GPS World

Tag: Editorial Advisory Board

  • EAB Q&A: Is the GNSS community failing to exploit the potential of CSAC?

    EAB Q&A: Is the GNSS community failing to exploit the potential of CSAC?

    “Is the GNSS community failing to exploit the potential of chip-scale atomic clocks (CSAC)?”

    Photo: Orolia
    John Fischer

    “Yes! And there are several CSAC suppliers, each with varying accuracies, power consumptions, and price points. These atomic clocks are no longer exotic scientific instruments but rather commercialized, proven devices that can be mounted on a circuit card at a reasonable cost. They offer extended holdover time in the absence of GNSS and help with spoofing detection by verifying the incoming signal. They provide exact frequency recovery on power-up (re-trace) for power saving modes. Defense, telecom, financial transactions, and autonomous navigation for cars and drones are all applications that can be made more resilient by these clocks.”

    — John Fischer
    Safran Navigation & Timing

    Jean-Marie Sleewaegen
    Jean-Marie Sleewaegen

    “Atomic clocks, including CSAC, are frequently used in GNSS timing applications, for example to keep accurate time during GNSS outages or to assist in identifying spoofing attacks targeting the time component. On the other hand, the long-term stability of atomic clocks is not particularly relevant in navigation applications where time is not the main output, and the additional cost, power consumption and size of CSAC are not justified.”

    — Jean-Marie Sleewaegen
    Septentrio

    Headshot: Ismael Colomina
    Ismael Colomina

    “Indeed. After the DARPA-NIST initiative and subsequent commercialization, affordable, accurate and stable chip-scale oscillators can be easily integrated into circuit boards providing additional measurements to PNT systems to improve positional vertical accuracy, as well as reliability and integrity. For example, in high-end mobile mapping systems operating in complex urban scenarios, their use helps detect GNSS outliers at a relatively negligible additional cost.”

    — Ismael Colomina
    GeoNumerics

  • EAB Q&A: Should countries build their own GNSS constellations?

    EAB Q&A: Should countries build their own GNSS constellations?

    “When Galileo was just an idea, its EU proponents used the argument of “political, economic, social and technological sovereignty.” Should countries such as Brazil build their own GNSS constellations?”

    Headshot: Ismael Colomina
    Ismael Colomina

    “When, almost 20 years ago, I was in Brazil giving talks about the future of Galileo and promoting its combined use with GPS, I was often asked the logical question as the EU Galileo sovereignty arguments were known. It is not for us Europeans to answer that question for other countries or oppose their plans. However, while being aware of the defense aspects of GNSS, we may ask ourselves whether an international cooperative approach could avoid a somewhat unjustified future proliferation of GNSS constellations.”

    — Ismael Colomina
    GeoNumerics

    Headshot: Jules McNeff
    Jules McNeff

    “GPS enables continuous access, free of fees and political encumbrances. A decision by any nation to bear the cost of creating a separate GNSS should be justified by realistic requirements for security or coverage that cannot be satisfied by GPS. Japan, South Korea and India are models for additional GNSS services driven by regional needs. For any new system, compatibility with other GNSS, as well as life-cycle costs, are the primary factors to consider.”

    — Jules McNeff
    Overlook Systems Technologies

    Headshot: John Fischer
    John Fischer

    “When Galileo was just an idea, the U.S. military’s GPS was the only viable global constellation. GLONASS was a rusting cold-war relic and BeiDou was in an embryonic stage. The U.S. military’s official policy was that any civilian use was not guaranteed and could be interrupted anytime. Therefore, no nation outside of the United States could depend on GPS and maintain its independent interests. However, today, any country could reasonably maintain its sovereignty by ensuring interoperability with all four — betting that at least one of those constellations would always be available to them. They don’t need their own system.”

    — John Fischer
    Orolia

    F. Michael Swiek
    F. Michael Swiek

    “Those are always nice-sounding words when trying to justify a monumentally huge expense. However, is there an actual need to justify that expense? Can the expense and burden of perpetual system operation and maintenance, along with technological innovation to keep pace with other systems and user requirements, be guaranteed over the long term? For the users, GPS can be seen as the gift that keeps on giving, whereas to the operators it is the gift that keeps on costing. So, do Brazil, or other nations, have the commercial or social need, technological foundation, economic resources and political will to initiate a new system and sustain it over the long term? Providing a GNSS constellation is not for the faint of heart or those of short-term vision.

    — Michael Swiek
    GPS Alliance

  • EAB Q&A: Could a new PNT constellation replace GNSS?

    EAB Q&A: Could a new PNT constellation replace GNSS?

    “Could a new PNT constellation using LEO satellites fully replace the services provided by the four existing GNSS constellations?”

    Mitch Narins
    Mitch Narins

    “From a pure capabilities standpoint, the answer is “Yes”. LEO constellations can provide the PNT performance metrics that users require. However, should this strategy be followed, it would lack the diverse, complementary solutions needed to ensure the safety, security, and efficiency of critical infrastructure. Many have recognized the need for resilient PNT solutions and identified system-of-systems approaches. Multiple satellite constellations — MEOs and LEOs (despite the number of platforms) — lack this needed resilience. A resilient system-of-systems should include satellites in multiple orbits and complementary ground-based PNT infrastructure, each providing needed performance and overall demonstrating resilience from diverse threats.”

    — Mitch Narins
    Strategic Synergies

    Photo: Orolia
    John Fischer

    “In theory, yes. With a much stronger signal (antijam) that is encrypted (antijam), they counter GNSS’s two main vulnerabilities. However, with a paid service business model, it is difficult to compete with a free service. Moreover, large constellations are needed to overcome GDOP. OneWeb, Starlink, et al. already have launched and will continue to launch large constellations, so they must compete with these high bandwidth communications constellations that can provide accurate PNT as a side service and don’t have a GDOP limitation because of their size. Adoption of a single-purpose PNT system will be difficult.”

    — John Fischer
    Orolia

    Bernard Gruber
    Bernard Gruber

    “Yes, it could. That said, as with any new product or technology, evolution of PNT capabilities will be dependent on competition, value or threats that undermine the current environment. Burgeoning systems such as Xona, Satelles or any number of augmentations utilizing “signal of interest” such as Starlink will rightly contribute to the evolution of enhanced PNT. Current advantages of LEO-based systems such as increased received power, decreased convergence time and numerical diversity are noteworthy, but replacing an investment of $100B+ government backed GNSS systems that adhere to well established policies and published ICDs is another.”

    — Bernie Gruber
    Northrop Grumman

    Headshot: Jules McNeff
    Jules McNeff

    “As my colleagues above note, the answer is yes from a technical perspective. However, in practice, not so much. Even with software-defined receivers, issues of signal reception and processing, interface standards, comm/nav service prioritization, security, integration into complex systems, integrity assurance, etc. make use of such nav services in lieu of purpose-built GNSS services impractical.”

    — Jules McNeff
    Overlook Systems Technologies 

  • Editorial Advisory Board Q&A: NATO Galileo and GPS integration

    Editorial Advisory Board Q&A: NATO Galileo and GPS integration

    How do/will/should North Atlantic Treaty Organization (NATO) forces integrate GPS and Galileo for position, navigation and time?

    Ellen Hall
    Ellen Hall

     

    “For improved resiliency, it would be a great move for NATO to integrate Galileo with GPS into their system. The ‘how’ will be difficult. Some of the challenges are that the EU consists of more than a single nation with which to negotiate complex security issues, such as whether NATO will be treated as a ‘third nation entity’ for the use of PRS. The initial Galileo development was difficult for all these reasons and the Europeans managed to sort it all out, so I’m confident that, if the desire is to do this, it can be done successfully.”

    — Ellen Hall
    Imminent Federal

     

    Photo: Orolia
    John Fischer

     

    “In the interest of operational robustness and the criticality of the use case, NATO should integrate GPS and Galileo capability at the earliest. Both GPS’ M-code and Galileo’s PRS are encrypted, providing anti-spoof capability and extra frequency diversity, making jamming of our forces more difficult. Crypto key management for both systems may be an extra burden, but a single receiver capable of operating with either system individually or both simultaneously would be key for interoperability — always a driving factor for NATO. The capability is available, and NATO should take advantage of it.”

    — John Fischer
    Orolia

  • Editorial Advisory Board Q&A: How could the U.S. develop GPS high-accuracy analogous to Galileo’s HAS?

    What would be required for the United States to develop and deploy a GPS high-accuracy service analogous to Galileo’s HAS?

     

    Headshot: Ismael Colomina
    Ismael Colomina

    “Galileo HAS is a particular implementation of a PPP-RTK service. U.S. companies are already providing similar fee-based services that are even more accurate than HAS. Therefore, there is no big technical challenge for the United States to provide a GPS HAS. Actually, the European Union already provides a HAS for GPS. It is more a question of strategy for GPS policy makers: which user segment to service with a HAS-like augmentation? What about other services analogous to Galileo’s OSNMA and the upcoming CAS [commercial authentication service] for resiliency purposes? In short, a HAS-like service would just require including it in the U.S. GNSS evolution roadmap.”

    — Ismael Colomina
    GeoNumerics

    Photo: Orolia
    John Fischer

    “The challenge is probably more political than technical. The U.S. government usually refrains from competing with commercial services. The prevailing attitude in the United States is that the private sector is more efficient than the public sector. Maybe the most practical approach is for the government to provide the authentication mechanism and open access to the data required, then allow the private sector to offer services. There isn’t a pressing need for high-accuracy GPS for transportation — it needs resiliency/reliability. However, precision agriculture needs it, so maybe sponsorship from the Department of Agriculture would be more effective than from the Department of Transportation.”

    — John Fischer
    Orolia

    Mitch Narins
    Mitch Narins

    “When I saw this question, my first impression (as a systems engineer) was to ask ‘For whom? For what applications? For which services?’ (Positioning? Navigating? Time/frequency?) Many have concentrated on accuracy, competing in a GNSS Olympics to see who can achieve ‘the best’ position accuracy and precision (repeatability). Finally, (thanks to Logan Scott) integrity is being pushed beyond just SBAS and GBAS, and real civil authentication of signals is being pursued. I can promise nanometers/nanoseconds if I don’t have to prove it’s true. While we finally understand the need for zero trust, we must still address loss of service by establishing real complementary PNT.”

    — Mitch Narins
    Strategic Synergies

  • Editorial Advisory Board: The “geodesy crisis” and GNSS satellites

    Editorial Advisory Board: The “geodesy crisis” and GNSS satellites

    What are your thoughts on the “geodesy crisis” and what do you propose to address it?

    Bernard Gruber
    Bernard Gruber

    “Evidence seems to be very clear that we, as a country, need geodesists and that there has been a decline in investments, training, and research in geodesy. While our decline relative to China may be shocking, it should not be surprising. U.S. industry and government relentlessly pursues STEM graduates, or those with relevant experience, but that does not meet current needs. Besides maybe surveying, it is unclear to the public what the geodesy profession is all about, why it is needed, and quite frankly, why it is an exciting career choice.”

    — Bernard Gruber
    Northrop Grumman

    Does crowding of low-Earth-orbit (LEO) space — with new satellites and space debris — pose any problems for the launch or operations of GNSS satellites in medium
    Earth orbit (MEO)?

    Ellen Hall
    Ellen Hall

    “This was a focused topic at SATELLITE 2022, where the discussion centered on the 6,000 tons of space debris circulating in LEO. Even the smallest piece of debris can be lethal to a satellite, so the key is to track and maneuver where possible. Add to that about 5,000 active satellites and plans to launch tens of thousands of additional ones into LEO over the next few years, and you have a serious problem to overcome. While there are treaties and plans for tracking and maneuvering these satellites, the debris is the real challenge.”

    — Ellen Hall 
    Spirent Federal Systems

  • Editorial Advisory Board Q&A: Location accuracy

    What is the most promising approach to increasing the location accuracy of smartphones?

    Headshot: Ismael Colomina
    Ismael Colomina

    “In addition to the use of increasingly available augmentation services, such as Galileo’s free High-Accuracy Service (HAS), I see two development directions that may help, particularly in the context of positioning in urban areas where smartphones are most used. One is the use of 3D city models — in general, 3D geoinformation — to compensate for multipath, non-line-of-sight and occlusion effects. The other is to use signals that are robust against those effects, which today are only available in geodetic-grade receivers.” — Ismael Colomina, GeoNumerics

    For the navigation of autonomous vehicles, will GNSS become essential, or will it be relegated to a secondary role by robotic navigation methods?

    John Fischer
    John Fischer

    “The PNT solution cannot be from a single source because autonomous navigation requires high integrity. Therefore, it’s not that GNSS will be relegated to secondary status, it’s that no one method will be primary. An intelligent fusion of diverse sensors —including GNSS — will provide the PNT solution along with an integrity metric that safeguards operation. The various sensors must agree. If they don’t, no trust can be put into the solution and autonomous navigation will cease. The definition of a new integrity metric that quantifies this trust level is needed.” — John Fischer, Orolia

    Ellen Hall
    Ellen Hall

    “Because GNSS provides high precision and widely available PNT, it will continue to be a critical component in navigation while working with computer vision, inertial measurement units (IMUs) and lidar through sensor fusion. As a secondary component, GNSS serves a vital role for localization and validation.” — Ellen Hall, Spirent Federal Systems

  • Editorial Advisory Board Q&A: What is the greatest strength of GPS?

    Compared to the other three GNSS constellations, what is currently the greatest strength of GPS? What is its greatest weakness?

    Bernard Gruber
    Bernard Gruber

    “I would submit that the greatest strength of GPS is its ubiquity. GPS really is everywhere — worldwide and accepted. It is a trusted and free continuous source, backed by the integrity of the United States, and used for location, navigation, tracking, mapping and timing in myriad applications. Spawned and integrated applications that rely on GPS are well into the high billions of dollars! As they say, ‘When you’re on top, people will be gunning for you.’ In the case of GPS, I would offer that that is its greatest weakness — overreliance without a backup for those users that should have one.”

    — Bernard Gruber, Northrop Grumman

    Jules McNeff
    Jules McNeff

    “I’ll second Bernie’s comments and add that the nearly universal trust in GPS, despite the protestations that it is operated by the military, is a result of decades of openness regarding its operation and improvement. Rare faults are acknowledged and repaired, and planned civil modernizations, though sometimes delayed, are developed with civil collaboration and are fully and publicly documented. Its success and consistency have made it a target, which would be a significant weakness but for a growing awareness of the need for complementary PNT sources to sustain the value it has created.”

    — Jules McNeff, Overlook Systems Technologies

    F. Michael Swiek
    F. Michael Swiek

    “On strengths, it is very simple: reliability, consistency, stability and transparency.”

    — Michael Swiek, GPS Alliance

  • Editorial Advisory Board Q&A: What will OCX bring?

    What improvements will the Next Generation Operational Control System (OCX) bring?

    Ellen Hall
    Ellen Hall

    “The OCX system is a part of an enormous modernization effort to enhance the ground control segment of the current GPS. This enhancement alone increases accuracy, but coupled with modernized satellites, the next generation OCX will increase and improve coverage and security of GPS. In terms of coverage, the Next Generation OCX will be able to fly twice as many satellites, including both legacy equipment as well as GPS IIIF satellites. In terms of security, the modernized receivers host anti-jam capabilities and information assurance features.”
    — Ellen Hall
    Spirent Federal Systems

    Bernard Gruber
    Bernard Gruber

    “The latest GPS modernization program was envisioned in the 1990s and started with the U.S. Air Force awarding the Lockheed Martin Team a $1.4 billion contract in 2008 to build the GPS III space system. As part of the modernization effort the initial OCX contract award was given to Raytheon two years later, in 2010, while a series of development contracts have been awarded, primarily Inc 1 and Inc 2, for the Modernized GPS User Equipment (MGUE) programs to L3Harris, Raytheon and then Rockwell Collins. The improvements of OCX aligned to the space and user efforts and substantially increased security protection of this world asset. Specifically, OCX controls all legacy satellites (GPS II) and civil signals (L1 C/A) and military signals (L1P(Y), L2P(Y)). It also controls the new modernized civil signal (L2C) and the aviation safety-of-flight signal (L5). Moreover, it also will have control functions for the MGUE signals (L1M and L2M (M-Code)), and the globally compatible signal (L1C). The next Block IIIF will finally upgrade capabilities to synchronize the entire system to include a worldwide network of dedicated monitoring stations, ground antennas and backup capabilities.”
    — Bernard Gruber
    Northrop Grumman

     

  • Editorial Advisory Board Q&A: Should all GNSS follow NavIC?

    Would it be beneficial for GNSS constellations to transmit signals at higher frequencies, such as in the S-band or the C-band, following the example of the Indian NavIC?

    Jean-Marie Sleewaegen
    Jean-Marie Sleewaegen

    “The S- and C-bands refer to frequency bands centered around 2492 MHz and 5020 MHz. The main advantage compared to L-band is the reduced effect of the ionosphere. However, this comes at the expense of higher propagation losses, increased phase jitter due to the lower wavelength, and extra cost in the receiver and antenna when combined with L-band. The added value for existing GNSS systems already transmitting multiple signals in L-band is probably low. However, because they are less congested than L-band, those bands could be attractive to new space-based PNT services.”
    — Jean-Marie Sleewaegen, Septentrio

    Alison Brown
    Alison Brown

    “The main challenge with adding additional bands to GNSS constellations (other than getting frequency allocations) is that these will not be compatible with any existing GNSS chip sets or fielded antennas. The cost/benefit analysis is unlikely to be attractive for most GNSS chip vendors to develop products with this capability.”
    — Alison Brown, NAVSYS Corporation

    Ellen Hall
    Ellen Hall

    “There are benefits that the higher bands can offer in GNSS, however the constellation and system must be designed to take advantage of them, which makes it very difficult for the legacy systems that were designed around L-band only to tap into any of these benefits. Higher bands have lower ionospheric distortion, which enables better single-frequency accuracy and unlocks some interesting multi-frequency capability, while shorter wavelengths can allow for smaller antennas in user equipment. However, the tropo/atmospheric distortion gets worse as well as the spreading losses. Another consideration for the higher bands is spectrum interference, as the S-band area especially is extremely busy.”

    — Ellen Hall, Spirent Federal Systems

  • Editorial Advisory Board Q&A: The fate of the SAASM P(Y) code

    Editorial Advisory Board Q&A: The fate of the SAASM P(Y) code

    Photo: Editorial Advisory Board

    The U.S. military is transitioning to M-code. When the transition is complete, what will become of the SAASM P(Y) code? What should be done with it? Should the U.S. government use it as a public authenticated service?

    Jules McNeff
    Jules McNeff

    “In my opinion (not speaking on behalf of the Defense Department), eventual use of the P(Y) code as a public authenticated service is not feasible based on both time and accessibility. Even with the transition to M-code, the legacy P(Y) code will continue to be used by the U.S. military and by U.S. allies and partner nations as long as there are military requirements for it. More importantly, public access to the encrypted P(Y) code would require general distribution of classified cryptographic keys and associated hardware/software by the DOD. That will not happen, even if the P(Y) code use is discontinued.”
    Jules McNeff
    Overlook Systems Technologies

    Bernard Gruber
    Bernard Gruber

    “Broadly speaking, GPS user equipment security architectures transition every 10 years (such as PPS-SM/AOCs to SAASM to Modernized CGM/MSI.) It can be argued that implementation of these security measures generally takes 10 years or longer to implement. SAASM P(Y) receivers will be around for a long time, implementation can be expensive, backwards compatibility is critical. Personally, I would like to see SAASM architectures evolve to support critical services within other U.S. government departments first, and then determine a path that supports a public service as threats, unfortunately, move forward.”
    Bernard Gruber
    Northrop Grumman

    Photo: Orolia
    John Fischer

    “Why not? Authentication protects against spoofing. I don’t know all the obstacles involved, but even if an internet connection is required to overcome the one-way limitation of GPS, that isn’t a problem for most applications. Our credit card transactions are secured this way, why not our PNT information? Decades ago, the U.S. Air Force gave the world a gift with the open GPS signal; they could do it again with a secure signal. The world would be a better place.”
    John Fischer
    Orolia

    F. Michael Swiek
    F. Michael Swiek

    “It’s premature to forecast when military operations will transition from P(Y) code even after M-code operations achieve Initial and Final Operating Capability (IOC and FOC). SAASM P(Y) code will continue to support military operations for an extended period since all MGUE receivers (both increments 1 and 2) are YMCA capable, meaning they support P(Y) code, M-code and C/A code operations. As a military-encrypted signal with military utility, military leaders must carefully weigh any potential P(Y) code transition and its impact on military operations.”
    Michael Swiek
    GPS Alliance

    Ellen Hall
    Ellen Hall

    “If P(Y) code is offered as a new service to the public, it will have to be maintained. This carries a great cost. This is a legacy product that had a specific military need, which has been replaced and improved upon by M-code. In today’s uncertain times, we need to be wise with our tax dollars. The cost to continue both SAASM and M-code is greater than the benefit to the public, in my opinion.”
    Ellen Hall
    Spirent Federal Systems

     

    Feature photo: U.S. Marine Corps/Capt. Joshua Hays

  • Editorial Advisory Board PNT Q&A: Promising alternatives to GNSS

    What is the most promising development or project in alternative PNT?

    Photo: Orolia
    John Fischer.

    “PNT from LEO (low-Earth orbit) satellites offers the most immediate alternative to GNSS because the signals are ~30 dB or more stronger, reducing jamming vulnerability. With these new constellations being launched to improve communications, PNT services can ‘piggyback’ on the secure two-way links and avoid spoofing attacks as well. Geometric dilution of precision (GDOP) will not be a problem in these large second-generation constellations with dozens of satellites in view. Wide bandwidth links should yield accuracies to rival GNSS. There may be subscription fees to get this added resiliency, but nothing worthwhile is ever free.”

    John Fischer,
    Orolia

    Bernard Gruber
    Bernard Gruber

    “It depends on the application. I believe that alternative PNT, and specifically systems that complement GPS/GNSS, will continue to drive forward at a very rapid pace. Quite frankly, the ‘affordability of GPS’ from a commercial and military user business case was impossible to ignore for years. Today, the threat to GNSS signals is very real. History illustrates that ‘alternative’ systems that employ environmental data (magnetic, celestial), radio navigation (Loran, VOR), sensors (gyros, accelerometers), seekers (SAL, EO/IR) and IMUs all have new and promising developments today.”
    Bernard Gruber,
    Northrop Grumman

    Thibault Bonnevie, SBG Systems
    Thibault Bonnevie

    “Inertially aided GNSS solutions are now mature and provide excellent navigation performance in many challenging conditions. On the research side, there are many exciting alternative PNT projects ongoing. RF-based solutions, such as Bluetooth/Wi-Fi or LEO satellite ranging, give promising results but are still subject to jamming or spoofing. Just like GNSS. Vision-based SLAM is probably the most exciting technology as it enables navigation in a wide range of situations and does not rely on any kind of infrastructure. It only requires low-cost sensors to be operated.”
    Thibault Bonnevie,
    SBG Systems

    Headshot: Ismael Colomina
    Ismael Colomina

    “We all know that predictions are hazardous, especially about the future. This said, I confess that I am particularly interested in the technical, regulatory and commercial development of the LEO-based PNT technology with either dedicated constellations, like XONA’s Pulsar, or broader scope ones such as Iridium Next, Starlink or Kuiper. While GNSS has progressed tremendously in recent times — it plays a large role in the navigation of autonomous vehicles — it is still vulnerable to intentional or unintentional jamming. Integration of LEO-based PNT with current GNSS and other motion sensors appears to be a fascinating field ahead of us..”
    Ismael Colomina,
    GeoNumerics