[ntp:questions] NTP architecture recommendation

David J Taylor david-taylor at blueyonder.not-this-bit.nor-this-bit.co.uk
Sun Aug 19 05:33:35 UTC 2007

Richard B. Gilbert wrote:
> Well, time is certainly one of the four variables that a four
> satellite fix gives you, the others being latitude, longitude, and
> elevation, but I don't see that time is in any way equal to position!
> UTC is the same in Paris, New York, and Los Angeles and those three
> positions are in no way equal!

Errors in the time delay of the signal from one satellite, whether 
deliberate or accidental, will result in errors of position.  Selective 
Availability (SA) is a deliberate reduction in the accuracy of the time 
measurement capability, resulting in a limitation on the accuracy of 
position measurement.  It would also make the UTC in Paris, Berlin and 
Stockholm differ slightly were UTC measured purely by GPS observations.


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