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    Re: Lightning Strike CN Exercise
    From: David Pike
    Date: 2019 Jul 11, 13:34 -0700

    If the vessel made 120nm in 24 hours, it’s probably a small to medium sized yacht.  If the on-watch team have done their job properly they should have logged the GNSS position at 16.00UTC, and the DR position should be accurate enough not to have to worry about position immediately.  The problem will be to ensure that vessel’s deviation has not been significantly altered by the close proximity of the lightening.  The magnetic bearing to Pearl Harbour should be available from the paper chart.  If there isn’t one, I would construct one using compass and protractor (I used a single mid lat at 17 degrees).  This gives PH as having a true bearing of 347(T) or 338(M) from the DR position. The azimuth of the Sun at sunrise works out at about 080T (I wasn’t really sure how the graphs dealt with an angle between the Sun and the observer’s longitude of 93 degrees).  I would turn onto the desired course allowing for tide and leeway and take the time and bearing of the sun again. After allowing for the motion of the Sun at 15 degrees per hour, I could work out the deviation on the desired course and adjust accordingly.  If I anticipated tacking or other need for manoeuvre, I could turn through 360 degrees and complete a four or eight point calibration swing noting the sun’s bearing and the time on N,NE,E,SE,S,SW,W,NW.  I would do this at every sunrise and sunset opportunity until the deviation settled.    DaveP     

       
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