[LEAPSECS] WP7A status

Matsakis, Demetrios matsakis.demetrios at usno.navy.mil
Thu Dec 18 11:24:35 EST 2008

The best way to get "Time" out of GPS is to apply the leap seconds and
subframe 4 corrections of the broadcast GPS navigation message to GPS
time, and get UTC(USNO) via GPS. Most GPS receivers do this
automatically. There can be calibration and latency issues, which are
usually but not always below 10 ns.

GPS time itself is provided for navigation solutions. That is why it
does not incorporate leap seconds, and that is also why GPS time is
steered by acceleration (not rate) to UTC(USNO), modulo 1 second, using
the so-called bang-bang algorithm.

The best reference would be the ICD-GPS-202, which is written in style I
would describe as "for engineers".

-----Original Message-----
From: leapsecs-bounces at leapsecond.com
[mailto:leapsecs-bounces at leapsecond.com] On Behalf Of Greg Hennessy
Sent: Thursday, December 18, 2008 6:53 AM
To: Leap Second Discussion List
Subject: Re: [LEAPSECS] WP7A status

> http://www.newscientist.com/article/mg20026875.400-calls-to-scrap-the-

> leap-second-grow.html

The report has a sentence "GPS time is not a reference, it is simply an
internal time for GPS system synchronization, as GLONASS time is and
Galileo time will be."

Is what it takes to be a reference documented any where?

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