GPS week rollover

Leica Geosystems is constantly working on software advancements to improve performance from the latest GNSS signals in order to increase user experience, productivity and compatibility. These improvements are passed onto Leica users as software upgrades for our latest GNSS products and also as updates to manage any major signal changes for legacy equipment.

The next big change is coming in April 2019 and GPS messages will be restructured before the system experiences the next end-of-week rollover.

You should ensure your GNSS is running the latest firmware version before this time.

What is GPS week rollover?

Occurring 6 April 2019, the transmitted GPS week number in the navigation message will rollover from 1023 to 0. The GNSS receiver must be able to handle this rollover otherwise it could result in an incorrect receiver date of 21/22 August 1999 (1024 weeks back). This wrong date might cause incorrect measurements and observation data.

The Global Positioning System (GPS) week number rollover occurs in the GPS legacy navigation (LNAV) message every 1024 weeks due to the GPS week number being represented by only 10 bits within the LNAV message. The next GPS week number roll over will occur 18 seconds prior to the 0000Z boundary (Coordinated Universal Time) between 6/7 April 2019.

How has Leica Geosystems prepared for GPS week rollover?

The week rollover has been simulated using a GPS signal generator. Tests have been done with Leica Geosystems GNSS receivers introduced since 2004. This includes the System 1200, GPS900, GS/GR/GM/GG product families.

The latest ME versions were installed in all tested receivers. Based on the performed tests, Leica do not expect that the GPS week rollover will cause any issues regarding signal tracking, positioning or observation data logging.

What do Leica users need to do?

If you have the latest firmware installed, we expect that no issues will occur. All currently operational Leica Geosystems GNSS receivers should not be affected by the GPS week rollover.

When GNSS software is not updated for a very long time, equipment may start to experience tracking issues as the satellite messages broadcast differ from those that the Leica GNSS is expecting.

The behaviour of older equipment with older firmware versions has not been tested and is unknown. We recommend that you ensure you have the latest firmware installed.

Do you need to upgrade to the latest firmware?

Contact your Account Manager or email us on