You follow your phone compass west and end up slightly off. Or you compare your compass to a topo map and the numbers don't match. The likely culprit: your compass is showing magnetic north while your map uses true north. The gap between them — magnetic declination — is invisible but real, and it affects every compass reading on every phone.
True North vs Magnetic North: What's the Difference?
True north (also called geographic north) is the direction toward the Earth's geographic North Pole — the axis the planet rotates around. It's fixed, consistent, and the reference point for all maps, longitude lines, and satellite navigation systems like GPS.
Magnetic north is where the Earth's magnetic field converges, located in northern Canada. It is not fixed — the magnetic pole drifts by roughly 50 km per year as the molten iron in the Earth's outer core shifts. Right now, magnetic north is several hundred kilometers from the geographic pole.
The angle between magnetic north and true north at your specific location is called magnetic declination. It varies by location and changes slowly over time.
| Type | Reference Point | Fixed? | Used By |
|---|---|---|---|
| True North | Geographic North Pole | Yes | Maps, GPS, aviation charts |
| Magnetic North | Earth's magnetic pole (northern Canada) | No — drifts ~50 km/year | Magnetic compasses by default |
What Is Magnetic Declination?
Magnetic declination is the angle — measured in degrees — between magnetic north and true north at a particular location on Earth. It can be:
- East declination (positive) — magnetic north is east of true north. The compass points east of where a map would show north.
- West declination (negative) — magnetic north is west of true north. The compass points west of map north.
- Near zero — in some parts of Africa and South America, both norths nearly align.
Declination examples (approximate, 2026):
| Location | Approx. Declination |
|---|---|
| New York City, USA | ~13° W |
| Seattle, USA | ~15° E |
| London, UK | ~1° W |
| Sydney, Australia | ~13° E |
| Anchorage, Alaska | ~18° E |
| Nairobi, Kenya | ~1° W |
These numbers change by a fraction of a degree each year. Current official values are published by NOAA (US) and the British Geological Survey (UK).
How Does Your Phone Handle This?
The behavior depends on the device and the app:
iPhone (iOS)
Apple Maps, the built-in Compass app, and most browser-based tools (including the MyDeviceScan Compass Test) report true north. iOS automatically applies the local magnetic declination correction using your GPS location. The raw magnetometer reads magnetic north, but iOS converts it before delivering it to apps.
Android
Android is more variable. The Sensor.TYPE_ORIENTATION and TYPE_ROTATION_VECTOR sensors return magnetic north by default on most devices. Google Maps corrects for declination automatically. Standalone compass apps vary — some apply declination correction, others show raw magnetic north. Check your compass app's settings for a "True North" or "Declination" option.
In a browser, the DeviceOrientationEvent.absolute flag signals whether the reading is relative to the Earth's magnetic field (true) or an arbitrary reference (false). Even when absolute, most Android browsers deliver magnetic north.
Why Does This Matter for Navigation?
For most daily use — orienting yourself in a city, checking which direction a road runs — a 5–15° difference is negligible. But it adds up over distance:
- At 10° declination, after walking 1 km you are about 175 m off course
- At 20° declination, after walking 1 km you are about 342 m off course
For hiking off-trail, cross-country navigation, or using a paper topo map with a compass, understanding and correcting for declination is essential. Most printed topo maps include a declination diagram in the legend showing the angle for that map's area.
How to Set Your Phone Compass to True North
iPhone
Open Settings → Compass and verify "Use True North" is enabled (it is on by default when Location Services is active). If Location Services is off, the Compass app falls back to magnetic north and displays a warning.
Android
- Open your compass app's settings and look for a True North or Declination Correction toggle.
- If the app doesn't offer this, switch to Google Maps or a dedicated hiking app like Gaia GPS, which applies declination automatically.
- Alternatively, look up your local declination on the NOAA website and mentally add or subtract the angle from every reading.
Quick Check: Is Your Compass Showing True or Magnetic North?
The easiest test is to align yourself with a known east-west road or a clearly marked cardinal direction (like a church facing true east), then compare what your compass reads. If it shows a consistent offset from what the map says, your app is likely showing magnetic north without correction. Use the MyDeviceScan Compass Test to see your live heading — on iPhone it reports true north, on Android it shows the raw magnetometer reading so you can judge the difference yourself.
🧭 Check your heading now: Use MyDeviceScan's free Compass Test to see your live heading in degrees. On iPhone it applies true-north correction automatically; on Android you get the raw magnetometer reading.
Frequently Asked Questions
What is the difference between true north and magnetic north?
True north (geographic north) is the direction toward the Earth's geographic North Pole — the axis around which Earth rotates. Magnetic north is where the Earth's magnetic field points, and it is located in northern Canada, hundreds of kilometers from the geographic pole. The angle between them at any given location is called magnetic declination.
How do I set my phone compass to true north?
On iPhone, Safari and Apple Maps automatically apply your local magnetic declination and report true north. On Android, go to your Compass app or navigation app settings and look for a "True North" or "Magnetic Declination" toggle. Some Android compass apps use magnetic north by default, so you may need a dedicated app like GPS Compass or your maps app to get a true-north reading.
What is magnetic declination and why does it change?
Magnetic declination is the angle between magnetic north and true north at your specific location. It changes because the Earth's magnetic core shifts slowly over time — the magnetic pole moves roughly 50 km per year. Declination also varies by location: near zero at some longitudes in Africa and South America, but reaching over 20° in parts of Alaska and northern Canada. Aviation charts and topo maps are updated periodically to reflect current declination values.
Why does my phone compass point differently than my map?
Most maps use true north (geographic north), while a basic phone compass may show magnetic north. Depending on your location, this difference can be 5–20°, enough to send you noticeably off course. Navigation apps like Google Maps and Apple Maps correct for this automatically. A standalone compass app may not unless you enable the true-north setting or it applies declination correction internally.
Does magnetic declination affect everyday navigation?
For casual navigation — finding which way a street runs or orienting yourself in a city — the few-degree difference usually doesn't matter. For hiking, off-trail navigation, or working with a paper topo map, the difference becomes significant. A 10° declination error over a 1 km walk puts you about 175 m off course, which in dense forest or featureless terrain can be disorienting.