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There is also a technique called precise point positioning or PPP which just
uses a single dual-frequency receiver plus precise satellite orbits and clocks
to achieve positions on the Earth's surface with decimetre accuracy.
-- Richard Langley
   Professor of Geodesy and Precision Navigation

On Wed, 7 Jun 2006, Lu Abel wrote:

>Richard Langley wrote:
>> 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.
>
>Judging by some of the replies in this thread, it's important for folks
>to know that these precise measurements are NOT locations on the face of
>the earth, but rather distances between two sensors.  One rarely sees
>surveyors out with measuring tapes any more, they all have GPS-based
>distance measurement devices.  But, again, they are measuring the
>difference between the location of two receivers based on the phases of
>the received GPS signals, not decoding P-code signals.
>
>Lu Abel
>


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 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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