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    Re: Question Re: Position by Calculation
    From: Gary LaPook
    Date: 2014 Jan 7, 09:56 -0800
    May I suggest that you use any table other than the Concise table in the NA? The other tables are easier to use and less likely to have some computation error creep in. Since you like the thin, LTM, try the also thin trig based tables such as HO 208 or Weem's Line of Position Book. You can check out these different methods of computation for yourself at the comparison of them that I posted here:


    From: Sean C <yhshuh@aol.com>
    To: garylapook@pacbell.net
    Sent: Tuesday, January 7, 2014 8:52 AM
    Subject: [NavList] Re: Question Re: Position by Calculation

    Thanks to all for the replies, they answered my question..
    Geoffrey, you asked: "Why should that be the case?"
    It wasn't so much the LTA itself that I suspected might produce such an error. In fact, when I briefly scanned the SHAs, GHAs and declinations, none of the figures exceeded a 0.3' difference between my figures and those of the software.
    I suspected a cumulative set of errors, possibly including the small random observation "errors" I threw in, a probable error in my plot (which I completed using a different method than I usually do) and perhaps an error caused by the 1° limitations of the concise sight reduction tables. The random error was intended to produce a nice 'cocked hat' instead of an exact fix, much like the few actual observations I've done at the local beach. And it did.
    What struck me as odd was that the triangle on my plot looked identical to the one on my computer screen, except it was shifted by about 5 nm due east. This caused me to suspect some goof while plotting the LOPs. That's why I wanted to cross check my plot first with a direct calculation.
    In short, I expect any computer program to be more reliably accurate than me when it comes to such things. After all, computers only do what we tell them to do (right?) and as long as I input the figures correctly and Rodger's math is good (and my experience shows it is), then I believe it is much less prone to error than my fallible hand and weary eyes.
    Sean C.
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