Now that GPS - the satellite-based Global Positioning System - is a widely used tool for members of the public, you'd expect the military to stop playing with it. Sadly, you'd be wrong - so Ofcom has stepped in to keep people informed.
GPS was originally developed for military use, but the ability to pinpoint your location with surprising accuracy has led to an explosion in civilian applications. The majority of motorists use GPS to power in-car satellite navigation systems, businesses use it to track delivery vehicles, councils to track buses, and it's near-impossible to find a smartphone that doesn't have a receiver built in.
The technology is still a military plaything, however. Like any plaything, the military often breaks it - surprisingly enough, on purpose - leaving users with inaccurate or unavailable positioning information.
Previously, the military has been reticent to inform the public that this is going on. Communications watchdog Ofcom has told them to do otherwise, with the result that it's now possible to get advanced warning of military GPS jamming tests throughout the UK.
"The Ministry of Defence conduct [sic] occasional tests on military systems which may result in some loss of service to civilian users of the Global Positioning System (GPS) including in-car navigation devices and networks which rely on GPS signals," Ofcom explains. "[However,] it must be emphasised that this notification process only warns of future jamming exercises that are brought to the notice of Ofcom and may not cover all jamming exercises."
The page - which is also available as an email notification list - outlines a range of GPS jamming exercises, with an ongoing test of multiple jammers by RAF Spadeadam in Cumbria likely to cause problems in the area until the 9th of December on weekdays between 0900 and 1600.
While notifications that the service may be down while the military tests its latest GPS-breaking toys will come as little comfort to those inconvenienced by the outage, it at least lets navigators know when they should dig out the paper map and compass when trying to find the local pub.