NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: I knew where we were, but where are we now?
From: George Huxtable
Date: 2006 Jun 27, 00:33 +0100
From: George Huxtable
Date: 2006 Jun 27, 00:33 +0100
Guy Schwartz wrote- |I guess I should have used a better sample question. I used Peter's formula | on a different example | 38 deg 45 min N | 122 deg 08 min W | traveling 50 Nm | course 045 ( for the change in Lat & long) | I was able to get the correct lat @ | 39 deg 20.4 min | but could not get the Long to agree | Computer 121 22.7 | I think I was getting 121 3.8? | | After digesting this responce I will try it again. | Guy I checked it using the Meridional Parts table (table 5 of my 1981 vol2 Bowditch) Taking Guy's figure for the two latitudes, MP for 38 deg 45 (MPa) is 2511.2 MP for 39 deg 20.4 (MPb) is 2556.6 (interpolating by guess for the extra 0.4) difference MPb - MPa = +45.4 Tan 45 = 1 Divide MPb - MPa by - tan 45 and we get the westerly change in long as -45.4 minutes (i.e. 45.4 min East) So the new long is 121 deg 22.6' Which agrees with Guy's "computer" result pretty well. How did he arrive at 121 deg 3.8' ? George contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
