On 2/16/14 11:55 AM, Jimmy D. Burrell wrote:
I've looked at several different manufacturer GPS datasheets now
regarding the 1 PPS output in an attempt to compare apples to apples.
Some of them rate their 1 PPS output as something on the order of
"PPS signals have an accuracy ranging 10ns" which seems ambiguous.
Does that mean the leading edge of their 1PPS is within 10ns of the
GPS clock? Or simply that the stability of their 1 PPS is within
10ns? Or both?
Perhaps there's an industry standard for these specs of which I'm
unaware?
Hah..
It's read the specs carefully and ask questions.
The datasheet for my (presumably much older) Globalsat ER-102 seems,
to me at least, to be much more clear stating "time reference at the
pulse leading edge aligned to GPS sec., +/- 1 us". Which I interpret
as the leading edge of my receiver's 1PPS is aligned with the GPS's
clock to within +/- 1 us.
And is that "always" within 1 us? or 90% or 2 sigma or ??
ANd is that spec assuming some accuracy of the underlying GPS. At 1 us,
it probably doesn't matter, but at 10ns, you start worrying about
position uncertainty.
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