Bush to consider shutting down GPS in extreme emergency

As long as GPS is avaible. Which isn't guaranteed, as we've learned - so
people will need an alternative. Which for this particular purpose would
be a very precise clock.

Juergen Nieveler

 

I agree that it is cheaper - but the question was wether it was
impossible to achieve the same result without GPS. I think you'll agree
that it IS possible to use an atomic clock of your own instead of GPS
to keep acurate time, and given a threat of GPS not being available, it
would be an attractive alternative to companies who need accurate time
for busines- critical purposes. If it's business-critical, cost isn't
as much of a factor.


Juergen Nieveler

 

Slightly reduced effectiveness without GPS. And we're talking about a
minor share of farmers who actualy DO use GPS already - most don't.

Which is the reason why the US Military wants to shut it down in the
first place, excpet for their own PG systems - which would still work,
as only the civilian part would be turned off.

The world can easily manage without that for weeks, if not months.

See above

Gosh, people would need to learn how to read maps again! We'll see tens
of thousands of people driving the wrong way !!!1eleven!

None of this is actually life-threatening ;-)

Juergen Nieveler

 

AFAIK, it's not begun, it simply hasn't stopped. Those damn poles just
keep moving about ;-)


Juergen Nieveler

 

Here is the current coverage of a satellite I'm currently tracking
from my location in central Iowa.
http://www.edu-observatory.org/gps/coverofPRN15.041217.16:05UTC.gif

 

Turn off all the satellites that a GPS receiver can see and then
calculate the numbers seen at all point on the earth and the DOPs
at those locations and you will find that the damage is not nearly
as *localized* as you might think. Do the calculations.

 

A twin has to be able to climb, with the gear and flaps retracted, with
the critical engine inoperative. But not at gross weight, and not at all
temperatures. It just has to be able to do it at some weight and
temperature. The flight manual has a WAT chart (weight, altitude,
temperature) that shows under what conditions the aircraft can climb
single-engine, and how fast the climb or descent will be. Few light
twins can climb single-engine at much above sea level and much above
standard temperature. Installing more powerful engines means more fuel
consumption, higher costs, etc. Everything is a compromise of some sort.

 

Certainly

DGPS is the bread and butter of the professional GPS community. Mapping,
minning, precision agriculture, survey (sub cm), and a host other applications.
See: http://www.edu-observatory.org/gps/dgps.html

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. Here's how it works:
http://www.trimble.com/gps/dgps.html
-- Trimble Navigation Ltd.

See: http://www.edu-observatory.org/gps/dgps.html

 

It's the FAA's job to pay for those. A tax is collected on every
passenger who boards any airliner and put into the airport trust fund to
pay for this. Certainly not every airport will get a precision approach,
but more are coming. And the lighting isn't necessarily required for a
precision approach - only to get the approach minima down to the lowest
possible. It's possible to have a precision approach to a runway with no
approach lights. The minima will be higher, of course, but it's still
better than an NDB approach that only gets the aircraft into the general
vicinity of the airport, or even a non-precision GPS approach that
encourages 'dive and drive' techniques. Precision GPS approaches are
coming.

 

No--it's much more complicated than that.

 

Time dissemination
http://www.edu-observatory.org/gps/time.html

 

Network Synchronization.

High-density OC-48 to OC-192 SONET systems require very precise sync systems.
Single digit nanosecond systems are the norm, and they use GPS+atomic clocks.

---Bob Gross---

 

Well, you need to look them up. The only requirement in Part 23, normal
and commuter aircraft, is that the aircraft demonstrate the ability to
climb with the critical engine inoperative, gear and flaps retracted.
There is no specification of weight, temperature, or rate of climb. The
manufacturer must provide a WAT chart to show the conditions where it can
climb. That's it. The US Codes of Federal Regulations are available at
http://tinyurl.com/3n7tx. Title 14, Aeronautics and Space, are at
http://tinyurl.com/6j27s. The various parts are a click away. Or if you
don't trust tinyurls, you can start at http://ecfr.gpoaccess.gov.

 

So you say--Where is your cost analysis?

So you say--Where is your cost analysis?

You asked what would be effected

The are many safety of life and rescue operations now using GPS. There
are certainly life threatening situations that GPS can make a difference.

 

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

 

albeit more expensive!

 

DGPS doesn't work without GPS...
http://edu-observatory.org/gps/dgps.htm

 

Nothing in life is "guaranteed" except death. Critical infrastructure like
GPS needs to be on all the time.

 

At what cost?

 

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


Juergen Nieveler