The Republic of the Marshall Islands (RMI) Maritime Administrator has released recommendations in response to a rising tide of Global Navigation Satellite System (GNSS) interference, which is increasingly affecting navigation, safety and operations in key maritime regions. The guidance comes as incidents of jamming, spoofing, and other disruption have surged since 2022, with reports showing thousands of vessels impacted in 2025.
Understanding the Threat Landscape
Interference with GNSS—arising from geopolitical tension and electronic warfare—is more than a technical annoyance. It poses serious threat to positioning, navigation, and timing (PNT) systems aboard ships. The potential consequences include navigational errors, operational delays, elevated safety hazards, and risk of entering restricted or hazardous waters.
Several regions are identified as high-risk:
- Asia, especially in the East China Sea, South China Sea, Yellow Sea, and Taiwan Strait, where spoofing and jamming have become more frequent and sophisticated.
- Baltic Sea, including the Gulf of Finland and Gulf of Gdańsk, with near-daily interference and expanding coverage.
- Middle East, especially in chokepoints like the Strait of Hormuz, Arabian Sea, Red Sea and Gulf of Oman. Conflict dynamics have worsened disruptions.
- Eastern Mediterranean and Black Sea regions, where ongoing conflicts and related electronic warfare activity have elevated GNSS disruption risk severely.
Key Measures Recommended for Mitigation
RMI’s guidance outlines a series of measures that vessel operators, shipowners, and maritime stakeholders should adopt to reduce risks linked to GNSS interference. These align with IMO recommendations and industry best practices.
Navigational Redundancy
- Use alternative positioning methods such as Inertial Navigation Systems (INS), celestial navigation, radar parallel-indexing, and visual fixes. Compare GNSS outputs with these aids.
- Keep paper charts updated; configure Electronic Chart Display and Information System (ECDIS) for manual dead reckoning and speed log input during GNSS disruption.
- Deploy multi-constellation / multi-frequency GNSS receivers (e.g. GPS, Galileo, GLONASS etc) to increase resilience.
Monitoring & Detection
- Install receivers with anti-jamming / spoofing features: Controlled Reception Pattern Antennas (CRPA), Receiver Autonomous Integrity Monitoring (RAIM), and signal authentication tools.
- Track indicators such as sudden positional jumps, elevated Horizontal Dilution of Precision (HDOP) values, mismatches between radar data and ECDIS, or echo-sounder depth discrepancies.
- Use real-time interference monitoring tools to detect and classify disruptions.
Crew Training & Procedures
- Conduct drills that simulate GNSS interference, so that bridge teams can clearly distinguish spoofing scenarios from jamming, and respond appropriately.
- Increase vigilance in high-threat areas: augment bridge watch, use manual plotting and radar monitoring more intensively, avoid overreliance on AIS overlays when anomalies appear.
- Plan routes to avoid known trouble zones when possible; use navigational warnings and coordinate with port authorities for daylight arrivals.
Report & Share Intelligence
- Prompt incident reporting to authorities such as the RMI Maritime Administrator, NAVCEN (US Coast Guard Navigation Center), NSC (NATO Shipping Centre), and regional monitoring networks. Include precise details: position, time, duration, and any system readouts or screenshots.
- Participate in collaborative intelligence sharing and monitoring initiatives to strengthen collective awareness.
Operational Planning & Equipment Preparedness
- Develop and maintain GNSS disruption response plans, including fallback to non-GNSS aids (like eLoran or R-Mode, where available).
- Consider installing advanced anti-spoofing / anti-jamming hardware, and systems that provide independent backup for time and location information.
What This Means for Maritime Stakeholders
For shipowners and operators, integrating redundant navigation systems and ensuring crew are trained for GNSS outage scenarios will become increasingly essential investments. Seafarers must be equipped and confident in using non-GNSS navigation aids and interpreting anomalous data. Policymakers and regulatory bodies could consider mandating reporting protocols and minimum resilience standards for vessels operating in high-risk zones. Logistics professionals and supply chain planners may need to adapt to route variation, delays, or additional safety checks stemming from interference events.
Though navigation technology has advanced rapidly, GNSS interference demonstrates that resilience and human oversight remain vital. The guidance from RMI provides a framework to anticipate and mitigate risk before incidents lead to more serious safety, operational, or geopolitical consequences.
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Source: Safety4Sea
