Maarten Wiltink wrote:
"In general" PPS will be off by anything up to half a second in either direction, distributed uniformly.
The sort of PPS source that ntpd normally uses is synchronised to the UTC second.
A GPS source showing an apparent offset of 2ms is much more likely to be doing that than just randomly being that close.
Your Caesium example is a pure frequency standard, but GPS needs an accurate common time across the satellites to provide a proper spatial solution. It needs very good relative time between satellites to work at all, and it needs quite good absolute time in order to exactly locate the fast moving satellites. In practice, it is marketed as a time standard as well as a position one.
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