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Re: Questions (Answered)
Gary E. Miller
Re: Questions (Answered)
Wed, 22 Jun 2022 21:19:20 -0700
On Wed, 22 Jun 2022 21:17:30 +0000
Ken.Hendrickson--- via <email@example.com> wrote:
> I have found more information that answers most (if not all) of my
> The gpsd.8 man page indicates that gpsd can use the Zodiac binary
Yup. But. I have never seen a Zodiac, and I don't think they have been
made in over a decade. The one and only Zodiac regression test we
have is from 2005. There may be some bit rot.
> Austin's Nerdy Things describes a microsecond accurate solution on a
> Raspberry Pi w/ 1PPS.
That should be easy.
> Finally, I found these IETF documents:
gpsd implements that.
The Linux kernel implements that.
Check out the Timeserver HOWTOs hereO: https://gpsd.io
> This will give me a stand-alone time-frequency standard that will
> work as long as GPS is available. Differential GPS would hold no
> value for me, nor be practical if using the system portable or mobile.
No need for DGPS if 1 micro second is your goal.
> This web page shows pictures of some of the components (OCXO, Jupiter
> GPS, PLL board, PLL board schematic):
> Can gpsd read the proprietary Zodiac binary message format? If not,
> I could write that software. Apparently, the time mark message which
> precedes the 1PPS pulse is only output in the 9600 bps binary message
> format, but not 4800 bps NMEA. (The UTC Time Mark pulse output
> message provides the number of seconds since the beginning of the
> week, about 0.5 second before the 1PPS signal.)
gpsd PPS can work fine with NMEA or Zodiac binary.
> What is currently the best way to utilize the 1PPS signal?
The ppscheck program from gpsd.
> Using the 1PPS signal seems to require being able to read the
> proprietary Zodiac binary message format.
No. But you'll get more data with the Zodiac binary.
> One objective I have, if possible, is to have a stand-alone time
> server with no internet connection. Is this possible? What would
> the gpsd requirements be?
> Does anybody use differential GPS?
> What would be required?
> differential GPS only improve the geolocation solution, or would it
> also improve a time solution?
It improves both. With GNSS time == position.
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
firstname.lastname@example.org Tel:+1 541 382 8588
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"If you can't measure it, you can't improve it." - Lord Kelvin
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