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    Re: That magic number: 3438
    From: David Pike
    Date: 2016 Nov 4, 12:57 -0700

    Robin you wrote:

     And of course

    angular size(minutes of arc) = radius of Earth(nautical miles)·length of ship(metres)/distance to ship(metres)

    works just as well

    Which I suppose is because in this case 3438 is being used as a constant and is effectively dimensionless.  I’m glad I read your post before sending my original question which was “What do you use if you’re teaching a class brought up to use metric?”  DaveP

       
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