A Congressional report has warned that the Global Positioning System used for many navigational devices could begin to fail next year. But tales of impending doom may be exaggerated as there is only a 20 percent  chance of any noticeable problems developing.

GPS works through a fleet of satellites around the world. There are up to 32 in orbit at any time, with 24 the minimum required to get full operation. The Government Accountability Office says underfunding and poor planning means that there’s a chance existing satellites will fail before their replacements are ready and in position. The first replacement satellite was scheduled to go into orbit at the start of 2007, but will not do so until November this year.

The committee forecasts that the chances of having 24 satellites in place will drop below 95 percent next year. It will then fluctuate (as old satellites fail and new ones become active) at levels below 95 percent for the following four years, at times falling to 80 percent. The 95 percent figure is significant as that’s the US government’s committed level.

It’s important to note these figures are estimates for the ‘long-term probability’ of maintaining at least 24 satellites, not the probability of maintaining that figure during a particular year. So the forecast effectively means that unless existing repair and launch plans are stepped up, there’s a one in five chance that GPS will have problems at some point.

If the number of working satellites dropped below 24, GPS would not ‘fail’ as such. The system would remain operational, but devices could not locate their position to such a precise degree as at the moment. Devices could also take longer to lock on to satellites and become operational.

The biggest risk would be for military uses, which require precise location detection with no margin of error, unlike an in-car satellite navigation system which can still do a passable job just by getting somebody to the correct street.

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Entry was posted on Wednesday, May 20th, 2009 at 1:25 pm under Navigation, Politics, Technology.

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