[aprssig] Y2K-Like Event for GPS Potentially Looming This April 6th

[Steve Noskowicz]

Dodged that bullet. My Nuvi 750 was done right.
Thanks, Steve
-- 
 Regards, Steve Noskowicz
 Science & Technical Advisor

--------------------------------------------
On Wed, 2/27/19, Stephen H. Smith via aprssig <aprssig at lists.tapr.org> wrote:

 Subject: [aprssig] Y2K-Like Event for GPS Potentially Looming This April 6th
 To: "TAPR APRS Mailing List" <aprssig at lists.tapr.org>
 Date: Wednesday, February 27, 2019, 12:43 AM
 
 
   
 
     
   
   
     From: 
           The
           Register (British IT News Site)
     <https://www.theregister.co.uk/2019/02/12/current_gps_epoch_ends/>
     
 
         
     Fun fact: GPS uses
 10 bits to store
           the week. That
           means it runs out... oh heck – April 6,
 2019
     Nav
           gadgets will be Gah, Properly Screwed if you
 don't or can't
           update firmware
     By Shaun Nichols in San
           Francisco 12 Feb 2019 at 21:37
       
      
     Older satnavs
         and such devices won't be
         able to use America's
         Global Positioning System properly after April 6
 unless they've
         been suitably
         updated or designed to handle a looming epoch
 rollover.
     GPS signals from
         satellites include a
         timestamp, needed in part to calculate one's
 location, that
         stores the week
         number using ten binary bits. That means the week
 number can
         have 210
         or 1,024 integer values, counting from zero to 1,023
 in this
         case. Every 1,024
         weeks, or roughly every 20 years, the counter rolls
 over from
         1,023 to zero.
     The first
         Saturday in April will mark the
         end of the 1,024th week, after which the counter
 will spill over
         from 1,023 to
         zero. The last time the week number overflowed like
 this was in
         1999, nearly
         two decades on from the first epoch in January
 1980.
     You can see
         where this is going. If
         devices in use today are not designed or patched to
 handle this
         latest
         rollover, they will revert to an earlier year after
 that 1,024th
         week in April,
         causing attempts to calculate position to
 potentially fail.
         System and
         navigation data could even be corrupted, we're
 warned.
     "GPS devices
         with a poorly
         implemented GPS Time-to-UTC conversion algorithm may
 provide
         incorrect UTC
         following a week number rollover," US Homeland
 Security
         explained in its
 write-up (PDF) of the issue this week.
     "Additionally,
         some GPS devices that
         calculate the week number value from a
 device-specific date
         rather than the
         start of the current GPS Time Epoch may provide
 incorrect UTC at
         some other
         device-specific date."
      As the
 Reg
         reader who tipped us off to
         the shortcoming noted, this could be a significant
 headache for
         data centers
         that use GPS timing for synchronization.
     "Decent vendors
         should have patches.
         But who has been thinking about this?" our
 tipster told us.
         "This
         could be a low-key Y2K style bug all over again, but
 with
         companies doing less
         preparation."
     Fortunately,
         devices on sale right now
         should be prepared for this rollover and handle it
 gracefully.
         Uncle Sam's GPS
         nerve-center GPS.gov
 says (PDF) receivers that follow
         the
         ICD-200/IS-GPS-200 specification should be able to
 deal with the
         week number
         overflow. This basically means newer receivers built
 after, say,
         2010 should be
         fine, provided they follow the specs
 and notice the rollover.
     To put it
         another way, if your gadget
         goes haywire in April, it's probably because of
 this. If it
         works as normal:
         brilliant, it's not affected. Consider yourself
 forewarned.
     GPS.gov also
         notes that the new CNAV and
         MNAV message formats will use a 13-bit week number
 to solve the
         epoch migraine
         right up until the planet becomes uninhabitable via
 climate
         change or we all
         blow ourselves up.
     For devices
         unprepared for the counter
         overflow, a firmware upgrade will be necessary to
 keep the
         things working
         properly. GPS.gov recommends those unsure about
 their readiness
         for the
         turnover, particularly enterprises, should consult
 the
         manufacturer of their
         equipment to make sure they have the proper updates
 in place. ®
      
   
 
 
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