[time-nuts] Frequency Ensemble

[Tim Lister]

On Mon, Mar 18, 2019 at 8:03 AM Rodger via time-nuts
<time-nuts at lists.febo.com> wrote:
>
> Tom,
>
> Thanks for the explanation of clock ensembles.  That answered a few
> questions I've had for a while.
> Regarding your comments on collecting raw time data from GPS and post
> processing it.  Can you provide any reference info, links, etc. with more
> detail on that topic?
> Clearly I'd need a GPS that outputs the proper raw messaging and the
> software for processing it.  I'm somewhat familiar with the techniques
> involved to improve GPS position data, but hadn't thought about it as much
> for timing.

As Bob says, the ublox chipsets from generation 6 onwards are probably
the best value as they can be configured to output the raw
measurements for precise position/time. There is info on configuring
these at OpenStreetMap and rtklibexplorer's wiki and blog respectively
and I also added a howto on my blog on doing this
(https://adventuresinprecision.space/howtos/precise-gps-positions/)

The OpenTTP project has code for capturing the raw data (ublox M8's
are supported right now, I am working on adding support for -6T and
the main developers are looking at adding support for the new ublox F9
chips) and software for doing the GPS Common View processing. I am
just starting to dig into this but need to get the last bit of the
ublox6 support working in order to give it some valid data to play
with. The other easily available GPS receiver that OpenTTP supports is
the Trimble Resolution T which I think has been "end-of-lifed" by
Trimble which has pros of being available cheap on ebay and cons of
not being able to buy a brand new "official" board unlike with the
ublox 8 and 9 receivers.

>
> Thanks,
>
> Rodger
>

Cheers,
Tim