If you've ever used a compass and tried to compare it to a map, you may have noticed something puzzling: the compass and the map don't quite agree on where "north" is. That's because there are two different "norths" — and they're increasingly far apart. Understanding the difference between magnetic north and true north is fundamental to navigation, surveying, and even understanding Earth itself.
The Short Answer
True North is Earth's geographic North Pole — the fixed point where Earth's rotational axis meets the surface. Magnetic North is the point that compass needles point toward, which is determined by Earth's magnetic field. The two are currently about 700 km apart, and Magnetic North is moving rapidly — about 55 km per year — toward Siberia.
Defining True North
True North (also called Geographic North) is the fixed point at 90°N latitude where Earth's rotational axis exits the surface. Stand at True North and every direction is south. The North Star (Polaris) sits almost directly above True North, which is why Polaris has been used for navigation for thousands of years.
True North is the reference for maps, longitude lines, latitude calculations, and most modern navigation. GPS systems give locations in terms of True North. Aviation, marine navigation, and surveying all use True North as the standard reference. The location is stable — it doesn't move (significantly) over human timescales.
Defining Magnetic North
Magnetic North is where the planet's magnetic field points downward — the place compass needles try to align with. Earth has a magnetic field similar to a giant bar magnet inside it, but the magnetic axis doesn't line up with the rotational axis. As of 2025, Magnetic North is located in the Arctic Ocean north of Canada, but it has been moving rapidly toward Russia.
Magnetic North isn't actually a single point — it's where the magnetic field lines converge most strongly. The field is generated by motion of molten iron in Earth's outer core, and the field is constantly changing in complex ways. Currently, Magnetic North is at approximately 85.7°N, 139.8°E.
Why They're Different
True North and Magnetic North are different because Earth's rotational axis and magnetic axis are not aligned. Earth's magnetic field is generated by convection currents in the molten iron of the outer core, and the resulting field doesn't align perfectly with the planet's rotation. The current angular difference between the magnetic axis and rotational axis is about 11 degrees.
This misalignment isn't unusual — most planets with magnetic fields have similar offsets. Jupiter's magnetic axis is offset 10° from its rotational axis. Saturn's is also offset. Earth's situation is normal for a planet with an active dynamo.
How Magnetic North Moves
Magnetic North has always moved, but its speed has increased dramatically in recent decades. Historical movement:
- 1831: Magnetic North was first measured by James Clark Ross in northern Canada.
- 1900–1980: Moved about 10 km per year.
- 1990s: Speed increased to 15 km per year.
- 2000s: Speed jumped to 40 km per year.
- 2010s: Speed peaked at about 55–60 km per year.
- 2020s: Speed has slowed somewhat to 35 km per year.
The rapid movement has forced regular updates to the World Magnetic Model — the global reference used by GPS, military, aviation, and other systems. The Model was updated in 2019 ahead of schedule because Magnetic North was moving so fast.
Magnetic Declination
The angle between True North and Magnetic North at any specific location is called "magnetic declination" (or "magnetic variation"). Declination varies dramatically by location:
- In Florida, declination is currently about 7°W (Magnetic North is 7° west of True North as seen from there).
- In California, declination is about 13°E.
- In Maine, declination is about 17°W.
- In Hawaii, declination is about 10°E.
- In London, declination is about 1°W.
Topographic maps print the declination value for the area, and good compasses allow you to set declination so the compass adjusts automatically. Without correcting for declination, hikers and navigators can end up significantly off course.
The Magnetic Field Is Weakening
Beyond moving, Earth's magnetic field is also weakening overall. The strength has declined about 9% over the past 200 years. The largest weakening is in the "South Atlantic Anomaly," a region of low magnetic strength over Brazil and Argentina. This weakening could be a precursor to a magnetic pole reversal, where Magnetic North and Magnetic South swap places.
Pole reversals have happened many times in Earth's history — the last full reversal was about 780,000 years ago. They don't happen overnight; the process takes thousands of years. A future reversal could affect satellite electronics, navigation systems, and possibly animal migration patterns. But it wouldn't threaten life on Earth — many such reversals have occurred without major biological effects.
How GPS Handles This
GPS systems use True North as their reference, with no involvement of the magnetic field. Your phone's GPS gives location in terms of latitude and longitude, which are measured from the rotational pole. But the digital compass in your phone uses magnetometers to detect the magnetic field, then applies a software correction (using the World Magnetic Model) to display True North. So your phone's "compass" function combines magnetic measurement with declination correction.
Navigation Implications
For practical navigation:
- Compass: Points to Magnetic North; needs declination correction for accurate True North readings.
- GPS: Gives True North directly; reliable for any direction-finding.
- Maps: Usually drawn relative to True North; declination must be applied when using a compass with them.
- Stars: Polaris is almost exactly at True North (about 0.7° off); reliable celestial reference.
- Sun: Can be used for rough direction-finding (rises in the east, sets in the west).
Animals and the Magnetic Field
Many animals use Earth's magnetic field for navigation, especially during migration. Examples include:
- Birds: Many migratory birds have magnetite particles in their beaks and use magnetic fields for direction.
- Sea turtles: Hatchlings use magnetic fields to navigate to the ocean and back as adults.
- Salmon: Use magnetic fields to find their natal streams during spawning runs.
- Sharks and rays: Have electromagnetic sensing organs that can detect magnetic fields.
- Some insects: Including bees and certain butterflies.
Whether the rapid movement of Magnetic North is affecting animal migration is an active area of research. Some studies suggest birds and other animals may be experiencing disorientation in regions with rapid magnetic shifts.
History of Magnetic Compass
The magnetic compass was invented in China, with first documented uses around the 2nd century BCE. It was originally used for fortune-telling and feng shui before being adapted for navigation around the 11th century. The compass reached the Islamic world by the 12th century and Europe shortly after. Early sailors didn't initially understand that compasses pointed to Magnetic North rather than True North — that realization came in the 15th century when Christopher Columbus and other European navigators began documenting "magnetic variation" during their voyages. By the 17th century, sailors regularly applied declination corrections to compass readings, though detailed declination maps for various ocean regions weren't available until much later.
The South Magnetic Pole
Just as there's a Magnetic North, there's a Magnetic South — currently located off the coast of Antarctica, between the continent and Australia. The two magnetic poles are not exactly opposite each other on the globe; their positions are determined separately by the complex magnetic field generated in Earth's core.
The World Magnetic Model
The World Magnetic Model (WMM) is the standard reference for Earth's magnetic field, developed jointly by the US National Geospatial-Intelligence Agency and the UK Defence Geographic Centre. Updates are issued every 5 years, but the rapid 2018–2019 movement of Magnetic North required an emergency update — the first in the model's 19-year history at the time. The current model is WMM2020, valid through 2025; WMM2025 was released to cover 2025–2030.
Key Facts
- True North is Earth's geographic North Pole; Magnetic North is where compasses point.
- The two are currently about 700 km apart.
- Magnetic North is moving about 35 km per year toward Russia.
- Magnetic declination varies by location and must be corrected for accurate navigation.
- Earth's magnetic field is weakening, and a future pole reversal is possible.
Fun Facts
- Polaris (the North Star) is almost exactly above True North — within 0.7°.
- Many migratory birds use Earth's magnetic field for navigation.
- Earth's magnetic field has reversed multiple times in geological history.
- The World Magnetic Model needed an emergency update in 2019 due to fast pole movement.
- Magnetic South Pole is off the coast of Antarctica, not at the geographic South Pole.
The Bottom Line
True North is the fixed geographic North Pole — where Earth's rotational axis meets the surface. Magnetic North is where compasses point, determined by Earth's magnetic field. The two are currently about 700 km apart and Magnetic North is moving rapidly across the Arctic. For accurate navigation, you need to know the difference and correct for "magnetic declination" depending on your location.