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    Re: Fix differences with 5 reduction methods...Read "clarifications"
    From: Gary LaPook
    Date: 2014 Jan 15, 21:34 -0800
    The important thing is the distance from each plotted LOP to the GPS position, not the "centers of the cocked hats" because various geometries affect these points which are not necessarily an artifact of the sight reduction method. Simply extend the LOPs so that they pass the GPS positions and then measure the perpendicular distance to each LOP.


    From: Randall Morrow <randall.f.morrow@kp.org>
    To: garylapook@pacbell.net
    Sent: Wednesday, January 15, 2014 2:52 PM
    Subject: [NavList] Re: Fix differences with 5 reduction methods...Read "clarifications"

    The three star sights each produced "cocked hats" of varying sizes. I used the incorrect but convenient method of bisecting the angles to arbitrarily locate the "fix" for each reduction method. There has been much discussion of the cocked hat conundrum in the past. With the exception of the NASR "hat", each reduction method produced the possibility of the fix being within 5 miles or less from the GPS. Blunders are always a possibility of course. It was my curiosity as to the diffrences in each methods handling of the same sight data that prompted me trying this. Just for fun, I have a more recent sight run with USNO intercepts from GPS of less than a mile. If you're interested, try to plot all 5 methods on the same page. It occurrs to me using clear plastic overlays successively might mb clearer. Here goes:
    12 January 14
    DR (GPS) lat 35*19.4 Lon 119* 05.5
    Watch error zero
    IC -0.3
    ZD +8
    Mirror artificial horizon
    Capella Hs 110* 47.0 at 18-47-44 a 0.7
    Deneb Hs 54* 30.4 at 18-49-40 a 0.8
    Diphda Hs 63* 23.2 at 18-51-11 a 0.2
    Always remember the possibility of (my)blunders

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