[ntp:questions] Re: Good GPS for attic?

David Schwartz davids at webmaster.com
Wed Feb 16 04:55:05 UTC 2005

"David Magda" <dmagda+trace050112 at ee.ryerson.ca> wrote in message 
news:86sm3xy2xe.fsf at number6.magda.ca...

> However, with navigation there is still the backup of intertial
> systems. If accurate time is important to someone, they would
> probably have a backup atomic clock. There's also WWVB and CHU for
> those in North America.

    The FAA currently does not require inertial navigation as a backup for 
GPS. They do currently require there be some backup available, and that GPS 
equipment be capable of evaluating its own accuracy. For the most important 
aviation applications of GPS (approaches), inertial navigation is not 
suitable as a backup.

    The FAA desperately wants to make land-based radionavigation obsolete. 
This is due to the cost of maintaining the network of radionavigation 
beacons. One of the holdups in using GPS as a full replacement has to do 
with the details of guaranteed reliability.


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