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

[Magnus Danielson]

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