[time-nuts] Ashtech Z12T

Tue Dec 4 11:30:56 UTC 2018

Hello JF

(Ccing to time nuts because probably still of interest)
The TTR6 is a single channel receiver so you had to install an observing
schedule appropriate to your geographical region, which specified which
satellite you would track at which time. The BIPM used to generate and
distribute these schedules every 6 months or so but stopped doing this 7?
years ago - I think this is what you mean by "ephemerides".

If you have N satellites tracked then you can reduce the time transfer
noise by sqrt(N) roughly speaking. You can either do common view, where you
match satellites at each location and time, and then take an average of the
differences, or all in view, where you average all of the satellites
visible at each location, and then difference. Common view gives you less
noise (because of better cancellation of eg the effects of the ionosphere)
on short baselines. However as the baseline increases in length, the number
of satellites in common view decreases and the statistical noise increases.
At distances of a few thousand km, all in view starts to win because more
satellites are used. You can improve the processing by doing things like
weighting  the satellites according to their elevation.

The current best method of doing GNSS time-transfer is PPP or precise point
positioning, and is a form of all in view, with much better post-processing
that uses both code and phase observatIons. You can do this with the
Septentrio receivers. But CGGTTS-based time transfer is still used in the
timing community.

Cheers
Michael

On Tue, 4 Dec 2018 at 9:19 pm, JF PICARD <jfphp at yahoo.com> wrote:

> Hello,
>
> Thank you very much for your explanations but, as a newbie in this immense
> domain, I have got some questions. With the Allen Osborne TTR-6 we received
> from the LNE SYRTE (french observatory)  and loaded the ephemiredes (data
> about the GPS satellites passing above us the next week or month) and we
> will follow satellite X, the Y... , we sent our received data and we got
> the data from LNE for the same satellite...
> How does the actual system operate with several satellites ? I haven't
> seen any mention (quick overlook in the data sheet) neither in the
> Septentrio nor in the NVS...
>
> Cheers.
>
> JF
> --------------------------------------------
> On Mon, 12/3/18, Michael Wouters <michaeljwouters at gmail.com> wrote:
>
>  Subject: Re: [time-nuts] Ashtech Z12T
>  To: "Discussion of precise time and frequency measurement" <
> time-nuts at lists.febo.com>, "JF PICARD" <jfphp at yahoo.com>
>  Date: Monday, December 3, 2018, 8:42 PM
>
>  Hello
>  There are many alternatives to the
>  Z12T. It all depends on your budget. I am guessing that you
>  want to establish legal traceability to your local UTC, is
>  that right?
>  Starting
>  at the top end, you can buy complete systems from Dicom and
>  Piktime. These cost about $25K and $40K respectively. These
>  are multi-frequency, multi-GNSS systems.
>  There are also some cheaper, single
>  frequency systems (GPS only)  available too, from a company
>  in Japan and one in the U.K. Just search for "time
>  transfer system".
>  Some NMIs in countries like Canada,
>  Australia, Japan, ... offer remote calibration services of
>  the kind you want to set up. These  are too far away for
>  common view but I suppose all in view would be the method in
>  this case ( you would still have traceability to your UTC
>  via the CIPM Mutual Recognition Agreement). Costs are
>  something like $5K per year, in addition to the
>  hardware.
>  You can just
>  buy a shiny new time-transfer receiver like the Septentrio
>  PolaRx5TRPRO with a geodetic antenna for about $20K. These
>  are the most popular in the timing community at the moment.
>  But other receivers like Javad and Trimble are good
>  too.
>  If single
>  frequency performance is good enough, and you're willing
>  to do a bit of work setting up software, then the really low
>  cost solution is something like the software from www.openttp.orgThe
>  main receiver supported, the NVS NV08C is less than $100.
>  You can get accurate antenna positions from this receiver in
>  a base rover configuration. All the rest is post processing
>  and there are various options here. You will also need a
>  counter/timer and the low cost solution here is the TAPR
>  TICC, which is also supported by OpenTTP.
>  CheersMichael
>
>  On Mon, 3
>  Dec 2018 at 10:21 pm, JF PICARD via time-nuts <time-nuts at lists.febo.com>
>  wrote:
>  Thank you
>  for answer and sorry for delay. Purpose is simultaneous view
>  of GPS satellites with the french official time laboratory
>  LNE SYRTE . The corrections factors from the laboratory will
>  enable to get with our high performance cesium about 5.
>  10-13  . Today the cesium is running alone. Discussion with
>  some people involved in this worlwide common practice spoke
>  about the Z12T but if there is anything more modern..
>
>  --------------------------------------------
>
>  On Wed, 11/28/18, Tom Van Baak <tvb at LeapSecond.com>
>  wrote:
>
>
>
>   Subject: Re: [time-nuts] Ashtech Z12T
>
>   To: "Discussion of precise time and frequency
>  measurement" <time-nuts at lists.febo.com>
>
>   Date: Wednesday, November 28, 2018, 10:12 PM
>
>
>
>   The Z12T is a bit old by now, although some
>
>   of us own or have used them. Z12 documentation is
>  available
>
>   on multiple archived Ashtech web sites. Lots of conference
>  /
>
>   technical papers describing time transfer with Z12T
>
>   receivers exist. AFAIK a number of national timing labs
>
>   still use them.
>
>
>
>   What is it you're trying to do? Do you
>
>   own a Z12T and are just looking for spare parts? Or are
>  you
>
>   looking for modern time transfer via GPS / GNSS? If so,
>  what
>
>   level of timing accuracy are you looking for? Perhaps
>  you
>
>   could explain a bit more what your actual request is,
>  or
>
>   what timing infrastructure you already have running.
>
>
>
>   /tvb
>
>
>
>   ----- Original Message -----
>
>   From: "JF PICARD via time-nuts" <time-nuts at lists.febo.com>
>
>   To: <time-nuts at lists.febo.com>
>
>   Cc: "JF PICARD" <jfphp at yahoo.com>
>
>   Sent: Wednesday, November 28, 2018 9:33
>
>   AM
>
>   Subject: [time-nuts] Ashtech Z12T
>
>
>
>
>
>   > Hello,
>
>   > I am looking for a time transfer
>
>   system Ashtech Z12T or equivalent. Thank you.
>
>   >
>
>   >
>
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