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    Re: Bowditch 2002
    From: Jared Sherman
    Date: 2002 Oct 3, 16:36 -0400

    Mitch-
    
    <1. Always round up, like a modern electronic calculator>
    
    But they don't. "Modern" calculators for at least 20 years have had the option 
    of round-up, round-off, or round-down available with sometimes varying 
    results. And the option sometimes to simply truncate the digits, i.e. 
    truncate at 2 places, 3 places, etc.
    
    And there's an additional source of error I suppose for degrees+minutes 
    figures as opposed to degrees+decimal. The latter is now the international 
    engineering standard for lat/lon positioning apparently, minutes and seconds 
    are another obsoletism we practice here.
    
    AFAIK any sine conversions break down the minutes into decimal degrees first 
    and then compute, but one could certainly prepare a look-up table with 60 
    values in it (rounded properly or not) and then add them. Another table, 
    another opportunity for a typo?
    
    In all cases, I've seen some LONG decimals come out of simple calculations, 
    like converting 7 minutes (from your 32d07m example) into decimals. Long 
    enough to exceed capacity and cause rounding routines to kick in on many 
    little creatures.
    
    Somewhere, something, I'll bet is running the wrong roundings--but the 
    practical difference in position? Have you tried reducing a sextant sight yet 
    to see what difference it makes?
    
    
    

       
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