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RACELOGIC Support Centre

What is GPS Rollover?


The Global Positioning System (GPS) provides accurate timing and ranging information. It also has the ability to transmit a proper date and time to a receiver, it does this by supplying the receiver with the current week number and the current number of seconds into the week. The receiver is then able to translate the week number and current seconds into a more useable format – day, month, year, and time of day.

The week number is a 10 bit field. A binary 10 bit word can represent a maximum of 1024 weeks (numbered 0 to 1023), which is approximately 19.7 years. Each 19.7 year period is known in GPS terms as an 'epoch'.

GPS week zero began on January 6, 1980. The 1024 weeks counter then ran out and rolled over on August 21, 1999. The week counter then reset to zero. The most recent Rollover event occurred on April 6, 2019, and the next time the counter will reach week 1023 and roll over is on November 20, 2038.

GPS Rollover Events

GPS Dates
Start: January 6, 1980
1st Rollover: August 21, 1999
2nd Rollover: April 6, 2019
3rd Rollover: November 20, 2038

Creating a Rollover Scenario with SatGen V3

If a GPS Rollover scenario is required, our SatGen V3 Software can be used to replicate the the rollover event. By using the date of the rollover event, a GPS scenario can be created. For example, the date  can be set to 6th April 2019 at 23:50.00 for a 20-minute duration. The scenario created will include the rollover event. More information on this is available here.

GPS Time Calculator

A GPS Time Calculator is available on our LabSat Website, this can be used as a reference or to assist with determining what week number is expected.

LabSat Rollover 3.png

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