GNSS isn’t enough to protect workboats from jamming and spoofing

But GNSS was never engineered to be robust against deliberate radio frequency interference. GNSS satellites orbit the Earth at altitudes ranging from 19,000 - 24,000km, which means that satellite navigation signals are weakened by the time they reach Earth, making them vulnerable to jamming and spoofing: where false positioning or timing data can be introduced in ways standard receivers may not immediately detect.

That vulnerability is no longer a theoretical problem. International agencies responsible for maritime safety and spectrum management have raised alarm at the growing incidence of harmful interference, and the operational consequences now extend well beyond military contexts.

Workboats are a high-consequence environment for GNSS disruption

Workboats operate where GNSS failures can have out-sized consequences: close to other traffic; near critical assets; and often under time pressure.

Whether supporting offshore energy, conducting survey work, towing, dredging, pilot transfer or emergency response, workboats depend on a steady flow of position and time inputs – not just for navigation, but for logging, tracking, coordination and the wider digital workflow that sits around modern operations.

In these settings, it’s not only the complete loss of GNSS that creates risk: the more dangerous scenario is often plausible-but-wrong data.

A spoofed position can look ‘clean’ on a bridge display, even while it quietly degrades situational awareness. And once incorrect data enters the onboard ecosystem, it can propagate into reporting and coordination systems, distorting the shared traffic picture.

The reality is that GNSS disruption is becoming a credible operational hazard, especially in regions experiencing elevated interference activity, such as parts of Northern Europe.

Different threats, similar consequences

Jamming and spoofing present different operational challenges. Jamming denies service by overwhelming receivers with noise, causing position and timing data to drop out or degrade abruptly. Crews may be forced to fall back on alternative methods, change operating profiles or pause operations entirely.

Spoofing is often more challenging because it is harder to detect. 

Counterfeit GNSS signals can appear legitimate, allowing navigation systems to continue operating while providing false information. A vessel may appear to be following a safe track when it is not, or may seem stable when it is slowly drifting. In workboat operations where proximity, timing and coordination matter, this kind of silent failure can escalate quickly.

Why resilience requires a hybrid approach

No single technology can fully address the risks of GNSS jamming and spoofing.

Improving resilience is not about replacing GPS: it’s about combining complementary technologies so that the failure or compromise of one input does not create a single point of failure across positioning, navigation or timing (PNT).

Multi-constellation GNSS is a sensible first step. Using GPS alongside Galileo, GLONASS and BeiDou improves availability under normal conditions and can help with some broad, unsophisticated interference. But it does not solve targeted jamming, and it does not prevent spoofing scenarios that can affect multiple constellations simultaneously.

Inertial navigation systems (INS) and sensor fusion add another valuable layer. By combining inertial measurement units with inputs such as gyrocompasses, speed logs, radar correlation and map-matching, vessels can maintain an estimated position through short GNSS outages. However, inertial systems drift over time unless validated or corrected by an external reference, and higher-grade systems that minimise drift can be costly. In practice, INS is best suited to bridging short disruptions, not replacing satellite-derived PNT.

Terrestrial alternatives are also receiving renewed attention as part of national resilience planning.

In the UK, eLoran is being developed as a nationally owned backup PNT capability, with initial operating capability targeted later this decade. Quantum navigation has shown promise in trials, but it remains largely in research and is not yet operationally available at scale.

Assured PNT is practical, but it must be positioned honestly

In the near term, Assured Positioning, Navigation and Timing (A-PNT) offers a pragmatic route to improved resilience: independent sources of position and timing that can operate alongside GNSS and provide cross checking when GNSS is degraded.

What makes LEO-delivered A-PNT different is signal strength and independence. Iridium’s PNT signal is delivered from Low Earth Orbit satellites and is described by Iridium as up to 1,000 times stronger than traditional GNSS at the receiver.

That stronger signal, combined with an authenticated service design, is intended to make the signal more usable in RF-challenged conditions and to strengthen resilience against jamming and spoofing, giving operators a second, independent reference to compare against GNSS.

But it’s critical to be clear about what ‘assurance’ means in real operations.

Ground Control’s Iridium PNT-based A-PNT implementations are designed to improve survivability when GNSS is absent or disrupted, and provide reasonable accuracy (<25 m in some conditions). They also come with practical considerations operators must plan around:

● Time to accuracy: reaching a reasonably accurate position may take 10-30 minutes after activation, because the solution improves as bursts arrive from passing LEO satellites

● Power profile: receiving and processing Iridium PNT signals typically requires higher power, reducing battery life compared with standard GNSS-based tracking if left continuously active

● Operational role: this is a resilience and integrity layer, valuable for cross checking GNSS and maintaining a usable independent reference, but it is not the same thing as harbour-berthing precision.

That distinction matters. The highest precision close quarters manoeuvres (for example, certain pilotage and berthing contexts) can demand specialised high-precision methods and tightly controlled procedures. A-PNT adds the most genuine value when the operational objective is continuity, integrity and graceful degradation, for example workboat transits, offshore manoeuvres, task-area operations, and situations where tens-of-metres accuracy is meaningful and a secondary reference improves decision making.

The key is not ‘one magic sensor’, but explicit cross checking and rules of use: if radar, visual cues, gyro, speed log and GNSS disagree, crews need a clear hierarchy for what governs, and when to slow down or pause a manoeuvre.

The human effect

Technology alone is not sufficient. Crews must understand how GNSS can fail, how interference may present itself and how to operate safely when satellite navigation cannot be fully trusted.

Operators also need procedures for identifying anomalies, escalating concerns and communicating effectively during interference events, including clear reporting routes and a shared operating picture that flags when ‘navigation integrity is uncertain’.

Treating GNSS disruption as a realistic operational scenario rather than a rare anomaly is a critical step towards preparedness. True resilience comes from a layered architecture that allows navigation and operations to degrade gracefully, rather than fail abruptly.

Redefining navigation resilience

GNSS transformed maritime operations, but its limitations are now increasingly clear. For workboats, the question is no longer whether GNSS can be disrupted, it’s how well operations continue when it is.

When GPS goes dark - or worse, provides misleading information - resilience is what protects crews, safeguards assets and keeps workboat operations safe and predictable.

Ground Control is a UK and US company delivering rugged satellite and hybrid IoT communications for remote, mission critical operations across industries requiring reliable connectivity. Founded nearly 30 years ago, the company is part of CLS, itself a subsidiary of the French national space agency, CNES.