An interesting article.
Will GPS fail when they say?, who knows, but I think it will be a long time without further investment before the system fails .
Why ?, Well you only need four satellites to give a reasonably accurate position, you can do it on three but quite possibly you could be anything up to 50 metres away from the shown position.
Anymore than four satellites and all they do is give you more accurate positional information, unless the good old USof A military gets a stroppy on and gets the satellites to give you incorrect positional information. This was done in the past and would move targets (the enemy) by quite a large margin. Now it does not happen, but who knows what goes on in the heads of military men.
The satellites used are anything from a few years to a lot of years old. Design life is as any piece of machinery finite, so maybe the satellite is gauranteed for 10 years, quite a few must be near their 'end of life'.
Fortunately there are quite a few satellites up there that are basically shut down, waiting for commands from ground to turn them on and replace a faulty or dead unit.
So to sum up, I would be very suprised if the system failed.
As a bonus there is also a Russian system, and (in it's infancy) a European system. So joy of joys, should the American system fail there are alternatives, but of coarse Garmin etc will have to sell you a new GPS at an inflated price.
Other technologies are available. We have a mobile phone network that covers most (but not my house) of the UK. All transmitter positions are known, so it is pretty easy to turn your mobile phone into a positioning system, a bit of software is all that is required.
A happy TomTom GPS user who still has maps with him, just in case.
Martin.
