"Actually, the chip rate has very little if anything to do with
    the overall accuracy;"

That's not how it has been expressed in the past (at the time GPS
NAVSTAR program was coming about as a DOD activity) ... perhaps
*newer* techniques have yielded *better* accuracy using

       "COURSE/ACQUISITION (C/A) code" (chip rate 1.023 MHz)

alone - but the C/A code was *initially* a means to 'bootstrap up'
and acquire the

        "PRECISION (P) code" (chip rate 10.23 MHz)

which was actually intended for precise position location by users of
the system.

The use of the L2 frequency (in the 1200 some MHz area) does allow for
some compensation due to atmospheric-imposed anomolies on the RF signals
as they make their way to the user ...

RF Jim



----- Original Message -----
From: "Dave Tweed" <pic@DTWEED.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, November 23, 2002 9:54 AM
Subject: Re: [OT]: (Report of) GPS anomalies


> RF Jim <jvpoll@DALLAS.NET> wrote:
> > 2) the military (and other qualified users) have access to
> > a 'chip rate' ten times what civilian users have with approximately
> > ten times the accuracy commonly availiable on 'civilian' GPS
> > receivers - aren't you?
>
> This is a common misconception.
>
> Actually, the chip rate has very little if anything to do with the overall
> accuracy; the quality of the correlators and local clock is the real
> limitation. The main reason military receivers do better is because they
> get access to two different carrier frequencies, which allows them to
> measure and compensate for atmospheric refraction in real-time.
>
> -- Dave Tweed
>

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