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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: USCG Student Example for Low Altitude
From: Antoine Couëtte
Date: 2013 Apr 25, 23:26 -0700

RE : http://fer3.com/arc/m2.aspx/USCG-Student-Example-for-Low-Altitude-Rudzinski-apr-2013-g23682

Hello Greg,

Thanks for this example.

From your chart, I can guess that for your published Azimuth of 077.5° you obtained an intercept (between GPS position itself and LOP) close to 0.8 NM (A).

I find i = - 1.4' (A) / AZ = 077°7

Our intercept difference (close to 0.6') comes from a difference in the Value of Refraction (the SUN is at quite a low height). As an example, the refraction differences between US N.A. and French N.A. Tables reach 1 full arc-minute by 0° observed height.

Best Regards

Kermit

AN INTERESTING QUESTION (Any reply anybody ?)

As the differences between both end results can be appreciable at such low altitudes, should the DIP correction be performed first, and then the Refraction correction, or the other way around ?

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