About GPS Week Number Rollover (WNRO) — TomTom Community

About GPS Week Number Rollover (WNRO)

AndreameAndreame Posts: 3 [New Seeker]
edited July 2019 in RIDER
I have a TomTom Rider 2nd Edition (also called a "2013" I think) and it has the GPS Week Number Rollover issue.
It seems to be taking TomTom a long time to come up with a fix so I'm asking here if TomTom could do a "temporary" fix, which is basically to STOP the device synching the time with the GPS network.

There's an option on the device to set the time, you enter the current time and then click DONE. Simple. Why not just leave it at that, but no, as soon as you walk outside and it picks up a GPS signal, it ignores the time you entered and goes back to midnight.

It must be easy to do a firmware update to just use the time entered manually and NOT to sync with the GPS system. i.e. disable something rather than try and fix it.

I'm sure this would make a lot of users very happy.


  • Ste7iosSte7ios Posts: 758
    Time is not only necessary to display it on the screen and calculate ETA but it's part of the GPS calculations that give the location. Without the EXACT time a GPS can't do anything.

    It seems that there is a 3rd party solution. Dig a little in the forum and you will find it.
  • AndreameAndreame Posts: 3 [New Seeker]
  • AndreameAndreame Posts: 3 [New Seeker]
    Perfect, the time is back! Thank you :3
  • tiljestiljes Posts: 254 [Supreme Pioneer]
    Time is actually not the issue. The wrong date is. TomTom cant handle years with 1999 (dont know what minimum year is needed).
  • Ste7iosSte7ios Posts: 758
    You’re almost right. It doesn’t handle years but weeks. For that it uses a 10-bit number to represent them so it can store weeks from 0 to 1023 (1024 values), that is about 19,6 years from the defined epoch (was was Sunday January 6, 1980 at 00:00:00 UTC, now it’s April 6, 2019...).

    It can still affect the operations of the GPS receiver and make it useless like a handheld GPS for naval usage I’ve...
  • tiljestiljes Posts: 254 [Supreme Pioneer]
    @Ste7ios Nope, the TomTom software doesn't care about the week number. It just relies on the information that the GPS chip provides. The chip provides the date as DDMMYY. The firmware of the GPS chip has to convert time-of-week (TOW) and week number into this date format. Some chips weren't prepared for the WNRO and therefor they now provide a wrong date. The TomTom navigation software apparently can't handle this old date and fails here.

    Same goes for other GPS operations: it's all handled by the GPS chip and its firmware. Fortunately this wasn't affected (which it also shouldn't be as the week number is not needed in calculating your position).
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