NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Fix Maximum Probability Positions
From: Geoffrey Kolbe
Date: 2013 Mar 24, 07:04 +0000
From: Geoffrey Kolbe
Date: 2013 Mar 24, 07:04 +0000
John Karl wrote:
In figure 1 of your paper, you show a circular area of uncertainty around your DR, which given no other information is reasonable enough.
But in figure 5 you show an elliptical area of uncertainty, for which I can see no justification.
Suppose, in figure 5, your course had been along the LOP1 so that DR1 was in fact on LOP1. What would your area of uncertainty around DR1 look like then? Since your original DR started out as a point (as shown in the figure) it would be circular, just as in figure 1.
The point about advancing an LOP along the vector of your course and distance run is that it does not create a new DR position, as you attempt to do. It retains the LOP as an LOP, but makes use of the estimated course and distance run information in a reasonable way to re-locate the LOP.
Celestial navigation is not actually a method of navigation. "Celestial navigation" is a misnomer. "Celestial navigation" does not give you course steered, distance run, or your most probable current position, which is what "navigation" is about - having a good idea where you are at any given moment in time. Position fixes using celestial bodies are a way to get an independent check on your DR position. The navigation method used is actually dead reckoning first, last and always.
It follows then that polluting your celestial fixes with where you arrogantly think you are is a dangerous way to proceed. It throws out the independent check.
In your figure 5, if your LOP2 is good, then that should give you cause for concern that your course steered was not what you thought it was. There may well be a current flowing to the East which you had not suspected. You, however, are not treating CN as a check on your DR, you are using CN in combination with estimated course and distance run to create a DR, which - I respectfully submit - is dangerous.
Geoffrey Kolbe
Other than Paolo Borchetta (and maybe a couple others, if any) replies to my posts on the relative merits of the traditional running fix (TRF) have really grappled with the concept under scrutiny. Many simply state that the TRF works fine and doesn't need improvement, but they give no justification for the assumptions behind the TRF.....
In figure 1 of your paper, you show a circular area of uncertainty around your DR, which given no other information is reasonable enough.
But in figure 5 you show an elliptical area of uncertainty, for which I can see no justification.
Suppose, in figure 5, your course had been along the LOP1 so that DR1 was in fact on LOP1. What would your area of uncertainty around DR1 look like then? Since your original DR started out as a point (as shown in the figure) it would be circular, just as in figure 1.
The point about advancing an LOP along the vector of your course and distance run is that it does not create a new DR position, as you attempt to do. It retains the LOP as an LOP, but makes use of the estimated course and distance run information in a reasonable way to re-locate the LOP.
Celestial navigation is not actually a method of navigation. "Celestial navigation" is a misnomer. "Celestial navigation" does not give you course steered, distance run, or your most probable current position, which is what "navigation" is about - having a good idea where you are at any given moment in time. Position fixes using celestial bodies are a way to get an independent check on your DR position. The navigation method used is actually dead reckoning first, last and always.
It follows then that polluting your celestial fixes with where you arrogantly think you are is a dangerous way to proceed. It throws out the independent check.
In your figure 5, if your LOP2 is good, then that should give you cause for concern that your course steered was not what you thought it was. There may well be a current flowing to the East which you had not suspected. You, however, are not treating CN as a check on your DR, you are using CN in combination with estimated course and distance run to create a DR, which - I respectfully submit - is dangerous.
Geoffrey Kolbe
