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    A less precise position may be more accurate
    From: Peter Fogg
    Date: 2006 Dec 13, 16:56 +1100

    The broad thrust of George's argument (see "Position lines, crossing")
    seems to be that a calculated position is not necessarily the actual
    position, and one should be aware of as much. Which is a fair enough
    contention, if not exactly fresh news.
    
    Many methods of sight reduction use data expressed to a tenth of a
    minute of arc, and render a result to the same level of precision. One
    way of acknowledging the uncertainties of a calculated position, I
    propose, is to express this rounded off to the nearest minute of arc.
    
    The implication is that the position is not necessarily at the
    intersection of these minute lines of long and lat, but rather may be
    contained in a rectangle (square at the equator) bounded by the
    half-way lines to the next whole minutes. Thus a bigger box than that
    implied by a position expressed to the nearest tenth of a minute.
    
    Yes, the actual position may not be contained inside the larger
    rectangle. But this proposal avoids the spurious and potentially
    misleading precision of the alternative.
    And has another advantage of simplicity. There is a good argument that
    the appropriate level of precision for nav from small boats is to the
    nearest minute, at best, even if calculations are made using the
    nearest tenth.
    
    This is not much more than another expression of the difference
    between precision and accuracy. The coarser the expression of
    position, the more accurate, given the potential for error.
    
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