Bush to consider shutting down GPS in extreme emergency

  • Thread starter Thread starter Fred
  • Start date Start date
Juergen said:
Yes. But when you first set up the clock, of course you WILL
synchronize it with the master clock in your country.
Click to expand...

It's not quite that simple.
From that point on it will keep acurate time.
Click to expand...

No, but it will keep pretty good time. You have to verify the
synchronization periodically.
The difference being?
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Obvious.
 
I think this whole discussion is moot:

Did Osama et al. use high-tech weaponry the last time?
Osama knows he can't compete in the high-tech arena, so he wont.

Nope, they used box-cutters.

And while the US as usual is looking into high-tech solutions (or wanting to
turn them off) Osama is thinking up another low-tech attack, which will
succeed because the US is staring itself blind on which high-tech toy to
create, use or to disable.
 
Vincent said:
Which is why it will be a free service for all but the most demanding users:
Click to expand...

Since satellite navigation does not have a "load" (no matter how many
users there are, the cost of operation is the same), what would a "most
demanding" user be like?
"Like GPS, GALILEO will be free of charge to basic users (open service).
Some applications will have to be paid for - those requiring a quality of
service which GPS is unable to provide."
Click to expand...

If GPS can't provide it, I wouldn't hold my breath about GALILEO
providing it.
It is easy to come to agreement if you are one country (like the USA)!
Here we have to deal with 20 countries with different cultures and different
priorities etc. I think it is remarkable that 20 countries reached agreement
so soon (a week ago every country agreed).
Click to expand...

They'll disagree on other things, rest assured.
The first sat will be launched end of 2005.
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And it will be in service by 2045.
 
Since satellite navigation does not have a "load" (no matter how many
users there are, the cost of operation is the same), what would a "most
demanding" user be like?
Click to expand...
Was in my post already:
"value added services with integrity provision and, in some cases, service
guarantees, based on a certifiable system"
If GPS can't provide it, I wouldn't hold my breath about GALILEO
providing it.
Click to expand...
If you emulate/copy something, you generally improve upon it (like the
Japanese did with German camera's). This is always the case with technology:
the first generation of manufacturers/adopters/users etc. has the
disadvantage when the second generation comes along.
For example: we still have hundreds of miles of copper wire for our phones.
Some emerging countries start straight away with glass fibre.
They'll disagree on other things, rest assured.
Click to expand...
No problem: Galileo is agreed on.
And it will be in service by 2045.
Click to expand...
2008
 
Vincent said:
If you emulate/copy something, you generally improve upon it (like the
Japanese did with German camera's).
Click to expand...

Yes, but that doesn't mean you will.
This is always the case with technology: the first generation of
manufacturers/adopters/users etc. has the disadvantage when the
second generation comes along.
Click to expand...

In Europe, it's more a matter of politics than technology, and politics
don't always move ahead.
For example: we still have hundreds of miles of copper wire for our phones.
Some emerging countries start straight away with glass fibre.
Click to expand...

But we also have electricity for our wires, whereas the developing
countries' glass fibre remains dark.
No problem: Galileo is agreed on.
Click to expand...

Sure, just like the euro.
 
As the 'footprint' for one satellite is slightly less than a
hemisphere of the earth and up to twelve of them can be received at
any particular locality how do you disable reception for a region?
Click to expand...

Alan,

I'm only speculating, but if GPS satellites were temporarily
switched off for exactly as long as they can be seen from a
particular target country, then that country would lose GPS
entirely, while a country on the other side of the planet would
not notice any failure.

However, a wide belt around the target country would lack GPS
service as well. Adjacent areas would probably not be able to
use GPS, countries farther away would experience limited GPS
service, only being able to receive GPS signals from one side.

Effectively you'd deprive a wide, roughly circular area of GPS
service, but far more than half the planet's surface would still
be able to navigate by GPS, some of it with reduced accuracy and
reliability.

Hans-Georg
 
This just isn't so. We lost an aircraft a few years back because it
couldn't maintain altitude with one engine inoperative. You need to read
CFR Title 14, Parts 23, 25, 27, and 29. Maybe it's so in the Great White
North, but not in the US.
Click to expand...

Stan,

I don't know the details, but would be very interested. The
fundamental fact, however, is that the entire justification to
have two engines is to be able to continue flying if one engine
fails. Obviously, immediately after takeoff this means that the
plane has to be able to climb slowly.

Flying a twin while knowing that it wouldn't be able to continue
after an engine failure seems undesirable to me. I'd rather have
a single then with its lower touchdown speed and much lower risk
of engine failure, generally less than 50% of that of a
comparable twin.

Hans-Georg
 
I'm only speculating, but if GPS satellites were temporarily
switched off for exactly as long as they can be seen from a
particular target country, then that country would lose GPS
entirely, while a country on the other side of the planet would
not notice any failure...
Click to expand...

I don't think it's quite as simple as that. Don't forget that at
higher latitudes it's possible to see satellites which are 'on the
other side of the planet' so more than an earth hemisphere would be
affected. It would be much easier to turn off the lot!
 
Hans-Georg Michna said:
I'm only speculating, but if GPS satellites were temporarily
switched off for exactly as long as they can be seen from a
particular target country, then that country would lose GPS
entirely, while a country on the other side of the planet would
not notice any failure.
Click to expand...

It doesn't work that way. Each satellite can be seen by half the world
at any given time.
 
Juergen Nieveler said:
Not because of lack of GPS, but because a lack of precise maps. Aerial
photography and the maps produced through it had at least as much to do
with better accuracy, and a good surveyor with a telescope and a
precisely defined starting point will be at least as (if not more)
accurate as a GPS receiver (civilian version).
Click to expand...

Wow! You can measure a point with a horizontal accuracy of less than 10mm?
 
On Fri, 17 Dec 2004 11:08:17 +0100, Hans-Georg Michna
Click to expand...
I don't think it's quite as simple as that. Don't forget that at
higher latitudes it's possible to see satellites which are 'on the
other side of the planet' so more than an earth hemisphere would be
affected. It would be much easier to turn off the lot!
Click to expand...

Alan,

now you're confused. Each satellite can be seen only from less
than half of the planet's surface.

Hans-Georg
 
Each satellite can be seen only from less
than half of the planet's surface.
Click to expand...

Yes, I agree, which is why, in an earlier post, I posted 'As the
'footprint' for one satellite is slightly less than a hemisphere of
the earth...'
 
On Fri, 17 Dec 2004 15:30:28 +0100, Hans-Georg Michna
Click to expand...
Yes, I agree, which is why, in an earlier post, I posted 'As the
'footprint' for one satellite is slightly less than a hemisphere of
the earth...'
Click to expand...

Alan,

not so slightly. It's quite a bit less.

OK, now we can argue about the exact meanings of slightly versus
quite a bit. (:-)

Hans-Georg
 
OK, now we can argue about the exact meanings of slightly versus
quite a bit. (:-)
Click to expand...

No thanks :-)

It's a long time since I did the math and based my statement on a
rough scribble. It's interesting, though.
 

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