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Old March 20th 17, 03:48 PM posted to rec.bicycles.tech
Jeff Liebermann
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On Mon, 20 Mar 2017 18:33:51 +0700, John B.
wrote:
Way back when, I went to considerable effort to learn proper
navigation. Sextant, HO tables and lessons from the lead navigator in
a B-52 squadron. What sort of took the shine off the effort was when I
did the usual three shot position and got a "cocked hat"that was about
a mile and a half on each side. When I told the Major about it he
commented that I was doing real good. I replied that I didn't think
that a triangle that was a mile and a half on each side wasn't very
accurate he assured me that it was "pretty good for celestial
navigation.... which is why we don't use that for the B-52's" :-)


Accurate navigation with an aviation sextant is far more difficult
than marine navigation. If you were doing celestial or lunar
navigation on the ground, using an averaging bubble sextant artificial
horizon, I would say 1.5 miles was doing very good. If you were doing
it while flying, amazingly good.

I'm told that marine navigation is easier. Many years ago, I dragged
a gaggle of middle skool slackers to the end of the local breakwater,
which features a miniature lighthouse that's almost exactly at -122.0
deg longitude.
http://www.lighthousefriends.com/light.asp?ID=836
It was a clear day and the horizon was clearly defined. It was almost
noon, so I started by showing them how to take a noon sight. I was a
bit more than a nautical mile off. Oops. I brought along a WWV
receiver for doing latitude, but the signal was too weak to be usable.
Using someone's inaccurate wrist watch, I located our position about 5
nautical miles away. Lunch and a side trip to the local amusement
park was sufficient to salvage my reputation.

Some additional navigation horror stories using Omega, Loran (lane
skipping), Navsat, inertial navigation, and direction finding using
radio towers, but this is getting too far of topic (whatever that
might be). The tower story is interesting. The FCC database records
the "location" of each radio station licensee. One might assume that
this means the location of the transmitting tower. Instead, it's
usually the location of the studios or offices. Someone published a
navigation map using the FCC locations instead of the tower locations
resulting in RDF (radio direction finding) receiving a bad reputation
for poor accuracy when used for navigation.



--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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