Maritime Autonomy and the Fragility of GPS

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The Global Positioning System, or GPS, synchronizes the movements of the world so seamlessly that most of us never think about it. Beyond guiding traffic, GPS facilitates a variety of transactions and regulates systems, for example, the timestamps on financial transactions. Scientists are even using GPS to analyze atmospheric anomalies and changes on Earth's surface, like volcanic eruptions. This deep integration is intentional; GPS is an exceptionally successful technology due to its low barrier to entry, proven performance, and global adoption. 

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Developed in the 1970s as a military tool, GPS took a pivotal turn in 1983 after Korean Airlines Flight 007 mistakenly entered restricted Soviet airspace and was shot down. In response, the U.S. government opened GPS access to civilians globally. Since then, its availability and growing precision have made GPS the backbone of global navigation, now relied upon by an estimated 3 billion people worldwide.

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This reliance also holds true at sea, where GPS is the cornerstone of all activity. The sea is a busy place with over 100,000 commercial vessels active at any time. With thousands more military vessels in the equation, clarity and coordination become critical.

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Although the ocean covers more than 70% of the Earth's surface, most maritime traffic is concentrated in narrow corridors. The Strait of Malacca alone sees over 94,000 ships annually. While the image of a lone ship on the horizon is accurate, it's only part of the picture. In reality, commercial vessels crowd busy lanes, submarines weave through complex underwater terrain, and naval ships patrol contested borders.

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Coordinating this traffic depends on a shared understanding of Positioning, Navigation, and Timing (PNT), made possible by GPS. It enables ships to hold positions within centimeters, lets cargo find the fastest route to port, and synchronizes maritime systems from radar to rescue. The Automatic Identification System (AIS), mandated by the International Maritime Organization (IMO) for most vessels, transmits each ship's position, identity, and course to nearby vessels, and also relies on GPS for accuracy.

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Together, GPS and AIS create a real-time picture of the maritime domain—a system of mutual visibility and coordination spanning thousands of miles. It works so well that nearly every element of modern maritime operations, from navigation and autonomy to trade and enforcement, is built upon it.

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And that's the problem.

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When a technology is this foundational, it becomes something else entirely: a single point of failure.

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And GPS is not invulnerable. Techniques such as spoofing and jamming are now regularly deployed in the Baltic, Eastern Mediterranean, Gulf, and elsewhere. AIS spoofing incidents increased 400% between October 2022 and April 2023. These incidents often involve the deliberate falsification of AIS messages, which can mislead maritime authorities and other vessels. These techniques create a denied environment where the shared language of GPS is lost, forcing operators to navigate with limited visibility.

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The ability to deny, degrade, or dominate positioning data has become a tool of coercion and control. Transparency and positioning fidelity underpin the rules of engagement at sea, and when eroded, fracture the logic of deterrence. GPS has enabled a remarkable era of coordination and autonomy, but its very ubiquity has made it a brittle foundation. As adversaries learn to manipulate or obscure that signal, the maritime domain must evolve. New technologies are emerging to reduce dependence on any single input, but true resilience is still taking shape. How systems, states, and non-state actors respond to this technological shift will define the future of encounters at sea.

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GPS at the core of all systems

Examining the systems that rely on GPS reveals its significance at sea. Take, for example, a naval vessel operating in contested waters. It may be supported by unmanned aerial vehicles (UAVs), uncrewed surface vehicles (USVs), and underwater unmanned vehicles (UUVs), all working together to enhance situational awareness. These systems collect and transmit data, and some can independently verify positioning information. Yet despite their sophistication, the vessel's core decision-making still hinges on accurate location data, typically provided by GPS.

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On the bridge, the crew monitors an Electronic Chart Display and Information System (ECDIS), which uses real-time GPS data to overlay the vessel's position onto digital nautical charts. This system highlights critical features such as traffic lanes, shoals, and separation zones, forming the crew's primary navigational reference. Alongside it, AIS continuously transmits the vessel's identity, course, and speed to nearby ships and coastal authorities. Both ECDIS and AIS depend on GPS for position and timing. It is central not only to collision avoidance but to maritime domain awareness across commercial and security operations.

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But in contested or degraded signal environments, that trust breaks down—because if the GPS data is spoofed or disrupted, both navigation and identification systems are compromised. Vessels may appear in false locations, broadcast incorrect identities, or fail to appear at all. The result is not just navigational uncertainty, but a breakdown in the shared situational awareness that modern maritime operations depend on. In such cases, the Inertial Navigation System (INS) provides a fallback—calculating position based on motion and time—but it is typically used to verify, not replace, satellite-based data.

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These and other technologies work together to form the sensor fusion stack, a layered mesh that mitigates risk. But fusion still centers on GPS. Most systems use it as a source of truth, anchoring both location and the interpretation of all other sensor data. When GPS is lost or manipulated, secondary systems continue to function but lack a reliable reference point. Their outputs diverge over time, increasing uncertainty. And when the false data is internally consistent, it can delay detection, leading systems and operators to trust incorrect information. Worse than creating noise, a believable false signal creates confident misdirection, fooling systems and operators for any given time before the misdirection is discovered.

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Reinforcing the Signal

Both public and private actors are working to develop multi-modal PNT alternatives to GPS. In most cases, the objective is not to eliminate GPS but to ensure continuity and integrity of navigation through layered, interoperable technologies that can function under contested or degraded conditions. The following technologies represent some of the most promising paths toward that objective.

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eLORAN

eLORAN, a modernization of the Cold War-era LORAN-C system, is among the most viable near-term alternatives to GPS. It uses low-frequency terrestrial radio signals from ground stations to deliver regional navigation data. 

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Its signals penetrate urban and maritime environments more effectively and can operate independently of satellite-based systems. Its low frequency makes it resilient to spoofing and a viable option in denied environments. 

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But most modern tech is not compatible with eLORAN, and the vast majority of towers were decommissioned due to the rise of GPS. However, pilot programs in the U.S., South Korea, and the U.K. suggest increasing interest in reviving the system. 

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LEO Constellations

Low Earth Orbit (LEO) satellites orbit between 500 and 2,000 kilometers above the Earth's surface. Their proximity affords faster signal refresh rates, stronger signal strength, and lower latency than medium Earth orbit GPS counterparts. Their speed makes their signals harder to spoof consistently, and their diversity adds a layer of resilience.

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Organizations and private actors are competing to develop the next generation of satellite infrastructure and claim ownership of this space. Iridium's Satellite Time and Location (STL) service is now operational, and Xona plans to launch Pulsar with services available in 2027. The European Space Agency is actively testing optimal frequency bands for LEO-PNT solutions.

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LEO constellations seem inevitable and viable, but private actors and broadband applications, like Starlink, complicate the space.

Quantum Sensors

Quantum sensors offer a radical departure from traditional satellite-based navigation. Accelerometers and quantum gyroscopes measure changes in position and rotation with extraordinary precision. Combined with atomic clock stabilization, quantum sensors can provide autonomous PNT capabilities for submarines, undersea vehicles, and stealth platforms operating far from satellite coverage. These systems enable navigation that is drift-free and signal-independent, even in fully denied or subterranean environments. 

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The U.S. Naval Research Laboratory, Boeing, and Q-CTRL are among the organizations developing and testing quantum navigation systems, but challenges remain. Quantum sensors are still expensive, require significant onboard processing power, and are not yet miniaturized for widespread deployment. Still, actors are actively investing in the space, and we can expect further developments.

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Celestial Navigation

Celestial navigation combines the centuries-old method of navigating by the stars with modern AI capabilities to create an altogether GPS-agnostic approach to navigation. Modern AI systems can perform rapid stellar fixes to calculate a vessel's position based on the relative positions of known celestial bodies.

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These systems leverage machine vision, optical sensors, and ephemeris data to recognize stars, planets, or even distant quasars. The process, known as optical navigation, is entirely unjammable, since no radio signals are transmitted or received. Tests have been promising. A test at the University of South Australia resulted in a fixed-wing drone achieving positioning accuracy within a four-kilometer radius.

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Promising, but the application is still niche, and the technology is primarily in research. For celestial navigation to transition into reality, it will require significant investment from stakeholders.

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Towards resilience

GPS has delivered extraordinary utility, powering not only global trade, travel, and timing but the very logic of modern maritime coordination. However, its success has also made GPS a single point of failure, with an increasing risk. As adversaries grow increasingly adept at denying or deceiving positioning signals, that technical risk becomes a strategic liability.

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While emerging technologies offer promise, the readiness gap remains substantial. Few alternatives are fully interoperable, field-tested, or deployed at scale. Most remain siloed in research environments, pilot programs, or defense prototypes. The sensor fusion stacks in use today can mitigate spoofing and drift, but they still revolve around GPS as the anchor of trust.

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This gap between vulnerability and resilience is not just technical—it's institutional. No clear operational standards exist for integrating alternative PNT sources. Civilian and defense infrastructures remain dependent on legacy systems. And investments in GPS alternatives lag behind the pace of threat evolution.

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To close this gap, states and their industrial partners must take clear, coordinated action across several critical fronts:

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• Mandate multi-source PNT architectures across maritime, defense, and critical infrastructure platforms. Redundancy must be designed into the system from the outset, rather than being added as an afterthought. This involves integrating terrestrial signals, such as eLORAN, space-based LEO constellations, and onboard quantum or celestial systems, into a unified operational standard.
• Accelerate fielding of GPS-resilient technologies. Procurement cycles should prioritize systems validated in denied or degraded environments, and acquisition strategies must reflect the urgency of contested signal environments.
• Fund the integration layer, not just the sensors. The future of navigation lies in the logic that governs inputs—AI-driven cross-validation, probabilistic fusion models, and real-time signal arbitration. Without investment in this cognitive layer, alternative PNT sources remain isolated capabilities rather than components of a resilient system.
• Establish shared norms and operational standards for resilient navigation. Interoperability among allied and commercial systems is essential. Common protocols for verifying, sharing, and prioritizing multi-source PNT data will be as important as the hardware itself in shaping a credible deterrent and a stable maritime order.

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The future of ocean sovereignty lies in signal sovereignty. This is not a niche concern—it is a foundational requirement for operational readiness, maritime security, and technological leadership. Nations that invest now in resilient navigation will be best positioned to operate in contested environments, enforce maritime rules, and maintain a strategic advantage.

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