[aprssig] GPS Epoch Rollover Findings

[n4lbl]

For your amusement:
New York City Has a Y2K-Like Problem, and It Doesn’t Want You to Know About
It
https://www.nytimes.com/2019/04/10/nyregion/nyc-gps-wireless.html

On Wed, Apr 24, 2019 at 11:33 AM Greg D <ko6th.greg at gmail.com> wrote:

> My Garmin eTrex Vista also works fine, as do the various GPS units in my
> 2010-vintage car.  But the old Garmin GPS-III is back in August 1999.  It
> also lost all the waypoints that I had on it when last used a decade or so
> ago.  I have a backup somewhere around here...  That it still powered up
> and (eventually) got a satellite lock was the big surprise.
>
> I should note, however, that the "DIED" pronouncement may be a bit Mark
> Twainian, as I believe the older units will still give accurate time (not
> date) and location information.  It should continue to function if you're
> using one within that limitation, and a sanity patch for the date shouldn't
> be too hard to do.  The GPS-III, for example, has a classic (RS-232) serial
> interface.
>
> Matthew, I only tried firing up the GPS-III once since the epoch
> rollover.  It did take a long time to get a lock, but that was inside the
> house (it never was good at that), and was doing a cold boot with no clue
> as to where anything was in the sky.  Did your TomTom continue to have a
> hard time getting a lock, after the first time?  How long does it take?
> That might be the fatal aspect to continued use of the older units.
>
> Greg  KO6TH
>
>
> Matthew Chambers via aprssig wrote:
>
> Here, my (really old) Tom Tom still kinda works but takes an eternity to
> get a lock, and has a lot of slop now it's location, in that it appears
> that I'm wondering all over even while sitting still, and it won't keep
> time, I've had to correct the time on it now the last couple times I've
> used it.
>
> My Byonics GPS2 puck that came with my TinyTrak 4 appears to be working,
> in that the TT4 is showing good GPS and it's beaconing, but due to lack of
> coverage, I have yet to get digipeated and relayed into APRS-IS so I can
> see what it's actually doing.
>
>
> Matthew A. Chambers, NR0Q
>
>
>
>
> On Wed, Apr 24, 2019 at 11:52 AM Stephen H. Smith via aprssig <
> aprssig at lists.tapr.org> wrote:
>
>> GPS expresses the current time and date with a?? series of binary
>> counters.?? This included a 10-bit binary counter for the current week,
>> meaning that it could only count 1024 (decimal) weeks (just under 20 years)
>> before rolling over from 1111111111 to 0000000000, and starting over.??
>> This 1024-week cycle is known as an "epoch".?? The previous epoch ended on
>> April 6th of this year.?? As of April 6th, a 16-bit counter for weeks
>> replaced the 10-bit one.?? This change will put off the NEXT epoch rollover
>> for 65,535 weeks - about 1200 years.
>>
>> Some older GPS hardware (actually firmware) couldn't handle either the
>> rollover from 1023 back to 0000, or couldn't handle the new longer 16-bit
>> counter format.?? Such devices quit working on April 6th of this year.??
>>
>>
>> Now that the GPS equivalent of "Y2K" (April 6th) has come and gone, here
>> are my findings testing a bunch of older GPS hardware.
>>
>>
>> -???? Radio Shack "DigiTraveller" (a faceless serial puck-type device
>> that looked like a flying saucer) -?? DIED
>>
>> -???? Holux GM-200?? USB-connected faceless mouse-type device - DIED
>>
>> -???? Rand McNally serial mouse-type device - DIED
>>
>> -???? 2nd-gen Delorme Earthmate small yellow unit with interchangeable
>> serial and USB cables (not the original large Earthmate) - DIED
>>
>> The Holux and Rand-McNally are visible in this pic on my website:
>> ???????? <http://WA8LMF.net/aprs/GPS-Antenna-Farm.htm>
>> <http://WA8LMF.net/aprs/GPS-Antenna-Farm.htm>
>>
>> -???? Tri-M "Super Skymaster"?? white hard-mount combo antenna/receiver
>> (shown in the inset photo of the above pic) survived and WORKS.?? This is
>> especially amazing, given that it was the oldest of all these units.
>>
>> - ?? Globalsat BC-337 compact flash/PCMCIA unit - DIED??
>>
>> -???? Garmin Foretrex 201 wrist-wearable that is actually a repackaged
>> version of the classic yellow Etrex - WORKS
>>
>> -???? Globalsat BU-353 (USB) and BU-355 (serial) mini-pucks available for
>> USD $30 on Amazon - WORK
>>
>> -???? Various unbranded generic units based on uBLox G7 chipset - WORK
>>
>> -???? Internal GPS of Kenwood TH-D72 APRS handheld - WORKS
>>
>>
>> __________________________________________________________________________________
>>
>> \Stephen H. Smith?????? wa8lmf (at) aol.com
>> Skype:?????????????? WA8LMF
>> EchoLink: ?? Node #?? 14400?? [Think bottom of the 2-meter band]
>> Home Page:?????????????????? http://wa8lmf.net
>>
>> Live Off-The-Air APRS Activity Maps
>> ???? <http://wa8lmf.net/map> <http://wa8lmf.net/map>
>>
>> Long-Range APRS on 30 Meters HF
>> ???? <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>
>> <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>
>>
>>
>>
>>
>>
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>>
>
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