The United States recently issued a renewed warning to mariners about significant GPS interference. According to the U.S. Maritime Advisory, this interference is resulting in lost or inaccurate GPS signals which severely affects bridge navigation, GPS-based timing, and communications equipment.
It must be noted that this renewed warning is non-specific to an area of the globe. But it does note over the last year, areas from which multiple instances have been reported include the eastern and central Mediterranean Sea, the Persian Gulf, and multiple Chinese ports.
The Maritime Executive mentioned that mariners are warned to practice caution when underway and before getting underway. The advisory reaffirms safe navigation practices when experiencing GPS disruptions as well as promoting prompt reporting.
The U.S. Coast Guard Navigation Center (NAVCEN) offers examples of techniques mariners can use if they experience GPS interference which includes employing radars to mark bearings and distances on a paper chart or switching to the dead reckoning mode with a radar overlay on electronic charts, and using parallel indexing with multiple radars while underway. They reiterate that situational awareness, including verified position and velocity, is crucial for safe and effective commercial operations.
Reports of interference or the more dangerous spoofing to convince mariners they are in a different position is very common in this industry. The US Coast Guard and Maritime Administration have issued several warnings to mariners. In June 2019, fourteen maritime organizations sent a letter to the US Coast Guard urging the commandant to raise the issue of jamming and spoofing of GPS and other systems with the International Maritime Organization.
According to experts, the source of these types of disruptions often go unidentified but they have the potential to create significant confusion and slow the movement of ships. The potential exists to create bottlenecks in ports and major sea lanes or even to cause accidents. Mostly the newer and larger commercial vessels face a greater danger relative to smaller and older ships.