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    Re: Sumner's Line (Navigation question)
    From: Bill B
    Date: 2006 Feb 13, 17:52 -0500

    For George, I still find the Bowditch editors' recounting ambiguous as is.
    I stand by my statement.
    
    For the reader, rather than refer to it as "tinkering" with the original,
    let me be specific. I was able to read through Sumner's book online Sunday.
    Unfortunately, many pages at the end were listed as "n/a."  Perhaps these
    are the plates.
    
    As to my observations:
    
    1. Tusker in Bowditch vs. Tasker in Sumner.
    
    2. The Bowditch account omits the last paragraph which relates actual
    position to DR position.
    
    3. The Bowditch account omits the DR latitude.  This is the major sin of
    omission, as if covers up (IMHO) that fact that latitude scale in the
    Bowditch figure is off by approx. 5 degrees.
    
    Which from my vantage point makes it like trying to put together a jig saw
    puzzle with missing pieces.  Worse yet, the puzzle does not match the
    picture on the box cover.
    
    If the numbers in Sumner's first example reflect the St. George LOP
    discovery:
    DR Latitude: 051d 37' N
    Declination: 23d 23' S
    Ho:          12d 10'
    GMT:         10:47:13 AM
    
    His 051d 37'time sight would put him at:
    051d 37' N
    006d 24.5 W
    
    His DR would have been (sight put ship 15' east of DR position):
    051d 37' N
    006d 39.5 W
    
    His true position (determined later)
    051d 45' N
    005d 53' W
    
    With the Bowditch diagram, his DR was approx:
    051d 32.5 N
    006d 39.5 W
    
    Bowditch-diagram Small's light(house):
    051d 44' N
    005d 44' W
    
    With all the facts in play, they inconveniently (for the Bowditch editors)
    put his true position north and west of Small's on their diagram.  Which
    hardly syncs up with a ENE course unless some hefty set and drift were in
    play.  (Apparently it is easier to delete text than it is to fix the
    latitude scale on a diagram.)
    
    After being able to nail positions (hopefully) down I extracted GHA and used
    that from his DR position with current equations to do and LOP.  It was off
    by 10 ft and 0.1d from the line I drew from Sumner's information.
    
    To help achieve closure on this, are there any good souls that might provide
    me with the latitude and longitude of Small's and Tusker/Tasker
    light(houses)?  Better yet, upload the Sumner plate of the the channel named
    after Saint George (Plate III?) to:
    
    navl@fisheriestrust.org
    
    Thanks
    
    Bill
    
    
    

       
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