GPS Shutdown in time of US "National Crisis"

[Jerricho]

Guess if you're IMC in Buttholenowhere you could be a spot of bother.

Netscape/CNN Article (http://cnn.netscape.cnn.com/ns/news/story.jsp?id=2004121521290001739682&dt=20041215212900&w=APO&coview=)

[FakePilot]

Ah,it would be a delight to all those who yearn for the glory days of VOR-whoring. Just turn off the INS first.

Because of Selective Service, I doubt anybody would try a serious pond hop without something to back up the GPS.

[Hand Solo]

Thats why the EU are developing their own version of GPS. For once a sensible and strategic use of our tax euros.

[FakePilot]

I think I heard that there is an agreement to shut down both in "time of war." Could be wrong, though. Might make sense if you consider that what's the point of you having the ability to turn off your GPS if the enemy can simply use the other guy's.

[411A]

Hmm, I guess the Europeans really don't know about the ability of the DoD to turn off the VOR's/DME's, NDB's, ILS's ...etc, in time of national emergency either.
Gosh, its been this way since the late 1950's and was put in place under Eisenhower.

News travels slowly, I guess.

[Jerricho]

I wouldn't just generalise "just Europeans" there 411A. I wonder how many pilot types (especially the weekend warriors ;) ) that are aware of this in North America.

[Airbubba]

Yep, this is nothing new, just a "journalist" looking for a headline on a slow news day...

See: http://www.faa.gov/ATpubs/MIL/Apdices/milapd17.html

[Jerricho]

Hey, thanks for the link Bubba! :ok:

[Loose rivets]

Not all that surprising, when you consider that many road signs in the UK were removed during WW11

[TheOddOne]

...and mostly didn't get put back again afterwards!!!
TOO

[Diverse]

What's the point in the US turning off the GPS system in times of war when it was for military reasons the system was developed in the first place. I thought everyone's use of it apart from the military use of it was secondary.

So they're going to spend billions in construction and maintenance of a system that they couldn't use for the sole purpose it was intended.

[TheOddOne]

Ah yes, but they can tell their folks when it's going to be switched off/jammed/interfered with. Presumably this can be done on a second-by-second basis so that the service can seem seamless for their own users but hopelessly inaccurate for the enemy.

You'll all no doubt seen NOTAM from time to time adertising intentional jamming of GPS for military purposes. Hopefully the commercial organisations who have GPS installed take note of this and rely on INS to a greater extent during these times. I know private pilots who rely utterly on their GPS - putting their lives in the hands of someone in a mountain in Colorado with a digit on the 'off' switch!

At least with VOR, NDB, DME ILS we've got our destiny in our own hands to a greater extent (or am I deluding myself again?)

Cheers,
The Odd One

[BEagle]

"I wouldn't just generalise "just Europeans" there 411A. I wonder how many pilot types (especially the weekend warriors) that are aware of this in North America.

Or indeed that there is anywhere outside North America?

Yes, in a real war I would indeed expect all radio navigation aids to be turned off. But since both civil airlines and private flying would also be likely to be banned, would it really affect anyone?

Y-code GPS would probably continue - but CA-mode would be off for the duration.....even with SA re-enabled.

[Jerricho]

Yes, in a real war I would indeed expect all radio navigation aids to be turned off

Agreed. But the term "national crisis" is a very wide statement.

[moggiee]

Still, your good old INS/IRS system should allow you to get close enough to identify the target/skyscraper visually. After all, this worked well enough until GPS came along.

I doubt that the last 2 minutes of the September 11th attacks were done on GPS/FMS.

[steamchicken]

IMHO, really safety critical GPS will only be possible with all three systems - GPS (indeed differential GPS!), Galileo when it comes on line, and let's not forget GLONASS. If you have three independent satnavs, you're getting somewhere.

[Groundloop]

I_FORD is completely wrong. GPS is still the responsibility of the US Department of Defense although GPS is now overseen by a committee co-chaired by the Secretary of Defense and the Secretary of Transportation.

See

http://gps.faa.gov/GPSBasics/index.htm

then follow links to

Interagency GPS Executive Board (IGEB)

followed by

U.S. Space-Based Positioning, Navigation, and Timing Policy

This is the full text for the new arrangements for the control of GPS.

[skyviews]

Sure I read somewhere that in the Gulf war (the first one) that they were messing around with the sats in order to degrade the service and make it inaccurate for the enemy/lay user.

[Groundloop]

My recollection of the first Gulf War was that Selective Availablity was turned off (ie the exact opposite of what SA is for) because the US did not have enough military grade receivers to issue to their ground troops and rushed around buying civil receivers which do not read the P-code. Therefore the C/A code had to be kept without SA degradation.

[no sponsor]

My understanding of GPS is that the channel for use by Civilians can be turned off, or degraded under selective availability, but the known military channel (and the other couple of unpublished channels) remain in use for those with the correct equipment.

[BahrainLad]

It's probably semantics but I'm wary when a government that considers that we are currently in "wartime" throws around phrases like "we'll only do x in a time of national emergency"......hype hype hype.

[Iron City]

Good Grief! This sure is a rumour network, and almost as full of misinformation as the journos everyone complains about!

The wire stories missed the important stuff and settled for sensational (no suprise there)

See http://ostp.gov/htmlFact SheetSPACE-BASEDPOSITIONINGNAVIGATIONTIMING.pdf

forthe fact sheet. The NSPD is classified but this is a good summary.

In case nobody was paying attention earlier this year the U.S. and EU agreed to make GPS and Galilleo compatible and to some extent interoperable and this has been worked on for years.

The EU business case for Galilleo talks about many many things besides aviation and in fact aviation is notexpected to be a major user in terms of numbers of receivers. This is fundamental to the EU plans for how to pay for Gallleo, which is not entirely clear. Possible avenues are taxes, user fees, encrypted signals that can only be used with a secret code that one pays for etc. And Galilleo is planned to have it's own precise service that is limited government/public interest (i.e. military) that is not necessarily usable by just anyone.

The GPS has never been turned off or wholesale degraded. Yes, it has been and is tested for different things. Ten years ago the US and Russia gave the services of GPS and GLONAS respectively to the world free of direct user fees and stated several years warning would be provided if this was going to be withdrawn. I haven't seen the notice yet.

In the internal US governance of GPS the IGEB (Interagency GPS Executive Board) is no more and is replaced by a National Space Based Positioning NAvigation and Timing Executive Committee supported by a Coordination Office. A friendly blue suiter will continue to do the day to day care and feeding of the system but the policy and the what to do is controlled from the top by this committee and coordiantion office.

[Ranger One]

WRT SA and military (i.e. P-code) receivers, it's always puzzled me that some third party (e.g. Chinese or Indian) have never produced a 'military' (high precision, unaffected by SA) receiver for civilian sale. US DoD might not like it, but they couldn't stop it.

Yes I know it's encrypted, and the engine shifts the crypto code regularly, but the Chinese are damned clever with stuff like that, someone could hack it if they put their mind to it I'm sure... it's pretty old tech by now...

Thoughts anyone?

R1

[411A]

Oh my gosh, the sky isn't falling after all.



GPS IMPORTANCE TO GA CONFIRMED BY WHITE HOUSE
President Bush has signed a new policy that guarantees the availability
and reliability of GPS for civilian use. And despite some exaggerated
press reports, there is no imminent threat that GPS will be shut down.
"GPS is absolutely critical to safety of flight, particularly in the
future as the FAA decommissions some land-based navigation aids and
transitions to a satellite-based system," said AOPA President Phil Boyer.
"This new policy recognizes that and adds even greater protections for
civilian use of GPS without user fees. This is tremendous news for
general aviation." AOPA provided significant input to the new presidential
directive on global positioning system policy, and was the only general
aviation organization to participate in the process. The White House
said Wednesday that any shutdown of the system within parts of the
United States would come under only the most remarkable circumstances.
But the presidential directive is very clear: The government is to
"provide uninterrupted availability of positioning, navigation, and
timing services." In other words, the GPS signal is supposed to be
available all the time to domestic users. (And it should be noted that
the government kept the GPS system operating during the aftermath of
the September 11, 2001, attacks.) For more on GPS policy, see
( http://www.aopa.org/whatsnew/newsitems/2004/041216space.html ).

G

[PAXboy]

The problem will be anticipating what is considered 'war'. Britain has been to 'war' six or so times in the past eight years (I think it is) but they are all off-shores.

For the next couple of decades, we can expect that 'war' will continue to be the local skirmish and local Iraq/Israel sort of thing. Another (truly) global war is probably some way off.

Can GPS be switched off/degraded sat-by-sat or is such a change system (world) wide only?

[*Lancer*]

One of the NOTAMs from 9/11:

FDC 1/9746 FDC SPECIAL NOTICE - EFFECTIVE IMMEDIATELY. SCATANA HAS NOT BEEN IMPLEMENTED, HOWEVER, DOD AIRCREWS ONLY WILL FOLLOW SCATANA PROCEDURES FOR FILING FLIGHT PLANS IN ORDER TO GAIN DEPARTURE APPROVAL. REPEAT: SCATANA HAS NOT BEEN IMPLEMENTED.

... they thought about it.

[OverRun]

In this rather theoretical discussion, let me throw in my two-bob's worth. I reckon that the US military do still deliberately degrade the accuracy of civilian navigation signals - the so-called "selective availability".

We were inspecting a road project in Australia, which was spread over a full 134 kilometres. The road department surveyors had been through the previous year and painted the exact locations on the surface of the road every few kilometres (for construction purposes), so we could cross-check the GPS, with locations determined the old-fashioned way using surveyor's rod and staff. We had a pretty rare situation where the exact location and the GPS co-ordinates could be exactly compared.

We were using an ordinary GPS (not differential) to pick up specific points - cattle grids, change of road surfacing, etc. The GPS was receiving plenty of satellites each time, and there was no reason for it not to work normally. The GPS was reset at the surveyed and known positions. After a few hundred metres of travel, it would be approximately 100 metres out of location. That is 100m in a random direction. This random 'error' would stay with us (being random in error each time we looked), neither decreasing or increasing in magnitude, for several kilometres until we reset the GPS. Then it would appear again after a few hundred metres of travel. The date? 20 November 2002.

What happened around that date? Not too much, apart from a lead-up to war. From the history sites: UN arms inspectors return to Iraq (Nov. 18, 2002). Bush signs legislation creating cabinet-level Department of Homeland Security (Nov. 25, 2002). The war actually started on March 19, 2003.

It would be easy to attribute this error to finger trouble, and indeed if it was just me and my fingers, I might somewhat sheepishly think this was so. But the inspection was a follow-up to one done about 6 months previously, and that had none of these problems. And even if we had made a mistake on one of the locations, I can't see it re-appearing for reset after reset. This is the first time I have had the chance to compare a GPS to 134 km worth of surveyor's marks.

While 100m error doesn't matter too much when one is navigating the airways, I wonder if it might present problems when one is using GPS for an instrument approach?

[*Lancer*]

Most airlines subscribe to the gold code anyway... even if selective availability is on for the civil code, it shouldn't affect navigation accuracy for airliners. On airways its not uncommon to have 3 aircraft passing 'exactly' one over the other.

[enicalyth]

Hi Guys

I was only speaking to Ozexpat just the other day too.

There are two senses of "Gold" code. One is the general computing meaning that it is not a beta or development version and even might be a super-grade one.

The other is a type of code invented by Mr Gold that tries to ensure that the matching of a code and a time-delayed version of itself is well-nigh impossible. This is for Code Division Multiple Access (CDMA) of 24 satellies on a common frequency. Regrettably Gold codes are a test of match but not immunity from multipath.

A better system would have been to use Coded Orthogonal Frequency Divison Multiplex (COFDM) but for backwards compatibility and reasons of historical frequency allocation this is not currently possible.

A Gold code (as opposed to a gold or non-beta code) is created in a polynomial generator and two of them are modulo two added and act as the carrier signal for the GPS data (modulo two addition again) that modulates the RF carrier in bi-phase shift keying.

This is how the single frequency coarse acquisition (CA) L1 signal is created. Selective availability and anti-spoofing is carried on the L2 signal which is "gold" in the sense that those authorised with a crypto key can get the full monty at all times. This L2 signal is quadrature modulated with the L1 and allows much more accurate atmospheric propagation corrections to be made amongst other things.

Sometimes people confuse "gold" with "Gold" and selective availability (L2 or SA) with anti-spoofing (AS). Thanks to 9/11 the US President decreed that SA would be switched off meaning that everyone can access L2 whether they are friend or foe, military or not. But the shrewd fellow said nothing about anti-spoofing which means (if switched on) you lose access to L2 again unless you have a special crypto key! Sheesh!! As long as AS is off everyone is happy and both CA and SA give the same result. If the President turns SA on then us civilians can only get CA. But with differential GPS and a technique known as codeless cross-correlation we can actually defeat Mr President so he has permanently (!!) given up with that trick. Instead he turns AS on and we cannot defeat that one.

So if by "gold" you mean access to the L2 signal then I agree. Except when anti-spoofing is turned on. Only NATO and special allies get the crypto key. Regardless of SA status it is anti-spoofing or AS which is the key to accuracy. NATO and co-alition partners are given AS crypto key capability. Airlines are not.

To discover the degree to which Anti-spoofing and jamming as well as satellite health and local terrain are likely to affect you then you must have access to the US GIANT program. Airlines don't. In Oz the ATSB appears to have managed something 'cos...

With the recent tragedy here in Oz it was possible for someone with crypto authority (those nice people outside Alice?) to run a GIANT analysis and also examine receiver memory in a French laboratory. However GPS is a simplex, passive device and there is a way for it to come out with the wrong answer even when it is not being spoofed or jammed or multipathed. For personal reasons I prefer not to go into this.

The whole construct of CDMA is inherently weak when it comes to multi-path, spoofing, single frequency assessment of ionospheric and atmospheric effects and jamming. This is deliberate because the military owners can degrade the signal(s) at will. Either electronically or by denying acces or both.

COFDM would be slightly better because it is highly resistant to multipath distortion. With CDMA it is regrettably possible to wander off track without knowing it, With COFDM that should not happen. So given a choice the military plump for CDMA and discard COFDM thus reserving the right to play sneaky pete if they have to.

Neither Glonass nor Galileo use COFDM by the way.

Despite being mature technologies all satellite navigation systems have left their owners with aces up their sleeves and unfortunately can lure you to destruction with their siren song. Which is "... I am incapable of going wrogn, worgn, wnorg so trussst in me, trusssst in me!"