For years, most mariners have treated GPS as a given: always on, always available, always trustworthy. But that assumption is becoming harder to defend. In March 2025, the IMO, ICAO, and ITU issued a joint warning expressing “grave concern” over the increasing number of jamming and spoofing incidents affecting satellite navigation systems used by maritime vessels and other critical services. IMO’s message was clear: interference with GNSS is not just a technical annoyance; it is a navigation-safety issue that can contribute to collisions and groundings.
That shift matters because the real danger is not always losing position altogether. Often, the bigger risk is trusting a position that looks perfectly normal on screen but is actually false. This is the essence of GPS spoofing, and it is why there is a growing need for a more resilient method of navigation among both professional and recreational navigators.
What is GPS spoofing?
The simplest way to explain spoofing is by comparing it to jamming.
With jamming, a GPS signal is blocked or degraded. The navigator sees a problem because the position may freeze, disappear, or become visibly unreliable.
With spoofing, the receiver is fed false information. The vessel appears to have a position, but that position may be wrong. This means that your boat’s icon shifts to the wrong location, the track line becomes misleading, and route monitoring starts to reflect false data instead of real movement. This is what makes spoofing harder to detect and potentially more dangerous than simple signal loss.
Why this matters in maritime operations
At sea, bad position data can create different problems depending on the vessel and mission.
For commercial operators, including fishing vessels, workboats, and patrol boats, the consequences can be immediate. Position integrity affects route monitoring, safe maneuvering, operations near infrastructure or hazards, and the crew’s ability to make quick decisions under pressure. TZ Professional is designed for the demanding needs of professional users, making continuity of navigation vital.
For leisure users, the operational stakes are different but still serious. A spoofed position can create confusion near headlands, traffic zones, harbor entrances, rocks, or shallow water. Recreational boaters are often more dependent on a single navigation display and may have fewer cross-checking tools onboard, which makes trustworthy situational awareness just as important.
In both cases, the lesson is the same: navigation systems are most valuable not when everything is perfect, but when conditions become uncertain.
A growing threat
The global concern is not theoretical. Public evidence shows the issue is accelerating.
The joint statement issued by the IMO, ICAO, and ITU explicitly warned of an increase in jamming and spoofing affecting satellite navigation systems.
Industry data reinforces that point. The Royal Institute of Navigation’s maritime interference report was compiled using input from more than 100 sector experts and 300 vessel captains, reporting that 75% of respondents believe the GNSS interference situation is not improving.
The growing need for resilient navigation
This is where the market is heading: not away from GNSS, but away from single-point dependence on GNSS.
Resilient navigation means having a workflow that continues to support decision-making when satellite position becomes unreliable. It means cross-checking, instrument integration, and maintaining continuity rather than treating navigation as all-or-nothing.
Dead Reckoning in TZ Professional
TIMEZERO has a particularly strong response to this problem, as the company has been making efforts to improve its software to directly address GNSS interference scenarios.
TZ Professional possesses a feature called Dead Reckoning that can be used when GNSS fails. In automatic mode, when heading and speeddataare available, the software continuously updates a Dead Reckoning “Ghost Ship,” based on the vessel’s previous confirmed position, heading, and speed. This allows operators to enable GPS deviation, comparing the GNSS position with the Dead Reckoning position, and can trigger an alarm if the difference exceeds a configured threshold.
This is a powerful tool because it is not just “backup navigation.” It is a practical continuity tool that helps crews detect when something is wrong, manage the situation, and continue navigating with greater confidence. This is exactly the kind of capability that turns spoofing from an invisible hazard into something operators can monitor and respond to in real time.
Integration with onboard sensors
The strength of this approach is enhanced by TZ Professional’s integration with onboard instruments and compatible systems. Dead Reckoning becomes more effective when supported by heading sensors, speed inputs, and other vessel data sources that help maintain a reliable estimated position when GNSS is compromised.
For example, TZ Professional’s Furuno radar overlay can be used to help refine the estimated position, giving navigators another way to cross-check the vessel’s location when satellite positioning becomes unreliable.
This sensor-driven approach is a key part of what makes resilient navigation possible. Rather than relying on one source alone, TZ Professional helps mariners combine multiple data inputs into a more robust navigation workflow.
Why this matters in TZ Professional v5.4
As concerns around GNSS interference continue to grow, the value of these capabilities becomes even more relevant.
The key message here is not that GPS should be replaced, but that it should no longer be treated as infallible. Professional and recreational navigators alike need tools that help them maintain continuity when conditions become uncertain. Dead Reckoning, GPS deviation monitoring, and onboard sensor integration all contribute to that goal.
Conclusion
GPS spoofing is dangerous precisely because it can look normal. A vessel may appear to be safely on track, while in reality, its displayed position is no longer trustworthy. As incidents continue to rise globally, the need for resilient navigation is becoming more urgent across the maritime industry.
That is where TIMEZERO stands apart. With Dead Reckoning, sensor integration, and professional-grade navigation tools built into TZ Professional v5.4, mariners have a practical way to detect anomalies, maintain situational awareness, and continue navigating with greater confidence when GNSS can no longer be fully trusted.
In a world of increasing GNSS threats, resilient navigation is no longer a niche consideration. It is becoming an operational necessity.