General information
GPS has its own date and time scale to express satellite positions based on counting weeks and seconds within a week. 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. Therefore the range starts from 0 to 1023 and is repeated every 1024 weeks (19.7 years). On Sunday, 6th January 1980 (Week 0) the GPS Time started, so that the first week number rolled over from 1023 to 0 on Saturday, 21st August 1999.
The next GPS End-of-Week Rollover will be on the 6th April 2019 where the transmitted GPS week number in the navigation message will rollover from 1023 to 0.
All currently operational Leica Geosystems GNSS receivers will not be affected by this rollover. Nevertheless, to ensure the best possible performance, it is a good practise to use the latest firmware.
How might this cause problems for the GS Sensors?
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.
How did Leica Geosystems prepare for the week rollover?
Extensive testing 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 firmware versions were installed in all tested receivers. Based on the results, it is not expected that the GPS week rollover will cause any issues regarding signal tracking, positioning or observation data logging.
What do Leica users have to do to avoid problems with this issue?
No customer action is required, as all currently operational Leica Geosystems GNSS receivers will not be affected by this week rollover. Nevertheless, to ensure the best possible performance, it is ALWAYS a good practice to use the latest firmware.
In order to ensure continuous operation of the receivers it is highly recommended to upgrade the measurement engine to the most recent firmware before April 2019:
| System 1200 and GPS900/GS09 receivers– GX, ATX, GS09: |
ME2: v2.127 (released 2012) ME3/ME3GG: v3.823 (released 2014) ME4: v6.215 (released 2013) |
| GS08, GS08plus, GS12: |
ME4: v6.402 (released 2014) OEM6xx: v6.402 (released 2014) |
| GS07, GS10, GS14, GS15, GS16,GS18T, GS25: |
ME4: v6.524 (minimum v6.402, released 2014) OEM6xx: v6.516 (minimum v6.510, released 2014) OEM7xx: v7.402 (any released version) |
John Tong
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