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    Re: A question for the geodisists
    From: Brad Morris
    Date: 2013 Dec 18, 01:03 -0500

    Hi Gary

    I encountered the same plethora of coordinates when trying to determine the location of Cape Belsham, on Elephant Island.

    I'm sure you thought of this but what the heck, here goes:

    I looked on satellite views of Howland Island.  Its one mile wide by two miles long.  Do all the coordinates you mentioned reference one unique point on the island, or do the coordinates just have to be somewhere on the island?  Is it a datum on the island that's referenced?  Or just the island?

    A 1 arc minute shift could mean east coast vs west coast.  Because, in general, once you are that close, you switch to coastal piloting.

    Brad

    On Dec 18, 2013 12:32 AM, "Gary LaPook" <garylapook@pacbell.net> wrote:

    No I can't, that is the question I am asking the denizens of navlist.

    gl



    From: Alexandre Eremenko <eremenko---.edu>
    To: garylapook---.net
    Sent: Tuesday, December 17, 2013 7:02 PM
    Subject: [NavList] Re: A question for the geodisists


    This is a long article about geodesy in general.
    Could you point the place in this article which on your opinion
    explains the reason of disagreement in coordinates?
    
    Alex.
    
    > Well, this pretty explains why.
    >
    > http://en.wikipedia.org/wiki/Geodesy
    >
    > gl
    >
    >
    >
    >
    > ________________________________
    >  From: Chris Presmeg <0886045615{at}neomail.co.za>
    > To: garylapook---.net
    > Sent: Tuesday, December 17, 2013 12:56 PM
    > Subject: [NavList] Re: A question for the geodisists
    >
    >
    >
    >
    > ________________________________
    > 
    > What has Geodesy to do with it?
    > ----- Original Message -----
    >>From: Gary  LaPook
    >>To: CHRISTOPHER PRESMEG
    >>Sent: Tuesday, December 17, 2013 1:07  PM
    >>Subject: [NavList] A question for the  geodisists
    >>
    >>
    >>________________________________
    >> On July 2, 1937 Amelia Earhart was attempting to find Howland island.
    >> Her  navigator, Fred Noonan, was using celestial navigation to fly the
    >> standard  single line of position landfall approach to the island. (see:
    >> https://sites.google.com/site/fredienoonan/discussions/navigation-to-howland-island
    >>  )
    >>
    >>
    >>The  Pacific Sailing Directions (1885) gives the location of Howland as
    >> 0° 49'  north, 176° 40' west. Bowditch (1920) gives it as 0° 49' 00"
    >> north, 176° 43'  09" west. Bowditch (1938) gives it as 0° 48' north,
    >> 176° 38' west. This is  still listed as the correct coordinates in H.O.
    >> 126.
    >>
    >>
    >>Some  have argued that Noonan was working with the old coordinates and
    >> was aiming  for 0° 49' 00" north, 176° 43' 09" west and so missed the
    >> island by about five  nautical miles. However, the correct coordinates
    >> were given on the June 1937  edition of the local chart, 1198, so we know
    >> that the correct coordinates had  been found sometime prior to Earhart's
    >> departure from the states so I would  think that the updated information
    >> would have been provided to her,  considering that the orders to assist
    >> her came directly from the White House  and the importance of the correct
    >> information would have been apparent to  anyone.
    >>
    >>
    >>
    >>I  have looked at Howland on Google Earth and it now appears that it has
    >> moved to  the east another mile! And the coordinates found on the most
    >> recent chart now  show it also at 0° 48' 00" north, 176° 37' west, one
    >> mile east of he published  location. How does the island keep moving? If
    >> this is the true location then  Noonan may have been aiming another NM
    >> too far to the west. There is a note on  the newest chart that says:
    >>
    >>
    >>So  it appears that the most recent movement resulted from changing the
    >> datum to  WGS 84 but it seems to me that an adjustment of an entire mile
    >> to the east is  very large compared to other such shifts. So, if Noonan
    >> was using the old  coordinates would he have been aiming six NM west or
    >> just five? And I think  that I remember this correctly, that the geodetic
    >> gratical used for map making  places the landmarks where they would be
    >> placed by celestial navigation. So if  the island really is a at 176°
    >> 37' west then this might help explain why they  couldn't find the island.
    >> I thought that the greatest difference between the  geodetic and the
    >> geographic coordinates, as far as celestial navigation is  concerned, is
    >> in latitude and that changing to WGS 84 wouldn't have such a  large
    >> effect on longitude. Can someone explain how shifting from one datum to
    >> another would cause this type of error in the celestial navigation.
    >>
    >>
    >>
    >>
    >>
    >>
    >>gl
    >>
    >>
    >>
    >>Attached File:
    >>
    >>(img/125785.howland
    >   pages from 1920 american_practical_navigator_an_epitome.jpg: Open  and
    > save)
    >>
    >>Attached File:
    >>
    >>(img/125785.howland
    >   position_page_1.jpg: Open and  save)
    >>
    >>Attached File:
    >>
    >>(img/125785.howland
    >   position_page_2.jpg: Open and  save)
    >>
    >>Attached File:
    >>
    >>(img/125785.howland
    >   ge.jpg: Open and  save)
    >>
    >>Attached File:
    >>
    >>(img/125785.howland
    >   chart 83116.pdf: Open and  save or View  online)
    >>
    >>
    >>:
    > http://fer3.com/arc/m2.aspx?i=125785
    > : http://fer3.com/arc/m2.aspx?i=125799
    >
    > : http://fer3.com/arc/m2.aspx?i=125803
    >
    >
    >
    >
    
    


    : http://fer3.com/arc/m2.aspx?i=125809

       
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