GNSS Jamming, Spoofing and A-PNT: Separating Maritime Navigation Facts from Fiction

For decades, maritime operations have relied on GNSS technologies such as GPS as the foundation of navigation. From ECDIS and AIS to fleet tracking, dynamic positioning, voyage optimization and security monitoring, almost every aspect of a vessel’s operational picture depends on accurate positioning, navigation and timing data. As a result, many operators have come to view GPS as a permanent, dependable utility that simply works in the background.

However, the maritime operating environment is changing. According to the 2026 Royal Institute of Navigation (RIN) Maritime GNSS Interference Report, 75% of mariners surveyed believe GNSS interference is increasing in frequency and severity. The report concluded that jamming, spoofing and other forms of interference now represent a significant safety and security concern for global shipping.

At the same time, the maritime industry is becoming more dependent on positioning data than ever before. Navigation, compliance, fleet management, security operations and digital reporting systems all rely on trusted location information. When GNSS integrity is compromised, the consequences extend far beyond the bridge and affect navigation, AIS, communications, timing systems and fleet monitoring simultaneously.

This growing challenge is driving interest in Assured Positioning, Navigation and Timing (A-PNT) technologies, but it is also creating confusion. What exactly is A-PNT? How does it work? Can it replace GPS? Is it accurate enough? And why are more maritime operators looking at solutions such as RockFLEET Assured powered by Iridium PNT?

To answer those questions, let’s separate fact from fiction.

Myth 3: The bridge crew would know immediately if GPS was being attacked

Many people assume that any interference with GPS would be obvious. But in reality, the nature of the attack determines how visible it is.

Jamming is often relatively straightforward to identify because GNSS/GPS receivers lose access to the signals they require. Position fixes may be lost, alarms may activate and navigational systems may indicate degraded performance, making operators generally aware that something has happened.

Spoofing, on the other hand, is far more subtle. Because the GNSS/GPS receiver continues to calculate a position, there may be no immediate indication that the data being presented is false. In some cases, a spoofed position may drift very gradually from reality, making it even harder to detect through normal operational procedures. This distinction is one of the key reasons why maritime organizations are increasingly looking beyond traditional GNSS-only navigation architectures.

Myth 5: A-PNT is intended to replace existing navigation systems

Modern maritime navigation has always been based on cross-checking information from multiple sources. Experienced mariners do not rely on a single radar, a single sensor or a single chart reference. Instead, navigational confidence comes from verification.

The same principle applies to positioning.

Radar, visual observations, ECDIS, AIS, gyrocompasses and GNSS all contribute to situational awareness, and A-PNT fits naturally within this layered approach. The ability to compare independent sources of positioning information gives operators greater confidence when data aligns and provides an early warning when it does not.

Rather than replacing existing systems, A-PNT provides an independent reference that allows bridge crews and shore-side teams to validate critical navigation data to confirm whether it can be trusted, identify potential GNSS anomalies and make more informed decisions.

Myth 7: Accuracy is all that matters

When evaluating positioning technologies, many operators instinctively focus on accuracy; while accuracy remains important, it’s only one part of the equation.

In a spoofing scenario, a GNSS receiver may report exceptional accuracy while still providing a completely incorrect position. A-PNT shifts the focus from accuracy alone to integrity and trustworthiness. In GNSS and GPS denied environments, understanding whether a position can be relied upon becomes just as important as knowing how many meters of accuracy it claims to provide. For maritime decision makers, trusted positioning often matters more than marginal differences in precision.

RockFLEET Assured combines authenticated positioning with practical operational accuracy. Performance improves when multiple Iridium satellites are overhead and, because the Iridium constellation naturally clusters towards the polar regions, positioning performance becomes even stronger at higher latitudes. For example, typical median positioning accuracy is approximately 25 meters in Norway (69°N) and around 42 meters in the Red Sea (19°N), providing a reliable independent position reference across global shipping routes.

For large commercial vessels, tankers, bulk carriers and container ships measuring well over 100 meters in length, this level of accuracy is highly operationally valuable. Whether validating a vessel’s reported position, supporting fleet monitoring or identifying GNSS anomalies, a trusted position accurate to within a few tens of meters is far more valuable than a highly accurate GPS position that has been spoofed or disappears altogether due to jamming.

Myth 9: GNSS only affects navigation

The term GNSS often leads people to think exclusively about chart displays and route planning, but in practice, positioning, navigation and timing (PNT) data underpins a much broader range of maritime operations.

Accurate position information influences AIS transmissions, fleet monitoring, voyage reporting, security operations, geofencing, compliance requirements and incident investigations. Timing information also plays a critical role in synchronising systems and maintaining operational consistency.

When GNSS integrity is compromised, the effects extend far beyond the bridge. An inaccurate position can quickly become an inaccurate operational picture across the entire organization.

Building Confidence in a Contested Navigation Environment

While the maritime industry’s utilization of GNSS has delivered enormous operational benefits, it has also introduced new vulnerabilities. Jamming and spoofing are not concerns discussed only in military circles, but are real world incidents across the world’s busiest shipping lanes.

The focus is shifting from simply obtaining a position to ensuring that the position can be trusted. That’s why A-PNT solutions such as RockFLEET Assured, powered by Iridium PNT, play an increasingly important role. RockFLEET Assured provides maritime operators with something increasingly valuable in today’s contested navigation environment: an independent, authenticated and resilient source of positioning information.

In a world where navigation systems can be deceived, resilience comes not from having more data but from having greater confidence in the data you use. The future of maritime navigation will therefore be defined not solely by accuracy, but by assurance, integrity and trust.

GNSS Vulnerabilities at Sea, and the Rise of Assured PNT Resilience

From commercial shipping lanes and port approaches to offshore energy platforms and autonomous vessel trials, trusted Positioning, Navigation, and Timing (PNT) underpins safety, efficiency, and regulatory compliance. Every decision from route optimization to collision avoidance relies on accurate and continuous positioning data, and for decades, Global Navigation Satellite Systems (GNSS), including GPS, GLONASS, Galileo, and BeiDou, have served as the backbone of maritime PNT.

These systems provide global coverage, high accuracy under ideal conditions, and enable reliable tracking of maritime operations at scale. However, there is a well documented rise in maritime GNSS/GPS disruption, including deliberate jamming and increasingly sophisticated spoofing attacks. The reality is, conventional GPS-based solutions were never designed for today’s contested, congested, and adversarial signal environment, with traditional GNSS/GPS signals increasingly exposed in ways that were not anticipated when they were first deployed.

Traditional mitigation and defence strategies attempt to address these risks but often fall short; as a result, existing GPS-based solutions are reactive rather than resilient. For instance, they can identify when something is wrong, but are not inherently designed to guarantee reliable, trusted positioning when GNSS is compromised. The result is operational risk that extends beyond safety and security, and to efficiency, insurance exposure, regulatory compliance, and ultimately, trust in maritime systems. This is where Assured PNT enters the conversation and where Iridium PNT positions itself as a fundamentally different approach.

This blog explores how existing maritime GPS solutions are no longer equipped for today’s evolving threat landscape, and how Iridium PNT enables reliable, trusted, and continuous maritime operations in compromised GNSS/GPS environments.

The Cracks in Conventional Maritime GPS

1. Anti-Jamming GNSS Systems

Anti-jamming GNSS systems were developed to suppress interference using directional antennas and filtering techniques. These methods work by attempting to block out noise and prioritise signals that appear clean. However, the threat landscape has evolved beyond simple interference. Modern threats don’t just jam, they deceive. Combined jamming and spoofing attacks create ambiguous signal environments where systems must decide which signals are real and which should be ignored. The result is confusion, with decision making becoming uncertain precisely when certainty is required.

2. Anti-Spoofing Technologies

Anti-spoofing solutions attempt to validate whether a signal is genuine or manipulated, and often rely on similar logic and assumptions as anti-jamming technologies of rules-based detection and signal validation. But the logic and assumptions are increasingly outdated. As spoofing techniques have become more advanced with greater precision and adaptability, these systems have struggled to keep pace. Signal mimicry is more precise, timing offsets are subtler, and attack patterns are adaptive – more closely resembling legitimate behaviour. This leaves anti-spoofing approaches in a reactive rather than predictive position, constantly trying to respond to threats that are evolving faster than the defences designed to stop them.

3. Multi-GNSS Receivers

Using multiple constellations (GPS, Galileo, GLONASS, BeiDou) is often framed as a way to improve resilience, but in practice, it introduces more inputs without addressing the core weakness. GPS, Galileo, and other systems share similar signal structures and operate in comparable frequency ranges, which makes them vulnerable to the same types of interference and spoofing. When disruption occurs, it tends to affect all constellations in similar ways, meaning having more signals does not equate to having more trustworthy information. If one is compromised, the likelihood is high that others are affected as well. This creates a false sense of redundancy, i.e., more inputs, but not more independence.

4. Differential GPS (DGPS)

DGPS enhances positional accuracy using ground-based correction signals, and in stable environments, it performs well. But accuracy is not the same as trust. DGPS still depends on the integrity of the underlying GNSS signal, and in a jamming or spoofing scenario, it remains vulnerable in contested environments. In fact, it can amplify risk by making incorrect positioning appear more precise, giving maritime operators a false sense of confidence in data that may already be compromised.

5. Terrestrial Backup System

Terrestrial backup systems (e.g., eLoran, radio navigation systems) provide an alternative to satellite-based positioning by using shore-based infrastructure. While effective in coastal areas, their usefulness diminishes rapidly beyond those boundaries. Coverage is inherently limited, and the cost and complexity of deploying such systems at scale make them impractical for global maritime operations. For vessels operating in the open ocean, these solutions cannot provide the continuity required for safe and efficient navigation.

The Core Issue is Dependency on a Single Domain

Taken together, these approaches reveal a shared limitation: they attempt to improve or protect GNSS/GPS, but they don’t remove dependence on it. Whether through signal reinforcement, interference detection, or redundancy within the same domain, the underlying dependency remains intact.

It’s worth noting that modern bridge systems can present a layered navigational picture by combining GNSS with radar, AIS, INS, and ECDIS. That improves redundancy, but in most merchant vessels GNSS still provides the primary position input, so interference or false data can still degrade overall situational awareness unless it is independently cross-checked.

Ultimately, there are a limited number of truly independent alternatives to fall back on, as most existing mitigations operate as layers within the same ecosystem rather than as genuinely distinct sources of truth. As a result, what appears to be redundancy is, in many cases, simply duplication within a shared vulnerability.

This is the critical gap that Iridium PNT and RockFLEET Assured are designed to address. Rather than attempting to further fortify GNSS-dependent systems, Iridium PNT reduces reliance on any single domain altogether, enabling a more secure, resilient, and multi-domain approach to assured navigation.

From Accuracy to Assurance

In today’s maritime and security operations, the core challenge extends beyond positioning accuracy, but trust in the data itself. Existing GNSS/GPS-based solutions, even when layered with mitigation technologies, remain dependent on a single domain that is increasingly exposed to disruption, deception, and interference. This creates a critical gap in trusted, continuous navigation at sea, particularly in contested or high risk environments where GNSS/GPS reliability cannot be assumed.

Iridium PNT and RockFLEET Assured directly address this gap by introducing a truly independent and resilient source of positioning data that operates outside the limitations of traditional GNSS. By combining multi-domain inputs with real time integrity assessment and prioritizing assured, trustworthy signals, they move maritime navigation from reactive detection to proactive resilience. The future of navigation at sea will be defined by this ability to operate with confidence in uncertain and contested GNSS/GPS environments. A-PNT is central to that future, and RockFLEET Assured is built to deliver it.

Why GPS Alone Is No Longer Enough [Infographic]

Maritime, aviation, and defense operations all depend on GPS for positioning, navigation, and timing. But, as our infographic highlights, that dependence comes with real risk: GPS is vulnerable to jamming and spoofing, and relying on it alone creates a single point of failure.

That risk is becoming harder to manage. Reported interference incidents continue to rise across key regions, including a 127% rise in Baltic incidents between Q1 and Q2 2025, more than 1,000 vessels affected in Sudan and the Red Sea in 2025, and 5,655 flights spoofed in the Nicosia FIR in July to August 2024.

Why Modern GPS Threats Demand More Than Anti-Jamming

For a long time, disruption was often discussed mainly as a jamming problem. However, attack methods evolve, and disruption can now shift rapidly between jamming and spoofing. These are not the same threat; jamming tries to deny the signal, whereas spoofing tries to deceive the receiver. A solution that focuses only on anti-jamming may still struggle when an attack alternates between blocking the signal and imitating it.

That’s why resilience has to be about more than signal protection alone. It has to be about maintaining a trusted source of positioning even when GNSS is disrupted, denied, or manipulated.

What A-PNT Actually Means

A-PNT is best understood as a resilience approach, not a single technology. As the infographic sets out, it adds redundancy, position cross checking, trusted timing, and operational continuity when GNSS alone cannot be relied on. A-PNT isn’t “one new signal replacing GPS”; it’s a broader strategy for reducing dependence on a single vulnerable source.

Where Iridium PNT Fits

Iridium PNT supports a broader A-PNT strategy by providing a completely separate source of PNT, with zero dependence on GPS. That independence is critical. If a backup still depends on GNSS somewhere in the chain, it may inherit the same vulnerability. Iridium PNT operates as a wholly separate system, giving operators an independent source they can use when GNSS is disrupted or cannot be trusted.

It also brings a major security advantage: the signal is encrypted and authenticated. In practical terms, that makes spoofing exceptionally difficult, because the receiver is not simply accepting any signal that appears plausible; it’s validating a trusted source.

Why That Matters Operationally

In the real world, navigation resilience is defined by whether a system continues to deliver trusted data under pressure. That means operators need more than a warning that GNSS has been compromised. They need:

• An independent source of position and timing
• Confidence that the source itself is trusted
• Continuity if infrastructure is damaged
• A solution that works with the systems they already use.

RockFLEET Assured is designed for use in contested and high risk operating environments. Its architecture supports flexible installation, with compute power in the above-deck unit and cable runs of up to 100 meters. That means the unit can be installed away from the bridge in a discreet location, making it harder to identify, harder to interfere with, and harder to damage deliberately.

If a cable is cut or a unit is attacked, what matters next is whether visibility disappears immediately. RockFLEET Assured includes backup battery capability, allowing continued transmission for a period even after cable loss. That additional continuity can matter enormously in a live incident. Even limited continued reporting can preserve situational awareness, support response, and reduce the risk of going blind at the worst possible moment.

Another key strength is flexibility. RockFLEET Assured can be used with our chartplotter, with a customer’s own chartplotter, or integrated into wider bridge systems. That gives operators multiple options to adopt resilient PNT capability without being forced into a rigid operational model. For many customers, the easier a resilient system is to integrate into existing workflows, the more likely it is to be deployed effectively and trusted by crews.

GPS Still Plays a Vital Role, But it is No Longer Enough on its Own

As jamming and spoofing attacks become more sophisticated, more deceptive, and more hostile, operators need more than detection. They need trusted alternatives, genuine independence from GNSS, interoperability with existing systems, and resilience that holds up in the real world.

A-PNT helps by reducing dependence on one vulnerable source. Iridium PNT strengthens that approach by providing an encrypted, authenticated, wholly separate, satellite-based PNT capability, and RockFLEET Assured makes that capability operationally useful: survivable, flexible, interoperable, and built for continuity under pressure. That is what modern navigational resilience looks like.

Why Navigation Resilience Is Becoming a Standard Security Deliverable at Sea

Given that 90% of international trade is carried by sea, maritime safety is fundamental. For most of the modern maritime era, the formula was relatively simple: assess the route, understand the threat environment, adapt operating procedures, and, when justified by risk, place experienced personnel on board to deter, respond, and protect. That approach still matters, but it is no longer sufficient.

Today, merchant shipping is delegating a far broader range of responsibilities to private maritime security companies (PMSCs). The remit is no longer limited to protection from physical threats; increasingly, it also includes support for the operational risks created by disruption to critical onboard systems. One of the clearest and fastest growing examples is navigation resilience.

For maritime security providers supporting secure fleet operations, advising owners and operators, and delivering risk-managed transit, this change is already taking shape in practice. Clients may not use the term “A-PNT” (Assured Position, Navigation, and Timing), and they may not explicitly ask for “navigation resilience”. But the expectation is there nonetheless: in the questions they raise, the incident reporting they request, and the operational standards they increasingly assume are in place. The reason is straightforward: when positioning fails at sea, it becomes a security issue whether anyone labels it that way or not.

Security Has Expanded Beyond the Physical

The biggest misconception in maritime security right now is thinking this is a niche technical issue, something for bridge teams, electronics specialists, or a ship’s IT provider, when in practice, it has become a frontline operational risk.

GNSS disruption, jamming, and spoofing are no longer rare anomalies confined to active conflict zones. Independent analysis by C4ADS has documented widespread maritime spoofing events affecting thousands of vessels, particularly in the Black Sea and the Middle East. Subsequent advisories from the U.S. Coast Guard Navigation Center (NAVCEN) and UK Maritime Trade Operations (UKMTO) have continued to warn of GPS interference affecting commercial traffic in multiple regions.

When a vessel loses trustworthy position and timing, the impact cascades fast. Routing decisions become uncertain, safety margins shrink, bridge teams hesitate, and in high consequence waters, uncertainty becomes vulnerability. That’s why navigation resilience is moving into the security deliverables category. Not because it’s a buzzword, but because the outcomes are security outcomes – the ability to maintain control, continuity, and confidence in the vessel’s movements. And, as shipping companies continue to lean on third party providers to manage risk, the responsibility is naturally shifting to the people who already own the security mission.

Merchant Shipping Is Outsourcing Resilience, Not Just Risk

For shipping companies, the response is familiar. When risk grows faster than internal capacity, they outsource. First that meant physical protection. Then it meant intelligence and route advisory. Now it increasingly means outsourcing resilience, especially where failure has immediate operational consequences. Navigation is one of the clearest examples.

The New Scope of PMSCs

PMSCs are increasingly being drawn into questions that would once have remained strictly on the bridge:

1. What happens if GNSS becomes unreliable mid-transit?
2. How quickly can we detect spoofing versus simple signal loss?
3. How do we keep the bridge team confident in the vessel’s position when the primary reference is compromised?
4. What proof can we provide after the fact – to the owner, to insurers, to regulators, and to internal stakeholders – that the vessel maintained safe navigation?

These are no longer theoretical or hypothetical concerns and possibilities; they’re operational questions and sit directly inside the modern security mission. Marine insurers and P&I clubs such as Allianz and Gard have already published guidance highlighting navigation system vulnerabilities as emerging operational risks. The Nautical Institute’s Mariners’ Alerting and Reporting Scheme (MARS) has also captured incident reports reflecting confusion and degraded situational awareness linked to navigation system anomalies. In many cases, the crew onboard is highly competent but not equipped with the tools or the time to manage GNSS integrity issues in a repeatable way. But it’s not a training failure – it’s an equipment and process gap.

Why A-PNT Is Becoming the Navigational Standard

Where RockFLEET Assured Fits into Modern Maritime Security

RockFLEET Assured, powered by Iridium PNT, enters the market at a moment when PMSCs are increasingly expected to provide resilience as part of secure fleet operations, not just protection from physical threats.

Just as importantly, it’s built for repeatable deployment at fleet level. The system is delivered as a single above-deck terminal, with mounting options to suit different vessel types and superstructure layouts, reducing the need for vessel-by-vessel customization. Its IP66-rated enclosure is designed for exposed marine conditions, and no below-deck electronics are required unless bridge view is selected.

What Changes Operationally for PMSCs

PMSCs often operate under heightened expectations for compliance, documentation, and professionalism. Clients – corporate security teams, fleet operators, insurers, charterers – expect measurable capability, not procedural reassurance. Without A-PNT, disruption remains ambiguous. With it, disruption becomes detectable, documentable, and defensible. That shift strengthens operational reporting, reduces decision latency on the bridge, and improves client confidence. It becomes a deliverable in a security modeland part of how PMSCs define secure fleet operations in 2026 and beyond.

The Future of Maritime Security

The maritime security industry is not abandoning its roots: physical threats still exist, high-risk areas still demand proven experience, and human expertise still matters. But the center of gravity is shifting as electronic disruption, contested signal environments, and hybrid risk become normalized features of global shipping lanes. International policy bodies, insurers, and national governments have all acknowledged this reality in recent years.

The most forward-looking maritime security providers are therefore evolving from personnel-based security offerings to layered security and resilience platforms. They are expanding into technical advisory, electronic threat awareness, and operational continuity support. They are positioning themselves as secure fleet partners, not just voyage contractors, and A-PNT is one of the cleanest, most valuable additions to that stack.

The next era of maritime security will be defined by who can keep ships operating safely and confidently when the environment becomes contested physically, electronically, and operationally. Navigation resilience is becoming a security standard because disruption is becoming the norm, so for PMSCs responsible for secure fleet operations, this is the moment to lead. The companies that adopt assured A-PNT now through solutions like RockFLEET Assured will be the ones positioned to define what security means at sea over the coming years or more.