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    Where is the Prime Meridian?
    From: Murray Peake
    Date: 2021 Dec 10, 11:12 -0800

    I'm interested in the practical achievable accuracy for finding the time given the position - a problem discussed in Henry Raper and John Letcher offers an approach as well.

    I was checking the accuracy of the Maritime Positions in Raper and looked at Greenwich Observatory which is in the tables, rather naturally at 0 degrees longitude. When I look at Google Maps though the Prime Meridian seems 2 arc seconds displaced from the Observatory buildings in Blackheath Avenue. How did that happen?

    Raper's quoted positions are to the nearest minute of longitude which I suppose limits the accuracy to 4 seconds of time. Is that the limiting factor given usual sextant accuracy and observaional errors in an artificial horizon?

    Best Wishes

    Murray

       
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