[LEAPSECS] Bulletin C and all that

Martin Burnicki martin.burnicki at meinberg.de
Tue Jan 27 07:20:10 EST 2015

Tom Van Baak wrote:
>> But there have been real bugs due to leap indicators remaining set too
>> long, leading to bogus leaps at the end of July. So in practice there is
>> less risk in allowing leaps only in June and December.
> Those real bugs are better fixed at their source than worked around in this manner. Ok, easy to say and hard to do, I know.
> Perhaps leap indicators should not be booleans but small wrapping integers. For example GPS makes use the low order 8 bits of the week number for almanac version checks. Perhaps the same could be done for leaps, especially if they are encoded as a TAI offset integer instead of +/- yes/no booleans.

The truncated week numbers are a good source for potential errors.

Especially the 8 bit WNls week number in the GPS UTC parameter set has 
to be untruncated to 10 or more bits by the firmware to compute the real 
point in time for a leap second.

If the current week number is off by more than +-127 then this is 
ambiguous. This has rolled over several time in the period where no leap 
second had been scheduled for 7 years, and all the time the 8 bit week 
number of the last recent leap second was broadcast.

Martin Burnicki

Senior Software Engineer

MEINBERG Funkuhren GmbH & Co. KG
Email: martin.burnicki at meinberg.de
Phone: +49 (0)5281 9309-14
Fax: +49 (0)5281 9309-30

Lange Wand 9, 31812 Bad Pyrmont, Germany
Amtsgericht Hannover 17HRA 100322
Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg, 
Andre Hartmann, Heiko Gerstung
Web: http://www.meinberg.de

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