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Re: [gpsd-dev] Very basic PPS question:

From: Andy Walls
Subject: Re: [gpsd-dev] Very basic PPS question:
Date: Sat, 19 Oct 2013 09:51:42 -0400
User-agent: K-9 Mail for Android

I'm no expert, but that is likely device dependant.

For the few devices I have worked with: the PPS pulse is for the top of the second that the device then reports via the serial stream.

I verified this once against NTP servers, for the device I am currently working with. (This is also how I found my device uses the wrong leapsecond correction after poweron, before it gets the almanac. I guess I'm a mild time-nut.)

I also found, on average over a 4 hour data collection, that the serial timestamp gpsd reports from my device, is ~450 ms delayed from the PPS. I use that value for the ntpd.conf fudge for my gpsd refclock.


"Eric S. Raymond" <address@hidden> wrote:
When a GPS asserts PPS, is it top of second for the in-stream 
data *preceding* or *following*?

I presume following, but I want an expert to confirm before I
put it in the HOWTO.

Sent from my Android phone with K-9 Mail. Please excuse my brevity.
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