# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Intercept and distance
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:

lat 41

dlong 20.7'     departure 15.6'  (from dlong*cos(lat))

dlat 6.4'

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?

Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)