NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Z tangent formula
From: George Huxtable
Date: 2005 Jul 10, 22:14 +0100
From: George Huxtable
Date: 2005 Jul 10, 22:14 +0100
At 08:42 07/07/2005, Peter Fogg wrote: >I've taken 3 sights at random to contrast a few different (?) methods of >azimuth determination. The first comes from the problem Mike Burkes posed, >that I worked out and posted here on the 2 July. > >Sun UL Azimuth - in decimal form, and to 3 decimal places if available >101 'Bennett book' azimuth tables >100.9 Sharp nav. calculator >100.982 NavPac >100.985 Z tan formula > >The other two come from the first other worked sights to hand. Details >available if anyone's interested. > >Miaplacidus Azimuth >183 'Bennett book' azimuth tables >182.6 Sharp nav. calculator >182.637 NavPac >182.665 Z tan formula > >Dubhe Azimuth >010 'Bennett book' azimuth tables >010.2 Sharp nav. calculator >010.238 NavPac >010.214 Z tan formula > >So I'm convinced, pending further tests, that the Z tan formula is a valid >and accurate method for determination of azimuth. The small differences seem >insignificant. It is not significantly more tedious or time consuming to >calculate, given a good scientific calculator, than the other methods. This >is because the calculator and NavPac require quite a lot of data to be >entered to give a result. > >However, I do wonder whether one method or another does give a more >precisely accurate result, although the answer is probably irrelevant for >most practical purposes. Am hampered, admittedly, by not knowing what >methods my calculator or NavPac use. Anyone have other formulas for >comparison purposes? Or ideas on this? But Peter makes it difficult (indeed impossible) for anyone else to reproduce his calculation, by omitting mention of the values of hour-angle, lat, and dec that he has used. If Peter will provide that missing-link, he might get some more informed responses. George. =============================================================== Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222, or from within UK 01865 820222. Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.