NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: AFM 64-5/ Raft book question
From: John Huth
Date: 2010 Jan 24, 13:17 -0500
From: John Huth
Date: 2010 Jan 24, 13:17 -0500
There are a number of other sources in addition to Gatty's book and the AFM - actually many editions of the AF Survival Manual. There is an analytic formula that you can write (I've turned it into an Exel spreadsheet) that give the relationship between date/latitude and length of day.
I've looked into this a bit, and I have yet to find any modern example of someone using this technique to find latitude, however. You can only use it close to the solstices, and it's useless around the vernal and autumnal equinox. Around the solstices, I reckon what with a lot of care, one might be able to do as well as 20 arc-minutes. I tried this in mid-October, and was off by 300 miles, however.
This technique was in widespread use by geographers to categorize different "climes" in Greek and Arabic eras. The common way of designating climes (zones of latitude) was by identifying them with the length of day during the summer solstice.
If you're interested in the analytic formula, and an Exel spreadsheet that implements it, let me know and I can post it.
John H.
On Sun, Jan 24, 2010 at 10:06 AM, Ronald P Barrett <ronaldpbarrett@yahoo.com> wrote:
Air Force Manual 64-5, Search and rescue, "SURVIVAL" , 1 Feb 1961, pages 104-105-106 covers Position Finding, 'Latitude by Length of Day.'
This manual and others AF Flight navigators' manuals are at present being sent to the Library of the Museum, "THE MIGHTY EIGHTH." The Mighty Eighths' library is right now being set-up as the AF Navigators' National archive.
Ron Barrett, President Air Force Navigators Observers Association (www.afnoa.org)
--- On Sat, 1/23/10, mike.boersma@gmail.com <mike.boersma@gmail.com> wrote:
From: mike.boersma@gmail.com <mike.boersma@gmail.com>
Subject: [NavList] AFM 64-5/ Raft book question
To: NavList@fer3.com
Date: Saturday, January 23, 2010, 9:47 PMOn the Google group there is a discussion on finding latitude from the length of day from these two sources. However, I am not finding this discussion on the Navlist archive. The posting occurred on 6 December 2009 and there is not a posting for this date on the archive. Could you point me in the right direction.
Thanks.
Mike Boersma
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