[time-nuts] GPS new L2C civil signal -- timing uses?

Normand Martel martelno at yahoo.com
Fri Nov 17 01:57:36 UTC 2006


...On a totally different (e.g. positoning) topic,
does anyone know if any major GPS equipment
manufacturer will commercialize dual frequency
(L1/L2C) GPS recivers?

...In timing, the interesting point i see is the
possibility to have a two-tier redudancy GPS
timesource (and eventually a three-tier redudancy with
the upcoming og Galileo).

For now, i will watch the sky for that guy with a big
white beard, a sleigh and eight reindeer... for that
brand new L2C time machine!!

73 de Normand Martel VE2UM
Montreal, Qc. Canada

--- Magnus Danielson <cfmd at bredband.net> wrote:

> From: "Christopher Hoover" <ch at murgatroid.com>
> Subject: RE: [time-nuts] GPS new L2C civil signal --
> timing uses?
> Date: Thu, 16 Nov 2006 15:40:57 -0800
> Message-ID: <005f01c709d8$aa8d95a0$7d01000a at fakie>
> 
> > 
> > >> Anyone know of the timing uses and properties
> of this 
> > >> new L2C civil signal vis a vis the existing
> civil signal?
> > 
> > > Do you mean beyond that of ICD-GPS-200C?
> > 
> > I don't know.  I am unclear of the relationship
> between that and the "new
> > L2C civil signal" referred to in the article.  
> > 
> > Are you saying both refer to the same thing?  If
> so, what are the
> > implications for timing apps?  (I'm happy to go
> back through the archives if
> > this has already been discussed.)
> 
> OK. The new GPS IIR-M sats (third going up UTC 18:12
> tomorrow) transmitts both
> the old L1 C/A signal as well as the new L2C
> signals. This is totally covered
> in the ICD-GPS-200D [1] (which is the one to use,
> not the ICD-GPS-200C, which I
> incorrectly directed you to). These three signals is
> unencrypted and when
> visible they allow for two-frequency measures on
> capable receivers with
> suitable two-frequency antennas. Based on
> traditional GPS theory, this allows
> the receiver to shift from a modelled delay of the
> ionsphere to a measure based
> model ionspheric delay and the implications on time
> measures is much reduced
> systematic error. Requirements for augmentation
> through reference stations is
> lowered if not eliminated. Naturally, hardware cost
> goes up since you now have
> two frequencies to deal with. If you are a teeny
> weeny serious you look ahead
> towards the L5 and Galilleo signal structures which
> certainly would require
> additional frequencies.
> 
> [1]
>
http://www.navcen.uscg.gov/gps/modernization/IS-GPS-200D_w_IRN_1_7Mar06%20NS.pdf
> 
> If we get our durty hands on the propper receivers
> (and we will) we, as fellow
> time-nuts, will have a much improved state. With
> Glonass in the rising on top
> of this, things looks good.
> 
> Oh, and to be clear, "L2C" is actually three
> different signals, C/A on L2,
> L2CM and L2CL. where you either have C/A on L2 or
> both L2CM and L2CL (at the
> same time).
> 
> Cheers,
> Magnus
> 
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