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    Re: Compass Error Corection
    From: John Huth
    Date: 2010 Jul 3, 10:19 -0400
    Joe - 

    I use a sine, but then draw a little diagram illustrating the small angle approximation, so that the people in the class can see the origin of the rule.  

    When I'm on the water, I typically just think "1 degree at 1 mile is 100 feet".   I also use my hands/fingers to figure the angular size of objects, like lighthouses when I'm on the move.  

    Obligatory historical note - I recently learned that Arab traders, Chinese traders, and Polynesians all used finger widths to figure the height of Polaris.   Of course, standardization always takes over and evidently Arabs standardized the finger width via the device known as a kamal.

    A "standard" finger is 1.35 degrees - just make sure it's the right finger.

    On Sat, Jul 3, 2010 at 9:53 AM, Joe Schultz <joseph_schultz@rrv.net> wrote:

    Apacherunner: do you use sine or tangent when developing the 1 in 60 rule? I quit using tangent, after seeing beginners convince themselves that the small distance/time has to be perpendicular to the large distance/time. No tangent and no opportunity for a bad habit. And Time/distancing then makes sense, knowing there will always be set/drift.

    For all but George: If I didn't like dreamers and historians then I would have said so. I happen to like the fact that I can turn darkness into light simply by moving my finger an inch or so.

    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'd like to think an educated man, and one who proclaims to not be a beginner to the sea or navigation terminology, could figure this out all by himself regardless of the flavor of English he's using. Perhaps the motive is really to satisfy a need to draw attention to yourself.

    But don't worry, George, as you're safe with me. I won't be here too much longer. Don't use the home internet enough to justify the expense, so am shutting it off at the end of the month. I'm just surprised that you didn't complete your foolishness by asking what "shoot" meant. It's not "gosh darn it," by the way.


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