[ntp:questions] Inexpensive OEM GPS units?

Chris Adams cmadams at hiwaay.net
Wed Nov 14 02:52:29 UTC 2007

Once upon a time, Steve Kostecke  <kostecke at ntp.org> said:
>What would be helpful is information about the observed performance of
>these inexpensive OEM GPS units. I've added a plot of my GPS-18LVC
>performance under less than optimum conditions and a snapshot of your
>daily MRTG plot for pixie to
>Would you mind updating that topic so that is shows the version of
>FreeBSD you currently have in use?
>BTW: It would be interesting to run a loopstats file from pixie through
>my plotting tool and get a closer look at your GPS performance.

I'm trying to figure out how accurate my setup is, and I've enabled
statistics gathering.  What can I make of the numbers?  How is the
offset arrived at (e.g. how can the offset from "true" be calculated)?

Is the tool used to generate the big plot in the middle available?

I'm running an old SVeeSix (NMEA mode) into an FTDI USB to serial
adapter (I am aware of the additional delays introduced by USB; that's
part of what I'd be interested in quantifying).  I'm using shmpps to get
my PPS signal signal to ntpd (no Linux kernel PPSKIT which AFAIK doesn't
do USB to serial anyway).

Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

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