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    Re: Compass Error Corection
    From: George Huxtable
    Date: 2010 Jul 3, 18:32 +0100

    I had written-
    I, for one, have to guess at Joe's meaning when he writes- "...an
    athwartship range is shot while steering another range."
    to which he replied, with heavy sarcasm-
    "Poor George.  Let's open our .pdf copy of Bowditch-2002 and find "Glossary
    of Marine Navigation," near the very end of the book.  Find the word
    "Range."  Hmmm, there are lots of possibilities.  But wait - Joe said
    something like "steering a range while shooting another athwartship range."
    We're shooting LOPs to visible objects, and reading some form of a
    horizontal angle indicator.  At no point in this discussion have we ever
    shot (or "ranged") a distance, such as with radar or an optical
    rangefinder.  Sooo.... ...."range" just might mean "two objects in line.""
    I had done just that, looked up my copy of Bowditch, before writing the
    above (and also Dutton, just to be sure).
    And that is indeed one meaning of the word range, according to Bowditch,
    who writes-
     "Range. Two or more objects in line. Such objects are said to be in
    range..." Which corresponds with the meaning of the word "in transit" that
    we would use on this side of the Atlantic.
    But it seemed unlikely that Joe had been using the word "range" with that
    meaning, because nowhere in Byron's postings were two objects shown in
    line. If that was his meaning, perhaps he will point out where those pairs
    of in-line objects are to be found. All of the observations discussed by
    Byron, that I can locate, were bearings of single landmarks.
    Indeed, if a vessel was steering along such a "range" as Joe describes,
    indicated by two objects in line, then the true bearing between them, and
    hence the true heading and compass error, could be taken straight off the
    chart, without any observations being called for at all. And if that vessel
    happens to find herself on another such range, athwartships, nothing needs
    to be "shot", her position is fixed from a look at the chart.
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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