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    Re: The Noon Fix
    From: Hewitt Schlereth
    Date: 2009 Apr 8, 17:30 -0400

    Frank, here's  a second to your remarks re Jim's method. Jim, your
    book sounds very apt for today's realities - Celestial is bound to be
    in the 'if all else failz'  category. I'm off to Amazon to buy a copy.
    
    Hewitt
    
    On 4/8/09, frankreed{at}historicalatlas.com  wrote:
    >
    >  Jim, you wrote:
    >  " It is not a running fix, since no lines of position are advanced or retarded. Or even determined."
    >
    >
    > If you're adjusting the sights for motion of the observer, that is 
    equivalent to a running fix. So unless you're explicitly reserving the 
    expression "running fix" for the case of plotted LOPs, I don't think there's 
    any problem calling it a running fix, and that may be helpful explaining the 
    method to navigators who already understand that concept.
    >
    >  This whole business of generating a fix by a series of sights around noon 
    is a subset of a general case which I have labeled (in the absence of 
    previous terminology) a "rapid fire fix". If you take a series of multiple 
    Sun sights, oner after another, over a fairly short time interval so that the 
    Sun's azimuth changes by a moderate amount (let's say twenty degrees), then 
    you can reduce these sights, perform a least squares analysis, and get a fix 
    that is surprisingly accurate. This is a type of running fix since each sight 
    has to be advanced/retarded based on the observer's motion.
    >
    >  In a general "rapid fire fix", the position is clearly more accurate in the 
    direction of the Sun's azimuth just as the particular case of sights around 
    noon yields a latitude that is more accurate than the corresponding 
    longitude. The accuracy in the perpendicular direction is lower but increases 
    rapidly either by multiplying the number of sights or by allowing for a 
    larger change in azimuth.
    >
    >  -FER
    >
    >
    >
    >
    >
    >  >
    >
    
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