Hi Jeff,
On 6/04/2019 3:30 pm, Jeff Zambory wrote:
Yes Steve, you are correct.
https://www.gps.gov/
Scroll down a bit and you can find a count down to the roll over. And it states
the time when it will roll over. Just what you have said.
Thanks !!!
I'll watch that and watch my receivers.
It seems, from posts here, that different receivers exhibit different
WNRO behaviour - with effects noted *before* the RO epoch.
I am curious about this and set my Garmin 16x to output as per a
snapshot below...
$PGRMF,1023,590391,060419,195933,18
...which is GPS week, GPS seconds, UTC date, UTC time and leap second count
As GPS seconds wraps around at 604799 (and GPS is incremented at that
moment) then there is 604799 + 1 - 590391 = 14409 seconds to go from
19:59:33.
14408 seconds = 4 h 9 seconds. 19:59:33 + 4:00:09 = 23:59:42.
This agrees with the www.gps.gov data.
So why are people reporting effects already ? My *guess* as to why some
receivers have reacted before the RO epoch is that attempts to address
the issue have been different depending on the vintage of the GPS receivers.
* Receivers manufactured just a few years before the first rollover
data would need to cross the 1023 - 0 week boundary a short-ish time
after manufacture. So some kind of offset would need to be added
to the week number. These units which have not had firmware updates
would presumably react early to the second rollover depending on the
date of manufacture.
* Receivers manufactured after the first rollover would presumably
react late to the second RO by the same logic.
* Receivers of any manufacture date which has had its firmware updated
regularly would presumably not be affected as the updates would keep
pushing the internal wrap around epoch further into the future.
* Old receivers (like my GPS 35 with no updates) already have gone
through one rollover (currently showing 21 August 1999) and will
presumably go back to 1980 dates with this rollover.
So - my bottom-line note to myself about this is that just because a
receiver looks fine tomorrow doesn't mean it won't fall over next week,
or next month, or next year, etc.
Cheers
Steve
P.S. for some reason time-nut posts arrive in my inbox uncorrelated to
their time stamps. So I find myself replying to later posts before
earlier ones. Gets a bit confusing for this Senior Citizen... LOL...
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