A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2016 Dec 10, 18:53 -0800
lat = 90 + dec - alt
= 40° 56.4'
GPS lat S 41° 06.5'
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.