[ntp:questions] how to have offset < 1ms

unruh unruh at wormhole.physics.ubc.ca
Wed Apr 14 21:20:04 UTC 2010

On 2010-04-14, Rob <nomail at example.com> wrote:
> nemo_outis <abc at xyz.com> wrote:
>> True, one can chase any number of will-o-the-wisps such as the causes of 
>> the network latency and asymmetry, but that is not the central problem 
>> posed by the OP.
> But it is!
>> In short, Unruh may be boring in his reiteration of his simple GPS 
>> solution, but that is because it works for a very wide range of problems 
>> - including this one!
> No, not at all.  The poster wants to be within 1ms of his chosen reference
> clock, and syncing to GPS is bringing nothing towards that.

No. He said he was using that machine as a reference and that he wanted
to have a time accuracy of 1ms. Now, that may mean that he wants the
onboard clock to be within 1ms of that landbased system, even if it is 5
hours out from true time, or it may mean that when the ship is in dock,
he wants to bring his shipboard clocks to within 1ms of true time. If it
is the former, then you are perfectly correct. If it is the latter, then
that landbased clock is a red herring. Only he can tell us wha the
really wants. And he is not doing so.

I would think he would want his shipboard clocks to be close to real
time ( so that he can for example know when the sun will rise, or the
stars will rise to be used for navigation) but maybe you are right that
he does not care about true time. 

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