How do you determine the correction for a magnetic compass?
I bought a watch that has an electronic compass and in the manual it says:
Declination adjusts the compass for the local magnetic fields. In some areas,
magnetic declination can be considerable. Declination is sometimes measured as
degrees negative and positive. Degrees East are considered positive and degrees
West are considered negative.
RE: RE: declination angle
I believe that the "declination" used in this case is the term used for
the angle at which the Earth's magnetic field is skewed in your local
area relative to true North. The magnetic pole is not located at the
North Pole but rather is down in the upper reaches
The lines of magnetic force radiate outward from that general
area and are by no means smooth and regular. The local value used to be
marked in the margin of USGS Topo maps (topographic maps issued by the
U.S. Geological Survey; such maps may be available at local public or academic libraries),
and it varies wildly in certain areas of the country. As I remember, there are some areas
less than 100 miles from here (
wrong and will point SW (southwest) instead of true north for example [my source:
a map of
Magnetic compasses are notoriously useless in the hands of anyone
without some significant training -- i.e.: geologists, retired surveyors, and
old (Boy Scout) merit badge candidates.
- ERIC CANALI
For more information, or a clarification, send your request to the
Following electronic mail address: < FAQ@planetarium.cc >.
Editorís Note: This Science question was answered by a very experienced amateur astronomer,
who also works as a part-time Tour Guide at the Allegheny Observatory in
Allegheny Observatory provides public tours two nights a week from April through October;
pre-registration is necessary, but the tours are free-of-charge.
For many years, Eric G. Canali was Floor Manager for the original Buhl Planetarium
and Institute of Popular Science in
. He also was a long-time member of the Pittsburgh
Amateur Astronomers' Association of Pittsburgh and is Founder of the South Hills
Glenn A. Walsh, Author and Editor of History Web Sites on the Internet:
Electronic Mail - < firstname.lastname@example.org >
* Buhl Planetarium,
* Adler Planetarium, Chicago:
* Astronomer & Optician John A. Brashear:
* Andrew Carnegie & Carnegie Libraries:
* Duquesne Incline cable-car railway,
††< http://www.incline.cc >