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    Re: Cannot dispense with the assumed position at sea
    From: Jim Thompson
    Date: 2004 Feb 20, 11:51 -0400

    > -----Original Message-----
    > From: Navigation Mailing List
    > [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Fred Hebard
    > Another point is that if you use a DR or EP as an AP for sight
    > reduction by calculator or computer and then use graphical methods to
    > plot azimuth and distance, the chart becomes pretty cluttered,
    > especially if your EP is fairly accurate.
    Interesting.  I have been brought up this year on the notion of using the DR
    position as an AP, but your post suggests why practicing navigators might
    prefer to use nearby more conveniently placed APs.
    > One other point about APs for use with tables.  You use a different AP
    > for each body, because they almost always have different LHAs.  This is
    > assuming a more-or-less simultaneous round of sights on more than one
    > body.
    Also interesting.  Our training this year has been to plot a DR for the time
    each sight was taken and use that position as the AP.  So a 3-body sight
    round will have 3 DRs.  The LOPs are plotted from the third (last) DR,
    effectively advancing the first two LOPs to the 3rd DR position.  This
    approach makes intuitive sense to me, but the plot does get pretty
    cluttered, and working out each DR position to its precise L/Lo coordinates
    is more tedious than using whole-degree APs.

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