Resetting the week count of GPS satellites (GPSWEEKROLLOVER)

Tomorrow, on April 6, 2019, the GPS satellite week counter (GPSWEEKROLLOVER) will be reset.

To transmit the week number (part of the time stamp), GPS satellites use 10 bits. This means that every 1024 weeks — about 20 years — the week number counter reaches the maximum value of 1023 and returns to zero. The first Saturday in April 2019 will mark the completion of the next cycle (GPS era) 1024 weeks, after which the counter will start counting from zero. This happened earlier in 1999 – for the first time since the launch of the GPS time reference since January 1, 1980.

Often a device that performs time synchronization functions uses U-Blox receivers. According to the manufacturer, receivers in GPS mode are able to work correctly with a counter of weeks at least 19 years from the date of manufacture of the firmware. Thus, the date of resetting the counter of weeks (April 6, 2019) should not affect the performance of the receiver, but errors may occur in the future.

Since resetting the week counters will only affect GPS satellites, this problem will not affect receivers working with GLONASS or GLONASS + GPS satellites.

According to the available information, TIM-LH receivers using firmware dated 2005 could be used in devices released from 2006–2013. Thus, potential problems with TIM-LH receivers may not occur earlier than 2025.

Earlier products (before 2006) could have built-in receivers manufactured by TRIMBLE. According to him there is no reliable information on this issue. For full use, these products are no longer suitable.
To prevent potential problems associated with resetting the counters of weeks on April 6, 2019, our company recommends:

• Determine the release dates of all devices that perform time synchronization functions that are in use. Thereby determine the number and type of devices with which potential problems may arise.
• Update software of communication controllers of the series This measure will help to completely protect the system from incorrect processing by the receiver of the situation with zeroing of the week counter of GPS satellites.
• Monitor existing systems after the date of reset of meters. We recommend that you make it possible to check the ability of receivers to correctly set the time after a “cold” start (power off the receiver).

If any problems arise, for the possibility of a detailed analysis of the situation and finding a solution by finalizing, please contact the technical support department by e-mail: tech@zora.ru with a detailed description of the problem and the device used (indicate type, serial number).