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Old 27-01-2011, 09:15   #1
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Challenge: US Turns Off GPS in Florida - What Is Your Backup ?

Much speculation has been given to "what if" the U. S. turns off GPS satellites.

Well, they have, albeit sporadically, for the next month in the Florida area.

Airline pilot alert here.

What is YOUR backup navigation plan?
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Old 27-01-2011, 09:21   #2
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Avoid Florida.
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Old 27-01-2011, 09:35   #3
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Navigation as follows, headng to Key West keep land on the starboard side. Heading to South Carolna keep land on the port side. If heading to the Bahamas keep land on the stern side.
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Old 27-01-2011, 09:43   #4
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It pays to know one's way around America's Wang.
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Old 27-01-2011, 09:45   #5
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one more reason to keep a DR line on a paper chart!
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Old 27-01-2011, 09:47   #6
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Compass, eyeballs, chart, DR. If you can't get along with these for an hour, you probably shouldn't be out there.
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Old 27-01-2011, 10:24   #7
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Avoid Florida.
Great answer!!

What's the reasoning behind this though? (the GPS being turned off, not the thread...)
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Old 27-01-2011, 10:34   #8
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In addition to the reasoning question, how are they shutting off GPS in Florida and not Georgia or Idaho or ...?
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Old 27-01-2011, 10:38   #9
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Great answer!!

What's the reasoning behind this though? (the GPS being turned off, not the thread...)
It's probably not being technically turned off, but being Jammed. If one uses a horizon calculator and translates the horizon figures given by the coast guard in the local notice to mariners of 150 miles and the FAA advisory for distances at altitude, they are consistant with a jamming transmitter broadcasting from the position indicated in the notice from an altitude of 15,000 feet. GPS frequencies are line of sight (GPS recievers can only see satellites above the horizon) so this makes sense.
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Old 27-01-2011, 10:43   #10
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Avoid Florida.
Thats easy if your in Toronto, but we live in Florida. Then again, we also have these things called paper charts. They were pretty accurate the last time we used them too.
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Old 27-01-2011, 10:45   #11
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Simply block signals coming from the direction of the jamming. A baking sheet should work.

Other than that, sail in the general direction of your destination. Don't hit anything.
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Old 27-01-2011, 10:53   #12
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I strongly suspect that this is a bunch of horse pucky! First, the satellites can't be turned off for one area. If one or two were to be turned off for some maintenance or other test then you'd still have a bunch and would get fairly good positioning.

It is possible that someone in the Dept of Defense could be testing some kind of "jamming" or misinformation hardware but I doubt if they would do it for the time suggested in this article.

I did a quick search of the GPS.gov, FAA, and PNT (US Space Based Position Navigation and Timing) websites and found no reference to any interruptions in service. In fact, the policies are to maintain constant service without interruption. Apparently there was a short interruption in the WAAS system due to malfunction/maintenance recently but it's back working.

But...it is worth mentioning that the GPS satellites are getting pretty old and near the end of their intended life. I don't think that we've put up any new ones for a very long time.

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Old 27-01-2011, 10:58   #13
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Its a conspiracy by tow boat companies and the govt to boost the economy
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Old 27-01-2011, 11:02   #14
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I strongly suspect that this is a bunch of horse pucky! First, the satellites can't be turned off for one area. If one or two were to be turned off for some maintenance or other test then you'd still have a bunch and would get fairly good positioning.

It is possible that someone in the Dept of Defense could be testing some kind of "jamming" or misinformation hardware but I doubt if they would do it for the time suggested in this article.

I did a quick search of the GPS.gov, FAA, and PNT (US Space Based Position Navigation and Timing) websites and found no reference to any interruptions in service. In fact, the policies are to maintain constant service without interruption. Apparently there was a short interruption in the WAAS system due to malfunction/maintenance recently but it's back working.
I don't know what you searched, but there are notices in both "Notices to Airmen" (Notams) put out by the FAA and in the "Local Notice to Mariners" (LNM) put out by the USCG. These are official US government publications. If this wasn't true these documents would not contain such advisories. If I was sailing within 150 miles of the published position I would plan on temporary GPS outages during the periods indicated.
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Old 27-01-2011, 11:02   #15
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But...it is worth mentioning that the GPS satellites are getting pretty old and near the end of their intended life. I don't think that we've put up any new ones for a very long time.
The plan was to have 24 operational satellites. But there are now about 30 operating, plus some spares. Several will be launched this year. And more in the next few years.
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