GPS rollover

Eric S. Raymond esr at thyrsus.com
Mon Mar 11 09:00:54 UTC 2019


Matthew Petach <mpetach at netflight.com>:
> On Sun, Mar 10, 2019 at 8:04 PM Stephen Satchell <list at satchell.net> wrote:
> 
> > So far as I can tell with NTP, there was no issue with time sources
> > becoming false-tickers, including my local GPS appliance.  FWIW.
> >
> >
> I believe the rollover is *next* month, in April.   :)
> https://ics-cert.us-cert.gov/sites/default/files/documents/Memorandum_on_GPS_2019.pdf
> 
> "This paper is intended to provide an understanding of the possible effects
> of the April 6, 2019 GPS Week Number Rollover on Coordinated Universal Time
> derived from GPS devices."

I'm a domain expert in this area - lead of NTPsec and GPSD.

Everything said in that memo is correct.  I would add only that it is
more normal now than not for GPSes to have a hidden pivot date. "For
example, a particular GPS device may interpret the WN parameter
relative to a firmware creation date and would experience a similar
rollover event 1024 weeks after that firmware creation date." Yes,
exactly.

It is therefore unlikely that your GPSes will become falsetickers on 6
April.  That's the good news.  The bad news is that they *will* go
poof some unpredictable number of weeks later.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>

My work is funded by the Internet Civil Engineering Institute: https://icei.org
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