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    Re: Position from a photo
    From: Geoffrey Kolbe
    Date: 2013 Jan 08, 06:57 +0000

    Hello Robert.
    Your imagination is indeed worthy of a Hollywood fantasy film script,
    I am sure you would find a move to the West Coast a profitable one ;-)
    The trouble is that without a time for the photo, you are in the end
    dependent of what is essentially a lunar to give you longitude, which
    results in an error of the order of 50 miles in longitude
    My more prosaic offering was to envisage three acacia trees standing
    in a triangle. Ropes are brought from each tree and tied together at
    the centre. A plumbline is hung from the join between the three ropes.
    There are (in the Southern part of the Sahara desert) two days a year
    when the sun is directly overhead. At that moment, the shadow of the
    three ropes on the ground will appear centered like the cross hairs
    of a telescopic sight on the shadow of the plumb bob on the ground.
    The moon rising (or setting) could be in the sky and a plate, with
    water in it, reflecting the top of the moon, could be carefully
    placed on the ground.
    This information would be sufficient to give the year and day and
    narrow down the time to within a few minutes from the altitude of the
    moon, but I can see no way to improve on that, except that our
    soldier writes the time on the back of the photo, or there is a clock
    in the photo somewhere.
    This scenario would appear to have been feasible in 1943, which was
    the last year of the desert campaign.
    Thanks again for your thoughts

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