NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Averaging
From: Jim Theriot
Date: 2004 Oct 19, 19:18 -0500
From: Jim Theriot
Date: 2004 Oct 19, 19:18 -0500
I am not a real navigator, celestial or otherwise, however in general engineering situations I don't take comfort from a consistent-looking set of plotted points, but certainly look for inconsistent ones to warn of problems. Having gone to the trouble of plotting points, another check is available: The relationship of altitude versus time of an astronomical body (the slope of the line and its curvature) is a function of the latitude of the observer and of the body's position in the *horizon coordinate system*, independent of which body is being observed (not strictly true for solar/lunar sights, since the function applies to the center of the body rather than the limb, and not strictly true for bodies not fixed on the celestial sphere, but possibly a useful approximation). A set of observations which plot with a 'nice' slope and curvature should not inspire confidence except to the extent that it matches this theoretical slope and curvature. Regards, Jim ------------------------- Jim.Theriot@posc.org POSC -- Energy eStandards 24 Greenway Plaza Suite 1000-B Houston TX 77046 USA +1.713.267.5109 -------------------------