GPS “Week-Rollover Problem” briefly explained
In the data signal of the GPS satellites, the date is coded in a 10-bit variable. With the 10-bit variable, a maximum of 1024 weeks can be generated in the GPS system. The week counter is then reset to zero. The first GPS week started on 6 January 1980 and the first week rollover was therefore on 21 August 1999. The second took place on 6 April 2019.
What is the impact of the Week Rollover?
The firmware date is often used by manufacturers as a feature to check the plausibility of the date generated from the GPS signal: It must not be older than the firmware date stamp.
Older GPS devices that have not received a firmware update will calculate the date based on an incorrect time base. So these devices output the date around the year 2000 from 07 April 2019.
What does the future hold?
The GPS signal will receive a modified structure and protocols. The time recording then takes place with 13 bits. GPS devices that work with the new protocols will not expect the coming week rollover again until about 158 years from now.
What about Holux GPS devices?
Many Holux products – especially older devices – suffer from the so-called GPS Week rollover error. With this error the determination of the date from April 6, 2019 does not work correctly anymore. The date is always calculated incorrectly in the GPS device – special attention should be paid to this during processing. There may be a readout error that prevents the download of log files from Holux GPS data loggers and/or provokes an error message regarding incorrect or missing log data.
Unfortunately Holux did not fix the problem for all Holux products. For many devices the manufacturer Holux – although technically probably possible – did not provide a firmware update. Also the software ezTour was unfortunately not adapted.
The following list is not guaranteed to be complete.
The following Holux GPS devices are affected:
- Holux GR-213
- Holux M-215
- Holux M-1200E
- Holux M-241
- Holux GPSport 245/245lite
- Holux GPSport 255
- Holux GPSport 260
Only a few of the Holux devices are not affected by the current GPS Week rollover:
- Holux RCV-3000
- Holux M-241+
- Holux GPSport 245+
- Holux GPSmile 6430/6562
Holux itself had published a list of GPS devices in April 2019 for which there will be no update or fix. The devices mentioned in this list are already included in the above list – see screenshot.
To what extent the remaining Holux devices with correct time recording can cope with the upcoming week rollover cannot be estimated without exact knowledge of the programming. The fact that Holux has apparently discontinued support for all products in August 2019, however, is not to be expected with corresponding updates for firmware and software. It is also not clear whether Holux GPS devices with currently correct time stamps can also cope with the new 13-bit time protocol.