GPS World

Category: Complementary PNT

  • PNT powers unmanned vehicles for transportation, ag and more

    PNT powers unmanned vehicles for transportation, ag and more

    Photo: SBG Systems
    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.)

    Photo: UrsaNav, Inc_
    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.

    The participants are:

    How do you define alternative PNT?

    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.

    Photo: SBG Systems
    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.

    Photo: SimonSkafar_E+_Getty Images
    (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.

    (Image: SBG Systems)
    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.

    Artist’s Rendering: Stocktrek Images_Stocktrek Images_Getty Images
    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.

  • $17M proposed for DOT resilient PNT initiatives

    $17M proposed for DOT resilient PNT initiatives

    Photo: E4C/E+/Getty Images
    Photo: E4C/E+/Getty Images

    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.

    Proposed Repeal of Timing Law

    More surprising to many than the significant increase in proposed funding is inclusion of a proposal to repeal the National Timing Resilience and Security Act of 2018 (NTRSA).

    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.”

    The study, “Analyzing a More Resilient National Positioning, Navigation, and Timing Capability,” takes a cost-benefit approach to the issue. One of its high-level findings is that government investment in a duplicate, GPS-like backup capability is not warranted.

    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.

    Controversial GAO report on DOD nav webinar June 15

  • ‘Take the bullseye off GPS before it’s too late!’ — PNT leaders at GWU webinar

    ‘Take the bullseye off GPS before it’s too late!’ — PNT leaders at GWU webinar

    A May 5 webinar about the GPS Backup Technology Demonstration by the U.S. Department of Transportation (DOT) provided valuable insights about the project and intended way forward for PNT efforts in the department.

    It also evolved into a policy discussion with former government leaders saying establishing alternative positioning, navigation, and timing (PNT) systems would make GPS safer by “taking the bullseye off,” and that “the time is now, before it is too late.”

    The webinar, titled “What Technologies Can Secure GPS?”, was hosted by the Space Policy Institute at George Washington University (GWU). A bipartisan constellation of civil PNT stars gathered to participate in the event.

    Featured in the webinar were:

    • introductory remarks by Robert Hampshire, chief scientist for the U.S. Department of Transportation (DOT). He has also been nominated to be DOT’s assistant secretary for research and technology.
    • a presentation by Karen Van Dyke, director, Positioning, Navigation and Timing for DOT, and Andrew Hansen of DOT’s Volpe Transportation Systems Center.
    • discussion of the issues by Diana Furchtgott-Roth, adjunct professor at GWU and a DOT deputy assistant secretary during the Trump administration, and Greg Winfree, director of the Texas Transportation Institute at Texas A&M University and DOT assistant secretary during the Obama administration, both of whom led civil PNT issues for the federal government during their time in office.
    • Scott Pace, director of GWU’s Space Policy Institute, serving as moderator; he was executive secretary of the Space Council during the Trump administration.

    Hampshire opened the event with an address that touched on Biden administration themes of “building back better,” modernizing infrastructure, reducing transportation deaths, making transportation more efficient, and preserving America’s technological leadership. All of these were linked to the need to improve PNT resiliency and reliability.

    Robert Hampshire, U.S. DOT chief scientist, speaking at GWU webinar on May 5. (Image RNT Foundation)
    Robert Hampshire, U.S. DOT chief scientist, speaking at GWU webinar on May 5. (Image RNT Foundation)

    Backup tech demo did not close any doors

    Van Dyke and Hansen then gave a presentation on the results of the department’s technology demonstration project.
    Van Dyke pointed out that, while “GPS backup” may be a popular term, we need complementary capabilities that come into play not just when GPS is unavailable but work alongside it and provide additional capability and resilience all the time.

    She also mentioned that the department is well aware there are more candidate technologies than those selected for the demonstration. Companies offering other ways of providing PNT will not be excluded from future consideration and efforts just because they were not part of the demonstration project.

    Also, while the government collected the data during the demonstrations, she acknowledged that the effort was designed to “showcase the technologies in their best light.” Further study, stress testing, and evaluation will be needed for any system or technology that might be of interest to the government.

    Key elements in the demos

    Hansen discussed the particulars of how the technology demonstrations were conducted and some of the results. While the department evaluated 14 measures of effectiveness during the project, Hansen said that two were key — accuracy and coverage per unit of infrastructure.

    All the technologies demonstrating timing showed accuracy that would be useful across a wide range of applications, he said. Positioning accuracy, though, varied from a “ones of meters to around 300 meters” depending on the technology.

    Hansen said that coverage per unit of infrastructure varied exceptionally between the technologies. These included satellite systems that provide global coverage with a fixed infrastructure, and radio frequency systems with widely different coverage areas per transmitter.

    He also observed that the technology demonstration project was not the end of the department’s technical inquiries. In fact, some of its results—such as eLoran performance in an underground scenario—were unexpected and are being further examined.

    Transportation has some of the most stringent PNT requirements for accuracy, integrity, availability, and reliability, he said. And not all safety-critical transportation requirements may be met by market-based business models. Commercial systems lack the open standards and specifications that have made GPS so useful and widely adopted. Hansen said that the department will be working on these issues going forward, as well as performance monitoring for alternative systems.

    A recurring theme throughout the webinar from all participants was that there is no single solution, no silver bullet, to achieve sufficient national PNT resilience. A systems-of-systems approach was needed. In Hansen’s words “a plurality of complementary systems” is required to ensure PNT reliability and safety, as well as efficient transportation.

    Take the bullseye off GPS! — An urgent national security issue

    While agreeing with the systems-of-systems approach, Greg Winfree pointed out that a first step still needs to be taken. He said that the nation has known about the need for alternate PNT since a 2001 report by DOT’s Volpe Center. Twenty years later, still no long overdue first step has been taken.

    Just establishing the first alternative and complementary system, Winfree said, will make GPS and the United States much safer. “We need to take the bullseye off of GPS,” he said. GPS is so critically important to this country that it is a very attractive target for those who would do us harm. Having even one just alternative in place would make it much less of a target.

    Diana Furchtgott-Roth pointed out that China, Russia, Iran and others have terrestrial systems that complement space-based PNT. About establishing alternatives, she said “The time is now, before it’s too late.”

    Provisions in the United States National Space Policy provide that “[a]ny purposeful interference with or an attack upon the space systems of the United States or its allies that directly affects national rights will be met with a deliberate response at a time, place, manner, and domain of our choosing.”

    Scott Pace also commented that an 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.

    Next steps

    One of the questions posed at the end of the session was about actions and expected accomplishments in alternate PNT at DOT in the next 18 months. When could the first alternative system be expected?

    The DOT technology demonstration report recommended that the department work next to develop standards and requirements for alternative systems. Current government employees were appropriately reluctant to say much more.

    Calling upon her recent experience in government, however, Diana Furchtgott-Roth that said she believed that the department needed time to stress test technologies, develop standards and finalize requirements. Since many capable technologies were mature, some already in operation, she thought the first capability could be up and running within a year after that.

    The only missing element according to Furchtgott-Roth is funding, and the focus needs to be on motivating Congress to provide it. The stage is set, she said, with all parties agreeing on the importance of resilient PNT.

    She observed that it is very difficult to get the two parties in Congress to agree, and to pass legislation. Yet this has happened three times in support of establishing GPS alternatives. And PNT is such a critical capability that the entire executive branch even came together to protect it last year opposing the FCC’s decision in the Ligado Networks application.

    She also related that, when she was in office, she requested $15M for the current fiscal year to do needed stress testing and standards development, but the funding did not appear in the budget.

    One reason could have been questions she was asked about whether it is the government’s job to pay for an alternative to GPS, she said.

    As a conservative economist her answer was and is a resounding “Yes.” The national need is beyond the business model of one company or private entity. That is something also suggested in DOT’s report on the tech demo.

    Also, “enormous value and vast efficiencies” come from one entity funding such a utility, she said. “Just as the government funds national defense, it should also provide a complement to GPS.”

    George Washington University’s Space Policy Institute reports a recording of the webinar will be posted on YouTube within the next week.

    Dana A. Goward is President of the Resilient Navigation and Timing Foundation.

  • DOT report: L-band, UHF, LF and fiber PNT needed to protect US

    DOT report: L-band, UHF, LF and fiber PNT needed to protect US

    In a report issued on Jan. 14, the Department of Transportation (DOT) outlined the results of its GPS Backup Technology Demonstration project. As officials had previously projected, it called for a system-of-systems approach using multiple complementary technologies.

    The report called for an architecture that included signals from space in the L-band, terrestrial broadcasts in the ultra high frequency (UHF) and low frequency (LF) spectra, and a fiber backbone to synchronize and feed precise time to terrestrial transmitters.

    The demonstration project and report were mandated by Congress in legislation passed in late 2017 and funded in early 2018. Delays within the administration resulted in the project beginning in early 2019.

    Monty Johnson of OPNT demonstrates precise time transfer through 100 kilometers of spooled fiber-optic cable. (Photo: RNT Foundation)
    Monty Johnson of OPNT demonstrates precise time transfer through 100 kilometers of spooled fiber-optic cable. (Photo: RNT Foundation)

    Demonstrations

    Of 21 firms that offered to demonstrate their wares, 11 were selected. They were:

    • Echo Ridge LLC and Satelles Inc. Satellite-based PNT technologies using the S and L bands, respectively.
    • OPNT B.V. and Seven Solutions S.L. Fiber-optic time transfer using the White Rabbit Precision Time Protocol technology.
    • TRX Systems Inc. Dead reckoning technology with inertial measurement units and localized map matching supplemented with ultra-wideband beacons.
    • Hellen Systems LLC and UrsaNav. eLoran that uses LF transmissions.
    • Serco Inc. Medium frequency R-mode.
    • NextNav LLC. Metropolitan beacon system using UHF frequencies.
    • PhasorLab Inc. and Skyhook Wireless Inc. Both use Wi-Fi frequencies. Phasorlab uses a dedicated network of transmitters. Skyhook leverages existing Wi-Fi access points.

    Five of the demonstrations were conducted at Joint Base Cape Cod, with the remainder at NASA’s Langley Research Center in Virginia.

    Timing demonstrations were assessed for system:

    • coverage (service availability) within an “appropriate area” (wireless systems only)
    • accuracy and stability across an appropriate area
    • long-term accuracy and stability of time transfer to a fixed location
    • time transfer availability and accuracy to a fixed location under challenged GPS signal conditions.

    Positioning was evaluated for:

    • coverage within a defined region
    • 2D and 3D dynamic positioning service availability and accuracy
    • availability and accuracy of static positioning
    • long-term availability and accuracy of static positioning
    • long-term availability and accuracy of static positioning under challenged GPS signal conditions

    DHS work referenced

    The report also mentions an earlier set of demonstrations done by the Department of Homeland Security (DHS).

    In December 2018, DHS’s Science and Technology Directorate performed the work through the Homeland Security Systems Engineering and Development Institute. The project “demonstrated a combination of position and timing use cases for dynamic vs. static and indoor vs. outdoor applications, along with a time-transfer use case for critical infrastructure applications.” Systems from Locata Corp, NextNav, and Satelles were evaluated.

    The DoT report says that eLoran was not part of the DHS effort because of the lack of transmitters in the area. However, “DHS had previously studied eLoran performance under a Cooperative Research and Development Agreement (CRADA) with Harris Corporation and UrsaNav and had an understanding of its capabilities.”

    A report of DHS’ December 2018 work is not publicly available, though DOT says it was used to inform their efforts.

    The only publicly available information from DHS about the eLoran CRADA seems to be a 2016 press release. A presentation and other information  is available on the UrsaNav website.

    Findings

    The 437-page DOT report is filled to the brim with detailed information about the project, individual technologies, and demonstration results.

    The Executive Summary says that, in addition to the findings from the DHS December 2018 effort (which were not listed), the DOT demonstration had four key findings:

    1. All TRL-qualified vendors offered showed PNT “performance of value” and one showed value in all scenarios.
    2. Neither eLoran company succeeded in the Static Basement Timing scenario.
    3. R-mode ranging did not meet the minimum technical readiness level (TRL) of 6.
    4. Deployment effort and coverage (infrastructure per unit area) are significant cost factors.

    Addressing the needs of critical infrastructure owners and operators, the report concluded the needed “technologies are LF and UHF terrestrial and L-band satellite broadcasts for PNT functions with supporting fiber optic time services to transmitters/control segments.”

    Reactions and way forward

    Government officials and industry observers alike have welcomed the report, though it does leave some questions on the table.

    One is about other national PNT needs. The congressional tasking was to report on GPS backup technologies for critical infrastructure and national security. The Jan. 14 report focuses on critical infrastructure needs. Information on national security requirements, some of which is classified, was provided to Congress separately by DHS and the Department of Defense.

    “Economic and homeland security are sometimes considered by agencies and Congress as subsets of national security, sometimes not,” according to one analyst. “So, we don’t know if the needs of first responders, delivery services, civil government agencies, and other essential users were ever formally considered. The good news is that the combination of systems identified, if implemented and made available to all, would likely meet the needs of most.”

    Other open issues are about implementing the report’s recommendations.

    Some have been quick to point out that the demonstrations were to inform the government, not part of a procurement.

    “If this was for an acquisition, it would have been done differently,” said one government retiree.  “Rather than having vendors set up and operate the equipment, government evaluators would have been much more hands on. And they would have made every effort to do all the trials at the same location.”

    Going forward, cost will also an important factor, as mentioned in the report’s key findings. “Depending on who you want to serve and where, the costs of different technologies vary by orders of magnitude,” said one provider.

    Reaction from those involved with the demonstration project has been generally upbeat with praise for DOT’s effort and anticipation of more progress.

    Typical were comments from Ganesh Pattabiraman, CEO at NextNav, who appreciated the real-world scenarios DOT used in the project. Regarding next steps he said, “We look forward to working with Congress on implementing the report’s recommendations.”

  • Open PNT Industry Alliance launched to strengthen national resilience

    Open PNT Industry Alliance launched to strengthen national resilience

    Coalition gives voice to PNT companies seeking open-market approach to backing up GPS/GNSS for critical infrastructure

    Open PNT logoSeveral GNSS and positioning, navigation and timing (PNT) companies have joined forces to create a new lobbying group, the Open PNT Industry Alliance. Founding companies include InfiniDome, Iridium Communications, Jackson Labs Technologies, NAVSYS Corporation, NextNav, OPNT, Orolia, Qulsar, Satelles and Seven Solutions.

    In the United States, the coalition believes the Executive Order on “Strengthening National Resilience Through Responsible Use of Positioning, Navigation, and Timing Services,” issued in February 2020 begins the process for a national alternative PNT policy.

    The Open PNT Industry Alliance also agrees with the U.S. Department of Homeland Security’s findings and recommendations in its “Report on Positioning, Navigation, and Timing (PNT) Backup and Complementary Capabilities to the Global Positioning System (GPS)” submitted to the U.S. Congress in April.

    The report was criticized by some lawmakers for inaccuracies and lack of depth, but several companies whose solutions were referenced in the report defended it, and have now joined in creating this new alliance.

    The alliance expects to support similar initiatives in other countries.

    The coalition is designed to fortify economic and national security by supporting government efforts to accelerate the implementation of backup PNT capabilities for critical infrastructure. Other companies sharing these views are invited to join the alliance.

    The Open PNT Industry Alliance will be introduced in an Orolia PNT Coffee Talk webinar on Thursday, Dec. 17, at 10 a.m. EST.

    A serious problem facing nations around the world is that GPS and other GNSS are susceptible to inadvertent disruptions and deliberate attacks. Such incidents have the potential to impair or incapacitate communications networks, transportation systems, energy production and distribution platforms, financial services operations and other types of critical infrastructure.

    With the scope, complexity and severity of disruptions and attacks evolving continuously, the combination of wide-ranging PNT solutions and emerging technologies offers superior protection to current threats by providing a backup to GPS/GNSS and improving national resilience.

    “Multiple forms of alternative PNT deliver the broadest possible range of operational and performance characteristics to meet the diverse needs of applications across all industry sectors, plus they can better adapt to future threats than a single technology with its inherent vulnerabilities,” said Michael O’Connor, CEO of Satelles. “The mission of the Open PNT Industry Alliance is to promote open-market concepts that preserve industry’s long-term ability to harness its inventive talent to protect GPS/GNSS with multiple solutions that are technologically advanced, commercially viable, and based on a sustainable long-term funding framework.”

    logosThe Open PNT Industry Alliance will share its expertise with governments to aid their efforts to set policies, define regulations, and enact laws that achieve their national resilience objectives while preserving competition in the open market. A principal purpose of the coalition is to stimulate and capitalize on the collective intellect of industry in a collaboration between the public sector and private sector.

    “The ingenuity of the private sector is spurred by competition and public and private investment, and this will drive the emergence of multiple GPS/GNSS alternatives that are cost-effective and evolve according to threat profiles, technological innovations, and market dynamics,” said Jean-Yves Courtois, CEO of Orolia. “Similarly, unbridled innovation will address new and still evolving use cases not supported by GPS/GNSS.”

    The coalition will work closely with governments as they consider plans for regulation of critical infrastructure sectors and funding for alternative PNT. Legislators and policymakers can best pursue national interest through a multi-technology approach to PNT resilience, the coalition stated in a press release. The coalition will advocate for the establishment of a robust and self-sustaining funding framework that allows for the development and adoption of multiple sources of PNT that meet the needs of various sectors and industries.

    “We believe a multi-technology approach to PNT resilience not only meets a more diverse set of critical infrastructure needs but also ensures a more robust approach to security by providing multi-layer resilience,” said Ganesh Pattabiraman, CEO of NextNav. “Delivering alternative PNT capabilities on an equal footing with GPS will require government policies and funding that ensure these solutions are cost-effective for critical infrastructure providers and sustainable over the long term.”

    The Open PNT Industry Alliance website has background on members and policy views, as well as information on how companies can join.