# NavList:

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

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Re: Lies, damn lies, and statistics...
From: Paolo Borchetta
Date: 2013 Mar 19, 13:44 -0700

I find the latest post of John Karl interesting in the aspect that it basically confirms that whoever suggests the two LOP approach with a third LOP as a "checker" and whoever suggest the three LOP approach from the outset are basically saying the same thing when it comes to evaluating the intersection of the LOP in order to take it as it is or establish an MPP somewhere between the DR position and the LOPs intersection (being the cocked hat or a perfect point). One method (2 LOPs) according to John has 89% probability that the position is withing the smaller contour the other (3 LOPs) has 98% probability to be inside the smaller contour (likely the symmedian point) with the contour shape being a a much fatter elliptical shape which helps in determining the MPP.
Next comes the issue of interpreting the plot on the basis of operational requirements.
In both the outlines cases the SD of 2 or 3 LOP's are the same, how we do achieve that from the operational view point? Error (if any) consistency appears to be the answer, this in my humble view translate in practical terms into the proper pre-computation and planning of the sight. 2 sights at 120deg to a certain extent offset systematical errors, together with the altitude of the bodies selected to be about the same to equalize possible refraction errors. Proper advancing of the LOP's needs to be considered as well.
The is always a point where math and real life meet........
My Two cents,
Paolo
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