Compass, in your browser.
Hold your phone flat and the dial turns to north. The shaded wedge shows how far the reading can be off.
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How to use it
- Hold the phone flat, screen up, at waist height. Keep it away from laptops, cars, steel tables and magnetic cases.
- Turn your body, not only the phone, until the direction you want is at the top of the dial.
- Read the heading in degrees: 0° is north, 90° east, 180° south, 270° west.
The heading is magnetic north. Your browser gives the page no way to tell how close it is, except Safari, which reports an accuracy; the wedge uses it when it can.
Why phone compasses go wrong
A phone measures the Earth's magnetic field, which is weak: about 22 to 67 microtesla. A magnet in a phone case, a car body or the steel in a desk can be stronger than that, so it bends the reading without any warning. Android's own rules allow the sensor a large built-in offset that the phone must learn and remove as you use it. That is why a figure 8 helps after a while, and why it does not help at all next to a fridge.
In reviews of the five most-installed compass apps, “wrong direction” is the biggest complaint by far: 17.7 % of the 1- and 2-star reviews we read. Most of those users did not know a magnet was the cause.
What the app does better
The Level & Compass app compares the field it measures with the Earth's field model for your area. When they do not match, it says “Magnet or metal nearby” instead of showing a confident wrong number. Pro adds true north and a bearing you can follow: “Turn 24° right to 297°”.
Questions
Does the online compass work on an iPhone?
Yes, in Safari. Tap “Use my phone as a compass” and allow motion access.
Does it work on a computer?
No. A compass needs the magnetometer in a phone. Laptops and desktops do not have one.
Is this true north or magnetic north?
Magnetic north. The difference (declination) depends on where you are: near 0° in parts of the central US and Europe, more than 15° in parts of Canada, Alaska and New Zealand. The Level & Compass app (Pro) shows true north from your rough location.
Why is my phone compass wrong by 20° or more?
Usually a magnet or metal nearby: a magnetic phone case or mount, a laptop, a car, steel in a table or a wall. Move away from it and the reading recovers. Phones also need their compass calibrated now and then.
How do I calibrate my phone's compass?
Move the phone in a slow figure 8 for a few seconds, away from metal. If the error stays, the cause is usually something magnetic near you, not the phone.
How accurate is a phone compass?
About ±3° at best, in the open, away from metal. Indoors and near steel it can be off by tens of degrees. The shaded wedge on the dial shows the possible error.