[ntp:questions] Re: Drift handling....

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Wed Jan 4 09:33:23 UTC 2006

Martin Burnicki wrote:
> Hi all,
> I've got the feeling that some clarification is required on drift
> values.
> Let's have a look at an example:
> Say you have some wristwatches and you want to check whether they are
> accurate, or not. On the television there is a clock displayed
> whenever a news programme is broadcasted. You trust that clock and
> see that one wristwatch goes ahead by 1 minute every day, another one
> by 20 seconds, and a 3rd one by just one second.
> Martin

Martin, I feel this is quite a good analogy.

(Although, with some British TV stations timekeeping is very bad: (a) they 
no longer broadcast either the time pips or a clock showing the time, (b) 
there is a processing delay of a few frames in analog TV due to image 
processing and (c) the delay in digital TV means it is several seconds 
behind analog TV.)

You don't normally expect the drift on your watch to change unless you do 
something stupid like drop it onto concrete, so if the news was off time 
one day, in the first instance you might like to believe your watch rather 
than the TV - the football had overrun it's time!  However, if the news 
gets further and further off time over a period of a few days, then 
perhaps it's your watch and not the TV station which is wrong!

[Your own leap-second results are most impressive, thanks for posting 


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