NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Emergency Meridian Altitude
From: David C
Date: 2016 Dec 9, 11:54 -0800
From: David C
Date: 2016 Dec 9, 11:54 -0800
Intuition told me that the longer the pole (not sure if it is called a gnomon) the less the effect of measurement errors. I decided that I could measure to an accuracy of 1mm. The base value is height 370mm length shadow 121mm. If I change the height by 1mm the altitude changes by 2.6'. I then calculated the error for multiples of the base value.
x1 2.6'
x2 1.3'
x3 0.9'
x4 0.4'
It seems the longer the better but........the longer the pole the bigger the error due to it not being vertical. I haven't worked that out yet. There must be an optimum pole height to minimise error.
