gary.buhrmaster at gmail
Jul 31, 2012, 9:20 PM
Post #6 of 12
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On Tue, Jul 31, 2012 at 8:52 PM, Gavin Hurlbut <gjhurlbu [at] gmail> wrote:
> On Tue, Jul 31, 2012 at 8:04 PM, Gary Buhrmaster
> <gary.buhrmaster [at] gmail> wrote:
>> (of course, ultimately, NIST is usually the root source in most
>> of the world).
>
> I think that used to be more true than now with the abundance of GPS
> devices out there. Any GPS device is a stratum one NTP clock
> source...
And while for (long standing reasons having to do with navigation) USNO is
the definitive source of the GPS satellites clock adjustments (being in space
and moving quickly means relativity matters), USNO and NIST do regular
comparisons, and will "adjust" as needed, although BIPM is charged with
providing the "definitive" UTC for the world (which is about averaging about
100 atomic clocks around the world). Also note that the GPS satellites
do not do leap seconds.
Of course, there is also the GLONASS and GALIEO sat sources, and
for obvious reasons the Russians do not use NIST/USNO or BIPM.
Gary
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