Secondary receiver uses eLoran to back up GPS time
Spectracom has been selected to provide Interference, Detection and Mitigation (IDM) capability to its SecureSync precision time and frequency reference system to support Rohde & Schwarz Benelux B.V. and the Netherlands Ministry of Defence for secure long-range military communications systems.
The upgrade, which is based on a secondary receiver that extracts precision timing signals from the eLoran system when GPS signals are not available, will increase the reliability of the overall communication system by further enhancing the resiliency of the precision timing core.
As part of its expanding set of resilient PNT solutions, Spectracom systems synchronize to a variety of precision references whenever and wherever available.
In this deployment, signals from the eLoran system are constantly monitored and act as the primary reference when GNSS signals are not available due to interference or jamming. This new capability supports the goal of a sustainable and reliable network for ongoing global operations.
The modularity of the SecureSync precision time and frequency platform allows customers and integrators to easily and incrementally increase system capabilities, such as multiple reference signals, as they become available.
South Korea will award a contract this month to secure technology required to build an eLoran system as an alternative to GPS, reports the Australian Broadcasting Company (ABC).
The South Korean eLoran plan envisions setting up coastal transmitters by the end of 2019, said Seo Ji-won, a government advisory panel member and professor at Yonsei University.
“The need for us is especially high, because of the deliberate signal interference by North Korea,” a South Korean government official told Reuters, as reported by ABC.
The latest jamming campaign from the North began on March 31. According to ABC, the jamming lasted nearly a week and affected signal reception of more than 1,000 aircraft and 700 ships, with the jamming originating from five locations along the border, South Korean officials said.
GPS vulnerability poses security and commercial risks, especially for ships whose crews are not familiar with traditional navigation techniques or using paper charts. Vessels such as fishing boats lack backup electronic navigation systems.
Air traffic was not usually affected because the GPS system is normally used as a backup in South Korea, not a primary navigation tool.
GPS in the United States and Europe could also experience malicious jamming attacks, reinforcing the need for a backup alternative such as eLoran.
“Even the best technology has a bad day,” Charles Schue told the New York Stock Exchange (NYSE), which relies very heavily on the best technology to keep the world’s financial edifice afloat. Vulnerabilities in the stock market were pointed up during a demonstration on April 19, showcasing how one positioning, navigation and timing (PNT) system can cover the chinks in another. Respectively, eLoran and GPS in this case.
Schue is CEO of UrsaNav, a company that has been developing complementary PNT solutions, specifically the high-power, low-frequency (LF), ground-wave technology that is eLoran, which UrsaNav calls “the most reliable, scalable, and future-proof available.” Schue spoke at the NYSE along with representatives from the Department of Homeland Security (DHS), the U.S. Coast Guard, Juniper Networks and Harris Corporation.
“2014 was a very bad year for GNSS,” Schue continued, citing the GLONASS full-system outage for 11 hours and Galileo’s wrong-orbit launch of two satellites. “This year, GPS, the gold standard, had an ‘oops’ and slipped from gold to silver, when one satellite kind of wigged out, a 13.7 microsecond error that contaminated 15 other satellites.” He ran a simulation that showed how, at one point, six GPS satellites were communicating bad timing to the Eastern seaboard, where the NYSE is located.
2016 has also seen renewed GPS jamming from North Korea.
The stock exchange, along with other global financial markets, relies on microsecond timing to properly execute all transactions. The U.S. air traffic management system likewise relies on high-precision aspects of GPS that are vulnerable to interference, jamming, and even occasional system failure. Many other industries, telecommunications principally among them, are also building infrastructures and applications that rely on GPS for precise timing, thus making them vulnerable as well.
One Back-Up Transmitter in Place
An eLoran transmitter in Wildwood, New Jersey, relies on three primary reference standards, three atomic clocks, just as each GPS satellite carries three or four atomic clocks. “The signals coming from space, the signals coming from ground, they’re very similar.” ELoran also has monitoring and control sites on the ground, just like the satellite system; it has differential reference stations, and of course eLoran receivers, playing the same role as GPS receivers.
Schue asserted that the cost of launching one GPS satellite into space would fund an eLoran system for the continental United States for 20 years. Also, that a lot of industries in addition to the financial community are building infrastructures and applications that rely on GPS for precise timing, and so are equally vulnerable.
The eLoran demonstration showed how the Wildwood station sent a timing signal 130 miles to the NYSE, deep within several urban canyons and enveloped in several layers of concrete, steel and glass. A GPS receiver in the room did not pick up anything. The eLoran receiver showed precise time, to the standard of NYSE requirements.
Equipment utilized included a Spectracom SecureSync providing time to the network, once it received it from eLoran.
On a screen display showing plus or minus 500 nanoseconds relative to Coordinated Universal Time, “that red line is us receiving eLoran timing at that antenna, 130 miles away, through the urban canyons, inside this building, right now at minus 14 nanoseconds.” The eLoran equipment transmitted and received two signals, with a data channel on one of the signals. “We could put the data channel on both signals, and we could put multiple data channels on both on there as well.”
Schue said another demo inside a downtown Boston hotel, 305 miles from the New Jersey transmitter, obtained 83-nanosecond accuracy. A 2015 test to an outdoor receiver in Bangor, Maine, 500 miles from the transmitter, logged 68-nanosecond accuracy.
Plus or minus 100 nanoseconds is the typical GPS performance. “We can do far better, and GPS often does far better than that.”
Initial operating capability for a wide-area eLoran service providing precise time for the continental United States would require four transmitter sites across the middle of the country. The corporate and government partners hope to use some repurposed Loran-C assets and turn them into eLoran stations. Wildwood is transmitting at 360 kilowatts; if transmitting at 1 million watts, or 1 megawatt, the signal could penetrate even further inside buildings. The cost difference between the two powers of transmitter is not significant.
Bringing six more continental eLoran transmitter sites online, for a total of ten, would add a back-up positioning capability in addition to timing. “This is very important, because with positioning, you get mobile time — a co-primary solution for position, navigation, and timing.”
Using a differential receiver would yield even better local-area accuracy for about 35 miles around a selected site, for high-priority locations. Such a higher-precision system for the nation’s top 50 metropolitan areas, top 50 airports, and top 50 harbors could be accomplished with 71 differential sites.
Concurrence from Government and Other Industry Partners
Spokespersons from the DHS, Coast Guard, Juniper Networks and Harris Corporation preceded Schue at the NYSE presentation, all giving similar perspectives on U.S. vulnerability in many aspects, due to reliance on GPS as a sole, unsupported source of precision PNT. “Of the 16 critical infrastructure / key resource sectors in the United States, 15 use GPS for timing. GPS timing is deemed essential for 11 of these sectors,” stressed DHS.
The founders of Chronos and UrsaNav have formed a new collaboration, named Taviga, that will focus on preserving and establishing low-frequency (LF) positioning, navigation and timing (PNT) networks in the United Kingdom, Europe and the U.S., using repurposed Loran-C or purpose-built eLoran technology.
Taviga aims to ensure timing and navigation for critical infrastructure, protecting it from cyber and other threats, and addressing the concern that over-dependence on single systems for PNT increases vulnerability.
According to a joint press release, “Taviga combines the founders’ decades of experience specializing in low-frequency (LF) PNT technology and industrial timing applications at national and international levels. Its objective is to provide a commercially operated assured LF PNT service.”
Partner with Government. Charles Curry of Chronos Technology Ltd. in the UK and Charles Schue of UrsaNav Inc. in the U.S. joined forces to launch Taviga Ltd. and Taviga LLC. Taviga anticipates working in partnership with government agencies and other entities that have a vested interest in reducing the vulnerability and improving the resilience of critical national infrastructure with a dependency on the GPS and other GNSS sources of PNT.
“We have been researching the precise timing capability of eLoran transmissions for over 10 years,” Curry said. “During that time, the system has never failed, and most impressively it has continued to deliver sub-microsecond time accuracy traceable to UTC in very challenging locations, including deep inside buildings.
“Our research program was supported by the UK’s Innovation Agency — Innovate UK through two flagship projects, GAARDIAN and SENTINEL,” Curry continued. “These two projects highlighted the vulnerabilities that threaten GPS signals (and in the future, Galileo) such as jamming, interference and spoofing. They also demonstrated how eLoran is a technically dissimilar source of PNT and not vulnerable to the same types of interference. eLoran is a truly complementary source of PNT, ideal for use in critical infrastructure applications such as telecoms, broadcasting, financial services and power utilities.
“Every government, academic and industrial study has resulted in the selection of the LF technology known as Enhanced Loran, or eLoran, as the best wide-area complement to GNSS,” UrsaNav’s Schue added. “There is no doubt that the combination of GNSS and eLoran provides the PNT resilience that most users require.
“Integrated GNSS-eLoran solutions can provide the proof-of-time and proof-of-position necessary to safeguard national infrastructure and for business continuity of operations,” Schue said. “Adding eLoran to the PNT mix enables or enhances capabilities of regional and purpose-built solutions. Overreliance on a single solution is neither prudent nor safe.”
Tests led by Chronos and using UrsaNav’s eLoran receiver engine have consistently demonstrated positioning accuracies of better than 10 m and timing accuracies of less than 100 nanoseconds in the area of differential eLoran reference sites.
Taviga’s goal is the long-term operation of an eLoran system for at least 10 years, a period that provides the necessary service assurance continuity to enable industrial users to invest with confidence in an eLoran-based timing and navigation service that complements their GNSS solutions. As users become accustomed to the capabilities and resilience of a combined GNSS-eLoran solution, Taviga expects to expand the service footprint worldwide.
Timing
Leap second lives on
The International Telecommunication Union (ITU) World Radiocommunication Conference (WRC-15) decided that further studies are required on the impact and application of a future reference time-scale, including the modification of Coordinated Universal Time (UTC) and suppressing the so-called “leap second.”
Leap seconds are added periodically to adjust to irregularities in the Earth’s rotation in relation to UTC, the current reference for measuring time, in order to remain close to mean solar time (UT1). A leap second was added most recently on June 30 at 23:59:60 UTC. The proposal to suppress the leap second would have made continuous reference timescale available for all modern electronic navigation and computerized systems to operate while eliminating the need for specialized ad hoc time systems.
A report will be considered by the World Radiocommunication Conference in 2023. Until then, UTC shall continue to be applied as described in Recommendation ITU‑R TF.460‑6.
Disconnect from the Sun? As a representative of the Lick Observatory of the University of California stated, “a problem is that simply omitting leap seconds would redefine the meaning of the word “day” so that it is not related to the sun in the sky, nor connected with the rotation of the Earth.”
“Modern society is increasingly dependent on accurate timekeeping,” said ITU Secretary-General Houlin Zhao.“ITU is responsible for disseminating time signals by both wired communications and by different radiocommunication services, both space and terrestrial, which are critical for all areas of human activity.”
Further studies will be coordinated by ITU along with several other international organizations.
Inertial/GNSS
Drone rules, registry
The Federal Aviation Administration announced in December an official rule and registration process for hobbyists who own small unmanned aircraft weighing more than 0.55 pounds and less than 55 pounds, including payloads such as on-board cameras.
The online registration system does not yet support registration of small UAS used for any purpose other than hobby or recreation — for example, using an unmanned aircraft in connection with a business. The FAA is developing enhancements that will allow such online registrations by spring of 2016.
The registration procedure is a statutory requirement that applies to all hobby aircraft. Under this rule, any owner of a small UAS who has previously operated an unmanned aircraft exclusively as a model aircraft prior to Dec. 21, 2015, must register no later than Feb. 19, 2016. Owners of any other UAS purchased for use as a model aircraft after Dec. 21, 2015, must register before the first flight outdoors.
Owners may register through a web-based system or paper-based process. There is a $5 registration fee, but the FAA is offering a full rebate for those who register before Jan. 20, 2016.
Under the rule, each aircraft must be marked with a unique number, although not necessarily the serial number. The goal is to help authorities track down an owner if a drone collides with another aircraft, flies too high or encroaches on an airport.
Owners using the model aircraft for hobby or recreation will only have to register once and may use the same identification number for all of their model UAS. The registration is valid for three years.
“We expect hundreds of thousands of model unmanned aircraft will be purchased this holiday season,” FAA Administrator Michael Huerta said. “Registration gives us the opportunity to educate these new airspace users before they fly so they know the airspace rules and understand they are accountable to the public for flying responsibly.”
Space maps of some of 13,986 satellites, below, and some navigation satellites, above (courtesy Esri).Alan Cameron
Advocacy in the U.S. capital urges augmentation of GPS/GNSS with eLoran and other “complementary terrestrial PNT services to increase resilience.” See the Resilient Navigation and Timing Foundation’s website, rntfnd.org. This is assuredly a good thing, a worthy cause.
I’ve come to believe, however, that true resilience goes beyond what we normally think of as position and timing sensors. Stimulus comes from a keynote lecture by Dawn Wright, Esri chief scientist, at the 2015 American Geophysical Union Fall Meeting. I hope Esri or the AGU will publish the lecture or post the video. For now, bear with my limited rendition.
In “Toward a Digital Resilience, with a Dash of Location Enlightenment,” Wright describes the new science of big data: the flood of info from satellites, sensors and other measuring systems; the issues inherent in large data sets; and the insight discovered through their manipulation and exploration. She talks to geographic information systems professionals, software makers and users, but her remarks resonate beyond that associated industry sector and well into that of PNT hardware, where we live.
Integrate, integrate, integrate! Interoperability and crosswalking with other systems and data sets. To make it reproducible, make it virtual — as in virtual, living journals. These are three of the eight ideas toward digital resilience that she espouses, making communities more resilient with tools and data.
I’ll return to this in a later editorial; there’s much around which still to wrap my head. But here’s the moral: resilient PNT will ultimately mean more than complementary sensors. It will entail a seamless mesh of hardware and software, of pre-existing and new data, much of it from sources we don’t currently consider PNT-relevant, of input from amateur app makers and users and more.
eLoran Antenna Park of 13, 200-meter masts at Anthorn, UK.
Readers of GPS World, its e-newsletters, website — and all interested PNT parties — are invited to register their opinion in the current poll at gpsworld.com/janpoll.
Should the U.S. government install a full eLoran network of broadcast stations to back up GPS in case of jamming, interference or other emergencies?
Yes.
No.
More study is needed before answering this question.
Don’t know.
Voters may enter their name in a drawing to receive a $50 gift card. Vote by Jan. 11, 2016.
Results will be published in the February issue of GPS World magazine.
The founders of Chronos and UrsaNav have formed a new collaboration, named Taviga, that will focus on preserving and establishing low-frequency (LF) positioning, navigation and timing (PNT) networks the United Kingdom, Europe and the United States, using repurposed Loran-C or purpose-built eLoran technology.
Taviga — named for timing and navigation — aims to ensure timing and navigation for critical infrastructure from cyber and other threats, and address the concern that over-dependence on single systems for PNT increases vulnerability.
According to a joint press release, “Taviga combines the founders’ decades of experience specializing in low-frequency (LF) PNT technology and industrial timing applications at national and international levels. Its objective is to provide a commercially operated assured LF PNT service.”
Charles Curry, founder of Chronos Technology Ltd. in the UK, and Charles Schue, founder of UrsaNav Inc. in the United States, joined forces to launch Taviga Ltd. and Taviga LLC. Taviga anticipates working in partnership with government agencies and other entities that have a vested interest in reducing the vulnerability and improving the resilience of critical national infrastructure with a dependency on the GPS and other GNSS sources of PNT.
“We have been researching the precise timing capability of eLoran transmissions for over 10 years,” Curry said. “During that time, the system has never failed and most impressively it has continued to deliver sub-microsecond time accuracy traceable to UTC in some very challenging locations including deep inside buildings.
“Our research program was supported by the UK’s Innovation Agency – Innovate UK through two flagship projects, GAARDIAN and SENTINEL,” Curry continued. These two projects highlighted the vulnerabilities that threaten GPS signals (and in the future, Galileo) such as jamming, interference and spoofing. They also demonstrated how eLoran is a technically dissimilar source of PNT and not vulnerable to the same types of interference. eLoran is a truly complementary source of PNT ideal for use in critical infrastructure applications that demand precise time and timing such as telecoms, broadcasting, financial services and power utilities.
“Every government, academic and industrial study has resulted in the selection of the LF technology known as Enhanced Loran, or eLoran, as the best wide-area complement to GNSS,” Schue said. “There is no doubt that the combination of GNSS and eLoran provides the PNT resilience that most users require.
“Whether the application is timing/frequency, aviation, maritime, land-mobile, or location based, integrated GNSS-eLoran solutions can provide the proof-of-time and proof-of-position necessary to safeguard national infrastructure and for business continuity of operations,” Schue said. “Additionally, adding eLoran into the PNT mix enables or enhances the capabilities of regional and purpose-built solutions. PNT resilience results from an eco-system made up of layered solutions. Over reliance on a single solution is neither prudent nor safe. It’s time for Taviga.”
Tests have been conducted as part of Innovate UK supported research projects GAARDIAN and SENTINEL, which were led by Chronos Technology Ltd and included UrsaNav’s eLoran receiver engine. eLoran transmissions from the UK, Denmark, Germany, France and Norway have consistently demonstrated positioning accuracies of better than ten meters and timing accuracies of less than 100 nanoseconds in the area of differential eLoran reference sites. Taviga will now seek to engage those governments and others in discussions as to how to transition their Loran stations to commercial operation.
Taviga’s goal is the long-term operation of an eLoran system for at least 10 years. This length of time provides the necessary service assurance continuity to enable industrial users to invest with confidence in an eLoran-based timing and navigation service that complements their GNSS solutions. As users become accustomed to the additional capabilities and resilience provided with a combined GNSS-eLoran solution, Taviga expects to expand the service footprint into other countries worldwide.
A Wide-Area Multi-Application PNT Resiliency Solution
By Stephen Bartlett, Gerard Offermans and Charles Schue
INNOVATION INSIGHTS with Richard Langley
WHERE HAVE ALL THE SYSTEMS GONE, long time passing?
Radionavigation systems, that is (and apologies to Pete Seeger). If we look at the 1990 Federal Radionavigation Plan (FRP), published by the U.S. Departments of Transportation and Defense, as I did in this column in March 1992, we see that there were 10 radionavigation systems in use by different user segments: Loran-C, Omega, very high frequency (VHF) Omnidirectional Range/Distance Measuring Equipment, Tactical Air Navigation, the Instrument Landing System, the Microwave Landing System, Transit, aviation radiobeacons, marine radiobeacons and GPS.
The latest FRP, issued in 2014, includes only seven or six and a half when you consider that marine radiobeacons were mostly phased out in the intervening years. Systems were shut down because with the advent of GPS, they were considered to be redundant. While there were attendant cost savings, the closure of the various systems has resulted in a dangerous virtual sole dependence on GPS for navigation without any backup.
Transit, was the first to go. It consisted of a constellation of six or seven active satellites in circular, polar orbits at altitudes of roughly 1,100 kilometers. The satellites transmitted signals on 150 and 400 MHz, and receivers measured the integrated Doppler frequency shift of the received signals. Transit was terminated at the end of 1996.
Transit was followed by the Omega hyperbolic navigation system. Omega consisted of eight stations around the globe transmitting time-shared carrier-wave signals on four frequencies between 10.2 and 13.6 kHz. The Omega system was closed down in September 1997.
The marine radiobeacons have been mostly shut down in recent years, although aeronautical beacons continue to operate. Radiobeacons are nondirectional transmitters that operate in the low- and medium-frequency bands. Some marine radiobeacons became Differential GPS stations and subsequently part of the Nationwide DGPS network. That network is being scaled back to provide only coastal and Great Lakes coverage.
And that brings us to Loran-C. Like Omega, it was also a hyperbolic navigation system. A receiver measured the difference in times of arrival of pulses transmitted at 100 kHz by a chain of three to five synchronized stations separated by hundreds of kilometers. At one time, the operation of Loran-C was the responsibility of the U.S. Coast Guard. Together with a number of host nations, the Coast Guard operated 17 chains of stations around the world, including one jointly operated with Russia. These stations provided coverage of the coastal areas of North America and the U.S. interior, northern Europe, the Mediterranean Sea, the Far East and the Hawaiian Islands. Additionally, several other countries operated Loran-C stations. Although moves were already underway to update the Loran technology, the Obama administration decided to terminate Loran-C in the U.S., considering it to be an unnecessary antiquated system. The Coast Guard terminated the transmission of all U.S. Loran-C signals in February 2010 and began dismantling stations.
So, is there no longer a viable non-GNSS alternative or backup system for GPS navigation? While there are other possibilities for time transfer, one of GPS’s other applications, there is no widely available substitute navigation system. Currently. However, as we will see in this month’s column, a new version of Loran — Enhanced Loran or eLoran — has been developed and is being tested on the U.S. east coast. Not your father’s Loran, eLoran seems to be the perfect solution for PNT resiliency.
Telecommunications, energy, finance and transportation are just four among the many critical infrastructure / key resource sectors that have come to rely solely on GPS for positioning, navigation and timing (PNT). In fact, the U.S. Department of Homeland Security (DHS) has determined that 11 of the 16 critical infrastructure sectors in the U.S. are critically dependent on GPS for timing. While we can start to imagine what a day without GPS might be like, we’d really rather not — it would be somewhat depressing and really quite dangerous. We would rather imagine a day when there is a wide-area complementary solution available that protects and augments GPS. In this article, we will delve into such a solution: Enhanced Loran, or eLoran for short. We will explain how it works, debunk some myths, speculate on how it could be used in the U.S. (and abroad), highlight the state of current technology and discuss the state of the possible. We will also summarize the state of eLoran in the world and where things might go from here.
What Is eLoran?
eLoran is the latest in the longstanding and proven series of low-frequency, LOng-RAnge Navigation (LORAN) systems, one that takes full advantage of 21st-century technology. It meets the accuracy, availability, integrity and continuity performance requirements for maritime harbor entrance and approach maneuvers, aviation non-precision instrument approaches, land-mobile vehicle navigation and location-based services. It’s a precise source of time (phase) and frequency. Additionally, eLoran provides user bearing (azimuth) and has built-in integrity. In full disclosure, however, eLoran is only a 2D positioning solution unless integrated with a simple altimeter.
eLoran is a low-frequency radionavigation system that operates in the frequency band of 90 to 110 kHz. eLoran is built on internationally standardized Loran-C, and provides a high-power PNT service for use by all modes of transport and in other applications. eLoran is an independent dissimilar complement to GNSS. It allows GNSS users to retain the safety, security and economic benefits of GNSS even when their satellite services are disrupted.
eLoran uses pulsed signals at a center frequency of 100 kHz. The pulses are designed to allow receivers to distinguish between the groundwave and skywave components in the received composite signal. This way, the eLoran signals can be used over very long ranges without fading or uncertainty in the time-of-arrival (TOA) measurement related to skywaves.
Although eLoran is based upon Loran-C, it has key differences:
All transmissions are synchronized to UTC (like GPS)
Time-of-transmission control
The ability to use differential corrections (similar to DGPS)
Receivers use “all-in-view” signals
Includes one or more Loran data channels that provide: Low-rate data messaging, added integrity, differential corrections (dLoran and/or DGPS) and other communications including navigation messages.
An eLoran receiver measures the TOA of the eLoran signal:
TOA = TOR – TOT = PF + SF + ASF + ∆Rx
where TOR is time of reception, TOT is time of transmission, PF is the primary factor (propagation delay through air), SF is the secondary factor (propagation delay over sea), ASF is the additional secondary factor (propagation delay over terrain) and ∆Rx is the delay due to receiver electronics and cables.
The primary and secondary factors are well-defined delays and can be calculated as a function of distance. The additional secondary factor delay is mostly unknown at the time of installation. Fortunately, the ASFs remain very stable over time. Any fine changes in ASF over time may be compensated for by one or more differential eLoran reference station sites providing corrections over the Loran data channel.
When eLoran is used for positioning, a minimum of three eLoran transmitting sites are needed to calculate a two-dimensional position fix and time. Time (phase) and frequency can be derived from a single transmitting site as well. With three sites, timing can be derived while a receiver is in motion. An integrated eLoran/GPS receiver can take advantage of combinations of eLoran and GPS transmissions to develop a PNT solution. Any additional measurements provide a means to improve the solution’s accuracy (using weighted least squares) or to protect the solution’s integrity (by receiver-autonomous integrity monitoring).
To achieve the highest accuracy levels, the user receiver corrects its TOA measurements with the published ASF values for the area and differential eLoran corrections received through the Loran data channel. ASF maps for specific geographic areas are distributed to users in a receiver-independent data format that is currently being standardized by the Radio Technical Committee for Maritime Services’ (RTCM’s) Special Committee (SC) 127 on eLoran. The ASF map data would be published by the service provider responsible for aids to navigation.
As described before, the measured ASF values remain stable over long periods of time. Any small changes in the published ASFs due to changes in propagation path characteristics or transmitter-related delays will be compensated for by differential corrections. For this, a differential eLoran reference station site is deployed within 20 to 30 miles (32 to 48 kilometers) of the area of interest. The reference station compares its measured ASFs against the published values and broadcasts corrections to the users through the Loran data channel. Figure 1 shows the principle of differential eLoran positioning in a maritime environment and is representative of its use in other modalities as well.
Figure 1. Overview of a representative eLoran system.
eLoran meets the application requirements shown in Table 1. While unaided, Loran-C does not meet the requirements for a multi-modal, redundant PNT system, specifically the position accuracy requirement. The U.S. first developed eLoran to reduce the positioning error and to enable the system to meet modal performance requirements.
Table 1. eLoran system performance requirements.
eLoran Applications
We are staunch advocates of GPS and believe it should be fully funded, kept technically advanced, protected, toughened and augmented. When GPS is available and trustworthy, it should be used. However, no technology is failsafe, and prudent users should not rely on a sole source for their PNT needs. GPS has been called “a single point of failure” for much of the U.S. economy and critical infrastructure. Applications and requirements vary widely from wireless network communications of ± 1.5 microseconds, to maritime harbor entrance and approach requirements of ± 20 meters, to phasor measurement unit requirements in the electric power grid of ± 500 nanoseconds.
It is important to recognize the challenge of providing assured PNT while also taking advantage of the efficiencies gained by implementing a common solution across all sectors, industries and users. Point solutions can provide complementary PNT for specific individual or modal needs, and any resilient PNT ecosystem includes multiple levels of redundancy.
Some key application areas in which eLoran can provide complementary PNT are telecommunications, energy, finance and transportation. We believe these will be some of the first sectors to adopt and exploit eLoran as a component of their critical infrastructure protection and possibly as a co-primary PNT solution alongside GPS.
Telecommunications Sector. A March 2014 letter from the Alliance for Telecommunications Industry Solutions (ATIS) to the National Security Telecommunications Advisory Committee contained an attached document, Recommended Updates to Telecom Vulnerability to Loss of GPS Signals Documentation, that outlined three areas of concern that ATIS has identified relating to the exposure of commercial communications systems to a loss of the GPS signal. Included in the documentation was the statement: “With the Loran systems decommissioned, GPS is currently the only technology that can meet synchronization requirements for E911 as there is no other widely available access to UTC time of day in the United States.” eLoran’s Loran data channel provides the UTC time-of-day information that the telecommunications industry seeks, as well as providing complementary timing (phase) and/or frequency solutions that would mitigate ATIS’s concerns about: (1) the size of the area and duration effects of a GPS outage, (2) the effects of spoofing, (3) the inability of oven-controlled crystal oscillators (OCXOs) to maintain phase alignment for 24 hours at 1.5 microseconds, and (4) the phase performance of OCXOs in varying temperature environments.
The European Telecommunications Standards Institute Primary Reference Clock mask is one tool used by the telecommunications industry to determine the quality of timing signals in telecommunication applications. Figure 2 shows that eLoran is able to meet maximum time interval error (a measurement of wander or time stability) requirements, often outperforming GPS. Testing was performed independently in a cooperative effort between the United Kingdom National Physical Laboratory and Chronos Technology Ltd., UrsaNav’s reseller in England.
Figure 2. Maximum time interval error plot of eLoran and GPS.
Energy Sector. At present, GPS is the only time source for phasor measurement unit (PMU) (also known as synchrophasor) and frequency data recorder (FDR) sensors used to collect data that measures the state of an electrical system and manages power quality. PMUs/FDRs are a necessary component of the movement to a smart-grid approach to improve energy efficiency on the electrical grid and in businesses and homes. PMUs and FDRs cease to work if the GPS signal is lost or unstable. In 2013, UrsaNav began working with the University of Tennessee at Knoxville (UTK) to demonstrate the capability of eLoran, alongside GPS, to provide the necessary timing accuracy for UTK’s high-precision FDRs to collect synchrophasor data from the U.S. power grid. The required accuracy of the timing reference source is ± 500 nanoseconds, needed by each device performing synchrophasor measurements.
The laboratory setup in Bedford, Mass., used side-by-side FDRs: one using a GPS receiver and one using an eLoran receiver. Other than replacing the GPS receiver with an eLoran receiver in one of the FDRs, no other changes were made. The eLoran signals were being transmitted from a former U.S. Coast Guard (USCG) Loran Support Unit in Wildwood, N.J., more than 300 miles (483 kilometers) from our Bedford laboratory.
“Raw” eLoran was used for the test, that is, with no differential corrections nor continuous receiver antenna calibration. Figure 3 shows the resultant frequency and phase angle comparisons between GPS and eLoran. Green is eLoran; black is GPS. Frequency comparisons are on the left, top and bottom. Phase angle comparisons are on the right, top and bottom. The bottom left graph is a blow-up of the area encircled in red in the top left graph. The bottom right graph is a blow-up of the area encircled in red in the top right graph. In both cases, eLoran performs on par with GPS.
Figure 3. Frequency data recorder outputs from GPS and eLoran.
Financial Sector. A European Securities and Markets Authority (ESMA) report, dated May 22, 2014, indicates that the majority of trading venues are already coordinated with GPS time, and further states that the deployment of these systems might be costly and technically challenging. ESMA’s view is that each trading venue and market participant should rely on an atomic clock to issue timestamps. An eLoran timing alternative would be less costly, less technically challenging, and, when used in concert with other solutions (such as GPS, atomic clocks or Network Time Protocol / Precision Time Protocol) would also provide trusted time. eLoran would provide absolute time over very wide areas, thereby allowing dispersed markets and users to take advantage of this synchronized time solution. Additionally, eLoran can often provide time indoors, using a magnetic field (H-field) antenna, thereby precluding the permits and expense required for a rooftop antenna installation. ESMA has asked for industry comment on its proposed requirement to synchronize clocks to the microsecond level, and invited industry responses to its preliminary view that business clocks be accurate at least up to the microsecond level.
Transportation Sector – Aviation. PNT use in air traffic management is illustrative. In accord with U.S. Federal Aviation Administration (FAA) planning, a principal surveillance source in the U.S. national air space (NAS) by 2020 will be Automatic Dependent Surveillance-Broadcast (ADS-B), where the required positional accuracy of aircraft relies on GPS position. Moreover, the independent validation and backup of GPS-derived positions relies on accurate time-of-arrival measurements at a network of 650 radio stations in the NAS that currently use GPS-disciplined clocks with accuracy down to 30 nanoseconds. These radio stations are critical infrastructure of the Surveillance and Broadcast Services (SBS) system, which provides ADS-B surveillance to FAA air traffic management (ATM).
The FAA recognizes the need for a backup to surveillance and navigation in the event of local, regional and wide-scale GPS outages, and is examining both near-term and long-term strategies for continuity of operations during those outages. Because of the long lead times for ATM technology insertion, near-term mitigation strategies out to at least 10 years are constrained by existing ATM ground infrastructure and current avionics capabilities. Long-term solutions are not so constrained, and may be based on new signals in space, new ground infrastructure and new avionics capabilities.
Surveillance. Beginning in 2020, ADS-B will be a principal surveillance technology. In recognition of the need for a backup if GPS fails, the FAA is planning to maintain a mix of beacon-interrogation radar and wide-area multilateration (WAM) in the near term. The long-term strategy is still very much in the evolutionary stage.
Navigation. Near-term strategies involve a mix of approaches based upon existing infrastructure and the current capability of avionics. A leading approach, referred to as DME/DME/IRU, uses two-way ranging to multiple Distance Measuring Equipment (DME) facilities augmented by the avionics inertial reference unit (IRU). This approach is practical and applicable more to air carrier aircraft than regional jets or general aviation. Other approaches rely to some extent on the use of very high frequency Omni-Directional Range (VOR) facilities. As with surveillance, the long-term strategy is very much evolutionary.
It is instructive to note that near-term solutions rely on existing radar, DME and VOR infrastructure because it is in place and is compatible with existing avionics. In the long-term view, new technologies with less costly infrastructure are likely to be more cost-effective, especially if they provide benefits beyond ATM applications. eLoran is such a technology.
Transportation Sector – Maritime. There is an increasing awareness in the maritime world that no single system can provide PNT resiliently under all circumstances. At this moment, GPS (with augmentations) is used on most commercial vessels, and in many cases integrated into systems we did not expect would need or use GPS-derived position or time. Even though the introduction of GLONASS, Galileo, BeiDou and other GNSS systems will provide some resilience, the underlying (satellite) technology remains the same, only providing relatively weak signals from space at mostly the same or close-by frequencies for compatibility and inter-operability.
The International Maritime Organization (IMO) recognizes the need for multiple PNT systems on board maritime vessels. The organization developed the e-Navigation concept to increase maritime safety and security via means of electronic navigation, which calls for at least two independent dissimilar sources of positioning and time in a navigation system to make it robust and fail safe. As a follow on, IMO’s Navigation, Communications and Search and Rescue Committee is considering performance standards for multi-system shipborne navigation receivers, which includes placeholders for satellite, augmentation and terrestrial systems.
The most viable terrestrial system providing PNT services that meet IMO’s requirements is eLoran. With three eLoran transmitters in good geometry, eLoran can provide sub-10 meter (95 percent probability level) horizontal positioning accuracy and UTC synchronization within 50 nanoseconds, sufficient to be the co-primary PNT solution with GNSS. The General Lighthouse Authorities of the United Kingdom and Ireland (GLAs) have installed UrsaNav’s differential eLoran reference stations to provide the world’s first initial operational capability (IOC) eLoran system.
Together with Loran transmitters in England, France, Germany, Norway and Denmark, the differential eLoran reference stations provide better than 10-meter positioning accuracy at seven ports and port approaches along the English and Scottish east coast. IOC was achieved at the end of 2014, with full operational capability planned for 2018. Other nations have either begun, or are exploring, similar projects.
Figure 4 shows the accuracy of an eLoran position at the differential reference station on the Humber River in England. Figure 5 shows the position accuracy while on board a vessel transiting outbound on the river from Humber to the North Sea.
Figure 4. Zero-baseline accuracy at Humber reference station.Figure 5. Onboard, en route accuracy on the Humber River.
Current State of eLoran Technology
eLoran technology has been available since the mid-1990s and is still available today. In fact, the state-of-the-art of eLoran continues to advance along with other 21st-century technology. eLoran system technology can be broken down into a few simple components: transmitting site, control and monitor site, differential reference station site and user equipment.
Modern transmitting site equipment consists of a high-power, modular, fully redundant, hot-swappable and software configurable transmitter, and sophisticated timing and control equipment. Standard transmitter configurations are available in power ranges from 125 kilowatts to 1.5 megawatts. The timing and control equipment includes a variety of external timing inputs to a remote time scale, and a local time scale consisting of three ensembled cesium-based primary reference standards. The local time scale is not directly coupled to the remote time scale. Having a robust local time scale while still monitoring many types of external time sources provides a unique ability to provide proof-of-position and proof-of-time. Modern eLoran transmitting site equipment is smaller, lighter, requires less input power, and generates significantly less waste heat than previously used Loran-C equipment.
The core technology at a differential eLoran reference station site consists of three differential eLoran reference station or integrity monitors (RSIMs) configurable as reference station (RS) or integrity monitor (IM) or hot standby (RS or IM). The site includes electric field (E-field) antennas for each of the three RSIMs.
Modern eLoran receivers are really software-defined radios, and are backward compatible with Loran-C and forward compatible, through firmware or software changes. ASF tables are included in the receivers, and can be updated via the Loran data channel. eLoran receivers can be standalone or integrated with GNSS, inertial navigation systems, chip-scale atomic clocks, barometric altimeters, sensors for signals-of-opportunity, and so on. Basically, any technology that can be integrated with GPS can also be integrated with eLoran.
Figure 6 shows a resilient PNT receiver that includes GPS, DGPS, eLoran and a dual-band (100/300 kHz) E-field antenna. The left-hand antenna, shown installed on the P&O Ferries’ Pride of Hull, is the resilient PNT antenna. The right-hand antenna is a standard GPS antenna.
Figure 6. Resilient PNT receiver and dual-band antenna.
World View of eLoran
Nine nations are operating Loran-C or eLoran stations, including Russia and China. It is our understanding that the Republic of Korea, India and the Kingdom of Saudi Arabia are pursuing the installation of eLoran technology or upgrading their Loran-C technology to eLoran.
The modernization and upgrade of the U.S. Loran-C system to eLoran was a congressionally mandated program jointly executed by the FAA and USCG from 1997 to 2009, and funded at $160 million. During this time, eLoran was successfully tested and demonstrated in all modes: aviation, maritime, land-mobile, location-based, and timing and frequency. Further, eLoran has been successfully in operation in the U.K. for several years. Every national and international government, industry and academic report has concluded that GNSS is vulnerable and that eLoran is the best complementary solution to help negate those vulnerabilities.
The U.S. terminated its Loran-C service, and thereby its nascent eLoran program, in 2010. Canada followed suit and terminated its Loran-C service as well. Shortly thereafter, DHS/USCG began dismantling or demolishing the modernized infrastructure. However, in December 2014, Congress directed that DHS/USCG preserve the existing, unused U.S. Loran-C infrastructure, unless the Secretary of Homeland Security certifies it is not needed for a system to complement GPS.
In March 2015, U.S. House of Representatives Resolution (H.R.) 1678, a bill that would require establishment of a strong, difficult-to-disrupt terrestrial system to complement GPS, and to serve as another source of PNT when GPS isn’t available, was referred to the Committee on Armed Services. The bill seeks to amend the language that provided for the establishment and management of GPS in Title 10, the section of law that deals with the armed services. We understand that other members of Congress have expressed interest and will be co-sponsoring the bipartisan bill. H.R. 1678 was introduced by Congressman John Garamendi (Democrat, Calif.) with Congressman Duncan Hunter (Republican, Calif.), Congressman Frank LoBiondo (Republican, N.J.) and Congressman Peter DeFazio (Democrat, Ore.) as the initial co-sponsors. In August, the bill was referred to the Subcommittee on Strategic Forces.
Additionally, in May 2015, the DHS and USCG entered into a cooperative research and development agreement with UrsaNav and Exelis (now part of Harris Corp.) to research, evaluate and document at least one alternative to GPS as a means of providing PNT information in the form of eLoran.
It is our understanding that the U.S. Congress is still considerably concerned about the lack of a complementary PNT solution to safeguard U.S. critical infrastructure and key resource sectors, and to protect our economy in the event of a GPS outage. Congress continues to press the administration for a resolution, in the form of a continental U.S. eLoran system, before our nation is placed at further risk.
Acknowledgments
The authors wish to acknowledge the assistance of Dr. Ron Bruno, Harris Corp., and Dr. Paul Williams and Chris Hargreaves, GLAs.
Manufacturers
UrsaNav provided the eLoran receiver and Symmetricom, now Microsemi, provided the GPS receiver for the timing tests shown in Figure 2.
STEVE BARTLETT is vice president of operations at UrsaNav, Inc., North Billerica, Mass.
GERARD OFFERMANS is senior research scientist at UrsaNav engaged in various R&D project work and product development.
CHARLES SCHUE is co-owner and president of UrsaNav.
FURTHER READING
eLoran
“Can eLoran Deliver Resilient PNT?” by N. Ward, C. Hargreaves, P. Williams and M. Bransby in Proceedings of The Institute of Navigation 2015 Pacific PNT Meeting, Honolulu, Hawaii, April 20–23, 2015, pp. 1051–1054.
“eLoran Initial Operational Capability in the United Kingdom – First Results” by G. Offermans, E. Johannessen, S. Bartlett, C. Schue, A. Grebnev, M. Bransby, P. Williams and C. Hargreaves in Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, Calif., January 26–28, 2015, pp. 27–39.
“Implementing a Wide Area High Accuracy UTC Service via eLoran” by G. Offermans, E. Johannessen and C. Schue in Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting, Boston, Mass., December 2014, pp. 124–133.
2014 Federal Radionavigation Plan (F, DOT-VNTSC-OST-R-15-01, U.S. Department of Defense, Department of Homeland Security and Department of Transportation, Washington, D.C., available from the National Technical Information Service, Springfield, Virginia, 2015.
1990 Federal Radionavigation Plan, DOT-VNTSC-RSPA-90-3 and DOD-4650.4, U.S. Department of Transportation and U.S. Department of Defense, Washington, D.C., available from the National Technical Information Service, Springfield, Virginia, 1990.
The X-47B unmanned combat aircraft receives fuel from an Omega K-707 tanker on April 22 while operating in the Atlantic Test Ranges over the Chesapeake Bay. This test marked the first time an unmanned aircraft refueled in flight. The X-47B is a tailless, jet-powered, blended-wing-body aircraft capable of semi-autonomous operation and aerial refueling.
STOIC Technology to Augment or Substitute for GPS
The Defense Advanced Research Projects Agency (DARPA) selected Rockwell Collins to develop technologies that could serve as a backup to GPS. The research, being conducted as part of DARPA’s Spatial, Temporal and Orientation Information in Contested Environments (STOIC) program, aims to reduce warfighter dependence on GPS for modern military operations.
Rockwell Collins will develop new architectures and techniques to enable communication systems that will support time transfer and positioning between moving platforms independent of GPS, with no impact on primary communications functionality.
“STOIC technology could augment GPS, or it may act as a substitute for GPS in contested environments where GPS is degraded or denied,” said John Borghese, vice president of the Rockwell Collins Advanced Technology Center. “The time-transfer and ranging capabilities we are developing seek to enable distributed platforms to cooperatively locate targets, employ jamming in a surgical fashion, and serve as a backup to GPS for relative navigation.”
Borghese added that the goal of the STOIC program is to develop positioning, navigation and timing (PNT) systems that provide GPS-independent PNT, achieving timing that surpasses GPS levels of performance. The program is comprised of three primary elements that, when integrated, have the potential to provide global PNT independent of GPS, including long-range robust reference signals, ultra-stable tactical clocks, and multifunctional systems that provide PNT information among cooperative users in contested environments.
For this third technical element, Rockwell Collins is tasked with developing multifunction communication system solutions that yield DARPA STOIC objective picosecond-accurate time transfer and enable GPS levels of relative positioning accuracy in contested environments.
“Future applications of STOIC technology could include a variety of precision relative navigation operations, such as autonomous aerial refueling and cooperative navigation and collision avoidance within unmanned aerial vehicle swarms,” Borghese said. “It also could support precise time transfer for networking operations in contested environments.”
ELORAN
Wildwood eLoran Tests Continue
The Wildwood, N.J.,eLoran 100-kHz transmitter continuously broadcast a signal from 0900 (EDT) on Oct. 20 through 1800 on Oct. 22, with plans to transmit further eLoran test signals from 0900 (EST) on Nov. 3 until 1200 on Nov. 6, and again from 0900 on Nov. 9 until1500 on Nov. 13.
The purpose of these tests is to gather data on differential Loran performance in the Boston Metro and D.C. Metro areas. “Besides fixed eLoran receivers at our N. Billerica, Mass., and Leesburg, Va., offices, we also have additional fixed eLoran receivers located at the USNO and at the Harris Corporation offices in Herndon, Va.,” stated UrsaNav. The company also plans to gather temporal and spatial decorrelation data in both Metro areas. Note that these signals are for test purposes only and should not be used for any other purpose.
In May, Exelis, UrsaNav, the Department of Homeland Security’s Science and Technology Directorate (DHS S&T) and the U.S. Coast Guard entered into a cooperative research and development agreement (CRADA) for testing and demonstration at former Loran-C sites, including Wildwood. The team will evaluate eLoran as a potential complementary system to GPS.
The sites are the legacy ground-based radio navigation infrastructure of the decommissioned Loran-C service that could be retained and upgraded to provide eLoran low-frequency service.The broadcasts will provide a usable signal at a range up to 1,000 miles.
INERTIAL
MEMS Perspective on SatNav Gathering
By Alissa M. Fitzgerald
In September, I attended the Institute of Navigation GNSS+ 2015 conference, where I chaired a technical session on commercial
micro-electro-mechanical sensors (MEMS). As the founder of a MEMS product development firm, I was eager to gain perspective from the world’s largest technical meeting and showcase of satnav technology, products and services.
Overall, the navigation community is enthusiastic about integrating MEMS into navigation systems. They like the idea of getting more data from small, relatively low-cost sensors. Recently, U.S. Secretary of Defense Ashton Carter declared his wish that we move to MEMS-based position, navigation and timing (PNT) information.
What navigators want from MEMS depends on who they are.
The “high integrity” navigators — the people whose systems land airplanes or steer self-driving cars — would like MEMS sensors with enough performance to enable accurate inertial navigation without GPS for at least 10 minutes. If a GPS receiver can’t see at least four satellites in the sky, it can’t produce accurate navigation data. High integrity navigators are the original developers of sensor fusion systems; they know that no one sensor is perfect, so they design systems to detect loss of a reliable signal, and then adeptly switch between sensor data streams as needed to maintain accurate navigation information. Ten minutes of GPS-independent inertial navigation buys you enough time to get to higher altitudes, out of a tunnel or around a skyscraper, to a position that improves your view of the sky.
The “consumer” navigators — the people who want you to help them find the nearest Starbucks in downtown San Francisco — would like better low-cost MEMS gyroscopes and magnetometers, specifically with improved stability, to improve pedestrian inertial navigation. Although pedestrians are relatively slow-moving compared to vehicles, a key challenge to their accurate navigation is maintaining inertial position fixes while their smartphones unexpectedly change orientation: waving about in a person’s hand or sliding around in a purse or pants pocket.
It’s clear we MEMS people need to spend more time with these end-users, to first understand how MEMS will integrate with their other sensors and GNSS, and then to derive the essential MEMS sensor specifications for each specific navigation system and use case. The quest for seamless navigation has been and will continue to be an exercise in sensor fusion.
Alissa Fitzgerald is managing member, A.M. Fitzgerald & Associates, a MEMS consulting firm serving diverse industries.
That is, in the People’s Republic of Boulder, Colorado. To those of us who live in Colorado, Boulder is known by this seemingly timeless but absolutely accurate appellation. This stunningly beautiful city located in the foothills of the Rocky Mountains, known as the Flatirons, is where the National Space-Based Positioning, Navigation and Timing Advisory Board (PNTAB), which provides independent advice to the National Executive Committee on Space-Based PNT (EXCOM) from outside the U.S. government, chose to meet in the waning days of October 2015. Ironically, they chose the same week as a Republican presidential candidates debate, which took place at the University of Colorado just a couple of miles away. The PNTAB was also concomitant with the ICG, the Tenth Meeting of the International Committee on GNSS (ICG-10), held Nov. 2-5, 2015. Both the PNTAB and ICG were held at the Boulder NCAR/UCAR facility, University Corporation for Atmospheric Research Center Green Conference facility.
PNTAB
The PNTAB serves a vital purpose. Board memberse advise the highest levels of the U.S. government (USG) concerning all matters relating to PNT. This open-ended charter covers a multitude of sins, and as the new PNTAB Chairman John Stenbit, stated clearly, it is important to focus on the doable, even if it seems difficult, but not to tilt at windmills. I have known and worked with John Stenbit for more than 25 years, especially during his two stints in the Pentagon, and I find him to be extremely knowledgeable and ethical. He is certainly well-spoken and gregarious, but he does not suffer fools, and is known to be resolute, which is a pseudonym for stubborn and hardheaded, but in a good way. I look forward to his chairmanship.
PNTAB Members at 16th Meeting in Boulder. New Chairman John Stenbit is center of last row. (Courtesy of gps.gov)
You can view the PNTAB presentations at the www.gps.gov website. While there, you will note there were more than 25 presentations, and most were excellent. Only a couple required the audience to consume copious amounts of caffeine to remain coherent.
In the end, the PNTAB adopted courses of action (COA) on which to formulate recommendations for the EXCOM. For our purposes, the pertinent COAs centered around two main subject areas: Spectrum protection and eLoran. The spectrum protection issues are fraught with equal parts litigious danger and tedium. Not coincidently, the World Radiocommunication Conference 2015 (WRC-15) kicked off in Geneva, Switzerland, on Nov. 2, just two days after the end of the PNTAB. Several of the PNTAB members attended the closing Saturday night PNTAB dinner and flew from Denver direct to Geneva Sunday morning, just in time for some minor jet lag adjustments, and then attended the opening ceremonies of WRC 2015 in snowy Switzerland.
I have had the dubious privilege of observing several International Telecommunication Union (ITU)-sponsored WRC sessions in the past, and it is certainly a critical spectrum decision-making body. (Seriously, folks, 26 days of talking and wrangling about spectrum? Praise the Lord the Swiss know how to brew strong coffee.) WRC 2015 wraps up on Nov. 27. In this regard, Ann Ciganer, who serves as an official PNTAB representative and the executive director of policy for the GPS Innovation Alliance (GPSIA, formerly the U.S. GPS Industry Council), is my hero. She has been working spectrum issues for more than 20 years. She has the fortitude of FDR and the patience of Job.
Since the spectrum and spectrum-protection issues are still being coldly debated in Geneva, let’s take a look at the PNTAB’s second major topic, eLoran. While eLoran was discussed ad nauseam, there was one definitive standout presentation given by my old friend and colleague Professor David Last. David is Professor Emeritus at the University of Wales (Bangor) and former president of the Royal Institute of Navigation (RIN). As he is wont to do, David held forth, with that wonderful, attention-arresting British public school accent, on eLoran matters before an appreciative audience. David presented his topic with equal parts passion and credibility. You can view his presentation material in its entirety (the PowerPoint slides, anyway) at www.gps.gov, but you will not have the wonderful experience of having him present it personally with all the attendant persuasion, and dry British humor and wit.
eLoran European Style
David immediately makes the point early on in the historical portion of his presentation that the U.S. first committed to Loran-C more than 75 years ago, and as recently as 2010 upgraded a majority of the sites to eLoran status only to have the current administration shut down Loran just after officially assuring the United Kingdom the U.S. would keep Loran up and running. Now the U.S. is in the position of looking for a backup and major terrestrial augmentation to GPS (GNSS) and is once again considering eLoran.
Professor David Last at 16th PNTAB
Professor David Last at the 16th PNTAB meeting. (Photo: Don Jewell)
Professor Last explained the difference between our viewpoints. “I see it from a British perspective, and a European perspective. I watch administrations in other parts of the world grappling with the same decisions the U.S. faces. The U.S., of course, is in a unique position: it is the source of GPS, the world standard in satellite navigation. And over the nearly 40 years since the first satellite was launched, the U.S. has taken the lead in learning to understand the role of GPS, from its military-only origins, through when it was a novelty with its first civil applications, through a period of hubris in which it was to replace every other means of navigation on land, sea and air, to its present role, so deeply embedded in your national life as to form a critical component of national infrastructure. The U.S. was first to recognize the vulnerabilities of GPS, to understand the threat they posed to your nation and to seek ways of mitigating them. That topic came to dominate technical conferences first in the U.S. and now around the world. And it has led to a policy debate of quite exceptional difficulty, one that is shared by all governments.”
The Message
What David did not come right out and say, although I maintain it was implied by his tone of voice and body language, is that this discussion is at times both energized and denigrated by those that refuse to acknowledge GPS or GNSS vulnerabilities and those that would be happy to see it revert to a military-only system — the proverbial ostrich syndrome. David made it clear that GPS vulnerability discussions must take place publicly in the U.S. because they are, in fact, global discussions. “All space-based PNT systems today are similar to GPS in concept and technology, and referred to by most users as GPS,” he said. “Very few bother or even know about Galileo, GLONASS and BeiDou. To them, it is all simply GPS.”
David went on to make his point by describing the ubiquity and pervasiveness of GPS and GNSS. “Now there is no area of transportation, commerce, industry or telecommunications in your country or mine that does not employ satellite navigation.”
Indeed, David described how other GNSS systems came about due to national pride, and yet they had no choice but to mimic GPS both technically and officially, since they must for safety-of-life concerns reside in the same regimes and crowded radio bands.
David stated, “Soon, these new GNSS became invested with immense national pride. Their vast cost had to be justified by claims of technical superiority. In reality, engineers know that their designers had no choice but to make them compatible with GPS, since GPS was decades ahead and the world standard. These new systems also had to squeeze alongside GPS in the narrow radio bands allocated internationally to navigation. Not surprisingly, indeed happily, all our new GNSS turned out to look very like GPS: versions of the same technology — with just a hint of garlic here, a whiff of curry there. This similarity is obvious to engineers and to navigators, though rarely to politicians.”
DOT Volpe GPS Jamming Report
Professor Last referred to the U.S. provider and user communities as groups that, prior to the important 2001 Volpe Report, failed to acknowledge that GPS had any serious vulnerabilities. That report was a watershed event for the future of GPS, and for me as a journalist. Among other jamming incidents around the country, a major jamming occurrence in San Diego harbor affected GPS-dependent systems (mostly those dependent on accurate timing) and users for miles around. It became a wakeup call for GPS and GNSS users globally; I wrote a Defense PNT column on it in this space in 2007.
David put it in perspective. “To understand the perceptions of those governments, wind back the U.S. story to before the Volpe Report on GPS vulnerability with its recommendations that led to your [PNT Advisory] Board’s policy of ‘Protect, Toughen, and Augment’. Despite the growth of jamming and even attacks by one sovereign nation on its neighbor, despite the appearance of low-cost spoofing, there has never been a Volpe Report anywhere outside the United States. The pre-Volpe culture of the denial of vulnerability is alive and well and living in Europe.”
“Thirty-seven years after the launch of the first GPS satellite, there is still little recognition by the world’s governments of how essential resilient position, navigation and timing have become to the critical infrastructure of their nations,” Last said.
After the Volpe Report came an industry report chaired by the Father of GPS, Professor Bradford Parkinson (Col, USAF, Ret), describing eLoran as the only cost-effective method of backup to GPS. The report was published globally, and then the United States completely failed to implement the transition from Loran-C to eLoran. At the time it failed politically, the Loran-C to eLoran conversion was 85 percent complete and only needed a small amount of funding for the future. Luddites within the U.S. OMB (Office of Management and Budget) managed to kill the program just short of completion. Unfortunately, the message to the world of GPS users was the U.S. had categorically rejected eLoran as a complimentary PNT system.
David presented the European point of view: “The Volpe Report, an FAA study, proposed and demonstrated Enhanced Loran (eLoran). GPS-like digital techniques were applied to the obsolete Loran-C low-frequency system. The result were astounding: it met the accuracy, integrity, availability and continuity standards of certain aircraft instrument approaches plus the very demanding port-entrance requirements of shipping, and it delivered precise timing to support telecomms. Brad Parkinson’s high-level study group of industry leaders said this was the only cost-effective GPS substitute for U.S. needs.
“The world outside the U.S. watched the Department of Homeland Security announce eLoran as the U.S. national backup to GPS and then completely fail to implement it! That message, that the U.S. does not need a complementary system and has rejected eLoran, is the current understanding of U.S. policy in many countries.”
Professor Last maintains the same eLoran drama is now being played out in Europe in real time. The UK developed its own eLoran system from the North of Norway to the South of France which, while it only officially achieved initial operational capability on Oct 31, 2014, has in fact been running flawlessly 24/7 for three years.
The message to the world, especially Europe, should be that the eLoran concept proposed by the U.S. FAA (Federal Aviation Administration) really works and is easy to implement. It has been, in fact, implemented and maintained in the UK by a mere handful of personnel.
However, according to David, the European eLoran system may never reach FOC (full operational capability) because currently Western Europe lacks any coordinated plan to respond to the vulnerabilities of GPS and all other PNT systems. Many have yet to embrace or even recognize the Volpe Report.
Indeed, several European countries are planning to shut down their eLoran systems supposedly since that is what we (the U.S.) did and it seems to be working for us.
David explains that “this [proven] system may never reach Full Operational Capability. Western Europe lacks any coordinated plan to respond to the vulnerability of GPS — why, who needs that when Europe has Galileo and EGNOS! The governments who control the Loran stations in Norway and France, observing that mariners no longer want Loran-C, plan to close down the transmissions just nine weeks from now, and demolish the infrastructure. After all, they say, that is what the U.S. did.”
Service Alternative
To paraphrase Winston Churchill, this was indeed not our finest hour. However David maintains there is a realistic commercial alternative: provide eLoran as a service. This is exactly what some in the United Kingdom and Europe are considering. It is a totally viable alternative, but David asserts that what would really help “is a positive signal from the United States.”
Continuing in the same vein, David posits “all is not lost. Responding to the future — indeed, the present — needs of the telecomms and broadcasting industries, and driven from the U.S., there is a commercial plan to take over and operate that European Loran infrastructure and sell its services to government and industrial users. If governments struggle to seize the initiative in this area, let the market — and good old greed — provide the mechanism for realizing the multiple benefits, paying the costs and making a profit. But I believe that this initiative will only succeed in Europe, if there is a positive signal from the U.S. The world listens to signals from the U.S., from the EXCOM, from this board.”
Unique Organizations
Historically, relationships between multi-GNSS systems are confrontational at best; however, David states clearly that Europeans realize the PNTAB and EXCOM are unique and unprecedented around the world. “These official government entities recognize and advocate for resilient PNT that is of major importance to critical infrastructures of the U.S. and other nations as well.”
In actuality, the U.S. has faced up to these vulnerabilities thanks to the PNTAB and EXCOM, two truly unique organizations. Undeniably, there is an incalculable polyphonic argument to be made concerning the vulnerabilities of space-based PNT systems such as GPS and how to mitigate them, but globally beyond the PNTAB and EXCOM, no one is officially having these critical discussions.
In the end, according to Professor Last, over the next nine weeks the immediate future of PNT really comes down to one critical question: “Will global PNT with eLoran be a global system or a nationally unique system?”
David supports his cogent argument for eLoran by giving excellent examples of GPS and multi-GNSS jamming supporting his insightful adage, “Space-based PNT systems live and die together.” They are all subject to the same vulnerabilities.
Wrapping up his refreshingly insightful presentation, Professor Last posed two questions to the PNTAB:
Does the U.S. see a role for eLoran as a complement to resilient GPS?
Does the U.S. recognize and encourage the move to GNSS receivers that take advantage of multiple constellations?
As one PNTAB pundit opined, “The critical issue for the U.S. government is we have to break the mold. The current administration is too often technologically controlled by Luddites and held hostage by low-level bureaucrats within OMB.”
Professor Last appropriately has the last word: “The bottom line for the PNTAB, EXCOM and USG is that the United Kingdom, nee Europe, is asking for support on eLoran.”
Until next time, happy navigating and don’t forget your GPS when you head over the bridge and through the woods to Grandma’s house. Happy Thanksgiving!
According to UrsaNav Inc., the Wildwood, NJ eLoran transmitter will be continuously broadcasting from 0900 (EST) on 21 October 2016 through 1200 (EST) on 22 November 2016. Wildwood will be broadcasting as 8970 Master and Secondary most of the time but occasionally may operate at other rates.
The team will evaluate eLoran as a potential complementary system to GPS. The capabilities and potential utilization methods of eLoran will be explored in depth to identify all strengths, capacities, and potential vulnerabilities of the technology.
The sites are the legacy ground-based radio navigation infrastructure of the decommissioned Loran-C service that could be retained and upgraded to provide eLoran low frequency service.
Under the CRADA, Exelis will use the former Loran-C assets to put eLoran signals in space for research, test and demonstration of the ability of eLoran to meet precise positioning, navigation and timing (PNT) requirements of government and privately-owned critical infrastructure.
The first station Exelis is broadcasting from is in Wildwood, N.J. The broadcasts will provide a usable signal at a range up to 1,000 miles.
In this exclusive interview, Admiral Thad Allen, former commandant of the U.S. Coast Guard, discusses PNT alternatives to GPS for navigation, including eLoran and the activation June 19 of a signal on an eLoran tower in preparation for a timing signal trial.
Art Kalinksi interviewed Adm. Allen during GEOINT 2015, held June 22-25 in Washington, D.C. Kalinski is the monthly columnist for Geointelligence Insider, part of the Geospatial Solutions website, a sister site to GPS World magazine.
Allan is an executive vice president at Booz Allen Hamilton, and a leader in the firm’s Departments of Justice and Homeland Security business in the civil market. In 2010, President Obama selected him to serve as the National Incident Commander for the unified response to the Deepwater Horizon oil spill in the Gulf of Mexico.
