Re: Lep seconds
- From: "Rob Kimberley" <time.bandit@xxxxxxxxxxxxxx>
- Date: Wed, 16 Jan 2008 12:13:30 -0000
Have come across requirements in MIL sat comms systems that need GPS time as
well as UTC. In fact I supplied a system to a MIL customer a few years ago
with two Zyfer GPS NTP servers - one set to provide UTC time and the other
set to provide GPS time.
Rob Kimberley
"David L. Mills" <mills@xxxxxxxx> wrote in message
news:fmij6g$odi$1@xxxxxxxxxxxxxxxxxxxxxxx
Joseph,
Please say what GPS equipment is used in the "big radar world" to deliver
TAI or even GPS. My expensive GPS receivers have no provision for other
than UTC. TAI is of course a constant offset from GPS give or take
laboratory nanoseconds. It would be interesting to learn why big radar
needs other than UTC.
Dave
Joseph Gwinn wrote:
Dave,
In article <flli7r$5iu$1@xxxxxxxxxxxxxxxxxxxx>,
"David L. Mills" <mills@xxxxxxxx> wrote:
Joseph,
Conversely, if a client syncrhonizes to a server strictly running TAI and
never signals leaps, NTP will deliver TAI. NIST, USNO and I have
discussed this serveral times and concluded the lessor of two evils is to
continue with NTP on UTC.
Yep. True enough. But GPS emits TAI (plus an offset), so one can claim
that configuring the NTP timeserver to emit GPS System Time (not UTC) is
to generate what is essentially TAI. This is widely done in the
big-radar world.
Joe
Dave
Joseph Gwinn wrote:
In article <T1199401837@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
david@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx (David Woolley) wrote:
In article <298286.52982.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
marknmbox-88@xxxxxxxxx wrote:
compliant. Is there a similar mod for NTP. I am
hoping that there is a mod that will cause NTP to
supply theoretical UTC (even if it is not ascci).
Both POSIX and NTP use UTC. Your problem is that you are not using
using UTC, but, rather, using TAI.
Actually, POSIX does *not* use UTC in the normal sense of the word, as
no leap seconds are applied.
The fundamental POSIX timescale counts what amount to SI seconds from
the POSIX Epoch, 0h 0m 0s UTC 1 January 1970. Every day contains
exactly 86,400 seconds.
That said, if one drives a POSIX box via NTP from a GPS timeserver set
to emit UTC (versus GPS System Time), time on the POSIX box will be
pretty close to UTC.
Joe Gwinn
.
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- From: marknmbox-88
- Re: Lep seconds
- From: David Woolley
- Re: Lep seconds
- From: Joseph Gwinn
- Re: Lep seconds
- From: David L. Mills
- Re: Lep seconds
- From: Joseph Gwinn
- Re: Lep seconds
- From: David L. Mills
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