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#10190 - 01/21/11 11:35 AM Unreliable GPS On Left & Right Coasts
wagga Offline


Registered: 10/07/09
Posts: 2248
Loc: Humbug Reach (Pop. 3)
East coast NOTAM.



"The Notice to Airmen said the GPS tests will be carried out beginning Thursday and are expected to last through February 22. They will cause spotty GPS signals in a several hundred mile radius centered off the coast of Florida."

"During the effective period, test events will be active for 45 minutes followed by 15 minutes of off time."

West Coast NOTAM.
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#10191 - 01/21/11 12:09 PM Re: Unreliable GPS On Left & Right Coasts [Re: wagga]
KevinR Offline


Registered: 11/03/09
Posts: 595
Loc: Manchester, NH
Thanks for posting that. I'll be using my GPS tomorrow on the west coast.

FWIW - I used it Wednesday on a hike up Argus, and didn't notice any issues with the GPS track created by the Garmin 60CSx. The only weirdness I've ever noted, and it was very limited, were some stray points created on a hike up Cottonwood Creek Trail (south of Lone Pine) a couple of years ago, and that I believe was caused by echos/bounces where the canyon walls are particularly narrow.

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#10192 - 01/21/11 12:48 PM Re: Unreliable GPS On Left & Right Coasts [Re: KevinR]
Steve C Offline


Registered: 09/22/09
Posts: 7719
Loc: Fresno, CA
Interesting. Here's another article: Bone in Its Teeth

Here's the GMap4 map of the location of the test center in California: (full screen version)



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#10194 - 01/21/11 12:59 PM Re: Unreliable GPS On Left & Right Coasts [Re: KevinR]
wagga Offline


Registered: 10/07/09
Posts: 2248
Loc: Humbug Reach (Pop. 3)
I think the disruption is at or above the elevation shown in the various zones. Which means hiking in Florida shouldn't be affected. I've never been there, but I don't think there are any 10,000 foot mountains.

On the other hand, on the West Coast diagram, you can see that one could easily be hiking above the service ceiling of quite a few small general aviation aircraft.

Why is this this happening?. I suspect it has something to do with denying exact geographical information to our enemies, while retaining the facility for our own military. Note that the US launched a heavy (20 tons, size of a city bus) secret military payload from Vandenberg on Thursday.
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#10197 - 01/21/11 01:10 PM Re: Unreliable GPS On Left & Right Coasts [Re: wagga]
wagga Offline


Registered: 10/07/09
Posts: 2248
Loc: Humbug Reach (Pop. 3)
Another thought: Some cell phone systems rely on receiving the atomic clock time signal from GPS satellites. Also, the Internet has some reliance on the GPS clocks to synchronize IP package queue/dequeue processes. That would break streaming video and VOIP, but not email & such. Both, however, can use local (internal) clocks to continue for some time.
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