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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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Bisectors and MPP
From: Doug Royer
Date: 2003 May 29, 10:36 -0700

```I post this only as an alternative method to what was discussed the last few
days.I have no idea which method would be more accurate to determine the MPP
or any systematic error.This is the method I was taught to find the MPP from
a round of sights.

Use bisectors to establish the MPP of a round of sights when each body's Zn
is seperated by more or less than 120* for a 3 sight round and 90* for a 4
sight round.It is imperative to use bisectors if all Zn's in the round of
sights are seperated by 180* or less.

Each angle formed by a pair of LOP's is bisected at the vortex of the 2
LOP's.Each bisector is drawn in the direction of the averaged direction of
the 2 Zn's of the pair.Extend each bisector an equal distance on both sides
of the vortex of the corresponding pair of LOP's.The point or area the
bisectors intersect or nearly intersect is the MPP.

Example:
Bn = (Znx + Zny)/ 2
Star 1 Zn = 224*
Star 2 Zn = 352*
Star 3 Zn = 256*
Bisector 1 = star 1 Zn + star 2 Zn = (224* + 352*)/ 2 = 288*
Bisector 2 = star 1 Zn + star 3 Zn = (224* + 256*)/ 2 = 240*
Bisector 3 = star 2 Zn + star 3 Zn = (352* + 256*)/ 2 = 304*

From the point where each pair of LOP's intersect draw a line through that
point useing the direction obtained with the bisector equation.

Where the averaged Zn's intersect is the MPP.

```
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