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    Re: Parallel Sailing question
    From: Brad Morris
    Date: 2019 Aug 1, 14:36 -0400
    CN is not strictly for navigation on the ocean, albeit the predominant use.  All of the heroic era of Antarctic navigation on land, water or ice was done via CN, whether by sextant or theodolite. 

    The problem is just a way to test that the student understands how the system of longitude works at 180° E/W and the relationship of nautical miles to arc minutes of longitude as one moves away from the equator.  The question may have gone a bit far way from that equator but, it makes grading the question trivial.  179E to 179W, 2° longitude at the equator is 120 nm.  At 80°S, its ~20 nm.  That's such a big difference that it is trivial to spot when grading that paper.  

    One nit pick is that they didn't specify a direction when moving from 179°E to 179°W along the parallel.  Headed west brings you from 179°E to 0° to 179°W, or a total of 358°.  That's just under 3780 nm, an equally correct answer. (Assuming I did the arithmetic correctly!!)


    On Thu, Aug 1, 2019, 2:17 PM Gary LaPook <NoReply_LaPook@fer3.com> wrote:

    The mountains get in the way.


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