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The underlying P-code (before encryption with the W-code to produce the
Y-code) is the same on both L1 and L2 and civil receiver manufacturers have
for years used this feature in dual-frequency receivers to provide
the civil community with capabilties far superior to those typically required
in military applications. As an example, at UNB we developed a machine
control system with 2-centimetre accuracy.
Some other observations concerning recent posts on GPS:
1) S/A cannot be selectively applied in a satellite to affect only a small
region on the Earth's surface. The foot print of a GPS satellite covers
virtually the whole hemisphere below the satellite.
2) GPS is managed by the U.S. Air Force bit is under joint civil-military
control. Officially:
"The Secretary of Defense shall:
Have responsibility for development, acquisition, operation, security, and
continued modernization of the Global Positioning System, while facilitating
appropriate civil and homeland security Department and Agency representation
and participation in these activities, and any decisions that affect civil and
homeland security equities."
3) One of the future Galileo frequencies coincides with the GPS L1 frequency.
Both systems will use the same frequency without interfering with each other.
4) Concerning jamming, people might like to read the following which I wrote
before the Iraq war:
.
-- Richard Langley
   Professor of Geodesy and Precision Navigation
   and Contributing Editor, GPS World Magazine

On Mon, 5 Jun 2006, Peter MacNeil wrote:

>       Red, Buddy,
>   True that with a proper application you can attain a PPS
>reciever for    extremely accurate GPS signals.  However, in
>said application, since the    device uses NATO
>crypto-graphic material, the individuals must pass a
>security    clearance check...minimum 6 months.  Trust me.
>   The quote is..."...they are tightly controlled by the US
>Government."
>   DGPS will give almost the same precision, however, they
>are incapable of    processing the P(Y) code in the L1 and
>L2 signal, giving extremely accurate    positions.
>   Why don't you try for an application and let me know how
>it    goes...(joke)
>
>
>
>
>
>      Peter I.  MacNeil
>Lieutenant  (N)
>Fleet Navigating  Officer Course
>Serial 0601
>NOTC VENTURE
> "There can be only  one!"
>
>


===============================================================================
 Richard B. Langley                            E-mail: lang@unb.ca
 Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
 Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
 University of New Brunswick                   Fax:      +1 506 453-4943
 Fredericton, N.B., Canada  E3B 5A3
     Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===============================================================================

   

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