“Vessels must pay attention to the fact that VTS and other shorebased stations may not recognize, identify and track affected vessels by AIS.”

Contrary to what meets the eye, this is not a sign that VTS have fallen asleep on the job. Rather more worryingly, it is an extract from a Swedish Sjofartsverket navigation warning. It reports that several large ships in Swedish waters have recently been subject to malfunctioning GPS and AIS sets.

Rumour has it that the US shut down one of the 31 GPS satellites a fortnight ago, but failed to issue a warning, leaving vessels in the Baltic somewhat tense as position data vanished, taking with it accurate AIS information.

Such is the dependence of modern seafarers on GPS data that this news is somewhat concerning. There has been no official explanation as to what caused the blackout – so does the deafening silence from the US military suggest a cover-up? Or is this merely a crazy conspiracy theory?

Whichever it is, it lends weight to the argument that Galileo, the EU’s rival system due to be operational by 2013, is more than an empty politicalgesture. Perhaps a separate satellite navigation system, removed from the whim of the US military, is a sensible precaution for safe navigation.