Why didn't GPS crash?

  • Published: 13 April 2019
  • More on the GPS roll-over.

    "In the Future the Modernized GPS Navigation (CNAV and MNAV) message has a 13-bit week number, which for all practical purposes solves this ambiguity"

    See me turn on my TomTom:

    If you want to see more hilarious tales about roll-over errors then, well, READ MY BOOK.

    Get it from Maths Gear and be guaranteed a signed first edition hard back.

    But it is also available on Amazon.

    - Sorry: I used “overflow” to refer to when the value bursts into the adjacent memory as opposed to just rolling back to zero. But an overflow can simply mean it has rolled over.
    - I add the extra week bits to the wrong side of the number! Unbelievable. I even point to the other side of the screen in the video. Somehow I totally missed this until it was too late. I’m surprised loads of people are not pointing it out. So far only Kyle K has noticed. Good on you, Kyle.
    - Let me know if you spot anything else!

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Comments • 770

  • DimensionDude
    DimensionDude  6 days back

    Dogs locate Matt Parker via GPS - Great Parker Smell.

    • Vince Perry
      Vince Perry  4 weeks back

      Aug 14 2176,or May 4 2147

      • Yaitz 331
        Yaitz 331  1 months back

        Wait, so if you looked at the GPS while one satellite had not yet rolled over and another one had, would it then give ridiculous location info?

        • BarnOwl
          BarnOwl  1 months back

          I had the same gps and now i miss it

          • AndreasIndustriePro
            AndreasIndustriePro  2 months back

            "it'll be fine"

            • arandomchannel
              arandomchannel  2 months back

              The word "epoch" rhymes with "epic"

              • ossapinhosfazemhumah
                ossapinhosfazemhumah  2 months back

                main takeaway here is: if you stare at screens all day you miss all of life's dogs

                • Alex
                  Alex  3 months back

                  A message to the GPS maintainers: Please use only storage capacities that are powers of two. Would it really hurt that much to go to 16 instead of 13?

                  • Ethanagor S-D
                    Ethanagor S-D  3 months back

                    between 6:15 and 6:24 is the only important part of the video because that's when the dog is on screen

                    • Garry Jones
                      Garry Jones  3 months back

                      Very interesting post.
                      I really like all this stuff.
                      Interestingly or not older computers think that time began on Jan. 4, 1980.
                      When an old computer loses its settings and returns to its default state, that is the only date it remembers in its BIOS software. (Pre flash upgrades). This can often be recreated by removing the cmos CR 2032 battery in the mother board. In fact even in new Windows systems you'll often find files with a creation date of 4th Jan 1980. I wonder if this is connected to the GPS date?
                      In the 70's I worked on mainframe computers. Storage space on disk drivers was money so files were given a File Retention Date (FRD) in the format YY/DDD. So 79/043 was the 43rd day of 1979 (when the programmer knew it would not be necessary to require the file after that date). After the FRD the physical space on the disk was released and could be overwritten. System files and other permanent files were given an FRD of 99/365. (The 31st December 1979).
                      In the summer of 1980 I asked an IBM software engineer what would happen on 1st January 2000. At first his answer was "We'll cross that bridge when we come to it". He gave it some further thought and eventually we asked the question on via shoebox modem to the IBM Knowledge base in the States. A rollover was not possible because computers would be overwriting themselves and deleting their own system and bootstrap files. It led to the first articles of the year 2000 problem and I got a (small) degree of notoriety.

                      • nekogod
                        nekogod  3 months back

                        Great vid, love the isle of wight

                        • Frank Yanish
                          Frank Yanish  3 months back

                          Most cell phones don't use GPS. They geolocate using cell towers.

                          • MANN[][][]
                            MANN[][][]  3 months back

                            If you reverse the battery you will kill the etrek GPS. ask me how i know lol

                            • martijn van weele
                              martijn van weele  3 months back

                              Speak for yourself. I'm not sorry.

                              • Rouverius
                                Rouverius  3 months back

                                TIL Why GPS didn't crash ... and Matt Parker's wife loves him very much. ;)

                                • L Dewey
                                  L Dewey  3 months back

                                  Brilliant, funny and enjoyable video! (At least you didn't drop your phone into a toilet... like I once did!) Keep these videos coming!

                                  • Angarsk100
                                    Angarsk100  3 months back

                                    "The military are convinced we'll be fiiiine... in 150 years, it'll be somebody else's problem, WE'll be fine"

                                    • nicolascrafterMC
                                      nicolascrafterMC  3 months back

                                      Why those old devices picks 4 satellites in 15 minute while a modern smartphone picks ~10 satellites in just a few seconds?

                                      • orsmplus
                                        orsmplus  3 months back

                                        My GPS unit is now useless, it doesn't know when it is between 1999 and 2099 :\

                                        • Jintaro Kensei
                                          Jintaro Kensei  3 months back

                                          Jesus man, lower the damn sfx.

                                          • Liquoricilicious
                                            Liquoricilicious  3 months back

                                            Hi Matt, why is my computer clock 3-4 minutes behind my other electronics?

                                            • Henry Giles
                                              Henry Giles  3 months back

                                              BRUH YOU WERE IN SANDOWN WHAT

                                              • Виталий Матин

                                                2\2147483647 = ... -1= PRIME

                                                • Mo Poppins
                                                  Mo Poppins  3 months back

                                                  Nice fingernails, Matt. Do you get manis?

                                                  • S.Vidhyardh Singh
                                                    S.Vidhyardh Singh  3 months back

                                                    It will be FINE!!!! 😎

                                                    • RATO
                                                      RATO  3 months back

                                                      that gps was on the date of my birth! hahaha

                                                      • Sarbir Grewal
                                                        Sarbir Grewal  3 months back

                                                        Hey, do you have a business email for inquiries?

                                                        • Orn Jonasar
                                                          Orn Jonasar  3 months back

                                                          My TomTom worked till I decided to set the clock on it manually - oops.

                                                          • piikkiniska
                                                            piikkiniska  4 months back

                                                            My similar eTrex works. Startup screen shows (c) 1999-2002. SW version is 2.14. It was last started in 2011 and as soon as it found the satellites it started to show correct date&time.

                                                            • Man Gear
                                                              Man Gear  4 months back

                                                              Yes, we're sorry!!! I just subscribed!!

                                                              • Animiles
                                                                Animiles  4 months back

                                                                I wonder how much of this video they'll be able to understand after 150 years. Languages naturally evolve, but with globalization there will be influences from all over the world.

                                                                • ToolkiT73UK
                                                                  ToolkiT73UK  4 months back

                                                                  @10:18 That looks a lot like Sonning on Thames..

                                                                  • gwaptiva
                                                                    gwaptiva  4 months back

                                                                    Meh, I have that exact TomTom :D

                                                                    • Lightning Corp.
                                                                      Lightning Corp.  4 months back

                                                                      Parker's GPS has been fixed

                                                                      • johnny chang
                                                                        johnny chang  4 months back

                                                                        If Black Holes weren't humongously wanton, can they indigest and overflow from overconsumption of matter and energy?

                                                                        • J Wydłubak
                                                                          J Wydłubak  4 months back

                                                                          Tracking time in computer systems with the GPS may not need the correct date returned by a receiver. What is most precious for such systems is the PPS (pulse per second). Once you've got it implementing a counter outside of a receiver is trivial.

                                                                          • Act Mgr
                                                                            Act Mgr  4 months back

                                                                            Everyone is watching this from the future! Imagine watching this video from the past, from BEFORE April 7th!

                                                                            • Nostalgia Catholic
                                                                              Nostalgia Catholic  4 months back

                                                                              Word from 157 years in the future:  Actually, the end of the epoch was no problem as it was coded around in a manner quite analogous to your relatively primitive "GPS" system (now simply called "PS1" for reasons which begin to be obvious even back in your time) for handling the rollover as implemented back in 2008 or so.  But this barely even matters now as the PS1 (for Positioning System 1 - by 2018 Google was already test marketing what we now call PS2 based on detailed image data which sadly became substantially unusable in 2146 for reasons I cannot talk about) now only has about a 5% portion of the market share, not enough to justify additional satellites, of which we are down to only 13 left, so PS1 doesn't even work except when at least four of those remaining satellites are visible (yet it still has those who swear by it for odd reasons)

                                                                              • caiwangheng
                                                                                caiwangheng  4 months back

                                                                                Man that dog is cute

                                                                                • Jakob Lindskog
                                                                                  Jakob Lindskog  4 months back

                                                                                  This leaves me with 2 questions:
                                                                                  1. Why 13 bits???
                                                                                  2. Why this stupid system with weeks?? My calculations show that the 10 bits would have done better work alongside the already needed 20 bits for measuring seconds into the week. With 30 bits for seconds since 1980, the rollover would be 34 years. For completeness sake, adding three bits to that would increase the range to 272 years. Alas, weeks are simply stupid

                                                                                  • L Dewey
                                                                                    L Dewey  3 months back

                                                                                    Our entire Gregorian calendar is the most stupid and archaic system! We should have 13 months with 28 days each, and January 1st should be numbered "zero" and occur on the winter solstice.

                                                                                • Andrew Moore
                                                                                  Andrew Moore  4 months back

                                                                                  You embraced!!!
                                                                                  I salute you

                                                                                  • Random Everything
                                                                                    Random Everything  4 months back

                                                                                    This is good to know. I have the same GPS and I'm happy to find out that it should work just find... just not the date of sunrise/set times which is not a deal breaker.
                                                                                    The reason It took soo long the first time to gain a signal is because it has been so long since you used it, and you likely used it a few hundred kms away from last point of use.

                                                                                    • Matija Tomic
                                                                                      Matija Tomic  4 months back

                                                                                      This hapoened in my mother's car. 2011 Peugeot 308. The option for sycing the date with GPS was set and the car thought it was year 2099, because... No point in car from 2011 to know year 1999 exists...

                                                                                      • DelphiTheDolphin
                                                                                        DelphiTheDolphin  4 months back

                                                                                        I bet the future viewers, if no WW3 wiped us from existence , think the "We're sorry" is more needed for the climate change we done in our time here.

                                                                                        • ejonesss
                                                                                          ejonesss  4 months back

                                                                                          another reason it did not crash is like the dns changer malware the government probably took over some key system and kept it running to prevent devices from crashing

                                                                                          • TheFlyerX
                                                                                            TheFlyerX  4 months back

                                                                                            I have the same gps device an its working showing my correct location and local time, but not the date. My GPS is living in the late 90s now.

                                                                                            • BoyWonder193
                                                                                              BoyWonder193  4 months back

                                                                                              My satnav broke 😂

                                                                                              • Dmitry Granicin
                                                                                                Dmitry Granicin  4 months back

                                                                                                Walking? Yeah that uses GPS. Driving? Nah mate, that thing is called a SAT-NAV.