26 ms·
GPS Time Rollover Failures Keep Happening, But They’re Almost Done
- sls 8y agoA bit off topic, but fyi Stephen, the mailhide widget at the bottom of your "About" page seems to be broken. I browsed your site beyond the article you submitted and wanted to mention that you may be able to use Ctrl-[ as a substitute for the missing Escape key on your iPad pro. I do that a lot on normal keyboards just to avoid the pivot movement and stay on the home row, as it's just a simple pinky stretch (assuming Caps Lock as an additional Control), and also map Ctrl-] to be the tmux escape for the same reason.
- sfoskett 7y agoThank you! I appreciate both tips!
- martinpw 8y agoMention of both Y2K and 2038 in that article made me realize that we are now closer to the latter than the former.
- protomyth 8y agoYep, and Y2K was mostly in your data center. 2038 is mostly in your walls.
- est31 8y ago> GPS is being modernized to use a 13-bit Week Number If you want to dig into the details, this is one of the specification documents of the GPS signal [1]. "Figure 40-1. Data Format (sheet 1 of 11)" displays the layout of the legacy messages LNAV, while "Figure 30-6.Message Type 33 -Clock & UTC" displays the layout of the new CNAV messages. You can see that WN in the old message has 10 bits only, while WN_{ot} has 13 bits in the new message. 13 bits are a bit short IMO. It's 157 years instead of 20. Just puts the rollover into that uncanny valley where you forget about it too easily. Instead, IMO one could have extended it to 32 bits directly, which would be enough for 82 million years. In the CNAV messages, there are 53 bits of reserved space around, so it's not like that bits are super scarce, and if they are you could take from the reserved space. [1]: https://www.gps.gov/technical/icwg/IS-GPS-200J.pdf https://www.gps.gov/technical/icwg/IS-GPS-200J.pdf
- stonogo 8y agoIf we're still using this protocol 158 years on we've got bigger fish to fry.
- grecy 8y agoIt's accurate to within a meter and works perfectly fine today, without us having to spend billions more on a replacement that could surely be spent on those pesky problems like healthcare or education. Why wouldn't we keep using it for hundreds of years to come?
- whatshisface 8y agoWhy stop at a meter?
- ac29 8y agoYou can get cm level accuracy with RTK: https://en.wikipedia.org/wiki/Real-time_kinematic https://en.wikipedia.org/wiki/Real-time_kinematic
- mehrdadn 8y agoThis looks amazing. Any idea if there are consumer level CPGPS devices?
- jrockway 8y agoThe error beyond this level is due to local ionospheric conditions rather than the protocol. Corrections can be transmitted to interested receivers, WAAS is an example of such a system. cm level accuracy is available with RTK. It works by comparing GPS signals from a known nearby location with that of a mobile receiver, providing what amounts to especially good correction. It works fine and you can get started at home for <$100. A new protocol that does better than what we have right now will take some major breakthroughs.
- ggggrans 8y agoGee, good thing I rely on GPS for absolutely nothing. As a non-essential service, it mostly feeds into the mass surveillance panopticon, and little else. You can get around just fine with a good paper map and observable defacto landmarks and street names. GPS may be convenient, but it feeds the evil of systemic privacy erosion.
- ahelwer 8y agoI've been raising awareness in outdoor recreation groups about this. Many people rely on GPS for rescue and navigation in the backcountry, and it's likely some will see a software failure this weekend.
- gsich 8y agoNavigation is not affected. (Unless there is some other bug that bleeds over from the rollover issue)
- Wehrdo 8y agoNot sure why you were downvoted; this is my understanding also. Could someone with deeper GPS knowledge chime in?
- ahelwer 8y agoIf you read my post, it ends with "...and it's likely some will see a software failure this weekend" - of course a properly-coded GPS device will be fine but the likelihood of the many thousands of different types of GPS devices out there all gracefully handling an event that happens once every two decades is basically zero.
- rightbyte 7y agoSatelite constellation (position in the sky) is date stamped right? If the internal clock date doesn't match the received the updates may be ignored.
- makomk 7y agoThe satellite position updates use essentially the same time format as the rest of GPS, as I understand it. So the problem comes when some GPS receivers try and use the latest information but base their calculations on an erroneous belief it's now 1024 weeks into the past, causing them to fail to find satellites.
- Animats 8y agoWhat time does the rollover occur? Is it based on UTC, or what?
- notimetorelax 7y agoI assume UT1: https://www.oc.nps.edu/oc2902w/gps/timsys.html https://www.oc.nps.edu/oc2902w/gps/timsys.html https://en.wikipedia.org/wiki/Universal_Time#Versions https://en.wikipedia.org/wiki/Universal_Time#Versions Which is roughly UTC, give or take multiple seconds.
- ahazred8ta 7y agoGPS atomic time rolled over approximately midnight UTC this Sunday morning, but ignoring leap seconds. GPS is 18 seconds ahead of UTC and 19 seconds behind atomic TAI. http://leapsecond.com/java/gpsclock.htm http://leapsecond.com/java/gpsclock.htm
- Z1515M8147 7y agoArticle is not correct: not every device on the planet will roll over. Many GPS chipsets, such as many uBlox devices, program an offset such as the date of device firmware compilation. This means that the rollover will in fact occur decades out from when users are expecting. The way to discover the real rollover date for ublox devices is to interrogate them with the ublox software to find the relevant message and add 20 years on top. For old ublox devices this field can actually be modified by the user to effectively reset the countdown. For other brands it could be a lot more difficult, though manufacturers docs should cover it. https://portal.u-blox.com/s/question/0D52p00008HKDTlCAP/gps-week-number-rollover-after-20-years https://portal.u-blox.com/s/question/0D52p00008HKDTlCAP/gps-...
- ambrop7 7y agoA properly programmed device should have no issue. A device only needs to know the date to within 10 years so that it can interpret the week number correctly. So if the device runs its own clock that it synchronizes to GPS, it should keep working indefinitely as long as that clock is running. Even if it doesn't run a clock while powered off, it could store the clock to non-volatile memory occasionally, and it would keep working correctly as long as it isn't powered off for more than 10 years.
- sfoskett 7y agoFind me these “properly programmed devices”! This is the core of the issue: bad assumptions and poor QA let bugs like this have an outsized impact. It’s our fault, folks.
- Maxious 7y ago"Multiple Boeing 787s in China experienced GPS 20 years rollover issue. Some aircrafts have to be grounded waiting for an update." https://twitter.com/ChinaAvReview/status/1114802018919411712 https://twitter.com/ChinaAvReview/status/1114802018919411712
- notimetorelax 7y agoAre software issues as common to other manufacturers?
- cedivad 7y agoYou guys remember a couple of days ago people were discussing this eventuality and consensus was "surely they aren't pulling timing information from GPS, unfiltered! It's an aircraft manufacturer we are talking about, they know what they are doing!" -- Well, no, they don't. It's almost like you could begin to see a pattern here.
- js2 7y agoIf you're curious about the history of GPS, there's a fantastic write up here: - https://www.gpsworld.com/origins-gps-part-1/ https://www.gpsworld.com/origins-gps-part-1/ - https://www.gpsworld.com/origins-gps-part-2-fighting-survive/ https://www.gpsworld.com/origins-gps-part-2-fighting-survive... There's also a documentary on Amazon Prime: - https://www.amazon.com/Lonely-Halls-Meeting-GPS-Documentary/dp/B07J2QW13V https://www.amazon.com/Lonely-Halls-Meeting-GPS-Documentary/...
- et2o 7y agoAwesome article, thank you for writing it. This is very off-topic, but how do you like the 2008 S Class? Are there reviews of it from a 2019 perspective anywhere?