GPS Jamming Trials in UK - GASIL

[FairWeatherFlyer]

From latest GASIL:

GPS Jamming
As described in AICs, the MoD will carry out GPS jamming trials during the next
few months. The fi rst will be around the Sennybridge training area (D203 in mid-Wales) between 7th and 18th September. There will be another over the sea South of Cornwall on 9th & 10th September, and finally another in East Sussex on 14 & 15 October.

http://www.caa.co.uk/docs/33/srg_gasil07of2009.pdf

Last one is near Bexhill according to this Safety Alerts (http://www.ukfsc.co.uk/information/safety-alerts)

[Lemain]

There is a considerable amount of GPS jamming around NATO fleets in the Mediterranean, at sea level. I don't know to what altitude the jamming extends or whether it is notified; it is not usually notified in Notices to Mariners (equv. NOTAMS). It is a very common practice.

[Seven Fifty Seven]

Already happened in Scotland.

[Sir George Cayley]

I found a website you can report GPS probs such as jamming to. I think it's www.nano.co.uk

Sir George Cayley

[411A]

As usual, the FAA leads the way...others follow.
ALL US scheduled GPS outages (IE: scheduled jamming trials, specifically geographically denoted) are broadly publicised well in advance, via NOTAMS to pilots and notice to mariners.
Normally, these exercises take place well after 11pm, local time, to cause the least disruption to airbourne/marine GPS navigation users.


Well then....wonder when Europe will actually wake up?
Answers on a postcard....:}

NB.
The US taxpayers provided the GPS system for use, free of charge...so don't complain.:rolleyes:

[Right Way Up]

As usual, the FAA leads the way...others follow

"Congressman: FAA actions displayed ‘malfeasance bordering on corruption’
FAA whistleblowers say jobs were threatened - News- msnbc.com (http://www.msnbc.msn.com/id/23942137/)

I think you'll find Italy is well ahead of the FAA! ;)

[airmail]

I may as well bite as well.

Firstly 411a, if you actually read the OP you will see that the trials have been communicated via various means before they happen. I don't know who started publishing trials first but at least I am able to read and understand what someone has posted :ugh:

Secondly, the US taxpayers did pay for GPS but the lack of forward movement recently within the US has led to the Galileo project which is funded by EU taxpayers and is far superior to GPS.

Bite mode off :}

[USav8or]

Airmail - you might be right but first once the project actually 'proves itself'... For now, it's just an EU tax drain...

This reminds me of the VHS - Beta debate - which one is better? ...imagine if the government decided to create it's own, an even better version of the tape player... ...and then all of a sudden the CD player gets invented... :ugh:


BBC NEWS | Science/Nature | Q&A: Europe's Galileo project (http://news.bbc.co.uk/2/hi/science/nature/4555276.stm)

IS GALILEO WORTH THE COST? (http://news.bbc.co.uk/2/hi/science/nature/4555276.stm)
There are many who have had deep reservations about the cost of Galileo from the outset - and, in particular, the uncertainties that exist about what the precise end-cost will be.
This prompted one sceptic to dub Galileo the "Common Agricultural Policy of the sky".
There is also an intense debate about the true scale of the revenue opportunities available. Who will want to pay for Galileo-enhanced services and how much will they be prepared to pay?
GPS was built at considerable cost by the US taxpayer but the returns for the American economy mean that investment has been repaid many times over. Early GPS entrepreneurs are now dollar billionaires, but how much room is left in the sat-nav market for others?
Also, the progress of the project has hardly inspired confidence. The private consortium of aerospace and telecom companies selected to build and operate Galileo collapsed last year. Infighting and political meddling were blamed.
Galileo has been bedevilled by delays and cost overruns. A group of UK MPs said recently that Galileo provided "a textbook example of how not to run large-scale infrastructure projects".
All that said, the European Commission is adamant that the potential benefits are huge. Even if the value of the future global sat-nav market has been overstated (at 450bn euros annually from 2025 in one analysis), the returns to the EU economy demand member states press ahead with Galileo, the EC believes.

[airmail]

USav8or

Fair comments - however I suspect that the same article could have been written when the US developed GPS.

Incidentally, I note that the article talks about how some people have made billions out of GPS, I read something quite recently that said the people that have made the most out of GPS (i.e. the owners of TomTom and others), are set up in places like the Caymans. Nothing like giving something back!

airmail

[USav8or]

"Fair comments - however I suspect that the same article could have been written when the US developed GPS."

I agree. In general, the only time I think a government should get involved is for military reasons... All governments are usually bad 'business owners' and that's why I wonder if EU should try to keep this project private...

"Incidentally, I note that the article talks about how some people have made billions out of GPS, I read something quite recently that said the people that have made the most out of GPS (i.e. the owners of TomTom and others), are set up in places like the Caymans. Nothing like giving something back!"

Well, all those companies have been sold and resold many times. Nothing new there... I think Tomorrow Technologies at one point were owner by UPS Technology, a company headquartered in Atlanta with more than 400,000 employees worldwide... Hopefully they "gave something back"... :)

Well, at least they gave me a job... ;)

By the way, my main point is that although I think Galileo will be a great project - by the time it's up and running there probably will be better and cheaper options out there... How do I know that? Very simple... Not only one but 28! governments (EU + Norway) are involved in this project... :D

[Rainboe]

I suspect the days of 'free use' of such a wonderful facility as GPS are drawing to a close. The two way nature of Galileo makes me suspicious its main added function aside from Distress calling is to give the facility to turn off for you if your subscription is not up to date!

I'm interested why GPS jamming trials have to take place? Are they trials of people who have jammed the amazing facility of GPS, or are they trials of how best to jam up a GPS system (why?). Can we look ahead to seeing GPS jammed to enforce complete take-up of Galileo (at a cost to every user)? Can we look ahead to seeing military action between the US and Europe over political manipulation of this sort? I am perfectly happy with GPS- its free functioning gives my car satnav (TomTom and Garmin I've been through- Tom Tom was crap) all the power I need. GPS powers aeroplanes for free. Why exactly are we developing Galileo at enormous cost (apart from Road Usage Tax reasons!)? A big project, but the whole thing stinks!

[AnthonyGA]

The military in the U.S. developed local GPS jamming techniques before turning off Selective Availability. SA was the deliberate, worldwide distortion of the GPS signal data to make GPS very inaccurate (off by as much as 100 meters), rendering it useless or even dangerous not only for the bad guys but also for many of the applications for which it is now being used. SA was added as an afterthough (like anti-spoofing encryption), after the military discovered that GPS was vastly more accurate than it had expected (15 meters, instead of 500). After effective local jamming techniques were developed, SA was permanently turned off.

For better or for worse, GPS is extremely easy to jam, which is one reason why it should not be relied upon as the sole means of navigation for aircraft. The military regularly conducts jamming tests in the U.S., and I'm sure jamming in active theaters is common, although obviously NOTAMs for the latter are not necessarily going to be published.

Galileo is another one of Europe's catch-up projects to try to show that it can do tech just as well as the U.S. On rare occasions, Europe is successful with such projects (e.g., GSM), but more often it just wastes taxpayer money and time while dozens of countries bicker endlessly with each other, turning practically every project into a political fiasco. It looks like Galileo may be going in that direction. And the idea of making people pay for something that is already free is highly illogical. Then again, pan-European projects like this often defy logic.

[Lemain]

AntonyGA Galileo is another one of Europe's catch-up projects to try to show that it can do tech just as well as the U.S. On rare occasions, Europe is successful with such projects (e.g., GSM),..... and Airbus, of course.

[411A]

....has led to the Galileo project which is funded by EU taxpayers and is far superior to GPS.


For not being in operation yet...quite a stretch.:rolleyes::rolleyes:

[Dan Winterland]

The reasons for developing a parallell system such as Galileo are obvious. GPS has been around for a long time and has it's limitations - the ability of it's owner to switch it off at will being a big one!

Galileo is far more advanced and will give far better accuracy. And it is in operation now. Only a few satellites are flying, but combined GPS/Galileo sets are on sale now and they use a combination of signal from all the satelites they can see - including Galileo's.

[FullOppositeRudder]

ALL US scheduled GPS outages (IE: scheduled jamming trials, specifically geographically denoted) are broadly publicised well in advance, via NOTAMS to pilots and notice to mariners.
Normally, these exercises take place well after 11pm, local time, to cause the least disruption to airbourne/marine GPS navigation users.It goes further than just those two groups. There are other enterprises which have come to rely on the GPS system in recent times. A very high percentage of agricultural enternprises (ground as well as air) use GPS guidance systems for tractors and other farm machinery, and most broadacre agricultural operations are done on "autopilot" with the driver/operator there just to do turns when required and monitor the operation at other times.

Off thread I know, but GPS has become just as essential to these operations as it can be for mariners and airmen.

[USav8or]

"The reasons for developing a parallell system such as Galileo are obvious. GPS has been around for a long time and has it's limitations - the ability of it's owner to switch it off at will being a big one!"


The EU will have the switch off ability too - pay or else... :rolleyes:

[EGMA]

I once flew overhead RAF Lyneham, the GPS had me directly overhead; visually I was at least a mile to the north.

Moral: Never believe anything a government tells you!

[CONF iture]

or ...
"Never believe anything untill it has been offically denied"

[angels]

It worries me that people are becoming too reliant on something that can break down or be switched off by the operator.

What back up is in place?

And also, why on earth do you need satellites for agriculture?? Surely when ploughing/harvesting you get to the end of the field you turn around and start heading back on a parallel course? :confused:

[Rainboe]

Can someone who understands better than me what the disadvantages of GPS accuracy are? I can understand if you can throw a nuke off target by a mile or so, you might have a totally razed airbase rather than a completely obliterated one, but who are the 'bad guys' using GPS for devious means? Are we trying to throw their road navigation off course? Why else bother with SA? We have perhaps one of the greatest facilities ever invented being allowed to the world for free, and people are putting an intentional spoiler in. Maybe I'm naive, but I really don't understand.

[BOAC]

We are not talking 'nukes' here - the problem arises if you try and lay down weapons using GPS when both sides are just a few hundred feet apart, as in 'Close Air Support'. As you say, a few 100mtrs for a nuke is not a big issue.

[Groundloop]

And also, why on earth do you need satellites for agriculture?? Surely when ploughing/harvesting you get to the end of the field you turn around and start heading back on a parallel course?

When your field is up to five miles long it probably gets rather tedious!

[thescouselander]

Rainboe, the problem is terrorists. A primitive gps guided cruise missile can be put together for very little money using off the shelf components. It's not that difficult either.

Gps jamming is one way to stop it.

[Blink182]

And also, why on earth do you need satellites for agriculture?? Surely when ploughing/harvesting you get to the end of the field you turn around and start heading back on a parallel course?Using satellite pictures and other methods , you can see which areas of your fields are most productive for agriculture , fertiliser is spread in differing densitys by way of GPS guidance of the tractor thereby trying to maximise the crop yield.

[chrisN]

Angels, there are some quite sophisticated uses of GPS in farming now.

For one example, found after a quick Google , see FarmerGPS - Welcome! (http://www.farmergps.ca) (or .com). Or do a search of your own if that interested.

I am not an expert. But while doing a survey on fertiliser usage with some local farmers, I encountered one who described his system (not the one in the reference above).

He used a company which sent an ATV over every field, taking soil samples at every 10 metre point, showing soil composition and characteristics. The system then plotted a “contour” map of the field, showing which parts were chalky, which not, which low on (e.g.) nitrogen etc. If you know nothing about farming, you would be amazed at how much it varies over a field, let alone from one to the next. Certainly true in East Anglia UK, and probably lots of other UK places, where the geology and microclimate changes a lot from one place to another.

The fertiliser typically comes in 3 parts, N, P and K. Instead of spreading a mixture with averaged proportions, each was spread by different spreaders on a GPS-controlled machine, using the survey data. The farmer told me it was fascinating to see one spreader wheel slowing down and another speeding up as it reached a bit low on P and high in K etc. Overall, it reduced the total usage and net cost of fertilising.

Other uses of GPS include semi-automatic combine harvester operation.

These and other things require reasonably high positional accuracy from the GPS.

If GPS were stopped, going back to old methods would be challenging, I suspect.

Chris N.

PS – At Precision Farming Tools: Global Positioning System (GPS) - Virginia Cooperative Extension (http://www.pubs.ext.vt.edu/442/442-503/442-503.html) there is what seems an excellent article on GPS, accuracy, etc. – intended for farming but the general descriptions look good to me.

[angels]

Blimey, all I wanted to know and more! Thanks.

I still get the feeling that we are becoming slaves to technology though.

I was held up at Dover for over two hours recently because the P&O booking computer crashed. They couldn't get anyone onto the ferries. The traffic was queuing up the hill out of Dover and because of that traffic people sailing with other companies couldn't leave either.

I was near the front of the traffic and on talking with various port employees it turned out P&O don't really have a Plan B for when their computer goes TU.

In the future, if we become over-reliant on GPS and it is suddenly turned off, how would the airline industry cope? Easily? With difficulty?

Not panicking, just wondering.

[AnthonyGA]

The accuracy of GPS isn't really a disadvantage, except for people in the military who are paranoid by profession and spend lots of time imagining ways in which their own technologies could be used against them. The military philosophy is to keep every technology classified forever so that the bad guys can never use it (and if civilians must suffer from not having it, so be it).

Fortunately, cooler heads prevailed with GPS, which is why the military was ordered to make it available to the civilian world.

The overreliance on GPS is a concern, and there is no obvious back-up. Galileo will not be a back-up, since it's just another version of the same technology. The problem is that there may be no back-up for satellite navigation in general, especially as government authorities foolishly decide to retire other forms of navigation to save money. If you have VORs or NDBs, you can still find your way home in bad weather. If you have only GPS, and GPS stops working, you're lost.

There are some circumstances in which GPS accuracy can lead to problems. One problem, already adumbrated here, is that GPS normally is used in conjunction with a database, and the overall accuracy of GPS in practice depends not only on the satellite longitude and latitude, but also on the accuracy of the database that tells equipment what lies at that latitude and longitude. This is why GPS might put you a mile north of an airport: chances are that the GPS was right on the mark, but the database was substantially in error.

Another drawback to accuracy is that it can put two aircraft in exactly the same place at the same time, which is bad. Two aircraft flying towards Big Mountain might still be thousands of feet from each other, but two aircraft flying towards the BGRSK waypoint might well blend together when they reach it, if they happen to coincide in altitude and time.

Still another drawback is excessive reliance on and trust in the technology by pilots who don't really understand how GPS works and what the potential problems with it might be. They come to believe that GPS is always perfectly accurate, and they might find out too late that it isn't. Some pilots talk as though they trust GPS altitude more than altimeter altitude, for example, when in fact the altimeter is orders of magnitude more accurate than GPS for altitude.

There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof.

As always, the smart aviator will use every available tool to maintain maximum safety in the air. GPS is all well and good, but it's still extremely important to have a Plan B. Airliners have this built in to some extent, with flight management systems that can combine information from multiple sources (GPS, IRS, VORs) to arrive at highly reliable conclusions; but private pilots in small aircraft who have got into the habit of navigating solely by GPS can get into deep trouble (as multiple NTSB accident reports demonstrate).

[Lemain]

Anthony, it's not like that with military. GPS is for delivery (guidance) and fusing (detonation) but never used alone as it is jammable. Cartography is the big issue with GPS, as you say. Cartography can be a long way out -- in my personal experience hundreds of metres, quite far enough to kill you. The real danger is that it seems to be so accurate while it is miles out. If only GPS could shrug and say "not sure", but that isn't built into the system.

[00nix]

For those who worry about SA or any other way of 'switching it off': be assured that the largest usergroup of GPS has been proven in recent months to be quite supported by government and does not even move/navigate.

Banks nowadays use GPS to time transactions as a microsecond delay on a volatile stock/currency market can cost/bring in (dependend on the party) serious money.

As for Galileo/all others: the 28 (or maximum of 30 +2) satelites that the US can put up (a 5 bit ID seemed sufficient in the 70's) are often insufficient (try living above 60 lat). As the optimal RF spectrum for sending time-sensitive signals through the atmosphere is not to wide, it only takes some simple programming to include multiple pseudo-range sources (be it NAVSTAR/Galileo/Glonass/Some Geostationary stations)

i.e. Don't see Galileo as a competitor/the future (depending on view) see it as addition: 20+ satelites in view and you have continued navigation between high buildings. (in aviation, that would probably be combined with a prospect of having a chat on the merits of keeping above MSA in relation to keeping your licence)

[EGMA]

On the subject of back ups ... I let the GPS & AP talk to each other, they seem to get on just fine. I am busy monitoring all the other navaids, or even looking at the map!

Just in case the lights go out permanently, I've still got a slide rule ...

[chrisN]

How much use will Galileo’s extra satellites be to our present GPS receivers? Are they compatible? Or will only new receivers that have both GPS and new Galileo capability be able to use both sets of satellites?

Chris N.

[411A]

In the future, if we become over-reliant on GPS and it is suddenly turned off, how would the airline industry cope? Easily? With difficulty?



Quite easily, with tried and true stand-alone enroute navigation technology, INS.
Having been personally using INS for enroute navigation since the very late nineteen sixties/early nineteen seventies on 707 aircraft, it can be very accurate, for the enroute case.

The Litton units were/are more robust, the Carousel units more accurate, in my experience.
Plus/minus one nautical mile enroute navigation (over long enroute sectors)accuracy is possible, IF the specific units are maintained properly.

[Dimitris]

Rainboe, the problem is terrorists. A primitive gps guided cruise missile can be put together for very little money using off the shelf components. It's not that difficult either.

Gps jamming is one way to stop it.

Some GPS rumors and non-rumors from SLF:

Rumor 1:

I think I've read somewhere that commercial GPS chip sets like http://www.sirf.com/products/GSC3LPProductInsert.pdf (http://www.sirf.com/products/GSC3LPProductInsert.pdf)have inbuilt max speed and max altitude just for that reason (60Kft, 1000knts in the link). It may not stop from using it on short range missiles, but longer range wont work.

Rumor 2:

One of the reasons Selective Availability (SA) was switched off is that during some 'recent' US deployment (Desert Storm? Balkans?), troops on the ground were using (on their own) commercial devices as navigation aid, which obviously where affected by the SA. Switching off SA made life of the troops on the ground easier.

Rumor 3:
UK is kind of against the militarization of Gallileo (using it to guide weapons), France and Germany want it. Could be because of better relationships with the USA, or maybe that the UK has suffered losses from European built guided weapons (Falklands, Exocet ASM), that with a military Gallileo signal will just get better.

Non rumor:
Gallileo when finished (2014+) wont be better in accuracy than the latest block of GPS satellites (Block III?). GPS will be superior by then. Gallileo is better than the current GPS satellites, but not the GPS of 2014+. The military signal of GPS may be even better by then (beam focusing etc).
Its the strategic independence in navigation that makes EC fund it fully after the failure of the PPP (Private-Public Partnership).
China is also chipping in some 300-400 million euros, they have their own local positioning system, and looking for a global one in the future.

[keith smith]

1.I know of no reason why Galileo should be superior to GPS,and anyrate it doesn't exist yet (just two demonstrators, the cheaper of which was from a UK university and saved the dayfrom losing frquency allocation to comms industry)
2. The benefit comes from combination of both systems(both sides have sworn that they will be mutually compatible).Doubling of number of satelliteswill inprove RNP considerably.
3.FAA have dilly-dallied over back-up. Among candidates are E-Loran (no timing for dreaded bankers), residualATC radar.INS would probably require
calibration, but not everyone has got it.(Litton have done it experimentally)
4.I am not sure Europe can produce thegoods. They havn't yet certified EGNOS, which is little more than a copy ofWAAS,which now is certified for hundreds of runway ends.
Keith

[Dan Winterland]

Dual GPS and Galileo receivers will be required. They are already on sale now (for marine and land use at least, I don't think aviaiton sets are available yet).

Galileo is more accurate. It's a new system whereas GPS dates from the 80s. The system can't develope much when the original satellites are still in use. Although GPS Block 2 satellites are flying and Block 3 are coming soon, they are still hampered by the limitations of the original system. Galileo achieves 1m accuracy in it's basic mode. It's also much faster to aquire and compute a position.

GPS has a problem in that the programme of replacing satelites is behind schedule. Recently, the US Government accountability office warned that full coverage may be lost in the near future due to this.

[reynoldsno1]

Galileo is far more advanced and will give far better accuracy. And it is in operation now

mmmmm

16 June 2009 Yesterday at the Paris Air Show in Le Bourget, ESA and Arianespace signed a contract for the launch of the first four operational Galileo satellites on two Soyuz launch vehicles from Europe’s Spaceport in French Guiana.


mmmmmmmm

[angels]

Anyone here know how to take a star fix?

Anyone know how to use a sextant?

Not taking the michael, genuinely interested.

[4Greens]

Yes, from my early years in the RN

[green granite]

I too used a sextant when I was doing the RYA yacht-masters course, never used it in anger though as I've always been able to use radio aids to roughly locate my position. This was in the 60's when Consol was still operating and radio beacons were thick on the ground.

[Dimitris]

1.I know of no reason why Galileo should be superior to GPS,and anyrate it doesn't exist yet (just two demonstrators, the cheaper of which was from a UK university and saved the dayfrom losing frquency allocation to comms industry)

First Gallileo satellite was not made by a UK university. It was made by a spin-off company of a UK university Surrey Satellite Technology Ltd (SSTL) - Home (http://www.sstl.co.uk/) . The company was created in the 80s and was bought recently by EADS Astrium.

If the link doesn't convince you PM me for more.

Again, Gallileo its not about making a superior system (at least at first) but about strategic independence...

[chrisN]

DanW wrote: "GPS has a problem in that the programme of replacing satelites is behind schedule. Recently, the US Government accountability office warned that full coverage may be lost in the near future due to this.”

Does anybody know what is really happening on this? I did some searches which suggest that there is no significant risk to the basic GPS system. The following suggest something rather different - no threat to present coverage, just a hitch in launching extra functionality.


Some people who seem to know what they are talking about say the following:


“CautiousOptimist” :
“ . . . There have been 2.5 generations of GPS satellite, with the third being developed currently. There are 32 satellites in orbit, the most recent being launched in March of last year and the oldest in 1993. To provide a fix accurate to 10 meters, a receiver needs to get signals from 4 satellites concurrently. . . . The Air Force is currently launching 5 new GPS satellites in the space of one year (March was the third). Presently, there are 31 active satellites, and one spare. When the one launched in March goes active, one of the current satellites will become the second spare. The system only allows for 31 active satellites at a time. 21 are needed for full coverage for the Earth, so there is significant redundancy in the current "constellation". By November, there will be 31 active, and 4 spares.

There have been delays in the third generation GPS satellites (Block III), due to new features (such as 10X power transmission, interoperability with Galileo, and resistance to jamming). But if we suddenly started losing satellites, current levels of service would be maintained with up to 10 satellites lost.

. . . . meant to say that, once the final 2 launches of the 2nd Gen satellites this year, the constellation will be able to continue service with the loss of up to 12 satellites, without additional launches.

[Excerpts from GPS system 'close to breakdown' | Technology | guardian.co.uk (http://www.guardian.co.uk/technology/2009/may/19/gps-close-to-breakdown) ]

---------------------
And from : GPS Satellite Glitches Fuel Concern on Next Generation - WSJ.com (http://online.wsj.com/article/SB124520702464422059.html) :

By ANDY PASZTOR

[re a satellite launched in March] “ . . experiencing performance problems in orbit. It hasn't become part of the "operational constellation" of more than two dozen other GPS satellites, and is slated to undergo a battery of tests expected to stretch through October to try to resolve the problems, according to an Air Force news release.


The GPS system, which serves both military and civilian users, provides precise time and location coordinates for everything from military missile launches and "smart" bombs to automated bank-teller machines to aircraft, ships and everyday vehicles. The Lockheed satellite is the first to include a new civilian frequency -- dubbed L5 -- designed for, among other things, use by future nationwide air-traffic control systems. But that signal, part of test package, apparently is interfering with other signals from the satellite and reducing their accuracy, according to industry and Air Force officials. The degraded signals are accurate only to about 20 feet, versus about two feet for typical GPS signals, industry officials said.


The issue is significant, according to these officials, because it could complicate deployment of a new family of Boeing Co. GPS satellites currently being built that also feature the L5 signal. Already years behind schedule and hundreds of millions of dollars over budget, the 12 satellites, which are scheduled to replace satellites currently in orbit, could face further testing and delays to ensure that they are free of interference problems. The Boeing satellites have a history of quality-control and manufacturing problems unrelated to the latest concerns.


. . . . Concerns over signal quality come barely weeks after a Congressionally-ordered study raised a red flag about potential erosion of GPS accuracy in the next few years due to launch delays and other challenges. If certain launches get delayed up to two years, the General Accountability Office report predicted, the Pentagon could have trouble maintaining the desired fleet of 24 fully-functional GPS satellites in operation.


The Pentagon responded by minimizing the potential risk, arguing that significant spare capacity remains on orbit and on the ground to handle unexpected problems. Gen. Robert Kehler, head of Air Force Space Command, said in an interview earlier this month that the GAO conclusions were overly pessimistic partly because they failed to take into account strategies the Air Force could use to extend the life of existing satellites. For example, Gen Kehler said, managing power output could give solar arrays longer life.


Despite some continuing quality-control issues with Boeing's IIF versions, Gen. Kehler said, "we're not going to have an issue" maintaining the current robust constellation.”

[beerdrinker]

Anthony
Quote"There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof."

Not totally true. In the USA there are now more LPV approaches than ILS approaches. LPV approaches use WAAS technology to give ILS like indications in the cockpit to help you fly down to CAT I limits. They currently go down to 200 feet and 1/2 mile RVR (Depending on the runway / approach lighting).

WAAS is a form of SBAS (Satelite Based Augmentation System). The Australians are leading the way with GBAS (Ground Based Augmentation System)at airports such as Sydney. GBAS is a much improved form of LAAS which never really got fully developed.