[ntp:questions] Start of new GPS 1024 week epoch

mike cook michael.cook at sfr.fr
Fri Aug 16 14:50:14 UTC 2013

Le 16 août 2013 à 15:34, David Taylor a écrit :

> On 16/08/2013 13:02, John Hasler wrote:
>> David Taylor writes:
>>> A pity that they haven't been able to find two or three spare bits to
>>> reduce the 1024 week ambiguity to nearer a half-century or even 100
>>> years.
>> From the Wikipedia article:
>> To determine the current Gregorian date, a GPS receiver must be
>> provided with the approximate date (to within 3,584 days) to correctly
>> translate the GPS date signal. To address this concern the modernized
>> GPS navigation message uses a 13-bit field that only repeats every
>> 8,192 weeks (157 years), thus lasting until the year 2137 (157 years
>> after GPS week zero).
> Oh, that /is/ good news, John!  Many thanks.  I couldn't see that from a quick scan of the referenced documents, so that's most helpful to know.
> I wonder whether there is any way to determine which satellites are sending this modernised message, perhaps they all do, or whether a particular receiver is using the full 13-bit field?  It's something I've not seen listed in various specifications I've read, but perhaps it's taken for granted after a certain date?
> -- 

I read that it was part of the L2 signal stream. So you would need an L2 receiver but that wouldn't guarantee that the firmware is using the full field.

> Cheers,
> David
> Web: http://www.satsignal.eu
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