Magnetic declination: The difference between true and magnetic north

The declination describes the angle between the geographic north direction (true north) and the direction in which a compass needle points (magnetic north). This difference arises because the magnetic north pole does not coincide exactly with the earth's geographic north pole. The declination varies depending on the location on Earth and also changes over time due to changes in the Earth's magnetic field.

What influences the declination?

• Position on the Earth: The declination depends on the location and can vary from -30° (western declination) to +30° (eastern declination) or more.
• Shift of the magnetic pole: The magnetic north pole moves at a speed of about 50 km per year, which influences the declination in the long term.
• Earth's magnetic field: The local variation of the magnetic field due to geological structures or metal deposits can slightly change the declination in small areas.

How is the declination measured?

The declination is given in degrees and can be positive (easterly) or negative (westerly). It is determined using special magnetometers or compasses that are aligned with true north while measuring the magnetic direction.

Practical significance of declination

• Navigation: In aviation, shipping and hiking with a compass, taking declination into account is essential to determine precise directions.
• Geophysical investigations: Declination plays a role in mapping geological structures and interpreting the Earth's magnetic field.
• Satellite navigation: GPS systems also take magnetic declination into account in order to link magnetic and geographical coordinates.

Interesting facts about declination

Did you know that declination is 0° in certain regions of the Earth? This is the case when geographic and magnetic north are exactly the same. However, such areas, the so-called "agonic lines", are rare and are constantly changing due to the movement of the magnetic pole.