A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2016 Jun 15, 20:58 -0700
I created a pseudo observation by determining the altitude of the Sun using an app on my phone and reading the time on my PC. I have reduced the sight by two methods. The intercepts are:
AP 3270 15'
Cosine formula/trig calculator 13'
Is this difference to be expected or does it indicate an error on my part?
Because I know the actual position (I measured it with my phone) and distances are small I reasoned that I could calculate the distance between the assumed and actual positions by plane trig. This distance should equal the intercept(????). Here is my calculation:
dlong 20.7' departure 15.6' (from dlong*cos(lat))
Applying pythagoras the distance is 17'.
I have three different numbers 13, 15 & 17. Have I made an error in my calculations or is this magnitude of differences to be expected? Maybe I am confused about the intercept, the distance or departure?
Thanks for your comments.