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    Re: A question for the geodisists
    From: Gary LaPook
    Date: 2013 Dec 19, 12:56 -0800
    You have described a circle. You input the longitude of your assumed position and at the end, by using the USNO website, you find your longitude is exactly the same as you input for the AP. I still don't have an answer to my question.

    gl



    From: Brad Morris <bradley.r.morris@gmail.com>
    To: garylapook@pacbell.net
    Sent: Thursday, December 19, 2013 12:27 PM
    Subject: [NavList] A question for the geodisists


    Hi Gary
    You wrote:
    " What would a celestial navigator determine the longitude of [Howland Island] to be if he took the observations tomorrow? "
    You know the answer to this question.  Make your AP (Assumed Position) right on the barely visible remnants of the airfield.  Use the USNO website to get HO for your choice of navigational stars.  Plot the LOPs and assign the fix. 
    In this manner, you will have eliminated observational errors and have tied the celestial observation to the satellite assigned position. 
    ++++++
    In reading thru the literature that Andres sent you, they mention that the position could shift by a half mile OR MORE.  {emphasis mine}.  So the delta between Itasca celestial and satellite assignment is merely in the 'or more' category.
    Brad
    On Dec 19, 2013 6:31 AM, "Gary LaPook" <garylapook---.net> wrote:

    That was interesting but still doesn't answer my question. I note that it shows an example of an island being shifted 1/2 NM but Howland was shifted one whole nautical mile.

    In 1936 officers from the Coast Guard cutter Itasca went ashore on Howland island and took sextant shots to determine the position of the island. The coordinates that they found were 0° 48' north, 176° 38' west and these were published in Bowditch (1938 ed.)  and are still published in H.O. 126. The newest chart shows the longitude to be 176° 37' west, one full nautical mile to the east. The chart states that this was due to shifting horizontal datums. But my question is really simple, what is the longitude of the center of the island as determined by celestial navigation, not by satellite? Were the Itasca's officers simply wrong and they should have also calculated the new value if they had been accurate? What would a celestial navigator determine the longitude of the island to be if he took the observations tomorrow?

    gl



    From: Andrés Ruiz <navigationalalgorithms---.com>
    To: garylapook---.net
    Sent: Thursday, December 19, 2013 12:44 AM
    Subject: [NavList] Re: A question for the geodisists


    2013/12/18 Gary LaPook

    So what is the answer to my question?

    Gary, this may be the key
    http://msi.nga.mil/MSISiteContent/StaticFiles/Files/NautChrts_GPS_index.htm
    --
    Andrés Ruiz
    Navigational Algorithms
    http://sites.google.com/site/navigationalalgorithms/
    Attached File:

    (img/125838.using nautical charts with global positioning system.pdf: Open and save or View online)

    : http://fer3.com/arc/m2.aspx?i=125838


    : http://fer3.com/arc/m2.aspx?i=125840
    : http://fer3.com/arc/m2.aspx?i=125850


       
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