[LEAPSECS] it's WP7A week in Geneva

M. Warner Losh imp at bsdimp.com
Mon Oct 5 21:06:54 EDT 2009

In message: <E1Muy8B-0003lK-DW at grus.atnf.CSIRO.AU>
Mark Calabretta <mcalabre at atnf.csiro.au> writes:


: On Sun 2009/10/04 12:49:06 +0200, Magnus Danielson wrote


: >Of course it cannot output a correct UTC solution until it has received

: >page 18 subframe 4, but it can store the leapsecond offset in

: >non-volatile RAM since last lock and for most of times that would give

: >correct UTC from first lock. How many if any receiver uses that, I do

: >not know, but it is technically possible, just as you store the almenac

: >data and last known position in order to accelerate those first 12,5

: >min. Recall, for this strategy to fail, the receiver must have been

: >turned off over a leap-second event. Most times it is turned off is not

: >a leap-second event.


: Given that leap seconds are announced six months in advance, how

: difficult would it be for GPS to disseminate that information

: and for receivers to store and use it?

They already do that.

However, it turns out there are a number of edge-case ambiguities that
make for interesting problems that have been talked about here...

The fundamental problem is that leap seconds are announced 6 months in
advance. This is too little time.


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