At 10:22 PM 9/22/01 +0000, John Farber wrote:
>Magnetic declination is not the same thing as magnetic deviation. I think
>you guys are talking about deviation from true North, whereas mag
>declination is the vertical angle the field lines make going into the Earth,
>and that varies by latitude.
Declination, not magnetic declination, is the bearing of a celestial body
from the observer. When coupled with elevation, a line of position can be
obtained, Cross two or better three, lines of position and you have a
geographic location or "fix". Talk to a navigator and you will understand.
True heading, plus or minus variation, is called magnetic heading, ie the
direction or bearing to the magnetic north pole. Add or subtract compass
error (deviation) and you have compass heading.
Variation in most parts of the world can be obtained by calling a local
airport, or, if you prefer, doing a search on the Web. Deviation of a
cheap Boy Scout compass is not worth calculating, but if you have a
sophisticated large bucket compass deviation can be calculated by using an
astrocompass which shows true heading. After adding or subtracting
variation you look at the compass and the difference is deviation Most
people who use large compasses (flyers, mariners) swing them every 15
degrees of bearing beginning at North. It takes quite a while..
If you point an antenna at a bearing where the signal is loudest you
have it made. A guess at True North is good enough and while this subject
recurs like the seven year itch, your antenna is OK if you use the shadow
method (bulky) or Polaris (easy)
Now, how many owls can be positioned on a non-polished element for maximum
gain and front to back?
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