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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Problems with AstronavPC
From: Paul Hirose
Date: 2004 Feb 15, 23:10 -0800
From: Paul Hirose
Date: 2004 Feb 15, 23:10 -0800
George Huxtable wrote: > > [Using the newly updated values for B(F) and L(F) as Lat and Long, rework > the calculated altitudes and azimuths, in 7.2.2, 7.2.3, and 7.2.4, and > obtain a new intercept p from (observed alt. - calculated alt.). For this > to be possible, the original values for dec., GHA, and observed altitude of > the body must have been retained.] George, that algorithm sounds identical to the direct computation method in my 1998 Nautical Almanac (the newest one I have). The paragraph that begins "If d exceeds about 20 nautical miles..." is reproduced verbatim in the Almanac. It includes a fully worked reduction, which makes clear that some values are retained: "The table shows the intermediate values of the calculation for the second iteration. In each iteration the quantities Ho, GHA, Dec and t do not change." Computation of standard deviations and error ellipses are not mentioned in the Almanac.