[IGS-RTWG-91] Re: Positions Against Phase Alignment
"Dr. Gerhard Wübbena"
gerhard.wuebbena at geopp.de
Tue Jan 29 07:37:30 PST 2013
I do not agree with your interpretation, that "the only useful and
reliable observations would be the reference signals on each frequency".
If you transmit untouched observables, i.e. the observables as obtained
from the proprietary receiver formats, and if your application requires
"phase alignment" you need the phase shift message only in very limited
You *do not need *a phase shift message
* If you have only phase observable per GNSS and frequency,
* if you have more than one phase observable for a frequency and if
you have overlapping satellites, i.e. both or all phases are
simultaneously tracked for the same satellites. In this case a
direct comparison of the phases yields the information about
In the majority of scenarios these cases will be the default. I.e. you
will have all the necessary information from the stream with untouched
Currently, there is only one scenario where a phase shift message is
needed if your application requires alignment. This is the tracking of
L2P and L2C without overlapping satellites. However, the alignment of
L2C is difficult in case of Flex Power (to be expected with L2C-IOC in
2014/15?). The current MSM-CDV does not support alignment in this case,
but it is defined in our proposal (see below).
In our joint MSM proposal with Alberding, BKG and DLR (attached, in case
you did not receive it) we defined the phase shift message to be
optional, because it is not needed in most cases and in order to allow
the generation of MSM streams by converter software if the phase shifts
are unknown to the converter. We think this is a better solution
compared to the necessity to throw away observations by the converter or
to violate the standard (this will make the standard unreliable). The
decision to throw away or to use observations should not be taken by a
converter software but by the receiving application. The receiving
application might not require alignment or might know through other
means how to do the alignment for the specific streams.
The current MSM-CDV gives you ambiguous phase observations unless you
define a mandatory phase shift message. However, such a message is not
defined in the CDV. With the CDV definition you will not be able to
restore the original observations, you may loose continuity of phases,
interfrequency and code-carrier biases (as used for MW-combinations)
will become ambiguous and may experience discontinuities. In case of
Flex Power you will have aligned or non-aligned phases and you have no
way to identify it. This will result in ambiguous and unreliable
streams. Not really an acceptable method in my opinion!
Dr.-Ing. Gerhard Wübbena #
Geo++ GmbH, Steinriede 8, D-30827 Garbsen, Germany ###
phone +49- 5131-4689-0, fax +49- 5131-4689-99 #####
Latitude: N52°25'51" Longitude: E009°36'30" #######
mailto:gerhard.wuebbena at geopp.de, web http://www.geopp.de #########
Ust-ID/VAT-ID: DE115829628, AG Hannover HRB 110343 ###########
Geschäftsführer/President: Dr.-Ing. Gerhard Wübbena #############
Am 29.01.2013 14:01, schrieb MacLeod, Ken:
> Hi Loukis,
> The Geo++ paper proposes that one can encode data in MSM format and NOT make an effort to phase align the data (no mandatory phase alignment message). In this case the only useful and reliable observations would be the reference signals on each frequency. Not really an acceptable method in my opinion.
> I think we can work with unaligned MSM phase as long as there was a mandatory phase alignment message, since RINEX 3.02 can accommodate this method and we have the information required to align the phase obs in RT.
> We will see what happens Thursday and Friday.
> From: igs-rtwg-bounces at igscb.jpl.nasa.gov [igs-rtwg-bounces at igscb.jpl.nasa.gov] on behalf of Loukis Agrotis [loukis at symban.co.uk]
> Sent: January 29, 2013 6:49 AM
> To: RTWG
> Subject: [IGS-RTWG-89] Positions Against Phase Alignment
> Dear Colleagues,
> Please see attached two papers taking positions against phase alignment at the RTCM meeting taking place this week in San Diego. The IGS has previously taken a position in favour of phase alignment. The outcome of the meeting may well be that the MSM formats are approved by majority of the people present, but in case there is another stalemate, I believe that there should be a serious discussion to see how a compromise could be achieved as soon as possible.
> Best Regards,
> IGS-RTWG mailing list
> IGS-RTWG at igscb.jpl.nasa.gov
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