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Re: [gpsd-dev] PPS over USB

From: Ed W
Subject: Re: [gpsd-dev] PPS over USB
Date: Mon, 07 May 2012 13:20:01 +0100
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On 06/05/2012 22:56, Terje Mathisen wrote:
BTW, I just picked up a NetGear 3800 for the BufferBloat firmware, I intend to point that router at the local S1, which should result in better timing than a PPS over USB solution.

Big problem... If you look on the chrony mailing list you can find a post plotting the divergence of worldwide stratum 1 clocks. I'm afraid the answer is that stratum 1 is not a definition of accuracy, just an observation on the clock source. In particular many have fixed offsets, poor stability, synced to radio clocks rather than GPS, etc.

From what you describe the bufferbloat project should ask for their own pseudo machine group and do some work to populate it with high quality servers s1/s2 that are cross synced. I could have some interest in getting involved with that.

Just for kicks add a bunch of ntp machines into your chrony config, wait 15 mins or so and then check the statistics. Bet you get a range of > 200ms ...

Good luck

Ed W

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