NavList:

"
I cannot recall where I read it but some text described the use of a (real) Pole as the assumed position for the purposes of St. Hilaire."

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The pole is used as the AP in polar flight navigation within ten degrees of the pole. It provides for simple computations, the Hc is simply the declination of the body and the Zn is the GHA (longitude) of the body

If the DR is far away from the meridian containing the body's GHA then the LOP will be curved significantly enough that the LOP needs to be adjusted by use of the Ellsworth tables to accurately represent the curved LOP.
(created by Lincoln Ellsworth for the flights in Antarctica see: http://pabook.libraries.psu.edu/palitmap/bios/Ellsworth__Lincoln.html)

gl
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