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    Re: Poor Line of Position Computer/popularity of slide rule sight reduction
    From: Brad Morris
    Date: 2010 Jan 15, 08:54 -0500

    Hi Chuck


    I think the economic issue to be quite relevant.  Let us divide the marine purchasing population into three categories.  The first would be Navy, the second Merchant Marine and the third Leisure Yachting.


    For the first category, Navy, we have a procurement officer who will attempt to obtain the very best he can for the budget allocated.  There will be 100’s of acquisitions of elements to reduce observations to lines of positions.  This, being a budgetary process, will naturally result in a cost effective solution.  The navigator will use the tools provided.  The single volume solution Ageton is highly cost effective.  It would appeal to a procurement officer.  The accuracy of the method would satisfy the requirements of open ocean navigation.  We should find Navy navigational logs using Ageton.  In my possession is such a World War II log and yes, he used Ageton.  Ageton is about 20 times cheaper than a Bygrave.


    For the second category, Merchant Marine, again we have a commercial process.  Unless the navigator is the purchasing agent for the shipping company and he doesn’t seem to care about money, then a cost effective solution would come into play.  The navigator would first spend his money on a quality sextant.  Perhaps later the navigator would spend some money on a reduction method, but it would have to provide a better solution.  The finely crafted instrument argument would pale in comparison to the loss of precision.


    For the third category, all bets are off.  Leisure Yachting has extraordinary variation, dependent solely on the whims and depth of pocket of the yachtsman. This category, being random, would not drive to dominate the market. 


    Let us now move to Air Navigation.  Charles Poor indicates that the navigator doesn’t need to know his position to the 1/10 th of a mile.  Knowing generally where you are in the air is far superior to knowing exactly where you were 15-20 minutes ago.  The Bygrave provides that feature, rapid, fairly accurate solution.  Its “good enough”.  Gary has found 2 arc minutes of accuracy when compared to other methods and gets an answer very fast when compared to other methods (computer excluded).    But unfortunately monetary considerations would also come into play here as well.  The thousands of military planes as well as the smaller numbers of long ranging commercial aviation would require a cost effective solution.  The tiny numbers of private aviation would hardly drive a marketplace. 


    I do understand the point here regards a finely crafted instrument.  I do love to play with the MHR-1.  It is a joy to use.  However, I jump to a tabular method (or computer reduction) the very moment I want to be as accurate as possible. 


    How does the Poor Line of Position computer compare in accuracy to a Bygrave or to the more accurate tabular methods?  What about the speed of solution?  It seems that both of these instruments (Bygrave and Poor) are targeted at Air Navigation.


    Best Regards



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