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    Re: Longitude of Greenwich Observatory
    From: Richard B. Langley
    Date: 2005 Dec 19, 09:38 -0400

    Polar motion is taken into account when establishing and maintaining the
    geodetic reference frames (datums). For an explanation of why a GPS receiver
    indicates 0 degrees longitude to be about 5.4 arcseconds or roughly 100 metres
    to the east of the Airy meridian, see
    
    -- Richard Langley
    
    On Mon, 19 Dec 2005, Michael Dorl wrote:
    
    >>
    >>Actually the Greenwich "discrepancy" was only 5.4 arc SECONDS of  longitude.
    >>But even that is unlikely and probably related to registering the  imagery. I
    >>would still like to know if that transit instrument at RGO is still  the exact
    >>zero of longitude. Has anyone on the list turned on a GPS receiver  while
    >>standing there?
    >
    >
    >See http://www.iers.org/iers/earth/rotation/polmot/O-1.gif
    >
    
    
    ===============================================================================
     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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