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    Re: Bowditch Table 15
    From: Bill B
    Date: 2005 Jan 24, 20:50 -0500

    Trevor wrote:
    
    > Jim's web page cites George Huxtable as saying that the second term of
    > the Table 15 equation should be included in the square root bracket. I
    > am not sure when George posted that information but it might explain why
    > your results are so different.
    
    I believe George to be correct.  My Bowditch only includes the first term
    under the square-root bracket, as I posted it.  But that makes no sense to
    square a number then take its square root without doing anything else to it.
    Setting up an Excel spreadsheet, it also does not come remotely close to the
    tabular values.
    
    So I calculated it with the second term, then second and thirds terms under
    the bracket.  Adding the second term under the bracket and leaving the third
    outside matched the table.
    
    It's a tiny file, so corrected formula attached.
    
    After a sanity check, I do believe it is the distance in nautical miles from
    the observer to the object.
    
    Assume an object 46'tall. I bob it so its top is tangent to the observed
    horizon and find height of eye to be 6'.
    
    Using the quick formula for geographical range, square root of 46 + square
    root of 6, times 1.17; my answer is 10.8 nm.
    
    Using the same procedure my bobbing translates to 0 minutes at 6' height of
    eye.  Correcting for dip, -2.4 minutes as angle used to enter table, with H
    - h = 40.
    
    Plugging into Excel, or interpolating (realizing the table is non-liner), my
    answer is again 10.8 nm.
    
    PS.
    
    Have just received George's Post.  The stated constants are 0.0002419 and
    0.7349 in my copy.  But then again, they got the formula a tad wrong. Back
    to Excel. 
    
    Bill
    
    
    
    
    

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