NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
The Darn Old Cocked Hat + Trimble
From: Hanno Ix
Date: 2013 Mar 17, 20:33 -0700
From: Hanno Ix
Date: 2013 Mar 17, 20:33 -0700
“ I
can either talk correctly or understandably – not both. “ - Heisenberg
David:
There
is an alternative to Heisenberg's one-liner: I
can talk incorrectly and still not be understood.
I
will concede: claim a) is wrong in fact and wording. It should be:
The
distribution of the distance Fix-TL is not a normal distribution.
It is a Rayleigh distribution.
Also,
I did not consider jerky movements of the target (TL) , nor an
incorrect placement of the TL on the map.
Terrible!
Withthout going into your math of my claim b):
A
little exasperated I looked for help in explaining what I had in
mind. I found a very good description of
navigation errors written by
the folks at Trimble. I have attached it. Apparently, they use the
same concepts
I was talking about. They arrive at pretty much the
same results and show the same plots
(e.g. Rayleigh histogram and appendix). It
is true I did assume knowledge of the TL, they do not.
This
difference does matter if you use GPS in air-to-air missiles or if you locate points recorded by history.
However consider this:
GPS: 6 feet radial error around the TL; 1/1000 of the CelNav error yet cumbersome.
CelNav: 6000 feet radial error (~ 1 sm) ; 1000 times GPS error but excellent fix
To me Bayesian Inversion Theory etc. is misplaced when it comes to
CelNav .
BTW:
In
my memos , I proceeded to describe my search for a minimum of the
error which involved moving
around the estimated location in relation
to the DOCH on a median. I did that with a simulation.
I think I
found quite a simple and practical approximation by saying the best
place to assume the
TL is at least close to the CG of the DOCH.
Regards
h
File:
