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Author Topic: GPS Network May Experience Errors in "Week Number" Rollback  (Read 364 times)

Offline Fansome

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From the ARRL:

GPS Network May Experience Errors in "Week Number" Rollback

The GPS network will encounter a small millennium bug of its own in April when the network's "week number" rolls back to zero. This known issue especially could affect those who use GPS to obtain accurate Coordinated Universal Time (i.e., UTC). In the GPS network, the number of the current week is encoded into the message the GPS receives using a 10-bit field. This allows for weeks ranging from zero to 1023. The current period began on August 1, 1999. On April 6, 2019, the week number rolls over to zero and starts counting back up to 1023.

This should not affect later-model GPS receivers that conform to IS-GPS-200 and provide UTC, but testing carried out by the US Department for Homeland Security (DHS) raised the possibility that some units may misinterpret the rollover, shifting the date back to January 6, 1980, or possibly to another incorrect date. An affected GPS not only may report the incorrect date, but time accuracy that is critical to precise location data could be compromised. A nanosecond error in GPS time can equate to 1 foot of position (ranging) error, according to DHS-published guidelines that explain the issue and suggest how to address it.

Offline Pigmeat

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #1 on: March 08, 2019, 1821 UTC »
So far, so good. No airliners dropping out of the sky.

Offline JimIO

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #2 on: March 08, 2019, 1941 UTC »
Must be what causes rollovers on the interstates.
My GPS said make a hard left when I was doing 65 on a straight road.

Offline Pigmeat

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #3 on: March 11, 2019, 1942 UTC »
Jim, I feel you. I don't know how many times a tree that stood by the road for decades jumped out in front of me when I was in my 20's? Oddly it was always just after the time bars called "last call". Happened to lots of people I knew then. Damned trees!

Offline SV1XV

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #4 on: March 21, 2019, 1941 UTC »
The announcement about GPS week rollover is also posted in our NAVAREA III:

NAVAREA III preview 0305/2019

MEDITERRANEAN AND BLACK SEAS

POTENTIAL PROBLEMS FOR USERS OF GPS RECEIVERS.

1. USERS OF GPS RECEIVERS ARE ADVISED OF POTENTIAL PROBLEMS DUE TO GPS WEEK COUNTER ROLL OVER ON 06 APR 19.

2. THE GPS SYSTEM TRANSMITS TIME TO GPS RECEIVERS USING A FORMAT OF TIME AND WEEKS AFTER THE START DATE OF 06 JAN 80. THE DATA FIELD IN THE NAVIGATIONAL
MESSAGE SENT BY GPS SATELLITES CONTAINING THE NUMBER OF WEEKS AFTER THE START DATE IS LIMITED TO A MAXIMUM OF 1023 WEEKS. WHEN THE GPS SYSTEM REACHES WEEK 1024,
THE SYSTEM WILL REVERT BACK TO WEEK ZERO.

3. SOME GPS RECEIVERS ARE KNOWN TO BE UNABLE TO MAKE THE TRANSITION FROM WEEK 1023 TO 1024. IF THE GPS RECEIVER IS OUTDATED OR LACKS PROPER UPDATES,
THE RECEIVER WILL REVERT TO READING THE WEEK ZERO AS AUGUST 1999. DURING THIS TIME THE INTERNAL CLOCKS OF THESE GPS RECEIVERS WILL EXPERIENCE A LACK OF ABSOLUTE
REFERENCE AND MAY GIVE THE WRONG TIME AND POSITION OR MAY LOCK UP PERMANENTLY.

4. SOME OF THESE GPS RECEIVERS ARE REPAIRABLE WITH UPGRADES AND OTHERS WILL BECOME UNUSABLE. USERS ARE ADVISED TO CHECK WITH THEIR GPS MANUFACTURER REGARDING THE STATUS OF THEIR RECEIVER.

5. FOR FURTHER INFORMATION SEE:

A. WWW.GPS.GOV/CGSIC/MEETINGS/2017/POWERS.PDF .

B. WWW.GPS.GOV/GOVERNANCE/ADVISORY/MEETINGS SELECT NOVEMBER 2017 AND THEN TIMING CRITICALITY NOTE ON GPS WEEK-ROLL-OVER

C. WWW.GPS.GOV/TECHNICAL/ICWG/IS-GPS-200J.PDF.

6. FAILURE TO VERIFY YOUR GPS RECEIVER COULD LEAD TO SERIOUS NAVIGATIONAL PROBLEMS PLACING LIVES AND PROPERTY AT RISK.

Offline skeezix

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #5 on: March 22, 2019, 0147 UTC »
Jim, I feel you. I don't know how many times a tree that stood by the road for decades jumped out in front of me when I was in my 20's? Oddly it was always just after the time bars called "last call". Happened to lots of people I knew then. Damned trees!

Whiskey bottles, and brand new cars,
Oak tree you're in my way
Minneapolis, MN

Offline JimIO

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Offline Pigmeat

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #7 on: March 29, 2019, 2043 UTC »
Jim, I feel you. I don't know how many times a tree that stood by the road for decades jumped out in front of me when I was in my 20's? Oddly it was always just after the time bars called "last call". Happened to lots of people I knew then. Damned trees!

Whiskey bottles, and brand new cars,
Oak tree you're in my way

My half-brother bought semi-new Firebird when he was about 20. He blew a turn ripping down a back road the first weekend he had it. The Firebird was launched into a large barn. He and that Firebird went in one side and out the other. The Firebird was totaled, the barn was wrecked, and my brother spent the next few years driving 500 buck beaters until he paid off that car and for barn repairs.

So much for his "Smokey And The Bandit" fantasies.

Offline SV1XV

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #8 on: April 07, 2019, 0730 UTC »
A smooth GPS week rollover for my main shack GPS receiver and BG7TBL GPSDO:

$GPRMC,235959.00,A,3800.*****,N,02344.*****,E,0.049,,060419,,,D*7F
$GPRMC,000000.00,A,3800.*****,N,02344.*****,E,0.046,,070419,,,D*74


See:GPS week rollover

Offline redhat

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Re: GPS Network May Experience Errors in "Week Number" Rollback
« Reply #9 on: April 21, 2019, 2106 UTC »
I noticed my old spectracom GPS clock was having issues during last nights show.  It hasn't been powered up since February, so maybe it needs some time to get its stuff together.  It is used as the house 10 MHz source to discipline the transmitter.

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