NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Sextant accuracy and deflection of the vertical
From: dpstephen
Date: 2003 Mar 18, 14:18 -0700
From: dpstephen
Date: 2003 Mar 18, 14:18 -0700
At Fred's request, here is a site where you can get information on deflection of the vertical and a program that will allow you to calculate delflection for a given location. http://www.ngs.noaa.gov/GEOID/ The program on that web page called deflec99 calculates deflections for given locations. Unfortunately the section of the page titled "what is a deflection of the vertical" is under construction and not working. However as I understand it astronomical latitude and longitude (from sextant or theodolite) are based on angles related to the vertical as defined by gravity (through water horizon or bubble horizon) and geodetic latitude and longitude are related to a line normal to the ellipsoid. I beleive that GPS latitude and longitude are geodetic. If I am confused here please correct me. Doug
