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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: MPP by Two Parameter Fit
From: Greg Rudzinski
Date: 2015 Feb 18, 17:05 -0800

Here is the 2 parameter fit for the 16 Sun observations:

Greg,
Thanks for sending these. Using a 2 parameter fit as described in the Nautical Almanac you get MPP
X = -0.4143
Y = -0.6092
corresponding to a point 0.73nm and 214.2 degrees azimuth from your AP. This I think is pretty much where you would pick it by eye from your plot. The root-mean-square distance of your sights from this point is 0.79nm.

If you introduce a constant offset in the least-squares fit you get
X = -0.5041
Y = -1.4736
D = -0.6042
This means that if it assumed that there is a systematic correction of 0.6' that needs to be added to each of your intercepts the MPP is at point 1.56nm and 198.9 degrees azimuth from your AP. The root-mean-square distance of your sights from this point is 0.78nm which is a negligible improvement . This probably suggests that is better to stick with the 2 parameter fit in most cases,
Regards,Robin

From: Greg Rudzinski
Date: 2015 Feb 17, 20:17 -0800

Robin Stuart has kindly performed a 2 parameter fit as explained in the Nautical Almanac on 16 Sun observations as seen plotted in the attachment.

Greg Rudzinski

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(f1-AH-LOP-Set-3-Plot.jpg: Open and save)

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