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    Re: Flight Levels CelNav; 02/10/2018
    From: Tracy Shrier
    Date: 2018 Mar 9, 17:42 -0800

    Thanks for running my numbers Gary, it's satisfying to the the confirmation. I hadn't looked closely at precession/nutation corrections yet. The examples in the introduction to Pub 249 don't show it's use, nor do my older references(Weems, the Navy Air Navigation series, and H.O. 216). Do you think the '40s navigators (the guys I'm mostly trying to emulate here) would have been applying this?  They were using H.O. 214 and 218 then, were these published annually with data current to the years equinox?

    And two more Polhemus questions:

    1) In using the 45° overlay I moved N41 up three latitude lines to get some plotting space from the edge of the disk. Am I correct observing that this should not create any error when plotting a single fix?

    2) Reading Lat - I assumed that one dosen't follow the Base grid from a point on the overlay to the Lat scale, but that one follows the curve of the Lat graticule to the Lat scale. Is this how you do it?

    Thanks, Tracy

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