NavList:

Here's the section from the article. Mostly it's a fairly standard, generic warning. It does reference a jamming incident covering a six-mile wide region near a "non-US port". Does that ring any bells for anyone? I vaguely remember someting like that at Lazaro Cardenas, the giant container port on the Pacific southwest of Mexico City, but it could easily be another incident. Needless to say, celestial would have been nearly useless in a circumstance like this one. Still fun! 

Coast Guard issues safety alert of GPS malfunctions

Navigation equipment on most modern vessels relies heavily on data from the U.S. Global Positioning System, or GPS. Most of the time, these systems work flawlessly, but last summer several ships lost their signal near a non-U.S. port, causing key navigational equipment to go dark.

Although the signal returned after about 6 nm, crew aboard these vessels used radar in heads-up display, magnetic compass and terrestrial navigation during the outage. The U.S. Coast Guard said the incident shows the value of backup systems and a crew that knows how to use them.

“These types of events highlight the potential detrimental impact to navigation caused by GPS interference or jamming and the importance in understanding how your vessel’s or facility’s equipment could be impacted by a loss of GPS signal,” the Coast Guard said in a safety alert issued last month.

GPS can fail on board a ship for many reasons, including poor installation, bad antenna positions or failing equipment, the Coast Guard said. Signals can be affected by human and natural sources, and through GNSS devices close to other radiating devices. Authorities have found instances where jamming devices were used to affect GPS signals. Such devices are illegal in the U.S.

The safety alert urges vessels that encounter signal disruption to report the problem to the U.S. Coast Guard Navigation Center (NAVCEN), which with other agencies will work to determine the source of the problem. Reports can be made online at www.navcen.uscg.gov or by calling [...].

Frank Reed