Bush to consider shutting down GPS in extreme emergency

[Mxsmanic]

But you agree that this can easily be done WITHOUT GPS, and that it
actually will be a bit more acurate than GPS, albeit
more expensive?

No. It's hellishly expensive without GPS, since it generally requires
moving the clocks physically or investing in extremely expensive,
specialized communication links.

GPS makes it all vastly easier and cheaper and more accurate.

 

[Mxsmanic]

But it can be done, which is my point.

It's not much of a point, since it's extremely impractical to do.

People enjoy the free ride while
it lasts, but if GPS wouldn't be available any more they'd find other
ways of making things work. The world wouldn't end, life would go on.

The same can be said of electricity. And yet doing without electricity
would be a worldwide catastrophe.

 

[Mxsmanic]

I agree that it is cheaper - but the question was wether it was
impossible to achieve the same result without GPS.

No, the real question is cost effectiveness. It makes no difference
that something can be done if it's too expensive to be practical.

I think you'll agree that it IS possible to use an atomic
clock of your own instead of GPS to keep acurate time ...

No, it's not, because there's no easy way to synchronize it with other
clocks.

 

[Mxsmanic]

And since you can't get a guarantee on the uptime of GPS, you'd be well
advised to plan for outages.

Or you can just replace the people who think that it's okay to turn off
GPS.

 

[Mxsmanic]

Name the cases.

Time synchronization is one example.

Name the cases in which terrorists can be stopped by turning off GPS.

There are various active methods to synchronize clocks at the far end of
networks.

Time standards have more stringent requirements than data networks.

 

[Mxsmanic]

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

Only slightly less than half. The satellites are in very high orbits.

 

[JetCaptain]

Wow! You can measure a point with a horizontal accuracy of less than
10mm?


Can you do that with civilian GPS?

Certainly [SNIP]
Differential GPS involves the cooperation of two receivers, one that's
stationary and another that's roving around making position
measurements. The stationary receiver is the key. It ties all the
satellite measurements into a solid local reference.

But the position of the stationary receiver has to be known - the more
precise the measurement of that point, the more precise the rest of the
measurements get. And if you got a precise reference point (or better:
two reference points), you can get the same degree of accuracy with
plain old surveying equipment.

Yes, it will take more time, and will take experienced surveyors, but
it can be done - so a shutdown of GPS wouldn't be that critical for
that line of work.

Not to mention that surveying isn't really time-critical work ;-)

But at what cost?

Sam

Your mantra seems at what cost for so many commercial activities. At what
cost of human life due to a possible terrrorist attack does it offset your
growing concerns over commercial impact. 10 dead, a 100, a 1,000, ????
Where is the trade off point in your mind?

In mine, the saving of the life of a single individual is enough for me.

Neither you nor anybody in this group knows for certain what threats we
face now or may face in the future. I have a full faith in our government
that they will endeavor to do the best they can to protect us. I am
comforted in knowing that they are looking at all scenarios on my behalf.

I have been following these threads and find them to be "straw dog"
arguments. That political motivation is behind them is unquestionable
since the thread topic is "Bush to consider shutting down GPS in extreme
emergency". Would the topic "Kerry to consider shutting down GPS in
extreme emergency" even be started or would it be toned down to read "The
DOD to consider shutting down GPS in extreme emergency"? I have no doubt
that Bush did not write the document that has everyone buzzing about. So
why do you accuse Bush? A political target that you disagree with?

Juergen Nieveler and a few others have by far presented the most compelling
arguments. My compliments to them. It seems that crass commercialism takes
precedence over human life judging by some of the comments in these
threads.

I particularly enjoyed the counterpoint by Jeff:
"The terrorists have won when the victim starts blaming themselves for
being
attacked."

Now sit back and ask yourself, what is the likelihood of GPS being
disabled? Where is your trade off point in human life lost to terrorist
attack versus commercial interests? Could civilian GPS even be used by the
terrorists requiring it to be selectively shutdown? Don't you really feel
better knowing that your government is actually planning ahead for your
protection?

Now will somebody please give me the name of a company that depends on GPS
timing signals down to the nanosecond for their business to operate and
does not have a contingency plan? Just one company please!

 

[JetCaptain]

Wow! You can measure a point with a horizontal accuracy of less than
10mm?


Can you do that with civilian GPS?

Certainly [SNIP]
Differential GPS involves the cooperation of two receivers, one that's
stationary and another that's roving around making position
measurements. The stationary receiver is the key. It ties all the
satellite measurements into a solid local reference.

But the position of the stationary receiver has to be known - the more
precise the measurement of that point, the more precise the rest of the
measurements get. And if you got a precise reference point (or better:
two reference points), you can get the same degree of accuracy with
plain old surveying equipment.

Yes, it will take more time, and will take experienced surveyors, but
it can be done - so a shutdown of GPS wouldn't be that critical for
that line of work.

Not to mention that surveying isn't really time-critical work ;-)

But at what cost?

Sam

Your mantra seems at what cost for so many commercial activities. At what
cost of human life due to a possible terrrorist attack does it offset your
growing concerns over commercial impact. 10 dead, a 100, a 1,000, ????
Where is the trade off point in your mind?

In mine, the saving of the life of a single individual is enough for me.

Neither you nor anybody in this group knows for certain what threats we
face now or may face in the future. I have a full faith in our government
that they will endeavor to do the best they can to protect us. I am
comforted in knowing that they are looking at all scenarios on my behalf.

I have been following these threads and find them to be "straw dog"
arguments. That political motivation is behind them is unquestionable
since the thread topic is "Bush to consider shutting down GPS in extreme
emergency". Would the topic "Kerry to consider shutting down GPS in
extreme emergency" even be started or would it be toned down to read "The
DOD to consider shutting down GPS in extreme emergency"? I have no doubt
that Bush did not write the document that has everyone buzzing about. So
why do you accuse Bush? A political target that you disagree with?

Juergen Nieveler and a few others have by far presented the most compelling
arguments. My compliments to them. It seems that crass commercialism takes
precedence over human life judging by some of the comments in these
threads.

I particularly enjoyed the counterpoint by Jeff:
"The terrorists have won when the victim starts blaming themselves for
being
attacked."

Now sit back and ask yourself, what is the likelihood of GPS being
disabled? Where is your trade off point in human life lost to terrorist
attack versus commercial interests? Could civilian GPS even be used by the
terrorists requiring it to be selectively shutdown? Don't you really feel
better knowing that your government is actually planning ahead for your
protection?

Now will somebody please give me the name of a company that depends on GPS
timing signals down to the nanosecond for their business to operate and
does not have a contingency plan? Just one company please!

 

[JetCaptain]

Wow! You can measure a point with a horizontal accuracy of less than
10mm?


Can you do that with civilian GPS?

Certainly [SNIP]
Differential GPS involves the cooperation of two receivers, one that's
stationary and another that's roving around making position
measurements. The stationary receiver is the key. It ties all the
satellite measurements into a solid local reference.

But the position of the stationary receiver has to be known - the more
precise the measurement of that point, the more precise the rest of the
measurements get. And if you got a precise reference point (or better:
two reference points), you can get the same degree of accuracy with
plain old surveying equipment.

Yes, it will take more time, and will take experienced surveyors, but
it can be done - so a shutdown of GPS wouldn't be that critical for
that line of work.

Not to mention that surveying isn't really time-critical work ;-)

But at what cost?

Sam

Your mantra seems at what cost for so many commercial activities. At what
cost of human life due to a possible terrrorist attack does it offset your
growing concerns over commercial impact. 10 dead, a 100, a 1,000, ????
Where is the trade off point in your mind?

In mine, the saving of the life of a single individual is enough for me.

Neither you nor anybody in this group knows for certain what threats we
face now or may face in the future. I have a full faith in our government
that they will endeavor to do the best they can to protect us. I am
comforted in knowing that they are looking at all scenarios on my behalf.

I have been following these threads and find them to be "straw dog"
arguments. That political motivation is behind them is unquestionable
since the thread topic is "Bush to consider shutting down GPS in extreme
emergency". Would the topic "Kerry to consider shutting down GPS in
extreme emergency" even be started or would it be toned down to read "The
DOD to consider shutting down GPS in extreme emergency"? I have no doubt
that Bush did not write the document that has everyone buzzing about. So
why do you accuse Bush? A political target that you disagree with?

Juergen Nieveler and a few others have by far presented the most compelling
arguments. My compliments to them. It seems that crass commercialism takes
precedence over human life judging by some of the comments in these
threads.

I particularly enjoyed the counterpoint by Jeff:
"The terrorists have won when the victim starts blaming themselves for
being
attacked."

Now sit back and ask yourself, what is the likelihood of GPS being
disabled? Where is your trade off point in human life lost to terrorist
attack versus commercial interests? Could civilian GPS even be used by the
terrorists requiring it to be selectively shutdown? Don't you really feel
better knowing that your government is actually planning ahead for your
protection?

Now will somebody please give me the name of a company that depends on GPS
timing signals down to the nanosecond for their business to operate and
does not have a contingency plan? Just one company please!

 

[Mxsmanic]

Earth is a sphere, it doesn't have "sides". Essentially, you'd set the
satelites to turn off the civilian transmitter over a certain part of
their trajectory, which would translate into a certain area of the
planet not having more than 2 active satelites over the horizon at any
given time.

No. Each satellite broadcasts to nearly half the planet at any given
instant, not to some narrow swath on the ground.

 

[Mxsmanic]

Think before you write.

Done.

 

[Mxsmanic]

But a single satellite isn't enough.

All the satellites work the same way.

As long as no more than 2 sats are
visible over the horizon at any given moment, using GPS is impossible
in that region.

Typically nearly half the constellation is visible at any given instant
from any given point.

And since the horizon is different for any point on the
planet, and the satellites can be set to turn their transmitter on and
off at any given time, you can select which satellites are active and
visible over the horizon at a given plave and time.

Nope, it doesn't work that way.

 

[Mxsmanic]

But it's also not nearly as close to a global shutdown as people seem
to think.

It's pretty much identical to a global shutdown.

a) It IS possible to shut down civilian GPS without taking down
military GPS
Yes.

b) The chances of terrorists using military GPS are slim at best

The chances of them relying exclusively on GPS are also very slim, if
one assumes that civilian users have contigency plans. Why would
terrorists not have contingency plans at least as elaborate as those of
civilians?

c) Civilian GPS can be degraded or shut down on a regional basis

No, not from the air. All jamming is done with local transmitters.

d) The world isn't going to end when that happens

It didn't end when the World Trade Center was destroyed, either,
although you'd never know it from the hysteria and paranoia that that
event seemed to produce.

e) If your company depends on GPS running 24/7, you might want to
rethink your contingency planning real soon

If your terrorist plans are critically dependent on GPS, you might want
to consider backups.

 

[Mxsmanic]

You still need surveys even if you have maps.

You have to survey to produce a map.

Because it's easier and faster for them.

And it's more accurate.

In a war zone?

Yes. Especially in a war zone. Getting lost is a serious problem in
wartime.

So non-US people don't really have any rights to demand GPS uptime.

It doesn't matter, since U.S. people are demanding it, too.

If power companies had 24h outages every month, they'd run into
trouble really fast, believe me.

So would GPS.

The accuracy of the civilian signal is quite bad actually ...

That depends on your equipment. One reason why the military insisted on
SA was that the civilian GPS was about a hundred times more accurate
than they had expected. And it's even more accurate now.

Civilian GPS is good for accuracy in the meter
range - a good surveyor can reach accuracy much better than that.

So can a surveyor's GPS equipment, even using civilian GPS.

Nope. But the on-board-units for the toll system will use Galileo when
it becomes available, and future civilian navigation systems will do
the same, simply because it will be more acurate than GPS.

I'll believe that when I see it.

 

[Mxsmanic]

Can you do that with civilian GPS?

Yes.

 

[Mxsmanic]

But the position of the stationary receiver has to be known - the more
precise the measurement of that point, the more precise the rest of the
measurements get.

You can use GPS to measure it.

And if you got a precise reference point (or better:
two reference points), you can get the same degree of accuracy with
plain old surveying equipment.

In time, yes.

Yes, it will take more time, and will take experienced surveyors, but
it can be done - so a shutdown of GPS wouldn't be that critical for
that line of work.

I don't think it would be much of a problem for surveyors. But they
aren't the only users of GPS.

 

[Mxsmanic]

Surely, you just need to be around a DGPS reference station.

And not even that, if you have plenty of time to make observations.

 

[Mxsmanic]

But it means that people will manage without GPS in restricted waters -
because they already do.

That leaves only a few hundred zillion square kilometres of
unrestricted, unmarked ocean to navigate.

 

[Mxsmanic]

And not to put a too fine point to it, but GPS is run and paid for by
the Pentagon ...

Who gives money to the Pentagon?

 

[Mxsmanic]

It's exactly how to run an airline.

No airline would continue to operate if it had to run all aircraft on
only a single engine.

Of course they do.

Not for NORMAL COMMERCIAL SERVICE.