[ntp:questions] Slow convergence of NTP with GPS/PPS

Unruh unruh-spam at physics.ubc.ca
Fri Oct 24 00:51:46 UTC 2008

David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:

>Unruh wrote:

>> Assuming the network noise is the 100us level, (which it is for example
>> between me and Regina 3000km away) you should get the accuracy easily to
>> 1ms in 1 sec. if all you want is the phase error. One packet exchange will
>> give it to you. 

>You have an unused network.  For about 20km between work and ISP it is 
>more like 100ms peak to peak.  (2Mb/s 1:1)

It is more like 20m. And even for 2000km (Vancouver to Regina) on the
public CanadaNet network it is only 40ms.

>> receiver would be better, especially if it know its location. Then within
>> seconds it would know the time to nanoseconds. If it has to diiscover its

>It's going to take at least 30 seconds to do that, as it will need the 
>detailed emphemeris data and that takes 30 seconds to transmit (it might 
>well pick the strongest signal and try to read the coarse ephemeris data 
>first; I'm not sure if that fits in the 30 seconds.

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