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    Re: Round-off
    From: Peter Fogg
    Date: 2009 May 18, 10:58 +1000

    Jeremy wrote:

    I've never heard of rounding to the nearest whole minute during
    reduction.  That doesn't seem too wise to me.  
     
    Jeremy, you're working from an elevated and generally fairly stable platform.  The relatively good accuracy you can expect may well be worth extra precision when it comes to sight reduction.
     
    Bill Buckley Junior was advocating simplified sight reduction for the needs of small-boat sailors, who can typically expect lower accuracy.  The result will be expressed to the nearest minutes of arc (longitude and latitude).  Not especially inaccurate due to rounding, I hope we have established this much, but potentially significantly inaccurate due to scatter in observations.
     
    To save me the effort of drawing a diagram (am supposed to be working!) imagine these intersecting lines (of long. and lat.) marking the fix.  Then draw a circle with a radius of 10nm around it (to choose a number). 
     
    Now the question becomes:  what is the point of refining that intersection, typically by a trivial amount, when the uncertainty due to observational scatter remains the same?
     

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