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Old 22-05-2009, 21:38   #1
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Continued Degradation of GPS?

A friend of mine said there was an article about the GPS Constellation degrading to 1000 foot accuracy...has anyone else heard about that?
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Old 22-05-2009, 21:43   #2
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It would not matter to me if they degraded GPS accuracy to a thousand feet as I don't rely on the GPS for my position. I use the GPS to generally orient myself to what I should be seeing around me if the position is correct, but I never believe the position until I check things out with my own eyes.

In many locations around the world, the charts are inaccurate, and the GPS isn't much of a help anyway. In Nuku Hiva, when I plotted my position, the spot was more than a mile inland.

I trust my depth sounder and my eyes.
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Old 22-05-2009, 21:53   #3
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I'm in with Maxingout in also not trusting GPS down to that level. Seen too much carnage from people who have, including at least 4 deaths here contributed to exactly that.

The GPS talk currently doing the rounds is due to some US Air Force dude (I think, some US big wig at least) saying that the old satellites are dropping out faster than being replaced. Also the new versions have only just been started to be thrown up into the sky, over 3 years late. But he did also say the system is fine even if a little fragile for a few years until the new birds are flying. Their (the AF) goal was to and still is, to have at least 4 birds visible to any spot in the entire world at all times. He sees no reason why they can't even if it means reactivating some of the old birds for temporary fill ins.
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Old 22-05-2009, 23:19   #4
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::nods:: Plus remember that GLONASS will be fully back and functional (it's currently degraded about 10% in coverage) by 2010. Galileo, a better system than GPS or GPS3 for civilian use, is expected to be fully online by 2012. Compass (Beidou-2) is also building out from the regional Beidou system.

Looks to me like the future for multi-system receivers is pretty good. Imagine having a unit pulling in from more than 100 possible satellites plus augmentation systems... Receivers have already been built for Beidou's M1, so it's just a matter of time.
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Old 23-05-2009, 02:25   #5
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A possible disruption in GPS service, because of delays in modernizing and deploying the constellation of satellites, was raised in a recent report by the Government Accountability Office (GAO). The GAO report prompted the Air Force Space Command to reassure the public that the GPS system is not in danger of failing.

See the GAO Report:

U.S. GAO - Global Positioning System: Significant Challenges in Sustaining and Upgrading Widely Used Capabilities

More:

GPS satellites not 'falling out of the sky': Air Force

Air Force waves off warnings about GPS accuracy - Technology - MiamiHerald.com
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Old 23-05-2009, 06:01   #6
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Originally Posted by Amgine View Post
::nods:: Plus remember that GLONASS will be fully back and functional (it's currently degraded about 10% in coverage) by 2010. Galileo, a better system than GPS or GPS3 for civilian use, is expected to be fully online by 2012. Compass (Beidou-2) is also building out from the regional Beidou system.

Looks to me like the future for multi-system receivers is pretty good. Imagine having a unit pulling in from more than 100 possible satellites plus augmentation systems... Receivers have already been built for Beidou's M1, so it's just a matter of time.
Are you saying that it will be possible for our current GPS units to utilize the various international GPS satellite signals without modification?
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Old 23-05-2009, 06:24   #7
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GAO is applying a little public pressure on the Air Force to use more of the Two Billion Dollars allocated for GPS Satellite maintenance.

Dave: Nuku Hiva has always been in the same place, and GPS will always read correctly. The problem is with neither of those two facts, but with the original navigators and cartographers who just screwed up.

Now this is interesting: Google Earth, free on the internet, is accurate where old charts are not.
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Old 23-05-2009, 07:10   #8
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Hud3: The Galileo system is designed to be used by current receivers, *if* they are programmable to receive the frequencies. Almost none have this option yet.

GLONASS has been around all along, but post-Gorbachev was allowed to deteriorate similar to the USA's GPS, so no one worried about adding their frequencies and algorithms to a non-commercial shipping satnav. But now they're teaming up with India to restore and improve both the constellation and the technology, and there are some new receivers available in India already. I have not heard if these are multi-system receivers or not, or if they're strictly commercial or not.

Compass signal has been cracked, not released publicly. I don't know if China has ever made plans to make the constellation's signal available to the public. This raises an interesting possibility: if the system is good and companies wish to market receivers using it, but the signal encoding is not released publicly, then clearly those receivers could not be manufactured in China. Anyway, I believe it was Stanford U that reported cracking the encoding, and they built a proof-of-concept receiver and published the specification for *that*.

Whatever the case, all of these countries except Europe are building their GNSS for military reasons first. The fact commercial aircraft and shippers can use it is a nice side benefit. And lowly sailors (and hikers, and people lost in Chicago in their cars) have almost no input or consideration in any of them - again, excluding the EU's Galileo system. I suspect multi-system receivers will be on the market in the next couple years, and they will mostly be any one of the other systems (mostly USA's GPS) + Galileo.

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Old 23-05-2009, 13:05   #9
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Thanks for the clarification, Amgine! Interesting topic...
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Old 29-05-2009, 10:22   #10
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There have been a couple of articles in recent issues of Ocean Navigator on this subject, including one referencing GAO findings/report. Might be worth while looking them up. As for the technicalities of the thing, way beyond me, though perhaps not the case with others. It does seem as if "old age" effects inanimite objects too, including those out in space.
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Old 29-05-2009, 11:12   #11
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The GPS system in this country is "too big to fail" - Sound familiar?
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Old 29-05-2009, 11:26   #12
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The GPS system in this country is "too big to fail" - Sound familiar?
Now there's a dose of reality. Sounds all TOO FAMILIAR & SCARY. I'll be learning how to use that sextant I bought 15 years ago.........i2f
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Old 29-05-2009, 11:37   #13
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Now there's a dose of reality. Sounds all TOO FAMILIAR & SCARY. I'll be learning how to use that sextant I bought 15 years ago.........i2f
Good idea in any case. Espically post lightning strike.

Anyway, I'm suprised no one has addressed Panbo's take on this, so I guess I will.

From the 20 May 2009 entry:
Quote:
... I've gotten several notes of concern about the situation, but I think boaters are about the last user group that needs to worry about it. We almost invariably use GPS in almost ideal conditions, puttering along at a relatively slow speed with a wide open sky view. And we don't care beans about altitude (except for going negative)! We were about the first to get into GPS because it was useful on the water before the full constellation of satellites was in place, and, if the system truly does break down, we may be the last. But we surely do value electronic positioning a great deal. So here's my question: If we're having trouble keeping GPS fit on a two billion dollar budget, why the heck is the government even considering saving a tenth of that by shutting down eLoran, a viable backup system?
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Old 29-05-2009, 11:38   #14
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You folks who doubt GPS accuracy must have stopped flying commercial now that GPS approaches are approved (and flown - daily!) for most everywhere?

There are lots of reasons that magical little box and you can have a differing opinion, but it not knowing it's coordinates will seldom be the cause. I doubt the US is going to give up on GPS now that most weapons systems and essentially all aviation rely so heavily upon it.
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Old 29-05-2009, 11:52   #15
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I had promised myself to dust off the sextant way before this subject came up. Just for the fun of it to use the heavens to find out where I am at. It will probably never be needed. I imagine there will be some satisfaction is just aquiring the skill........i2f
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