On 8/28/21 10:25 AM, Robert DiRosario wrote:
For GPS receivers that give 1 PPS output the spacing between pulses
is, obviously, very accurate.
Are the pulses synchronized to something, like UTC seconds, or does it
vary from one
manufacturer to another, or even one unit to another?
GPS seconds (which are very close to UTC, except for the fact that UTC
is an ensemble time, which technically isn't available until it's been
processed).
Your receiver documentation should say whether it's the rising or
falling edge of the pulse.
Some receivers, just to make things exciting, generate the pulse by
gating an internal clock, so at the nanosecond level, there's a
variation due to the internal clock not being synced with GPS, but free
running. Some receivers will tell you what the offset is in some data
message. Or, it won't, and you have to measure it (or average over many
seconds, which is what GPSDOs do).
A simple question you ask and it can lead you down such a rabbit hole
with hanging bridges, steps, etc.
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