GPS Week Number Rollover – What it is and how it affects your GPS

Learn why GPS Week Number Rollover occurs, how it affects the date and functions in GPS devices, and which Raymarine products are affected.

GPS Week Number Rollover occurs every 1,024 weeks, which corresponds to approximately 19.6 years. When the GPS satellite system's week counter reaches its limit of 1,023, an integer overflow occurs and the value resets to zero. The last time this happened was on April 6, 2019.

All GPS receivers use this week counter to calculate the current UTC date. Therefore, the date of launch or manufacture of the GPS chipset determines when your GPS will reset. The formula is simple:

Launch date + 19.7 years = reset date

Example: A GPS device manufactured in 2003 will reset in 2023. This means that in 2023, your system may start displaying the date as 2003, affecting functions such as tides and currents.

Are Raymarine products affected?

Raymarine states that no current products with GPS receivers are affected by the rollover. This includes:

• Axiom 2 & Axiom MFDs
• Element series
• Dragonfly
• RS150 and AR200

Even older products such as a/c/e/eS/gS MFDs, RS130, and RAY52-70 are not affected.

Older products and potential problems

Some older products may have date-related performance issues now or in the future. Although the GPS receiver can still provide accurate position and SOG/COG, the date may be incorrect. This affects functions such as tide calculations.

Actions if your GPS is affected:

• Check the list of affected GPS products.
• Verify the position fix. If it is incorrect, perform a cold start of the GPS.
• If the error persists, the GPS may need to be replaced.
• Systems that require accurate dates should be updated with a new GPS receiver.

Illustrations and tables:

See the images below for detailed information on GPS Week Number Rollover and affected products:

Tip: Always check compatibility and update older GPS devices to avoid problems with dates and navigation functions.