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Compass corrections



Hello everyone,

I have been following this thread for a while and the original post has
received many excellent suggestions, including a web site that
calculates the difference between True and Magnetic North.  Since the
original post indicated the use of an Army-type compass (notoriously
inaccurate most of the time), perhaps I can add to the confusion from my
perspective :-).

1) Keep Murphy's Law in mind at all times!

2) If using a compass - keep it as far away as possible/practical from
any metal.

3) Prior to using the compass, try to obtain a second, and placing them
at least 3 feet [~ 1 meter] apart, read the difference between them
(while pointing both in   the same direction).  There is bound to be
"undiscovered" error, albeit fairly close between the individual units.
Go ahead and experiment.

4) Probably the very best source for the current angular difference
between True and Magnetic North is, the USCGS.  One must remember also,
that there are magnetic anomalies all over the planet and your QTH
may/may not follow the "rules".

5) If you have a portable GPS unit, most models will show you where
either or both True/Magnetic North lies relative to your QTH depending
on the GPS's features.

6) Someone suggested looking at the Compass Rose at an airport.  Don't
even think about it!!!!  The FAA, cops and specially aircraft take such
a "runway/taxi way incursion" VERY seriously!

7) One current source for accurate information is, the purchase at your
local airport's FBO's [Fixed Based Operator] pilot supplies shop a map
known as: "Sectional Chart" for your area.  It is issued every 56 days
(in some cases the issue date is a few weeks later) by the Government
and it is mandatory for pilots in General Aviation to have it to fly
legally - even if they are Instrument rated.  Look for your location,
i.e., town, city, etc.  At the bottom of the map you will find the
current difference between True and Magnetic North.  If you do not know
how to read this chart, then by all means ask for help.  The price of
this map is approx. US$6-7.00.

8) Finally, (whew:-) if your QTH happens to fall between two lines,
interpolate. Incidentally, the Sectionals are designed to indicate
Magnetic North.

Hope these tips will give some help to those of you who need/want it.


73 de Attila the Hun
[a.k.a. WB2GZM/VK3JJH]


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