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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: ex-meridian problem
From: Bruce Stark
Date: 2001 Feb 17, 3:54 PM
From: Bruce Stark
Date: 2001 Feb 17, 3:54 PM
Sometimes an experiment can help clarify things. Suppose our dead reckoning puts us about 30� N, 145� W. It's a little before noon. We get a true altitude of 69� 20'. The sun's declination is 10� N, his GHA 140�. With this data, using the Ex-meridian tables, we get a latitude of 30� 8' north. But since we aren't sure of our DR longitude, we work the problem again using 146� west. That gets a latitude of 29� 54'. Obviously, if we plotted this and drew a line from 30� 8' N, 145W to 29� 54' N, 146� W we'd have a chord of a circle. The sun's geographic position would be the center of the circle and his zenith distance the radius. Bruce
