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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)
>>
>>
>>:
> https://navlist.net?i=125785
> : https://navlist.net?i=125799
>
> : https://navlist.net?i=125803
>
>
>
>

   

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