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    Re: Emergency Meridian Altitude
    From: David C
    Date: 2016 Dec 10, 18:53 -0800

     lat = 90  + dec  - alt

       = 40° 56.4'

    GPS lat S 41° 06.5'

    Error  10.1'

    I wonder if the error is actually 6.1'?  The reason being that in my original calculation I ignored the sun's semi-diameter.  Drawing a ray diagram in my head I concluded that I was measuring the sun's upper limb. That means subtracting 16.2' from the alt  or adding it to the lat.

    Given the very rough way I made the measurements I will be very surprised if my sight really was this accurate. Can someone please advise on the correct way of dealing with semi diamer when measuring  altitude with a peg in the ground?  I have modified my equipment with some wooden blocks, some blue tac, a plastic  square and some masking tape and taken another set of sights. I will not process the data until I know the correct way of dealing with the semi-diameter.

       
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