[Tfug] A sense of time

[johngalt1]

Good info. thanks for the post.

----- Original Message ----- 
From: "Louis Taber" <>
To: "Tucson Free Unix Group" <tfug at tfug.org>
Sent: Tuesday, August 14, 2007 10:03 PM
Subject: Re: [Tfug] A sense of time


> Time again,
>
> I couldn't locate the documentation, but I seem to remember that you can
> slew the clock to set it to a new time on some UNIX type systems.  So the
> time at any given instant is moving toward the new setting and not making 
> a
> finite jump.  With ntp (Network Time Protocol) it is not really an issue.
> ntp in general is a MUCH better way to go than trying to set the time
> yourself.

You could mess around with the drift value, but why?

> If you really want to know what time it is get a GPS receiver, not an
> "Atomic Clock".  An "Atomic Clock" looks at a single 60kHz signal from 
> Fort
> Collins CO.  This signal is usually not adjusted for the signals time of
> flight.

 Not sure what the error in accuracy between a clock updated by radio and a 
GPS is, but I won't be discarding my atomic clock.

> A GPS receiver figures out where it is specifically  by looking at
> the various time of flights.  If you have access to L2 it also compensates
> for the lensing effects of the atmosphere.  Internally a GPS receiver will
> know what time it is to about 10-20ns.  About the time it takes light to
> cross a medium size room.  A system with a GPS receiver connected to it 
> with
> a PPS (pulse per second) and serial connection can be set up as a stratum 
> 1
> ntp server.  If this is on a fast local area network, all of the connected
> systems can be quite accurate as well.  At least good enough to snipe on
> e-bay.  - Louis

Amusing..

Yeah, but why reference ultra accurate GPS time for eBay? In that case, eBay 
time is the standard.

http://viv.ebay.com/ws/eBayISAPI.dll?EbayTime&_trksid=m40
















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