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Rhosyn Mor · 19-05-2009, 08:06

in the Guardian today was this piece
GPS system 'close to breakdown' | Technology | guardian.co.uk

Fascinating stuff for a sailor, they talk about at least partial
GPS system degredation by next year

Highlander40 · 19-05-2009, 08:49

Does anybody know what happens to chartplotters when bad data or no data comes in? A guy on the dock said that his Garmin blacked out the screen. My Raymarine did the same thing but I can't tell why. I am worried that the backlight may be flakey.

ad_astra · 19-05-2009, 09:59

This is unlikely to affect mariners. Essentially, there is a chance that one or more GPS satellites may fail before they are replaced. However, 4+ satellites are visible from any location on the face of the earth. Only 4 satellites are necessary to determine position, additional satellites only provide higher precision. Accuracy would still be good to several tens of feet, instead of several feet, with the loss of a few GPS satellites.

Now there is an outside chance that enough satellites could fail before being replaced that there would be sporadic outages in some locations, but this is an incredibly unlikely scenario.

Celestialsailor · 19-05-2009, 10:14

Yes...This is nothing more than another example of poor media reporting and hype. Even when 1/2 the satellites we have now were up, the system worked fine. There is no way the military based system would be allowed to be compromised.

TaoJones · 19-05-2009, 10:44

Quote:

Originally Posted by Celestialsailor

Yes...This is nothing more than another example of poor media reporting and hype. Even when 1/2 the satellites we have now were up, the system worked fine. There is no way the military based system would be allowed to be compromised.

Yes, except . . . except that the entire GPS satellite array is vulnerable to a sudden high intensity solar-radiation storm. Such an event could take down the whole array at once. And just as such events have occurred periodically throughout our planet's lifetime, it is a certainty they will occur in future. The problem is that our advanced technological systems have not yet had to cope with a high-intensity EMP (electro-magnetic pulse).

In a study for NASA by the US National Academy of Sciences, published in 2008 and reported earlier in 2009, the following proposition was advanced:

"While a severe storm is a low-frequency-of-occurrence event, it has the potential for long-duration catastrophic impacts to the power grid and its users. Impacts would be felt on interdependent infrastructures, with, for example, potable water distribution affected within several hours; perishable foods and medications lost in about 12-24 hours; and immediate or eventual loss of heating/air conditioning, sewage disposal, phone service, transportation, fuel resupply, and so on ..."

A free summary is available in pdf format here (free registration required), and the entire report is available for purchase.

The bottom line is that relying only on the GPS system for navigation is risky, at best. Every serious mariner should be capable of navigating the "old-fashioned way."

TaoJones

svHyLyte · 19-05-2009, 10:55

See the following: GAO Says GPS III Launch Delay Could Drop Constellation below 24 Satellites | Inside GNSS

ad_astra · 19-05-2009, 11:09

Taojones, I'm going to respectfully disagree with you. That same report which you quoted from goes on to outline specifically what the expected difficulties GPS will experience due to solar flares. The answer is not a catastrophic satellite failure -- these satellites are designed to deal with all sorts of EMP. The main problem GPS would experience would be a temporary blackout caused by excitation in the ionosphere, i.e. the blocking of radio signals. The satellites themselves would be unharmed.

That said, I agree wholeheartedly that no one should ever rely on one system of navigation exclusively.

**sandy daugherty** · 19-05-2009, 12:31

Scare Tactic. The feeding frenzy for federal dollars inevitably produced many new versions of the "Washington Monument Ploy" Several decades ago the National Park Service responded to budget cuts with the announcement that they would have to close the Washington Monument. A press frenzy and public response led Congress to back down. Those are the two essential elements; a sympathetic or ignorant Press and enough jaz to elicit a public response.

footnote: Galileo seems to be bogged down; fears of a US satellite failure, or a chance to shine at the US' expense could prompt a better stream of Euros in that direction!

**David M** · 19-05-2009, 12:39

"a lack of investment means that some of the crucial GPS satellites could begin to fail as early as next year."

So some are "crucial" and others are not as crucial? There are over 30 satellites now, losing a few, at worse, would only mean a slight reduction in accuracy. No one particular satellite is any more important than another. This author does not know what he is talking about.

My city does the same thing every time we are faced with a budget shortfall. They threaten to cut back police and fire protection...not cut the meter maids, the library staff or the street sweepers.

Cheechako · 19-05-2009, 13:27

The fact finding commission looking into the continuance or discontinuance of Loran has recommended to the Obama Administraton that the system be kept as a backup in case of GPS system failure..... Solar flares are reality, just takes a big enough one or an EMP.

hugosalt · 19-05-2009, 18:22

Can't say what politics are at work with this latest report...but I do know
that we have launched and will launch 3-4 next generation GPS 2F satellites
this year. One was launched in March replacing a old Sept. '96 satellite...
another scheduled to launch on Aug. 21st and then another Nov/Dec.... all this
year replacing old satellites...and more to launch next year...switching from
20 year old Delta 2 rockets to new Delta 4 rockets...Seems their committed
to keeping us in the game!

hugosalt · 19-05-2009, 18:28

Forgot...the old satellites will be kept in service in back up rolls...making
a case the system is becoming redundant/more reliable.

captain58sailin · 19-05-2009, 18:41

Loran C was at best, a general navigation guide, at the time it was better than nothing, when GPS came along it blew Loran C out of the water. I wouldn't ever rely on only one way to navigate, if you use that gob between your ears, usually one can find one's way around.