NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Cannot dispense with the assumed position at sea
From: Doug Royer
Date: 2004 Feb 19, 12:18 -0800
From: Doug Royer
Date: 2004 Feb 19, 12:18 -0800
All positions at sea may be called assumed positions!They are all where you were,not where you are.Errors or conditions while shooting the sight or reduceing the data may have you not where you believe you were.Nothing in real life is perfect. Perhaps I missunderstand what you are trying to convey.Perhaps it is a function of wording between what you call an assumed pos and my definition. For me an assumed pos or positions are what one uses in lue of a dr or ep pos when reduceing a round of sights.An AP is the position chosen to reduce the sight instead of the dr or ap pos. One choses the assumed pos to be the closest whole degree of Latitude of the dr or ep latitude.The longitude of the AP is chosen by useing the whole degree of longitude of the dr or ep,subsituteing the ' and " of the body's LHA for the " and " of the dr or ep longitude.One choses this assumed longitude to stay with in 30' of arc of the dr or ep longitude. You can then enter reduction tables or solve for the nav triangle to find the intercept and AZ thus finding the LOP or the fix if a round of sights were taken. One can also use the dr or ep pos to solve the nav triangle with out useing an AP. Am I not understanding what you wrote or is it a matter of definitions? A celestial EP will only be as good as the AP. The more one has to guess at the AP, then the less confident one can be about estimating where the vessel is on the celestial LOP.