|
.
Magnetic Declination |
|
A compass points to magnetic north, not true north. This angular difference is called magnetic declination (also called magnetic variation). It is different for each place on earth and is slowly changing over the years. To learn more about magnetic declination, visit Chris M. Goulet's excellent Magnetic Declination FAQ page or the The Geomagnetic Field AQ by the NOAA
This program uses the World Magnetic Model to calculate declination values between the years 2000 and 2005. New coefficients for 2005 to 2010 will be published at the beginning of the year 2005 and an updated version of this program will be available shortly afterwards. The accuracy of the model is claimed to be better than 1 degree, but greater errors are possible due to local factors like ore deposits, mountain ranges or power lines which the model does not account for. The 'Azimuth Display' switch controls how azimuth values are displayed in Planetarium. If [True] is selected, the azimuth values are shown as bearings to true north. If [Magnetic] is selected, the azimuth values are corrected by the declination and show the bearing you would read on a magnetic compass. To indicate magnetic bearings in compass view the label beneath the number shows 'AzM' instead of 'Az.'.If [Magnetic] is selected, a line for magnetic north is drawn in the compass display while 'N' always points to true north. |