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But the U.S. economy is heavily dependent now on GPS so it is extremely
unlikely that the complete GPS system would be shut off -- about as unlikely
as the European Union deciding to shut off the future Galileo system. Also,
the U.S. military no longer "controls" GPS. It has been under joint
military/civilian "control" for some time now.
-- Richard Langley
   Professor of Geodesy and Precision Navigation

On Wed, 5 Apr 2006, Marcel Tschudin wrote:

>Please correct me if I should be wrong: Since GPS is controlled by the US
>military it only needs a decision from the US administration to swich it
>off. This is, to my understanding, the reason why Europe decided to set in
>place their own system called EUREKA.
>
>Marcel
>
>
>On 4/5/06, Lu Abel  wrote:
>>
>> With all respect, Gordon, it would take a lot more technology than the
>> terrorists have to turn off GPS much less to make it give incorrect
>> positions.   GPS uses satellites.  One would need satellite-killer
>> missiles to "turn off" GPS.  Only two or three countries (USA, Russia,
>> China?) have the technology (which, BTW, includes the technology and
>> infrastructure to track and identify the target before saying to the
>> missile "go get 'em").  To make GPS give the wrong position would
>> require taking over the US's GPS control centers and I'm sure the US
>> military has put a lot of thought and effort into preventing that.
>>
>> There are GPS jammers available on the arms market, but they work only
>> over a small theater of operations.  Nowhere I'd be sailing, hope you
>> won't be there either.
>>
>> Last but not least, terrorists are interested in, well, terror.  I
>> suspect they'd far rather kill a few thousand of their perceived enemies
>> than inconvenience them by turning off GPS....
>>
>> Lu Abel
>>
>> Gordon Talge wrote:
>> > Just for the heck of it, I wonder what would happen,
>> > if some terrorists managed to turn off the GPS system, or
>> > maybe even better, have it give the wrong positions.
>> >
>> > I have noticed that a lot of people seem to say they keep
>> > a sextant and tables, etc, for backup. The problem that I
>> > see with that is it takes a lot of practice to get good at using a
>> > sextant and working out sights by hand. Someone who has
>> > only tried out their sextant on a calm day or on the beach,
>> > may find it hard to get a decent shot on a pitching boat
>> > or ship, and then work out a sight where one slip of a
>> > plus or minus, or wrong column, would make it all for naught.
>> >
>> > BTW,
>> >
>> > Has anyone seen those German films of the U-Boats during World War II
>> > in the North Atlantic pitching and rolling? I start getting seasick
>> > just watching it. I saw one where a German Officer was taking a noon
>> > sight on a sub like that. They may have been the enemy, but they
>> > sure had guts. (It took guts to stand up to them too)
>> >
>> > -- Gordon
>> >
>> >
>>
>


===============================================================================
 Richard B. Langley                            E-mail: lang@unb.ca
 Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
 Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
 University of New Brunswick                   Fax:      +1 506 453-4943
 Fredericton, N.B., Canada  E3B 5A3
     Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===============================================================================

   

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