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Only the legacy “L1 C/A” GPS signal contains a 10‑bit week number.
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Septentrio fully supports the “modernised” GPS signals, called “L5”, “L2C”, and “L1C”. Most GPS satellites are already transmitting a 13-bit week number, which will only roll over in the year 2137. Couldn’t the GPS system use more than 10 bits for the week number?
![gps week number rollover gps week number rollover](https://blog.rapid7.com/content/images/2019/04/GPS_og-1.jpg)
In Central European Summer Time, this corresponds to 01:59:42 CEST on Sunday 7 April 2019. Note that this corresponds to 23:59:42 UTC on 6 April 2019, because GPS time is unaffected by so-called leap seconds. The second rollover will happen at midnight (GPS time) of 6-7 April 2019. The first rollover happened at midnight of 21-22 August 1999. So, both receiver manufacturers and users are well aware. Government has issued an official statement to remind of the upcoming rollover. A specific note highlighting the fact that the week number rolls over has been part of the official GPS signal specification since at least 1993. It is the result of a system design choice which is well known and documented. Is the GPS week number rollover an unexpected event? So the transmitted week number jumps back to zero every 1024 weeks (about 20 years). After the maximum value is reached, the week number “rolls over” to 0 and starts counting again. As a result, the transmitted week number can have a value from 0 to 1023 (= 2 10 - 1). In the 1970s, when the GPS system was originally designed, 10 bits were assigned to the week number in the navigation data. The GPS satellites transmit the time in two parts: the week number (the number of weeks since time zero) and the elapsed number of seconds within that week. The starting point (time zero) of GPS time was chosen to be midnight of 5-6 January 1980. Questions & Answers (Q&A) What is the GPS week number and why does it “roll over”?
Gps week number rollover free#
If you have a Septentrio GPS (GNSS) receiver, feel free to also consult our Support Notification document about the upcoming GPS week number rollover. GPS week numbering and how it is processed within the receiver