This technical note details anticipated operation of the SiRFstar series of products, when
operating through the next GPS week number rollover event occurring on April 6th 2019.
The Global Positioning System (GPS), has its own date and time scale for expressing satellite positions, based
on counting weeks, and seconds within a week. To limit the size of the numbers used in the data and
calculations, the GPS Week Number is a ten-bit count in the range 0-1023, repeating every 1024 weeks. Week
0 started at 00:00:00 UTC on Sunday, 6th January 1980, causing the first week number 'rollover' from 1023 to
0 to occur at 23:59:47 UTC on Saturday, 21st August 1999. The next GPS week rollover occurs on April 06th
Maestro anticipates no operational issues with any of its SiRFstar GPS or GNSS products listed in below list,
during or after the GPS Rollover event. This has been determined through extensive simulator based validation
of our products.
Simulator based testing of future real-world events contains an inherent limitation, in that the simulations may
not reflect real world events at the rollover event. Actual events on the day may deviate from the expected
scenarios. This risk factor cannot be eliminated and should not be discounted. In addition to this limitation,
testing of predicted orbital data, both Server Generated Extended Ephemeris (SGEE) and Client
Concerned products: A1035-H, A1080-AB, A2035-H, A2100-AB, A2135-H, A2200-A, A2235-H, A5100-A, A5135-H.
The purpose of the test was to validate correct operation before, during and after the GPS week number
rollover from 1024 to 0 occurring on 6th April 2019.
The tests checked that:
1. Navigation operated as expected, with no gaps, drops in SV tracking or incorrect positions occurring.
2. GPS week number reset to zero.
3. TOW reset to zero seconds.
4. Time and date fields indicated the correct date in 2019 after the rollover event.
Tests were run using SiRFstar standard EVKs connected to a Spirent simulator as a part of our standard test
environment. Receivers were initialized and a scenario run simulating the 2019 rollover event. Receivers were
monitored for correct behavior.
No issues were observed in any tests.
Various spot checks were performed with differing scenarios, such as cyclical low power operating modes and
powered off during the rollover event, and no issues were observed.