Clarification about the term "GPS Shutdown"

well ironically most GPSs will tell you where you are with precision, but
can't tell you which way you are facing - but a compass can. Looks like a
more or less tied game...
We have magnetite ore deposits around here that cause some local eratic
needle swings. My old uncle used to carry 3 compasses and take the best 2
out of 3. Before you think that's crazy, let me point out that NASA did
exactly the same thing with space craft navigation systems!!

For me, a compass and a paper map as well as a GPS are essential for
navigation:
1. A compass is easier to use to maintain headings. I set my GPS datum to
that of the paper map, set it to use "true north" heeadigs, and dial the
declination into the compass. Now I can just get a bearing from location to
target from the GPS and walk it using the compass. If I have to dodge
around a pond, I can jut get another correected GPS bearing and walk it.

2. If the GPS batteries die, I have enough information with map and compass
to get where I want to go just fine.

If the administration shut down civilian GPS tommorrow I'd be very
inconvenienced since I use it for rough survey work, but with map and
compass I'd still get by just fine. I believe that for those interested in
navigation problems, a good understanding of map and compass is essential
and very useful in understanding GPS.

By the way, compass can tell you where you are. How about triangulating on
two known points on the horizon? "Where you are" is relative. Sometimes
accuracy of a few feet doesn't matter. In fact, we are assuming here the
only form of navigation other than GPS is compass. How about LORAN?
sextant (yup - I have my grandpa's)? Good navigation on both land and water
has been around for a long time (see the movie "longitude" for an
interesting sidebar), and GPS is very useful, but very new to the party.

 

Having used map and compasses for about 60 years, I rely on them. GPS is a
wonderful assistant - but never trust one method of navigation alone.
Always know where you are on the map so if the fog surprises you in the
mountains, make sure your GPS does not take you over a cliff! It may
hurt....

 

One of the things it can provoke is a crippling halt to GPS, which

Exactly what infrastructure would sustain crippling damage by a short halt to
GPS? Maybe......
Airplanes falling out of the sky because they can't find airports? (GPS is a
luxury system on aircraft - IRS, INS, ADF, VOR, TACAN (military), LORAN, ILS,
and GLIDESLOPE are Primary systems, and lets not forget our gyro stabalized
magnet compass systems for heading information)
Trains running off thier tracks? Trucks running off the highway? Surveyors
building a bridge across the wrong river? Ships sailing in the wrong ocean?
Millions of lost hikers?
GPS shut down for 24 hours...It's the end of civilization as we know it!!!

 

Not quite. You can stand in one spot with a GPS, then walk ten metres,
then take another fix, and you'll know exactly which way is north.

Not by itself.

If you don't know where you are, you don't know of any other "known
points," either.

And notice that compasses alone were never very useful for navigation.

 

What did you use as backup to your map and compass?

 

Many forms of transportation.

Possibly ... or hitting mountains.

Just because they're older? Which of them is "most primary"?

 

Which of course shows that outside this group people DO have
contingency plans in case civilian GPS has to be turned off in a hurry



Juergen Nieveler

 

It's a mystery then how people have managed to navigate with only map
and compass for ages...

So you're a 2nd Lieutenant? ;-)

True, a compass alone won't help - but a compass and a map in the hands
of somebody who knows how to use them are just as accurate as GPS.
Using map and compass is slower, but more reliable... a compass doesn't
need batteries.


Juergen Nieveler

 

Yes it is. Commercially available, off-the-shelf. Used in IT
departments around the world, or for example as emergency power in
hospitals.

Maybe not for your home utility service - it's quite a bit different
for companies.

Yes, before the project was scrapped he planned to use a cheap GPS
receiver to guide a large model airplane. Much easier than designing
inertial guidance.

That would probably be taken into account before deciding to turn off
GPS. However, there COULD be a situation when turning off GPS might
seem the better alternative, and that's all the White House said. Just
because you can't think of a reason why GPS could be down doesn't mean
it's not a good idea to prepare for that situation.


Juergen Nieveler

 

With a containerized diesel generator running in the backyard to power
my servers for the duration of the (planned, I admit) power outage,
like I did a couple of months ago?


Juergen Nieveler

 

An option that isn't always available and is also inconvenient - which
is why some receivers include a small electronic compass.

Of course. You have to have a map, and have to know how to use it.

You should always at least know on which map sheet you are, and unless
you're traveling through a featureless desert you should be able to see
terrain features that stand out and can be recognized on a map.

A compass is VERY usefull if you want to find the magnetic pole. Try
doing that with GPS ;-)

Juergen Nieveler

 

Backup for a map is more difficult, but every boyscout learns to find
North without the aid of a compass - that's REALLY child's play.

Of course, even with GPS you'll still need a map - the raw coordinates
aren't really usefull for navigation, unless your GPS has a "Leap over
mountains and swim through rivers"-feature. GPS saves time because you
don't have to triangulate your position with a compass anymore, but
without a map GPS is useless.

Juergen Nieveler

 

Not a single one of which would catastrophically fail.

Because all those other navigation systems suddenly failed as well, and
ATC couldn't see the plane on their radar, and somehow the pilots
weren't able to look out of the window anymore? If an aircraft would be
in such a desperate situation, they'd declare inflight emergency and
get a military escort - problem solved, the military aircraft would
still be able to navigate.

Depends on which part of the flight. For transoceanic flights it would
be LORAN, for final approach ILS...


Juergen Nieveler

 

They haven't. Accurate navigational methods are a recent development.

Only if he already knows where he is.

 

How is it done?

If you know where you are, that's half the trip.

I've regularly used GPS without a map.

 

Why not?

It's surprising how failures actually occur in real life. Very often a
single point of failure leads to disaster, even with lots of backup
systems.

Where would the military escort go to find them?

How can it change?

 

Yes.

It's called Galileo.

 

It depends on the nature of the target and the nature of the attack. A GPS
receiver costs a few dollars and weighs a few ounces. An INS is heavier, more
expensive and more difficult to integrate. If you just want to randomly lob a
missile into a city, then that doesn't require much precision.

While this whole thread is a bit (a lot) out of control, we're discussing things
at the edge of unliklihood... one unlikely, but plausible, is an offshore (or
from w/i the US) attack using a simple UAV dependant on GPS to hit a power
station containment dome with, say, 4000 lbs. of Semtex. You can set S/A to a
high value, but I don't believe it can be skewed to guide something off track.
So there's still a probability of a hit. You can shut down the C/A code
completely and deny GPS navigation completely... the UAV runs into a hillside
and blows up. You restore C/A after 24 hours or so. Very little inconvenience
to avoid atmospheric dispersal of radioactive dust and gas.

It would be better, perhaps, to have spoofing and jamming xmtrs installed near
all facilities like that above, and for all we know that may be in the works,
and that would be a more controlled and localized means of denying GPS w/o major
disruptions.

And how much disruption? I still hold that GPS might cause cellphone networks
to behave poorly, and some networks to bog down. Power companies might have to
isolate their grids more resulting in some power outages. Airline, corporate
and private pilots would just continue to use VOR/DME, NDB, INS, LOC/ILS, etc.
according to their eqt. list, and hardly think anything of it. Police and fire
would have to rely on maps and dispatcher aid... but society will not come
crumbling down. SCATANA has been in existance for decades and what the
announcement amounts to is a variation on the theme. SCATANA has never been
fully invoked (it was partially following Sept. 11).

While a few people here have dreampt up a few simple scenarios for terrorist
attacks that rely to some degree on GPS, you can be sure that there are a
variety of governmental, military and consultant think tanks that are dreaming
up a much longer detailed list of ever diminishing plausibility scenarios. For
each risk there is corresponding list of deterents and actions. A number of
them will look at infrastructure as both risk and solution in defeating and/or
mitigating an attack.

Cheers,
Alan

 

Not in a number of plausible cases. That is the point.

Low cost, accurate guidance.

Guide an unmanned boat into an LNG facility loaded with Semtex.

Guide an unammed aircraft into a nuke station conatinment dome, loaded with Semtex.

There are alternatives to shutting off GPS to defeat or mitigate these attacks,
and in the case of the LNG terminal, they are already heavilly guarded against
such an attack. But there are hundreds of similar targets.

I'm not suggesting it. I hate the idea. But the US Gov't has publicly stated
that it is a possible defence.

1) Mx, You have not named a single critical thing that is wholly dependant on
GPS (though asked repeatedly by me and at least one other poster).
2) I have answered your questions about both the effect of GPS loss in terms of
degraded service in communications; inconvenience in some areas and absolutely 0
danger to aviation.

I don't care if you're persuaded, and from past exchanges with you elsewhere I
have little hope. The fact is that you know little about the workings of GPS at
large and you believe far too much in universal dependance on it. It is true
that it is an enabler in many areas. But those areas can tolerate loss of
service without serious detriment to society or individual for a brief (and
mostly a very long) period of time. I doubt that there is anyyhing in existence
that is so dependant on GPS as to present a hazard or danger the moment GPS
signal is lost. And if there is it should be immediately decommisioned or
rectified. You have still not named any such facility, serice, system or
anything that is so dependant on GPS.

You've tediously harped on the effect of major GPS loss. I've countered
reasonably: a) it won't be so bad; b) the duration will be short c) workarounds
are many.

Unmanned Boats, UAV's.

Cheap, easy, accurate. UAV's have been around since WW II, probably before.
But nothing has enabled their stunning emergence over the past 10 years as much
as a single resource called GPS which allows low cost, low weight, accurate and
reliable guidance.

Cheers,
Alan