The U.S. Department of Transportation (USDOT) on January 15 released the final Complementary Positioning, Navigation, and Timing (PNT) and GPS Backup Technologies Demonstration Report to Congress.
The report included two recommendations:
1. DOT should develop system requirements for PNT functions that support safety-critical services.
2. DOT should develop standards, test procedures, and monitoring capabilities to ensure that PNT services, and the equipage that utilizes them, meet the necessary levels of safety and resilience identified in Recommendation 1.
"Recognizing that the transportation sector has some of the most stringent performance requirements in terms of accuracy, integrity, availability, and reliability, developing system requirements that focus on safety and resilience will allow determination of which requirements are currently met, and which requirements may require further commercial innovation," the authors wrote. "DOT supports open safety standards to promote private-sector innovation and commercial product development."
USDOT’s Volpe National Transportation Systems Center (Volpe Center) conducted field demonstrations of candidate PNT technologies that could offer complementary service in the event of Global Positioning System (GPS) disruptions.
The purpose of the demonstrations was to gather information on PNT technologies at a high Technology Readiness Level that can work in the absence of GPS. Because GPS relies on signals broadcast from satellites in Medium Earth Orbit (MEO), signal strength at the receiver is low and thus vulnerable to intentional and unintentional disruptions.
The Volpe Center, through a competitive acquisition process, selected 11 candidate technologies to demonstrate positioning and/or timing functions in the absence of GPS.
1. Echo Ridge LLC: Augmented Positioning System
2. Hellen Systems, LLC: eLORAN system
3. NextNav LLC: Metropolitan Beacon System
4. OPNT B.V.: OPNT embedded timing switches
5. PhasorLab Inc: Hyper Sync Net
6. Satelles, Inc: Satellite Time and Location service
7. Serco Inc: R-Mode (Ranging Mode) technology
8. Seven Solutions S.L.: timing services based on White Rabbit protocol
9. Skyhook Wireless, Inc: Precision Location System
10. TRX Systems, Inc: NEON Personnel Tracker
11. Ursa Navigation Solutions, Inc. (d.b.a. UrsaNav, Inc.): eLORAN system
The demonstrations were conducted in March 2020 at the National Aeronautics and Space Administration (NASA) Langley Research Center in Hampton, VA, and Joint Base Cape Cod in Bourne, MA. The results from the demonstrations were evaluated against 14 measures of effectiveness.
There were four key findings from the DOT technology demonstration:
* All TRL-qualified vendors demonstrated some PNT performance of value, but only one vendor (NextNav) demonstrated PNT performance in all applicable use case scenarios.
* Neither eLORAN technology succeeded in the Static Basement Timing scenario.
* One technology (R-Mode ranging in the MF band) did not meet the minimum Technology Readiness Level (TRL) of 6.
* Deployment effort and coverage (infrastructure per unit area) are both significant cost factors.
The findings indicate that the best strategy for achieving resilient PNT service is to pursue multiple technologies to promote diversity in the PNT functions that support transportation and other critical infrastructure sectors in urban, rural, and maritime areas.
“The results of the thorough scientific research conducted by this demonstration effort indicate that there are suitable, mature, and commercially available technologies to back up or to complement the timing services provided by GPS. However, the demonstration also indicates that none of the systems alone can universally back up the positioning and navigation capabilities provided by GPS and its augmentations. This necessitates a diverse universe of positioning and navigation technologies,” said Diana Furchtgott-Roth, USDOT’s Deputy Assistant Secretary for Research and Technology.
The report details the results of USDOT activities covering GPS backup demonstration planning, the PNT technologies demonstrated, the government reference system used to collect and verify results, and an information framework to convey measures of effectiveness of the demonstrated technologies.