solution of choice today is GNSS, and we should define it as primary or co-primary. Next, we should acknowledge that when the primary solution is available and trustworthy, it should always be used, or at least considered. Finally, the primary solution should continually be compared with alternatives to ensure safe and secure provision of PNT to the user. Thus, an alternative PNT solution is one that is readily available; provides an easy and seamless transition to/from the primary or other alternatives; allows continuity of operation at a possibly degraded, yet usable, level of accuracy, availability, integrity or continuity; and is dissimilar enough from alternatives to withstand the effects that might be affecting the primary solution.
Do you agree with the U.S. DOT’s assessment, cited above, of what it will take to make the national PNT much more resilient and reliable? If you do, how do your offerings fit into that framework?
RH: While there are intricate differences in the signals generated by the primary PNT systems, they are all quite similar in terms of frequency and power and are all vulnerable to the same types of interference. Achieving the most resilient solutions will require the use of alternative RF bands and non-RF sources. Having a variety of alternative PNT sources will allow users to integrate the method most applicable to their platform constraints. Integration across the various PNT sources will need time synchronization to take full advantage of the alternate PNT systems. Our offerings work concurrently with GNSS, providing simulation and testing of GNSS and alternative PNT as true complements, while also offering the ability to measure timing accuracy in real time.
DS: Yes, we agree with the DOT’s assessment. However, to be clear, the DOT does not require “LF and UHF terrestrial and L-band satellite broadcasts for PNT functions with supporting fiber-optic time services to transmitters/control segments.” It stated that to achieve resilience, systems “…should involve a plurality of diverse PNT technologies…that show strong performance, operational diversity, operational readiness and cost-effectiveness.” Their demonstrations showed that those technologies they called out meet these criteria. Our solutions have been leading this resilient approach by offering several diverse, alternative PNT references.
We have fielded time-server equipment that operates from both GNSS and eLoran. Our standard offering time servers are equipped with multiple references from GNSS, network-based time services from NTP, PTP and PTP WR; internal references from disciplined atomic clocks; wireline references from IRIG, 1PPS or ASCII time code; and LEO PNT reference from the STL signal.
(Image: SimonSkafar_E+_Getty Images)
L-band or more generally the use of geostationary satellites was until very recently the only communication link for PNT augmentation services, although these signals are weak and easily disturbed or masked, especially at high latitudes. Resilient navigation will clearly need to allow multiple downlinks for corrections such as terrestrial networks (4G/5G) or satellite-based internet. In the mid-term, we expect the correction delivery over IP to become the standard, and L-band corrections to be used as a backup only. All our high-performance products already include an NTRIP client able to handle the IP corrections very easily.
JA: This is certainly one option. Largely, it is borne out of a need to compensate for the disadvantages of GNSS. This larger range of frequencies would provide a range of satellite-borne signals that have different penetration characteristics and information carrying properties but the same core purpose. Therefore, somebody making use of such a system will be better able to receive these signals even when under obstructions. Of course, some obstructions will still be impenetrable to GNSS signals and there is a long way to go to developing a comprehensive solution that can deal with timing differences when the signals travel through objects. It is likely that some other source of timing information, for example through the proposed fiber-optic services, will be necessary to smooth out these issues. Although we will see this much-needed upgrade to cover the shortfalls of GNSS employed, many other alternatives will start to take prominence. It is difficult to say which solution will win out, and it is likely that an upgraded GNSS will continue to dominate for the next decade or two at least. In terms of our offerings, we are exploring all possibilities and keep our core technology open to any position localization method. Of course, we will welcome any new technology that is a viable and improved method of PNT.
CS: I have long been an advocate of a system-of-systems approach simply because there is no PNT solution available yet that works everywhere, under all conditions, for all users, all the time. Many solutions provide only a component of PNT: an INS provides position (the “PN”), and an atomic clock provides time (the “T”). However, an INS does not know “where” it is without initialization and updates, and an atomic clock does not know “when” it is without initialization and updates. Fiber is awesome but is not wireless. Many alternatives depend upon GPS/GNSS as a necessary input. Others are augmentations that depend upon GPS/GNSS as inputs and not direct alternatives, such as space-based or land-based augmentation systems. Some are mode-dependent — such as VOR, DME, ILS, and TACAN for aviators — and thus not useful to other modes: time/frequency, maritime, land-mobile or handheld.
So, yes, we agree with the government’s assessment that low-frequency (LF), generally referring to eLoran in the United States, is the best, very wide area, terrestrial, wireless alternative, and is an essential component of any resilient PNT framework. Irrespective of whether the implementation is Loran-C, eLoran or LFPhoenix, LF is the lowest cost terrestrial PNT solution per million square miles of coverage. All our offerings are focused on the LF portion of the resilience framework. Our offerings easily integrate with any existing PNT technology and have proven in real-world government testing their ability to survive heavy jamming and spoofing environments.
What markets and applications do you target?
RH: Spirent Federal provides simulation test solutions to U.S. government and affiliated organizations. Applications range from core GNSS receiver development to real-time, hardware-in-the-loop system integrations. We have a long history of supplying the U.S. government and contractors with first-to-market products, from Y-code, SAASM, inertial and M-code, to sensor fusion of the latest alternative signals and sensors. We provide test solutions to safety-critical applications that are expected to have the same level of operational performance both in GNSS-available and GNSS-denied environments. Providing a single test platform that can help validate performance in both environments has received positive responses from users in the autonomous vehicle industry.
DS: Aerospace and defense, data-center and communication networks, public safety, industrial control, search and rescue, and space.
Autonomous self-driving mobility solutions move people and goods at appropriate speeds in urban and campus environments. (Image: SBG Systems)
MN: SBG targets a large range of applications including from a relatively small BVLOS drone for remote operation to large hydrographic vessels or airborne survey. We divide the applications into two main categories:
Surveying and mapping, where the inertial navigation system is used to stabilize the measurements from a lidar, sonar or camera to generate high-precision maps.
Control applications, where the PNT and orientation solution is used in real time to feed autopilot or to stabilize a camera. These applications include unmanned vehicles, machine control, camera pointing and more. High resilience is then critical to ensure safe navigation.
JA: Two main applications we are targeting with alternative PNT are surveying and ADAS systems. Both of these applications often make extensive use of lidar systems. We are therefore looking at lidar-based simultaneous localization and mapping (SLAM) algorithms to aid PNT or to provide relative position localization without GNSS. In cases when GNSS is totally unavailable, it is usually possible to set up ground control points. Although these cases are limited, they give much more flexibility in options. Anticipating a future where autonomous driving is the norm and not the exception, new building projects will need to be planned with the adequate systems in place to allow for them, and this will include a system such as UWB.
CS: Our employees have been involved in the design, development, deployment or sustainment of every Loran-C and eLoran system site in the world (transmission, control or monitor) since the mid-1970s, including components of the Russian Chayka system. Our service provider and end-user technologies are operationally proven in commercial and military environments. We specifically target the maintenance and upgrade of existing systems, as well as the implementation of new systems, globally.
Which of your products directly address the need for alternative PNT?
RH: In a broad sense, Spirent offers a market-proven and innovation-driven solution portfolio for the simulation of inertial sensors through the SimINERTIAL and SimSENSOR product lines, seamlessly integrated with our GNSS simulation. Spirent is actively engaged with several alternative RF vendors to incorporate signal simulation capability and will offer an alternative RF navigation product in 2021 called SimAltNav Replay. This product will allow for concurrent GNSS and alternative RF signal simulation. Additionally, Spirent offers many other alternative PNT solutions for testing resilient systems for connected vehicles and sensor-fusion algorithms for tactical and military-grade systems. We are developing new products to incorporate an open Ethernet interface allowing for open-source Ethernet-based sensor simulation.
Remotely controlled rovers are used to test and practice complex tasks in Mars-like desert environments. (Artist’s Rendering: Stocktrek Images_Stocktrek Images_Getty Images)
DS: Our time servers are equipped with high-quality precise internal time references such as OCXOs or atomic clocks and then disciplined by external references such as GNSS. They are resilient because they can operate precisely for long periods in GNSS-denied situations as standalone devices in holdover mode or from multiple alternative references, such as:
network-based NTP, PTP and PTP WR time services
wireline references from IRIG, 1PPS or ASCII time code
LEO PNT reference from the STL signal
eLoran when available
They are also resilient because they detect and mitigate interference from the GNSS signal before it can corrupt the PNT solution.
Our GNSS simulators are adding alternative PNT features to provide a complete test and evaluation solution for resilient PNT systems. We have recently added INS/IMU test features and have integrated with Anritsu’s cellular test stations to evaluate and qualify combined GNSS/cellular location functions. Orolia GNSS simulators support generation of custom GNSS signals and playback of IQ waveforms, and provide complete toolsets for GNSS jamming and spoofing testing. This allows creation of the threat environment to allow evaluation of alternate PNT signals as backup or alternative to GNSS. Orolia offers an open-source framework allowing any end user to develop their own sensor plug-in leveraging the Skydel simulation engine.
Our Resilient PNT for Defense product line includes the VersaPNT, which uses alternate non-GNSS PNT sensors such as IMUs, barometers, wheel ticks, INS and non-GPS-based LEO satellites. Alternate RF navigation or non-GNSS sources of radio frequency (RF) are of interest in highly degraded or contested signal environments. Interest is focused on low-Earth-orbit (LEO) constellations. These systems offer high receiver signal power (relative to GNSS) and a secure and resilient link to augment GNSS.
MN: All our products are designed to answer to challenging GNSS conditions, starting with our Ellipse series, which includes an industrial-grade IMU capable of coping with short-term GNSS outages. Its miniature size allows integration in robotics and also makes it suitable for cost-sensitive applications. Our Apogee and Horizon series, with their navigation-grade IMUs, are the most resilient systems in the event of GNSS outages. These products reach very high-end performance in real time, but become exceptional when used with our post-processing software Qinertia. Tightly coupled algorithms make the solution capable of coping with long-term GNSS outages.
JA: We have previously created solutions using retroreflective strips for path following with driving robots. and we are also compatible with Locata’s system, a large infrastructure solution popular for automation in shipping ports. More recently, we have released an offering for UWB in an integration with Pozyx. This is perfect for GNSS-denied environments as a direct replacement for what GNSS can provide in terms of position information. We are also exploring alternative ways to synchronize clocks and get timing information. This year we have developed PTP functionality on all of our devices. Alternative PNT is going to be vital as we look to the future of navigation and thinking about how we can navigate flawlessly anywhere and address more complex environments, particularly urban areas.
CS: We are focused on the provision of terrestrial low-frequency equipment and systems for primary, co-primary, alternative, complementary and backup PNT. We provide all the products and services required to design, develop, install, certify, operate and maintain Loran-C, eLoran and LFPhoenix equipment and systems. We provide the technology to perform coverage diagrams and site surveys; all the equipment required at a transmission site; all the equipment required at a differential reference station or quality-of-service site; all the equipment required for a monitor and control site; ASF measurement and analysis equipment; and various models of end-user equipment (including receivers and antennas) for the timing/frequency, maritime, aviation, land-mobile and handheld markets.
Orolia Defense & Security delivers M-code-enabled timing and synchronization to Lockheed Martin
In September 2019, Lockheed Martin was awarded a contract to develop the U.S. Army’s Sentinel A4 radar system, an air and missile defense radar that will provide improved capability against dynamic threats.
The following November, Orolia Defense & Security announced the availability of M-code military GPS receivers in its flagship SecureSync — the first time server approved by the Defense Information Systems Agency.
Orolia is supplying SecureSync units for Lockheed Martin’s Sentinel A4 radar. (Photo U.S. Army)
This May, Orolia delivered a shipment of M-code-enabled SecureSync mission timing and synchronization units to Lockheed Martin, marking a key milestone for the Army program. SecureSync with M-code provides enhanced resilient positioning, navigation and timing (PNT) capabilities and improved resistance to existing and emerging GPS threats, such as jamming and spoofing.
Lockheed Martin selected Orolia’s SecureSync M-code as the A4 system’s resilient time and frequency reference solution in part due to its modular, open architecture – the same characteristics that are the cornerstone of the radar’s design – making integration a simple process and ensuring future upgrades.
“As a trusted Lockheed Martin partner, Orolia is proud to support the development of the Sentinel A4, which will be a key asset to our warfighters for decades to come,” said Hironori Sasaki, president of Orolia Defense & Security. “Making M-code available now in a readily configurable and scalable form factor is a critical step in advancing our forces out in the field, whether in the air or on the ground,” Sasaki added.
The next-generation of U.S. military systems are fortified with M-code, and Orolia leads the industry in M-code solutions for navigation warfare (NAVWAR) environments.
Orolia is supplying SecureSync units for Lockheed Martin’s Sentinel A4 radar. (Photo U.S. Army)Image: Orolia
The U.S. Office of Management and Budget (OMB) seeks to extend Trump policies and repeal timing law counter to its own study and industry input
The Biden administration’s budget proposal delivered to Congress last week includes $17 million for the small Department of Transportation (DOT) office responsible for leading civil positioning, navigation and timing (PNT) efforts for the nation. This is a marked increase over the $2 million allocated in 2020 and estimated $5 million being spent this fiscal year.
At the same time, it seeks to repeal the National Timing Resilience and Security Act of 2018 that mandated DOT establish a terrestrial timing backup for GPS. This, despite the findings of a recently published RAND study completed for the Department of Homeland Security (DHS), and other input from a telecommunications industry group.
Proposed Spending
The administration’s budget proposes $17 million for the DOT Office of Research and Technology to be split among three areas of effort.
Monitoring and detection. The first is a $3.5 million “(GNSS) performance monitoring and interference detection” project. This is a one-time request that is expected to be followed by a request for $1 million in yearly funding to maintain and operate the capability.
While these may not seem like sufficient funds to many, DOT is tasked with working with other departments and agencies, and to leverage existing capabilities. The National Geospatial-Intelligence Agency (NGA) is specifically named as an important partner with DOT in this effort. NGA already has responsibility for issuing worldwide navigation warnings for U.S. interests. It also has access to a wide variety of information that could be used for the project.
Signal authentication. Another $3.5 million is proposed for Executive Order (EO) 13905 Implementation and GPS Signal Authentication. The EO was issued in February 2020. It seeks to leverage market forces and education to create additional sources of PNT and encourage users to access them. This approach has been criticized by many as unworkable without extensive regulation and mandates for users, while still not addressing the majority of American companies and users.
$1.5 million of this $3.5 million will go to further implement the EO through development of a “PNT threat space model” and otherwise support inter-department PNT profile and research and development efforts.
$2 million would be allocated for a one-time investment in GPS signal authentication to “result in the development and validation of requirements for data and signal authentication capability for civil GPS,” reads the proposal. DOT has regularly requested much greater sums to establish civil signal monitoring, leading many to believe the requirements are already well known. One industry observer suggested this could be “a study in lieu of action.”
GPS Backup. $10 million would be spent for “GPS Backup/Complementary PNT Technologies Research,” essentially follow-on studies to the DOT GPS Backup Technologies Demonstration. “These efforts will further develop PNT modeling, simulation, and testing tools, as well as standards and performance monitoring tools needed to evaluate integration of diverse positioning, navigation, and/or timing technologies into end-user applications. This work will also support development of cyber-secure receivers,” reads the proposal.
One congressional staff member expressed shock at seeing that provision. “The act was the epitome of thoughtful, bipartisan congressional effort,” the staff member said. “It was co-sponsored in the Senate by Markey and Cruz, for crying out loud. You can’t get more bipartisan than that. To have this dumped on us without any notice or consultation is amazing. It is not something I would expect from this White House. I am not sure how serious a proposal it is.”
Some observers on the hill and elsewhere have opined that, rather than the repeal proposal being a well-vetted administration policy, it is an effort by OMB staff held over from the previous administration to carry forward and preserve President Turmp’s Executive Order 13905 and other PNT policies. Rather than focusing on establishing a GPS backup capability, they instead urged PNT users to find and pay for alternatives on their own.
Harsh Tone, False Assertions
Compounding the surprise is the exceptionally harsh tone in the proposal, and assertions that many claim are outright false.
Among the problems with the language seen by observers is its assertion that NTRSA seeks to establish a single backup for GPS services.
“It’s unclear to me where such an assertion is supported in the record,” said Greg Winfree, former Assistant Secretary at DOT in the Obama administration. “NTRSA requires the department to incorporate findings from the GPS back-up demonstration program. That project found a variety of systems are needed to protect America,” he said. “NTRSA does require establishment of at least one system, which is incredibly important. Without at least one alternative in place, GPS is one of highest priority targets for our enemies. We have to get the bullseye off of GPS. NTRSA does that.”
This point on national security was reinforced by Scott Pace, head of the Space Policy Institute at George Washington University (GWU). Pace was executive director for the Space Council in the Trump administration. At a recent GWU webinar on the topic, he commented that having an alternative to GPS will contribute to national security and improve global stability. It will “lower the pressure on us to escalate and respond” should GPS satellites be damaged, or services disrupted, he said.
China, Russia, and other nations have terrestrial PNT alternatives to GNSS already in operation. This imbalance creates strategic and tactical problems for the United States, according to many analysts.
The proposed budget also describes NTRSA’s goal of providing at least one backup as “inefficient, anti-competitive and potentially harmful to the existing market for back-up/complementary PNT services.”
“Exactly the opposite is true,” according to Diana Furchtgott-Roth, GWU economics professor. Until January of this year, she led civil PNT issues within the Trump administration as a Deputy Assistant Secretary for Research and Technology at DOT. “DOT’s Complementary PNT and GPS Backup Technologies Demonstration Report, published in January, specifically stated that a variety of technologies are needed to complement GPS. What is the most cost-efficient in an urban area is not necessarily the most cost-efficient in a rural or maritime area.”
“PNT is a utility used by every American. Having affordable complementary service available to people in rural and urban areas is the height of efficiency. It is unquestionably in the interests of national and economic security. In fact, access to at least one alternative should be free so to encourage adoption and best protect the nation,” she said.
“GPS is now a free service provided by the government, and the government is responsible for making sure that it is reliable. GPS outages would cause harm across a broad range of economic activities, including emergency services, general aviation, pipelines, and the electricity grid,” according to Furchtgott-Roth.
No-So-New and Contradictory Research
The proposal to repeal NTRSA cites “recent federal analyses” as part of its justification. One of these is likely a report done for the Department of Homeland Security (DHS) by the RAND Corporation. Touted in a press release last month as “new research” and labeled “Published 2021,” the work was actually completed in 2019. DHS representatives have said the delay in publication was needed for review and approval.
Yet the report was the basis for a DHS report to Congress submitted in April 2020. This has caused some to opine that its publication was timed to reinforce OMB’s effort to repeal NTRSA. “You don’t submit reports to Congress based on un-reviewed, un-approved material,” said a retired DHS official. “The timing of its release is clearly deliberate.”
At the same time, it found that government investment in a national timing network, such as the one mandated by the NTRSA, is likely warranted. Saying that a complete backup for all GPS services in all parts of the country is not cost-beneficial, the study says there are some “…federal initiatives that do appear to be cost effective or close to cost effective.” These include “Timing-only backup through fiber/FirstNet, eLoran, or STL [Satelles].”
According to the retired DHS official, this directly contradicts OMB’s assertion that NTRSA should be repealed. “Either they didn’t read the whole thing, or they counted on most people not reading farther than the top-level recommendations,” he said. “And those top recommendations were clearly selected to match OMB’s desired outcome.”
Telecommunications Industry Cites Need for NTRSA Provisions
The May 2021 “Report to the President on Communications Resiliency” also runs counter to claims made in the budget proposal. In it, the president’s National Security Telecommunications Advisory Committee (coordinated by DHS) cites the need for GPS alternatives in telecommunications and urges President Biden to fund them. It specifically mentions the need for a national timing architecture, and cites the provisions of NTRSA several times as a step in the right direction.
The industry group Alliance for Telecommunications Solutions also sent letters in May to congressional leaders urging funding for GPS alternatives.
Continuing the Discussion
Congress has become increasingly dissatisfied with executive branch actions on resilient PNT over the last decade.
The most recent evidence of this is an extensive and highly critical report of the Department of Defense’s approach to PNT resilience released May 10 by the Government Accountability Office (GAO). Among its recommendations was to not rely on GPS as a primary PNT source but look to more resilient technologies.
While President Trump’s 2020 Executive Order did not make precisely the same recommendation to civil users, it did focus on “responsible use” of PNT and transitioning to using additional, non-GPS dependent sources.
The question still under discussion is how far the government should go to support such a transition.
Seasoned observers regularly comment that Congress has the “power of the purse” and every president’s budget is “dead on arrival” regardless of which party controls the White House.
It seems clear that resilient PNT will be a topic of lively debate between the Congress and the White House, as well as internally on the hill, for the foreseeable future.
New technologies use a variety of inputs to help ensure seamless navigation, even when GPS reception fails because of interference or jamming.
Honeywell has successfully demonstrated multiple alternate navigation technologies for military aircraft. These new products are intended to help ensure seamless navigation — even when GPS signals are blocked, interrupted or unavailable.
For military operations, GPS-jamming — intentional or not — can block vital signals from conveying critical information regarding positioning, navigation and timing (PNT). In these instances, it’s important for military vehicles and aircraft to be equipped with alternative navigation technologies, like celestial or vision navigation, to maintain operational readiness.
“For military operations, not having access to critical positioning and timing information can make or break a mission,” said Matt Picchetti, vice president and general manager, Navigation & Sensors, Honeywell Aerospace. “We’re very excited to roll out this robust lineup of alternate navigation solutions, which are specifically designed to address the needs of our military customers and give them the added layers of redundancy needed to successfully carry out their operations, even if they lose access to GPS signals.”
Illustration: Honeywell
Alternate navigation technologies provide a different means of measuring position, velocity and heading when GPS is disrupted. These technologies include:
Vision-aided navigation. This technology uses a live optical or infrared camera feed and compares it with maps to provide a passive, not jammable, highly accurate alternative PNT solution that provides GPS-like accuracy in GPS-denied or jammed conditions.
Celestial-aided navigation. Honeywell’s celestial-aided navigation technology observes stars and “reference objects” orbiting the earth such as satellites, which have known positions and velocities. This technology compares those reference objects to stars and can determine position and velocity, the same way a GPS receiver can.
Magnetic anomaly-aided navigation. This navigation technology measures magnetic strength using sensors and compares this data with known geographical magnetic maps to accurately identify the position of the aircraft relative to the Earth.
Prototypes of these alternate navigation systems will be available in 2022, with initial deliveries expected to start in 2023.
Honeywell navigation systems are used by nearly every aircraft flying to guide millions of passengers to their destinations. Since 1914 when the first autopilot used Honeywell gyroscopes to hold the plane stable during flight, Honeywell has delivered more than 500,000 high-performance inertial sensors across several platforms on land, in the air and at sea.
The U.S. Army’s Assured Positioning, Navigation and Timing/Space Cross-Functional Team has approved the Navigation Warfare Situational Awareness Abbreviated Capability Development Document (A-CDD), signed March 25.
The A-CDD validates the operational need and enables experimentation and rapid prototyping for NAVWAR-SA capabilities for the warfighter.
NAVWAR is deliberate offensive and defensive actions to assure friendly use and prevent adversary use of positioning, navigation and timing information. NAVWAR supports Multi-Domain Operations as an enabler to precision fires, movement and maneuver, force tracking, and a host of data networks that tie personnel and weapon systems together into a joint or coalition force.
NAVWAR-SA provides the capability to detect, identify and locate sources of interference that deny or degrade reception of PNT. It is intended to validate PNT signal integrity and provide users with indication and warnings of the presence and intensity of interference.
NAVWAR-SA will also characterize the operating environment through the integration of multiple sensors that are able to detect, identify and geolocate sources of intentional and unintentional interference.
William Nelson, Director, APNT CFT
“This A-CDD will enable us to accelerate critical NAVWAR technology development and streamline the process of expediting an operationally relevant system to our warfighters,” said Willie Nelson, director for the APNT/Space CFT. “This capability will enhance our ability to provide real-time situational awareness of PNT reliability to soldiers and commanders on the battlefield, which will enable Long-Range Precision Fires and support freedom of maneuver of large scale ground combat operations.”
NAVWAR-SA will give the Army Forces the ability to “sense” the PNT environment in real-time, allowing commanders and units to maneuver with confidence and with precision when the global positioning system is degraded or denied. This is critical element of NAVWAR operations.
The APNT CFT coordinated with organizations across the modernization enterprise to get the NAVWAR-SA A-CDD approved. The Army Capability managers for Space and High Altitude played a major role in developing the written requirement and getting it through the approval process.
“The requirements provided in the NAVWAR-SA A-CDD are a first step in developing dedicated NAVWAR capabilities for our soldiers and are a key enabler in enhancing lethality in combat operations,” said Col. Tim Dalton, Army Capability manager for Space and High Altitude director.
The A-CDD details methods to leverage new and existing solutions for rapid prototyping, testing and soldier assessment. The APNT/Space CFT will utilize the “buy, try and decide” process to accelerate the development of critical enabling technologies and streamline the process of transitioning a scalable, interoperable and agile capability to the field. This process will inform NAVWAR-SA requirements for current and future Army systems.
“NAVWAR-SA will strengthen the Army’s ability to conduct military operations in PNT-challenged environments,” said David Pinckley, NAVWAR director for the APNT/Space CFT and chairman of the NATO NAVWAR Capabilities Team. “The unfortunate reality is that our systems will continue to be challenged by our adversaries so we are working with our joint and coalition partners to preserve military capabilities while mitigating impacts of interference.”
NAVWAR is one of the three APNT/Space CFT Signature Efforts, which will deliver offensive and defensive NAVWAR capabilities in conjunction with existing Department of Defense NAVWAR policies.
Joint and coalition forces conducting military operations will employ NAVWAR-SA to coordinate and implement mitigating actions to overcome PNT challenged environments.
The APNT/Space CFT plans to assess and test NAVWAR-SA prototypes later this year, during Project Convergence 21 and the CFT’s annual PNT Assessment Exercise at the White Sands Missile Range, New Mexico.
The JNC, sponsored by the Military Division of the Institute of Navigation, will be held Aug. 24-26 (FEDCON U.S. ONLY) at the Northern Kentucky Convention Center in Covington, Kentucky (Greater Cincinnati, Ohio).
The Classified Sessions (Secret U.S. ONLY) will be held Aug. 27, at the Air Force Institute of Technology on Wright-Patterson Air Force Base, Ohio. Visit requests and approvals are required for all session attendees.
View the JNC 2021 program and register at ion.org/jnc.
JNC 2021 is the largest U.S. military positioning, navigation and timing (PNT) conference of the year, with joint service and government participation.
Four new panel sessions have been introduced to this year’s technical program, which will host leaders and decision makers as they discuss and debate
MGUE Integration
Rapid Agile Development and Manufacturing
the National Critical Infrastructure Threat
Combatant Command Joint Urgent Operation Need (Secret, U.S. Only).
The technical program will focus on enhancing dominance and resilience for warfighting and homeland security PNT, and will include keynote addresses from:
William B. Nelson, director, Assured Positioning Navigation &Timing (APNT) Cross Functional Team (CFT), U.S. Army Futures Command
Ray Chartier, Jr., Safety of Navigation Mission manager, National Geospatial Intelligence Agency
General David D. Thompson, vice xhief of Space Operations, United States Space Force
Bradford Parkinson, Stanford Center for PNT
Attendance Restricted for JNC Technical Sessions
Conference attendance for both FEDCON (U.S. ONLY) (Aug. 24-26) and Classified Sessions (U.S. ONLY) (Aug. 27) will be screened by the Joint Navigation Warfare Center. Visit requests and approvals are required for all technical participants.
The exhibit hall is open to any registered conference attendee or exhibiting company representative, and all materials shall be designated DISTRO A/Publicly Releasable After Review.
Government-issued photo ID will be required to access all conference events.
If you have questions, contact the Institute of Navigation at [email protected] or by calling +1-703-366-2723.
