NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The Noon Fix
From: John Karl
Date: 2009 Apr 13, 20:47 -0700
From: John Karl
Date: 2009 Apr 13, 20:47 -0700
Peter-- Yes, Table one is the same correction we have been talking about. The entries in the table are computed from Corr = 0.016667* Vground*4 min* Cos(Zn). The 0.0166667 is one knot of speed in miles per minute. This is exactly what we have been saying the correction is for a moving ship. BTW, this correction is substantially in error at high speeds as the time between observations gets longer (Not relevant for sailors). But I'm surprised this simple linear correction works so well for the highly nonlinear altitude equation. The Coriolis force of Table 9 is unrelated. It's the same force that makes winds aloft run nearly parallel to the isobars instead of perpendicular to them. The same force deflects the bubble in a bubble sextant from the vertical. The Coriolis force is v*W*sin(A), v is the velocity of the craft and w is the earths rotational speed (in radians per time), and "A" is the angle between V and W. --JK --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
