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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: A question for the geodisists
From: Gary LaPook
Date: 2013 Dec 17, 21:26 -0800
From: Gary LaPook
Date: 2013 Dec 17, 21:26 -0800
No I can't, that is the question I am asking the denizens of navlist.
gl
From: Alexandre Eremenko <eremenko@math.purdue.edu>
To: garylapook@pacbell.net
Sent: Tuesday, December 17, 2013 7:02 PM
Subject: [NavList] Re: A question for the geodisists
gl
From: Alexandre Eremenko <eremenko@math.purdue.edu>
To: garylapook@pacbell.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=125806