# NavList:

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

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Re: Stop and smell the equations
From: Bruce J. Pennino
Date: 2013 Apr 8, 20:11 -0400
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Frank and All :

My, my...bad to worse...seems a bit......harsh....

By the way, instead of using a "tangent  offset"  calculation method for a dip equation, I redid the geometric dip more correctly using right triangle geometry and trig,   based solely on the equivalent  radius of the earth .  This way,  geometric dip  K was calculated to be 1.06 as Frank and others have mentioned. Due  to refraction correction and experience, the adopted value is 0.971, or so.

I took my Blue Hills data and "backed out" a K (based on this data only)  of .94 for HoE of 676.5 ft, and K= .92 for Hof E of 627.0 ft.   This data seems ok, more or less. More scatter in my other data. It appears that we are trying to refine a small percentage of the total dip equation....roughly  7% or so.  Seems tough to do especially at small values  of HoE.  I'm going to try to get more data at HoE above 10-15 ft, and look for an opportunity for 100 ft or more.

Best regards

Bruce

----- Original Message -----
From: Frank Reed
Sent: Sunday, April 07, 2013 7:29 PM
Subject: [NavList] Stop and smell the equations

A little advice: slow down... stop and "smell the equations". :)

Know what I mean? You can't just grab one random equation after another and throw it at Excel and assume that means you've understood something. You have to slow down and think about what the equations are saying. What are they for?

The present discussion of dip is spiralling rapidly into the abyss. It's gone from bad to worse. But this can be fixed with some effort. Stop and enjoy the beauty of the math: stop and smell the equations. :)

-FER
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