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    Re: The Noon Fix
    From: James N Wilson
    Date: 2009 Apr 8, 11:19 -0700
    George:
     
    I have wrestled with this problem, and only reluctantly called the position determination by the method a fix. Longitude is determined at noon, but it is based on data taken before and after noon. It is not a running fix, since no lines of position are advanced or retarded. Or even determined. I do discuss a bit the error sensitivity, but not as completely is in the reference, my 1985 Navigation paper.
     
    I originally calculated Dhs at two different times bracketing LAN, thus allowing for the different slope of the adjusted hs vs WT line. I abandoned that in the interest of simplicity. For the example I used, that made LAN eight seconds earlier. I considered that was not worth the extra effort, considering other errors.
     
    I didn't explore much at the extremes of Latitude and, as you have pointed out, there are some where the Sun is never visible. So, the method does have its limitations.
     
    Thanks for your proper critique. As for the details of the arguments, there's not much more in the two and a half page book. It was not intended to be a treatise, but a description of a backup method. The resultant surprise benefits were thoroughly examined to be sure that they were true, but that's the extent of the effort.
     
    Jim Wilson

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