A C wrote:
Let us assume that the pulse from the GPS receiver is off from the
master UTC clock tick by about 3 ms due to a variety of delays in the
overall system starting from the satellite and working its way down to
ntpd. (No arguments about how I get to that number, we're just assuming
this is the case).
What's your basis for assuming all the error is attributable to the PPS,
rather than the other sources contributing to ntpd's time solution.
The GPS receiver should have solved for the time of flight from the
satellite to better than 100ns for GPS to be able to achieve its stated
accuracy. If the time of flight solution was out by 3ms on just one
satellite, your position error would be about 500km. Even if was out
by the same fixed amount for all satellites, you'd have a position error
of around 30 metres.
Nearly all the GPS offset will be attributable to the last few feet -
most of it within the PC.
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