How to find north with your phone

1Three ways to find a direction

Compass app: the magnetic sensor measures the Earth's magnetic field, and the operating system combines it with the orientation sensor into a heading. It works instantly and anywhere – as long as nothing bends the magnetic field.

Map app: the viewing cone on the map comes from the same magnetic sensor and has the same weaknesses. Only while you walk or drive does the map show your direction of travel from GPS positions – standing still, that does not help.

The sun: its direction can be computed for any place and time, relative to the geographic North Pole. Sight the sun, know its computed direction, and you know true north – independent of any magnetic field. That is what SunCompass does.

2Why the phone compass is off: declination and deviation

Magnetic declination (in navigation also called variation) is the angle between magnetic and true north. It is known and computed with the World Magnetic Model 2025 (WMM2025) by NOAA/NCEI and the British Geological Survey; in 2026 it is about 3 to 5.5° east across Germany, close to zero in the UK and about 12° west in New York. SunCompass corrects for it at your location.

Deviation is the pull of iron, steel and magnets near the compass – the term comes from seafaring, where the ship's own hull deflects the needle. No model knows it. The World Magnetic Model explicitly describes only the Earth's main field; according to NOAA, even natural anomalies of the crust exceed 10° in places, and man-made disturbances are not included at all.

A simple calculation shows how quickly deviation grows. A compass aligns with the horizontal part of the Earth's magnetic field, and that is weak: around 18 to 21 microtesla in Germany and about 20 in London, according to the World Magnetic Model. A stray field at right angles to it turns the reading by arctan(stray field ÷ horizontal field). As little as 3.5 microtesla gives 10°, 11.5 microtesla gives 30° – field strengths easily reached close to steel beams, speaker magnets or a magnetic phone case.

3Finding north with SunCompass

Open SunCompass in the browser and allow your location. The compass runs straight away on the magnetic sensor, corrected for declination. A line at the rose tells you what the reading currently relies on.

Tap “Sight the sun”. The camera opens with a crosshair and a line at the altitude where the sun is right now. Tilt the phone to that altitude until “Altitude matches” appears, then pan sideways onto the sun and tap “Sun sighted”.

“To the compass” takes you back to the rose. It now shows true north and keeps running on the phone's gyroscope, without the magnetic field. If the magnetic sensor disagrees by 3° or more, SunCompass shows the difference – so you see how much your surroundings interfere.

The gyroscope drifts slowly. After about ten minutes SunCompass reminds you to sight again. With the magnetic compass, hold the phone flat; after a sighting the compass works in any position.

4What it is good for

Satellite dish on a steel mast: the target azimuth for the satellite comes from SatFinder. With a magnetic compass right at the mast you easily aim 20° off – more than the dish forgives. With the sun sighting the direction is right even at the mast.

Solar panels and balcony PV: check the orientation of a roof or module to within a few degrees, even between gutter, railing and mounting frame. What orientation means for the yield is what SolarFinder calculates.

Hiking and outdoors: find the cardinal directions when the phone compass is uncalibrated or jumps around – without a network connection once the page has been loaded.

Motorhome and camping: in and around a steel body a magnetic compass is badly disturbed. The sun still gives you the direction for satellite antenna and solar panel.

5Limits: night, clouds, the sun near the zenith

At night and under complete cloud cover there is no sun to refer to; the magnetic compass remains. Below 5° altitude SunCompass does not let you sight, because buildings and trees hide the sun and its azimuth changes quickly near the horizon.

When the sun is very high, sighting becomes less precise: a sideways aiming error grows in the direction by the factor 1 ÷ cos(sun altitude). In Central Europe and the UK the sun never climbs much above 66°, so the factor stays below 2.5. In the tropics, where the noon sun stands close to the zenith, sight in the morning or afternoon instead.

Your location need not be exact, but it must be right: about 10 km is enough. If it is 100 km off, the sun's direction at 50° latitude shifts by 1 to 3°, most at noon in summer.

6Without a phone: shadow stick and watch

Shadow stick: push a stick upright into the ground and mark the tip of its shadow. Wait 15 to 30 minutes and mark it again. The line from the first to the second mark runs roughly from west to east, because the sun moves west and the shadow east. The method is most accurate around noon and near the equinoxes.

Watch method: point the hour hand of an analogue watch at the sun; in the northern hemisphere south lies roughly halfway between the hour hand and 12, in summer time between the hour hand and 1. It is rough: your longitude within the time zone, the equation of time and the tilted path of the sun easily add up to 10 to 20° of error.

Both methods are fine for rough orientation on a hike. For a satellite dish or the orientation of a solar panel they are too inaccurate.