What people tend to forget is that there is already a second satellite navigation system: Russia's Glonas. Admitedly, it's in pretty poor shape.
RecSAR wrote:
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Certainly the EU plans an independent GPS service and as I understand it, they are attempting to design a system that is independent of any single controlling organisation.
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I say: Somebody has to have their hand on the switch. You can't have two dozen command stations issuing different commands.
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The current GPS is owned by the US military, and as a result, GPS satellites are moved to areas of "interest" to increase accuracy, thereby depleting the level of coverage elsewhere.
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I say: Do you have copies of the publicly-published orbital elements which show satellite orbits being changed? These things can't be kept secret since many GPS receivers allow display of the orbit data.
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In times of conflict the US military can turn off GPS coverage completely.
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I say: The US military couldn't function without at least the military part of GPS. SA was turned off during Gulf War I since the US military didn't have enough military GPS sets and wanted the better accuracy with the civilian sets they were using. SA was also turned off at times during Yugoslav events. It is promised that SA will never be turned on again. US industry is very dependent on the civilian side. What could happen is US jamming of the civilian signal in a battle area.
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In addition, I see to recall that the Galileo proposal is a move towards a second generation GPS service with significantly greater accuracy for all users.
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I say: As I understand it, Galileo accuracy will depend on how much you pay as a user. Free users won't get much better than GPS, probably not as good as GPS with WAAS. Right now, ordinary GPS is better than most maps. Even very cheap GPS receivers have inbuilt WAAS.
Plain vanilla GPS is not good enough for precision approaches for two reasons: it takes a long time to notify of a sick satellite, and the accuracy isn't good enough. Both are cured with a satellator near the airport.
Since atmospheric effects are of concern at real-time extreme accuracy, I'd imagine that Galileo will want satellators for precision approaches.
Right now, I understand there is operational testing of GPS approaches at Vail, Colorado.