GPS Directorate to test legacy receivers in February

January 28, 2019  - By

U.S. Coast Guard issues testing notice on GPS Week Number Rollover.

The GPS Directorate has released a Federal Register Notice announcing plans to execute a test in February to investigate legacy receiver week roll-over behavior and analyze any off-nominal behavior exhibited, according to a U.S. Coast Guard notice.

Photo: andrey_l/

Photo: andrey_l/

The 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 April 6/7 2019.

In most cases, any negative response from a GPS receiver caused by a problem accounting for the 10-bit week number roll over would likely affect the calendar conversion from GPS time to UTC date/time and could result in the GPS receiver thinking it had jumped backward in time by 1024 weeks to 21/22 August 1999.

To participate in the test, submit the answers to the nine questions in the Federal Register Notice to the SMC/GPE mailbox by Feb. 4. After the submission of the questionnaire, the team will schedule individual meetings with interested civil vendors to further discuss their participation in the test in more detail.

1 Comment on "GPS Directorate to test legacy receivers in February"

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  1. William K. says:

    This could be an interesting experiment, because all of the good quality systems should still be functional now, only 20 years later. Unlike consumer junk, the vast majority of navigation equipment is built to last a long time. The problems will be in the software, and the ability to externally adjust it. So we will learn who was thinking ahead and who was presuming that the equipment would no longer be in use. This affects some of my devices as well, so I will learn.