Preparing for the GPS week rollover 2019

Are your GNSS systems ready for the GPS rollover?

What is happening?

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.

Why is this rollover happening?

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 rollover will occur 18 seconds prior to the 0000Z boundary (Coordinated Universal Time) between 6th and 7th April 2019.

How did Leica Geosystems prepare for the 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, Viva GNSS and GR/GM/GG product families. The latest firmware versions were installed in all tested receivers.

Based on the performed tests, we do not expect that the GPS week rollover will cause any issues regarding signal tracking, positioning or observation data logging.

What customer actions are needed to ensure their operations won’t be disrupted?

To guarantee you will be unaffected by this event, please ensure your equipment is updated to the latest measurement engine firmware. To confirm if your firmware is up to date, please refer to the Leica myWorld portal. Alternatively, you can access the firmware versions through the instrument controllers.

If your measurement engine is not meeting the minimum requirement for the rollover, please contact M&P on 0151 357 1856.