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The Suez Canal is one of the world’s most strategically important maritime choke points. Approximately 12% of global trade passes through a waterway that, in some locations, narrows to only a few hundred meters across.

At the same time, the region has experienced repeated and well-documented Global Navigation Satellite System (GNSS) disruption events.

Examples include:

• In 2019, the U.S. Maritime Administration issued warnings regarding significant GPS interference affecting vessels near Port Said and the Suez Canal approaches.
• In April 2024, more than 100 vessels simultaneously reported false positions due to spoofing activity.
• Since 2023, maritime and aviation operators across the Eastern Mediterranean and Egypt have reported persistent GNSS degradation and interference.

Importantly, these events are not necessarily criminal in origin. In many cases, they are the byproduct of state-level electronic warfare activity associated with air defense operations, counter-unmanned aircraft system systems (UAS), and intelligence, surveillance, and reconnaissance (ISR)-denial capabilities.

The result is an increasingly contested navigation environment where positioning data can be degraded, denied, or — perhaps most dangerously — silently corrupted.

The operational implications for the Suez Canal are significant.

The Canal is a highly constrained transit environment characterized by:

• dense vessel traffic,
• limited maneuvering space,
• strict traffic management,
• and extremely low tolerance for navigation error.

In this context, even small positioning inaccuracies can become operationally consequential.

Between 2013 and 2016, UrsaNav worked with the General Lighthouse Authorities of the UK and Ireland (GLAs) to implement and trial differential Loran capabilities at seven locations along the eastern coasts of England and Scotland.

Differential Loran is a critical component of modern eLoran systems supporting harbor entrance and approach (HEA) operations.

Published GLA trial results documented measured horizontal positioning accuracy of approximately seven meters (95%), well within the International Maritime Organization’s 10-meter HEA requirement. These performance levels were maintained at distances of at least 40 kilometers from the differential reference stations.

The implications for maritime choke points such as the Suez Canal are substantial.

Historically, Loran systems have already been successfully deployed in similar environments. In the early 1980s, Loran service was implemented along the Suez Canal and became an integral component of the Canal’s Vessel Traffic Management System (VTMS) before eventually being displaced by GPS adoption.

Modern eLoran could once again provide a terrestrial layer of resilient, co-primary positioning, navigation, and timing (PNT) architecture capable of maintaining continuity of operations during GNSS disruption events.

This concept is not new.

In 2003, the Royal Institute of Navigation’s Journal of Navigation proposed the Suez Canal Integrated Navigation System (SCINS), envisioning a resilient navigation architecture combining terrestrial and satellite-based capabilities.

A modernized implementation could provide:

• assured positioning during GNSS disruption,
• increased operational resilience,
• improved vessel traffic continuity,
• and, potentially, greater flexibility than today’s convoy-based transit model.

The broader implications extend well beyond the Suez Canal.

Resilient terrestrial PNT capabilities would strengthen navigation assurance across:

• major shipping lanes,
• ports and harbors,
• offshore energy operations,
• narrow straits,
• and heavily congested maritime corridors such as the English Channel.

The maritime industry has already seen how deeply bridge systems depend on GNSS availability.

During GPS jamming trials conducted by the GLAs in 2008 and 2009 aboard the NLV Pole Star and THV Galatea, disruption effects were observed across numerous shipboard systems, including:

• automatic identification system (AIS),
• radar,
• gyrocompass systems,
• electronic chart display and information system (ECDIS),
• digital selective calling (DSC),
• voyage data recorders,
• and dynamic positioning systems.

Modern maritime trade has been built on the assumption that GNSS is continuously available and inherently trustworthy.

That assumption no longer holds — particularly in contested regions and strategic maritime corridors.

As Captains Matt Shirley and Dana A. Goward recently noted in When GPS Fails: Why Maritime Needs Resilient Navigation, published by Hellenic Shipping News Worldwide, GNSS disruption is no longer hypothetical. It is an operational reality affecting shipping activity in regions that include the Persian Gulf, Baltic Sea, and Eastern Mediterranean.

Resilient PNT is therefore no longer optional.

Multi-constellation GNSS improves capability, but it does not eliminate systemic vulnerability. Interference awareness must become operational rather than theoretical, and independent PNT sources must be integrated into both shipboard bridge systems and shore-based traffic management architectures.

Because when GNSS degrades, the industry does not simply lose precision.

It loses trust, operational continuity, efficiency, and, ultimately, money.

And those costs are carried by shipowners, operators, insurers, ports, supply chains, and consumers worldwide.

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From the beginning, tactical Loran systems reflected a balance between coverage, portability, infrastructure, and mission requirements.

The Evolution from Fixed Systems to T³

Early Loran systems were large, fixed installations by necessity, designed to meet demanding technical performance requirements. Advances in transmitter, antenna, and control technologies gradually enabled smaller, more portable solutions with advantages for specific operational needs. These developments led to modern tactical, temporary, and transportable (T³) systems.

Today, both fixed and deployable systems remain relevant because they solve different problems and can perform well with different inputs.

Several nations are evaluating a mixed approach: fixed systems for broad regional coverage, deployable systems for targeted operational needs, and combinations of both where mission requirements demand flexibility.

Experience Across the T³ Spectrum

Our personnel have worked with several T³ Loran and eLoran systems over the years.

We supported, and later replaced, the Air Transportable Loran System (ATLS) at the former Loran-C transmission site in Lampedusa, Italy. We worked with the U.S. Air Force tactical Loran-D system, which included configurations that used tri-tethered aerostats to elevate transmit antennas. We served as a subcontractor on the triple-CONEX box solution currently deployed at the Anthorn, UK eLoran site.

We also designed, developed, deployed, and operationally tested a prototype T³ solution for the U.S. Army, and contributed to two “mini-chain” Loran-C implementations: one along the Saint Lawrence Seaway and another supporting the Suez Canal region.

Our current T³ transmission system combines a transportable transmitter, eLoran signal generation, monitoring, and control capability with a purpose-built transmit antenna. The system has been deployed and redeployed in Canada, multiple U.S. locations, and Germany.

A Practical Example: Fixed and T³ Working Together

A hybrid architecture can provide compelling operational benefits.

Consider the Middle East. The Kingdom of Saudi Arabia operates eLoran transmission sites at Afif, Salwa, Ash Shaykh Humayd, and Al Muwassam. Complementing this fixed infrastructure with representative T³ deployments in the Red Sea and Gulf of Aden region could extend high-quality positioning coverage through the Gulf of Aden, across the Bab el-Mandeb Strait, and into the Red Sea.

Deployable sites in locations such as Djibouti, Yemen, and Somalia could provide positioning accuracies better than 10 meters in key operational areas. At the same time, users could benefit from reception of high-power signals from fixed Saudi sites, particularly Al Muwassam and potentially more distant transmitters such as Salwa and Afif.

This example illustrates an important point: Fixed and deployable systems are not competing solutions. In many environments, they are complementary capabilities.

Build the Right eLoran Architecture for Your Mission

There is no universal answer to PNT resilience. The optimal architecture depends on geography, operational objectives, coverage requirements, deployment timelines, infrastructure constraints, and long-term sustainability considerations.

Whether your use case calls for fixed infrastructure, a deployable T³ capability, or a hybrid approach, selecting the right technology strategy matters.

UrsaNav has experience across the full spectrum of Loran and eLoran implementations, ranging from legacy tactical systems to modern T³ solutions. If you are assessing resilient PNT options, consult with our team to identify the technology and architecture best aligned with your operational requirements. Contact us at Info@UrsaNav.com.

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Discussions surrounding alternative, complementary, and backup Positioning, Navigation, and Timing (PNT) systems often begin with a single assumption: global coverage is the primary objective.

For critical national infrastructure, that assumption deserves reconsideration.

For energy grids, telecommunications, transportation systems, emergency services, financial networks, and defense operations, sovereign coverage may be equally — if not more — important than global reach. National resilience begins with trusted infrastructure under national control.

At the same time, interference against Global Navigation Satellite Systems (GNSS) continues to increase worldwide. Jamming, spoofing, and meaconing events are now routinely observed in contested regions and near strategic infrastructure.

Importantly, space-based alternatives are not immune to disruption. Low Earth Orbit (LEO) systems remain vulnerable to interference affecting both uplink and downlink communications. Recent disruptions to commercial satellite services in the Middle East have demonstrated the operational realities of this threat environment.

Historically, terrestrial PNT systems played a foundational role in resilient navigation and timing.

While the Transit (NAVSAT) system introduced accurate satellite-based global navigation capability, it did not initially provide continuous real-time positioning and was primarily intended for military applications. Earlier terrestrial systems such as Decca Navigator and Loran provided highly effective regional navigation services, while Omega later became the first globally available continuous terrestrial PNT system accessible to civilian users.

Notably, all major PNT architectures — including modern GNSS constellations — rely on extensive ground infrastructure and international coordination to function effectively.

This highlights several strategic realities:
• There is no “global” PNT capability without terrestrial infrastructure.
• There is no globally available service without international cooperation.
• There is no space-based PNT capability without communications dependencies.

A sovereign terrestrial PNT architecture directly addresses these dependencies.

In a sovereign eLoran deployment:
• the ground segment remains entirely within national borders,
• communications infrastructure is nationally owned and controlled,
• reliance on foreign or commercial space-based assets is minimized,
• and the system can be hardened against both physical and cyber threats.

Spectrum coordination may still require international cooperation, but operational control remains national.

Equally important, terrestrial systems avoid many of the cost, launch, sustainment, and lifecycle complexities associated with space-based architectures.

When GNSS signals are available and trustworthy, they should remain at the forefront of modern PNT solutions. However, resilience requires trusted alternatives when those signals become unavailable, degraded, or compromised.

This is where eLoran becomes strategically significant.

As part of a layered “system of systems” architecture, eLoran provides the resilient terrestrial foundation for sovereign PNT capability — supporting national resilience, infrastructure continuity, and operational assurance in contested environments.

In an era of increasing dependence on precise timing and positioning, sovereign terrestrial PNT is no longer simply a backup capability.

It is strategic infrastructure.

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Erik will present in Session S3.3 (eLoran) on Wednesday, 29 April.

If you are attending and interested in the future of secure and resilient positioning, navigation, and timing (PNT) technologies, we invite you to join his session or reach out to schedule a meeting.

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If you are attending and would like to schedule a meeting with Chuck, feel free to contact him through LinkedIn.

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UrsaNav® Chief Business Development Officer Erik Johannessen will be there connecting with customers, industry peers, and new partners across the positioning, navigation, and timing (PNT) community.

If you are curious about enhanced Long-Range Navigation (eLoran) and the work we do, message us through LinkedIn to schedule a time with Erik and learn more about the resilient PNT solutions we deliver worldwide.

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Note that NIST did not mention that (e)Loran can operate in a Two-Way Low-Frequency Time Transfer (TWLFTT) mode. TWLFTT can provide a terrestrial, layered time-transfer network wherein time is transferred between any two (e)Loran transmission sites that can receive each other’s signals. UrsaNav tested this theory as part of our first CRADA with the USCG Research and Development Center, which started in 2012. Note that TWLFTT is completely “sky-free”.

Note also that there has been a lot of “hay” made from (e)Loran competitors that there are no miniature LF receivers. This is simply not true. Even at the 60kHz signal that WWV uses (40 kHz lower than Loran), timing receivers are easily chip-scale. See page 148 of NIST 2187. Further miniaturization is not an issue of science or technology; it’s simply a matter or market demand.

There were a couple of statements in NIST 2187 that we found extremely troubling, and which we are bringing to the attention of the authors:

“Beginning in the early 1990s, the Loran-C stations were synchronized with GPSDCs, with the Hewlett-Packard GPS Smart Clock used as the primary reference at many station sites after about 1997. This direct synchronization to GPS did, of course, invalidate the premise that Loran-C, and the proposed eLoran system that followed, were GNSS independent, which made them unsuitable as a GPS backup system.”

GPS was not fully operational until 1995. GPSDCs were NOT used operationally at any North American Loran-C stations, and at no other international Loran-C stations of which we are aware before 1999. The USCG did test various methods of distributing UTC to the Loran stations, including TWSTT and GPS Common Mode, starting around 1993, but these tests were never moved into full operation. The USCG started installing Time-of-Transmission Monitors (TTM) at the transmission sites in the late 1990’s and early 2000’s. The initial installations were at only at few test sites, and then only at the Master transmission stations. It was not until later that the TTMs were installed at all Loran-C stations in North America as part of the redesign of the Frequency Standard Rack. The TTM included a GPS disciplined quartz oscillator, but the system was not directly connected to the station timing generation equipment, and was not used to control the transmissions. The TTM only reported the difference between the transmission times and UTC, as referenced against a local, survey-grade GPS Timing Receiver. It is not correct to suggest that these GPS Smart Clocks were used as “the primary reference”; they were an external reference against which the three Primary Reference Standards at the transmission sites were compared, originally manually and then via software. The primary reference for generating the timing of Loran transmissions has always been the three rubidium or cesium standards.

Starting in 2003, the first version of the Timing and Frequency Equipment (TFE) was installed at North American Loran-C stations as part of the Loran Modernization and Upgrade Program. Although not intended, this first version did not provide sufficient separation between GPS and the transmitted Loran signal. The software allowed the transmission sites to be steered without bound using GPS as an input. This software error was subsequently corrected in later versions of the TFE.

A well-designed eLoran system would have no direct connection to any external timing source, whether it be GNSS, TWTT, microwave, or fiber. All of these sources might be monitored, but there would be an air-gap between them and the triple ensemble of Primary Reference Standards. The system would be purpose-built to not allow an external timing reference to be able to “walk” the station’s timing away from UTC, and the system could operate for a defined period without an external reference of any sort. The fact that a modern eLoran transmission site might use GPS or another GNSS as external references is not the same as saying they are directly synchronized to them.

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LOCATA AND URSANAV ANNOUNCE TECHNOLOGY PARTNERSHIP FOR RESILIENT PNT

Russia’s recent threat that it could blow up all the GPS satellites with its new anti-satellite technology (ASAT) should come as no shock to those following space-related events. In the past, China shot down one of its own Low Earth Orbit Satellites (LEOS) using a medium-range ballistic missile, and the United States used a modified antiballistic missile to shoot down one of its own spy satellites. Blowing up satellites, solar flares, ever increasing hazards from “space junk”, and thousands of new satellites in the launch queue all make space a congested and increasingly dangerous place.

Locata Corporation and Ursa Navigation Solutions, Inc. (“UrsaNav”) today announced a Technology Partnership specifically aimed at providing resilient PNT (Positioning, Navigation, and Timing) solutions to national governmental and commercial interests globally. Combining Locata’s high-accuracy local-area and UrsaNav’s very wide-area PNT produces a potent solution which lessens any nations’ dependency on easily disrupted and increasingly vulnerable space- based signals.

Read Full Press Release: https://www.ursanav.com/wp-content/uploads/Locata-UrsaNav-Partnership-Press-Release-07DEC2021.pdf

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