[time-nuts] Re: ublox gnss receiver data

[Michael Wouters]

Hello Jorge

Correcting myself here:
The CGGTTS V2E spec says
"The dual-frequency CGGTTS for the different constellations will be based
on the ionosphere-free combinations of the following signals:
ï‚· GPS and GLONASS: C1 or P1 & C2 or P2
ï‚· Galileo: E1 & E5a
ï‚· BeiDou: B1I & B2I
ï‚· QZSS: C1 & C2"
and then further says this should be called "L3P" for GPS
even when C1+C2 is used.

Regards
Michael

On Sun, Sep 18, 2022 at 7:23 AM Luiz Paulo Damaceno via time-nuts
<time-nuts at lists.febo.com> wrote:
>
> Hi all!
>
> I'm testing ublox's ZED-F9T GNSS receiver for time transfer applications
> and i've observed few things at data processing. This receiver is being
> feed with external 49.58 MHz coming from a synthesizer that is locked to
> Symmetricom's 5071A cesium frequency standard since we've removed its TCXO
> to make the time transfer tests.
>
> For the tests, I've processed .ubx raw data, then RINEX 3.04 data with
> RTKCONV present at RTKLib software. After that,  I was able to see the
> following RINEX observation types:
>
> G    4 C1C L1C C2X L2X                                      SYS / # / OBS
> TYPES
> R    4 C1C L1C C2C L2C                                      SYS / # / OBS
> TYPES
> E    4 C1X L1X C7X L7X                                      SYS / # / OBS
> TYPES
> C    4 C2I L2I C7I L7I                                      SYS / # / OBS
> TYPES
>
> The main question is: why L2 data for GPS is classified by "X" for code and
> phase?
> I've tried to process it with NRCAN's PPP software, but only had success
> when changed "C2X" and "L2X" to C2C and L2C.
>
> Now... Other things that I cannot explain and occurred:
>
> 1 - For the case that i've not changed X for C, i cannot process CGGTTS
> data for L2C frequency for GPS constellation. Only L1C clock data.
> 2 - For GLONASS and BeiDou constellation, without any changings in the
> observation types I can see L3P clock data, with coherent MDIO and MSIO
> values I guess...
> 3 - After changing GPS observation types for C2C and L2C, I have two files:
> L1C clock data and L2C clock data.
> 4 - After changing GPS observation types for C2P and L2C, i was able to
> have CGGTTS L3P data for GPS Constellation, but i guess that data is not
> valid because the receiver is not receiving "P" code in any frequency, even
> if use biasC1P1 file, the data shouldn't be real, right? So... Why is MDIO
> and MSIO also valid?
> 5 - I can see only GALILEO's E5b data, and L1 data seems to be not
> available.
>
> I've uploaded a few files to you to see some results in those files. I'm
> using the r2cggtts program and the input files are "rinex_nav_mix" and
> "rinex_obs".
>
> Link for the files: Google Drive
> <https://drive.google.com/drive/folders/115TAVbOOMkpxXbt4JLnR94nODbRFEgys>
>
> For the files, -rp2 means that i've changed original observation data
> (258_ubx.obs) from L2X to L2P type, also C2X to C2P type. For that, my
> question is: why GLONASS and BeiDou, even having an "P" code on the
> receiver, are able to generate L3P data? Rember: I've only changed X to P
> observation type for GPS constellation, everything else remains untouched.
>
> If you have links and other sources with works related to this I will
> appreciate it! Thanks.
>
> Best regards,
>
> Luiz
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