GPS Sustainability

[BILLY THE KID]

"so the missles were just fired and then they crossed their fingers as to where they were gonna hit , they were nailing targets from ships out in the middle of the gulf."

1. You need to understand GPS was not then and is still not now the only navigation system which allows this type of strike accuracy

"this maybe what they want the world to think , its not like they are gonna advertise that they got their military firepower down to knocking the whiskers off of a feild mouse ."

2. It is fairly well known what is and what is not capable. Reds under the beds are another problem!

so was wondering do the pentagon email you or call on the red phone ?

cause unless you either the U.S president or one of the joint chiefs of staff then how can you be so sure ?

[SatNav]

1. Obviously the type of questioning is becoming quite silly and of no relevence and serves no purpose to the issue.

2. Once things get to this stage then can not see any point in continuing quite silly and rather childish discussion.

3. The following link might be helpfull to those that have some real interest in understanding the actual subject and if I get any further relevent infomation will put it up otherwise I have no intention of muddling with stupid comments from people who have no understanding of what they are on about.

http://blogs.agi.com/navigationAccuracy/?p=196

[Chine]

As an aside and with reference to GPS sustainability/fallability, the US authorities recently conducted an excercise where they intentionally jammed GPS signals in a particular area to measure the effects of potential terrorist action.

The effect was significant to the point where AIS networks collapsed. This has renewed calls for eLoran funding to back up the GPS.

[SatNav]

1. Outside of the "Americian" perpective the majority of the world including Australia gets nothing out of updating Loran.

2. Loran of any verison does nothing for Australia.

3. On jamming White Sands Missile Range (New Mexico) used to host a yearly jamming jamboree open to anybody to go and play in a safe jamming environement. This has been so popular they have in recent years charged participants and is now almost by invitation only. Some interesting stuff went on during these "jam"borees.

4. Again on jamming Australia (pushed by AirServices Australia) was the first and at last look the only country in the world to have legislated jamming devices. If the rest of the world is serious with regard jamming then they should follow this lead otherwise any talk about jamming and justification of other systems is hollow.

[peterbo3]

This is interesting. I pulled it off The Hull Truth.


Have a look at this article:

http://www.cringely.com/2009/05/waas-up/

From the article:

The Government Accountability Office, a Federal watchdog agency, reported on May 7th that the Global Positioning System of satellites used for navigation and many other business and scientific purposes as well as for proving that your teenage son was actually driving down the Interstate at 100 miles-per-hour last Thursday night when he claimed to be bowling, well that satellite system is in danger of becoming unusable because satellites are not being replaced quickly enough by the U.S. Air Force.

Only it isn’t true.

Right now on Google News you can find more than 400 stories all saying the same thing with varying degrees of alarm. The Air Force is three years late in launching a new generation of GPS satellites. The replacement program is over-budget by more than $700 million. The whole mess has been incompetently run and ought to be fixed. All this is true. What isn’t true is that it matters very much to the real world operation of the GPS system or its users.

The GPS system has 31 satellites in orbit right now, the oldest of which has been operating since 1990. For the system to work perfectly it must have 24 or more satellites functioning. The GAO says it is only 80 percent certain that the Air Force can maintain full coverage before replacement satellites can be launched. This lack of confidence is not based strictly on the idea that eight or more satellites will go dark over the next couple years, but that some undetermined number of satellites will go dark, the Air Force will make no progress in replacing them, and that the remaining satellites will be unable, for some reason, to be moved into new positions, filling gaps in coverage. That’s quite a combination of improbable events and makes me very suspicious of the 80 percent number.

For the GPS system to work requires that the receiver in your car, airplane or iPhone be able to simultaneously track at least three satellites (four if you require altitude information). If your receiver can show the satellites it is tracking (many can) you’ll see the number in sight is usually five to seven satellites with the rest being over the horizon and out of view.

If your GPS equipment was purchased in the last couple years it probably makes use of the Wide Area Augmentation System (WAAS), which is a system of ground stations and two geosynchronous satellites that help your receiver correct for ionospheric variations that can slightly degrade GPS performance. Without WAAS your GPS is only accurate to 7.6 meters. With WAAS accuracy is about one meter. The reason we care about this is because GPS is used now to land airplanes and the difference between 3.8 meters above the runway and 3.8 meters below the runway could ruin your whole day.

In addition to improving GPS accuracy over North America (and just North America — there are different systems for Europe and Japan), WAAS also effectively adds two virtual satellites to the GPS constellation. These are the two geosynchronous reporting satellites, which for ease of use in the system are treated by receivers like regular GPS satellites except they for some reason don’t seem to move in the sky. For WAAS-enabled GPS receivers, then, it is possible to maintain acceptable accuracy with only ONE (not three) of the regular GPS satellites in view.

The chances of the GPS system going down are very remote — FAR lower than the 20 percent suggested by the GAO. That’s because the GAO ignored completely in its analysis the implications of WAAS.

So what’s going on here? Why is this even a story?

The Air Force is late and over budget and the GAO wants to make a point of that. The best way to make that point is by putting the technical story in the worst possible light, which the GAO has done to an extreme that I think is excessive. This is just political infighting.

What’s worse, though, are those 400+ news stories that miss the point entirely. Where is a professional and questioning press? It looks to me like 400+ media outlets rewrote the GAO press release and left it at that, giving-in to the fear-mongering that has become the way government policy is promoted these days.

Some stories quoted experts saying a failure isn’t likely. Some stories said the GAO likely has a non-technical agenda. But I couldn’t find any stories that put the whole thing together and questioned whether there was any news value at all.

We need smarter, better-informed, and less gullible reporters. THAT’s the story.
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[tunaticer]

Well that is another version of the story, but which one is more correct or more probable? That is the question.
As for WAAS, I am fairly sure that system does not operate effectively anywhere but in the good old US of A. Leaves a fairly stark hole in the story of using WAAS in Australia to land planes with i think.

Either way we will find out in time which way it will swing in reality and sooner or later it will become a user pays service in its replacement form, they will not replace it without charging for the new services.