NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ducruy Jacques
Date: 2013 Jun 11, 12:53 -0700
Hello,
The "longitude method" is very "classic" : in France, we used the Borda's formula for the calculation of apparent time.
The problem is the latitude : if your DR latitude is incorrect, the apparent time is also incorrect. So, you calculate the longitude only after the observation of meridian altitude : with the latitude of 12 hours and the dead reckoning, you can calculate the latitude for the moment where you take the observation of the morning.
Another method is based on the "Pagel coefficient" (after 1847) ; this coefficient is used for "corrected" the longitude of the morning calculated with the DR latitude. But the correction is only possile after the observation of the meridian altitude.
Good evening
Jacques
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