If you wish to participate in this test, please submit the answers to the questions in the Federal Register Notice to the SMC/GPE mailbox by February 4, 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. The next GPS week number roll over will occur 18 seconds prior to the 0000Z boundary (Coordinated Universal Time) between April 6/7 2019. 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. The newer message types (CNAV and MNAV) use 13-bit binary numbers to represent the GPS week number, so the issue should not occur in the future when more receivers are using the newer GPS signals.The Global Positioning System Directorate has released a Federal Register Notice announcing plans to execute a test in February 2019 to investigate legacy receiver week roll-over behavior and analyze any off-nominal behavior exhibited.
#Gps week number upgrade
GPS is currently undergoing a modernization program to upgrade the signals with new modulation and data message structures.
From Wialon side, we’re unable to prepare for WNRO since we can’t predict which trackers will be affected and which data they will transmit to Wialon. At a minimum, we recommend consulting your GPS device manufacturer to confirm that the issue has been fully tested and will not occur. In these cases, we want to verify that an issue will not occur. Conversely, gpswk will convert a GPS week number to the year, month and day of the Sunday of that week. The official presentation on the issue from gps.gov details the issue, and the U.S. DESCRIPTION gpswk takes a user input date, given as year, month and day or year and day-of-year, converts to the GPS week number and writes the result to stdout. At 23:59:42 UTC on (Midnight GPS time, which differs by 18 leap-seconds from UTC), the 10-bit GPS Week Number broadcast by the constellation will. At 23:59:42 UTC on (Midnight GPS time, which differs by 18 leap-seconds from UTC), the 10-bit GPS Week Number broadcast by the constellation reset to zero for the second time since the beginning of GPS on. GPS device is a core component of a critical timing system – ask yourself – what is the impact to my system if the GPS receiver stopped operating or put out wrong GPS or UTC information where DOY day-of-year and GPSWK is the GPS week number.GPS device has been fielded for more than 10-15 years without firmware updates.You should be concerned, though, if either of the following applies: Should you be concerned?īecause this it is the second time the GPS week rollover will occur, many receiver manufacturers have prepared for it, and newer receivers will continue to operate without issue. Some GPS trackers that utilise the date and time function, may not be able to cope. As we approach the end of the second epoch, which will fall on 6th April 2019, we may well see problems caused by the rollover. The first epoch started when GPS was launched in January 1980 hence the first epoch of GPS time came to an end on 21st August 1999. At the end of each epoch the receiver resets the week number to zero and starts counting again – a new epoch begins. Each 19.7 year period is known in GPS terms as an “epoch”.
A binary 10-bit word can represent a maximum of 1,024 weeks, which is approximately 19.7 years. The week number is encoded into the data stream by a 10-bit field. The potential problem revolves around the way that GPS handles the week element of the data that forms part of the navigation signal.
On April,6 or after it some GPS trackers may start to perform strangely. The week counter then reset to zero, and it has been. Therefore, every 1024 weeks, the week number rolls over to zero. The GPS system stores the current week number as a 10-bit number. Affected devices have a GPS chip (these are generally the cellular 2/3/4G versions regardless of whether you use a sim). The 1024 weeks counter ran out and rolled over on August 21, 1999. On 6 April 2019 there will be a Global Positioning System (GPS) week number (WN) rollover on Coordinated Universal Time derived from GPS receivers and devices. It is to do with how long GPS devices can hold dates. This day will mark a special rollover of the GPS week number, or WNRO, that helps receivers tell time more precisely. The GPS Week Number Rollover 10-bit issue (more here) happens every 19 years. If you use GPS trackers in your business, April 6, 2019, is probably a date worth marking in advance.
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