Bush to consider shutting down GPS in extreme emergency

You can be in the middle of the Empty Quarter and still do it with GPS
alone.

 

By definition, when he became President.

 

Mxsmanic wrote:

The average is an increasingly accurate position, but it is not your _true_
position.

 

The Aviation Trust Fund currently has a multi-billion dollar surplus.
But it is being used as an offset for the rest of the deficit, so it's
not being spent at the rate it should. But there are many small airports
getting improvements. Plus, IMO, a precision approach with high minimums
is better than a non-precision approach with the same minimums. Dive-
and-drive is dangerous.

 

No. The President is a civilian, even as CinC of the military.

 

Yes, but it still had to be placed horizontally, and GPS units at the
surface were used for that. I'm not sure how the depth was surveyed;
even at the surface, GPS is not very good at measuring altitude with
precision (nor was it designed to be).

 

The day of his inaugarition. He is Commander-in-Chief of the whole
armed forces, wether they like it or not.


Juergen Nieveler

 

For the channel tunnel? You realise that the surface is called the
"British Channel", and is a rather large body of water?

Rubbish. You don't need GPS to dig a straight tunnel - you need
something that projects a straight line, for example a laser. Which is
exactly what they used.

Juergen Nieveler

 

And because they are unknown, you can't proof that they won't justify
the drawbacks. QED.


Juergen Nieveler

 

But it's not your true position, only an approximation.


Juergen Nieveler

 

Hint: Spirit levels aren't rocket science anymore. They might have used
GPS to survey the start points, though that wouldn't be strictly
necessary, but they sure as hell didn't need GPS when they started
digging the tunnel itself.

Please get a clue - tunnels are below ground, and you DON'T go digging
vertical shafts every hundred meters to fix your position with GPS,
especially if the vertical shaft would have to pass through hundreds of
feets of rock and large body of water...


Juergen Nieveler

 

He remains a civilian.

 

Yes. Opaque to both GPS signals and light.

There are thousands of references that say they used GPS, so unless
there is a vast conspiracy to conceal the real methods used, GPS was it.

Lasers don't penetrate the waters of the Channel or the rock below any
better than GPS signals do.

 

I meant horizontally in terms of east, west, south, and north.
Horizontal positioning in the GPS sense, latitude and longitude.

GPS made sure that the tunnel was still on the planned path.

You don't have a line of sight for lasers or visual surveying through
water and rock, either.

 

I don't have to. The burden of proof is on the person who feels it is
necessary to shut off GPS. The dangers of doing so are apparent in
abundance, but the advantage has not yet been shown, or even described.

I think not. Nothing has been demonstrated, and that's just the
problem.

 

What other true positions do you have in mind?

 

Take a trip to Greenwich. Stand on the Meridian. Turn on your GPS
receiver. Note that it won't show exactly 0°, even though you're
standing on the exact line that DEFINES the 0° Meridian.


Juergen Nieveler

 

Unimportant for a tunnel. You plan which direction you dig in, and
check wether you are digging straight.

No. GPS doesn't work underground - period.

Because the lasers were used to sight through the tunnel, not through
the rock. You place a laser at the start of the tunnel, and if you can
still see it at your end of the tunnel the tunnel is more or less
straight.

Just how do you think people built tunnels like that? Do you think they dig a trench and drop the concrete tubes in from above? Some tunnels ARE built like that, and in that case GPS would be usefull, but that's not how the Eurotunnel was built, that method only works for small tunnels that cross shallow rivers.


Juergen Nieveler

 

That's a price understatement...

Maybe you should read up on what a "tunnel" is before you make a fool
of yourself.


Juergen Nieveler

 

I read up on how the Chunnel was surveyed and constructed, and thus
avoided making a fool of myself in advance.