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Re: [gpsd-dev] gpsd for time sync on Ubuntu remix too hard for normals -
Re: [gpsd-dev] gpsd for time sync on Ubuntu remix too hard for normals - how to improve?
Sun, 05 May 2019 21:41:42 -0700
> Time quality as you think about it does not matter here. If we could sync to
> within 50 ms, that is completely good enough. We are talking about lining up
> a ~13s transmission window and a 2s guard time with other stations. People
> who set their computers manually to WWV can succeed.
I assume the time accuracy determines how far the receiver has to search.
Does that take a significant amount of CPU time? Or do you just have to stay
within the guard band?
If your target is 50 ms, I see two problems.
The first is that some old but popular receivers have 100 ms error band after
you correct the offset. Sample here:
My model is that they have a 100 ms clock internally that drives the
scheduler, or something like that.
The other is that the offset correction probably depends on the brand/model of
GPS unit you are using. More likely on the chip set behind the label.
At any rate, you setup recipe may need a setup section for each type of GPS
unit and/or you may want a list of known-good units.
Things may get a lot easier of you can relax your goals to 100 ms.
These are my opinions. I hate spam.
[gpsd-dev] Best way to avoid systemd woes for NTP?, Greg Troxel, 2019/05/05