Thread: TomTom News & Announcements

Originally Posted by biggerdave

See this:- [Only registered and activated users can see links. ] and in more general detail:-
What’s the Key Issue?
The Global Positioning System provides accurate timing information to many of our critical systems – power grid, communications, financial markets, emergency services, and industrial control to name a few. It also includes the ability to transmit the proper date and time to a receiver by supplying the receiver with the current week and the current number of seconds into the week. This allows the receiver to translate the date and time into a more typical format – day, month, year, and time of day.
However, the field that contains the week number is a 10-bit binary number. This limits the range of the week number to 0 – 1023, or 1024 total weeks.
GPS week zero started January 6, 1980. The 1024 weeks counter ran out and rolled over on August 21, 1999. The week counter then reset to zero, and it has been recounting ever since. The next time the counter will reach week 1023 and rollover to zero is on April 6, 2019.

Should I Be Concerned?
Because this it is the second time the GPS week rollover will occur, many receiver manufacturers have prepared for it, and newer receivers will continue to operate without issue.
You should be concerned, though, if either of the following applies:

Receiver has been fielded for more than 10-15 years without firmware updates
Receiver is a core component of a critical timing system – ask yourself – what is the impact to my system if the GPS receiver stopped operating or put out wrong GPS or UTC information

In these cases, we want to verify that an issue will not occur. At a minimum, we recommend consulting your receiver manufacturer to confirm that the issue has been fully tested and will not occur. Many manufacturers have already issued compliance statements, and we expect them to continue to do so over the next year, up until the event occurs. To be sure that your system will not experience any failures related to this issue

----------------------------------------------------------------------------------

Further details (credit Entwood from another forum), and I quote:-

Talking to someone who knows a lot more than me about GPS and this "possible" problem... and he tells me that what TT are saying is probably a load of rubbish !!

Apparently the end of the epoch Week Number Rollover is exactly what it says ... it is a WEEK NUMBER rollover ... so the only devices that are affected are those that use/calculate "weeks" and utilise the "week number" index !!

As most SatNavs don't even use date/day information but simply use "time" then they will NOT be affected !!

He sent me to this site to show me that he wasn't talking rubbish, and sure enough, down the bottom is this little crumb of information ..

[Only registered and activated users can see links. ]

"This situation won’t affect a receiver’s ability to navigate and/or calculate precise time, but it has the potential to create week, month and year timestamps that are wildly wrong. Applications which rely on GPS data at that level may be seriously affected."

So to summarise, maybe TT are just over-reacting? Time will tell of course!