If your mobile is equipped with a compass, it may no longer work correctly. In case this happens, it is essential to calibrate it: in this way, your mobile will again tell you in which direction it is pointing. But how is the mobile compass calibrated? The solution is the figure eight trick, a move that restores the reliability of the compass.
Whenever you use applications such as Google Maps, you use GPS to locate you, but it is not the only sensor included in your mobile that collaborates to put you on the map: the compass or magnetometer tells the Maps app where you are pointing your phone. This is essential to know where you are going while you walk for example: the better the compass is calibrated, the less time you will waste during the journey.
Trace a figure eight in the air with your mobile to calibrate the compass
As for the compasses that you surely used during your childhood, the sensor that cell phones generally integrate detects the earth’s magnetic fields to indicate which cardinal point the top of the mobile is pointing to. Thanks to this, you will not only know where the sunrise is or how to orient yourself in the open field, but you will also have a key aid in applications such as Google Maps: knowing in which direction you should start the route.
The magnetometer included in smartphones is a tiny sensor that can be altered by small electromagnetic fields generated by the mobile’s own circuits, it is also affected by other devices or metal surfaces nearby where you can put the smartphone (or circle it). For this reason, it is usual that this sensor does not clearly detect the magnetic north pole; you will therefore need a calibration that will help you separate the earth’s magnetic field from the rest of the magnetic interference. This is where the eighth turn comes in.
Maybe a warning appeared on Google Maps that your mobile’s compass needs calibration and for that you need to draw some kind of figure eight in the air. And that’s exactly what you need to do:
- Hold the phone tightly in your hand, it is easy that in one of the turns it can fall.
- Rotate your wrist to the right while moving your hand slightly in that direction.
- Take a turn in the air in the opposite direction, to the left.
- Join the two movements in a loop and repeat them for about twenty seconds or until Google Maps (or any other app) tells you that the compass is already calibrated.
Once you have calibrated the compass the point that represents you on the map will point in the right direction. This way you can go in the direction you want without having to move for the GPS to detect the direction.
In general, you shouldn’t need a compass calibration, it will all depend on several factors:
- You are in an environment with magnetic interference. Inside the car it’s usually quite common, for example.
- If you haven’t calibrated for a while.
- It highly depends on the quality of the phone . The more categories your mobile has, the better the sensors it will have incorporated; they will therefore experience less interference.
Not all mobiles include a compass among their functionalities: it is likely that yours does not. In this case, you will only know where the phone is pointing if you move before the GPS detects it. And you won’t have to calibrate it
Why is it necessary to calibrate the mobile compass?
We have already explained how the phone’s sensor roughly works: the magnetometer detects the earth’s magnetic field and transfers the information to the system. Due to the interference suffered by this sensor, it is common for it to go out of adjustment; creating distortions in the magnetic plane that the system recorded: These distortions prevent the phone from positioning itself precisely in space. With one last aspect to keep in mind: the compass does not work alone, since it relies on the accelerometers and the gyroscope (if the mobile includes it, something already very common) to position the phone in the space.
To have your Google Maps show you with the blue arrow pointing in the right direction (and not moving), the app takes data from:
- the magnetometer. The compass itself obtains data from the various magnetic fields that surround the mobile to create a low precision three-dimensional plane (X, Y and Z axes).
- accelerometers. These sensors tell the phone if it is moving in the X and Y axes. That is, it allows the system to know the orientation of the mobile (vertical or horizontal) as well as the movements that affect it.
- the gyroscope. This sensor precisely positions the phone in the three axes of space: X, Y and Z.
When the compass cannot determine what the earth’s magnetic field is because it suffers from interference, moving the rover in a figure eight allows the system to compare the readings obtained in the three axes of space (X, Y and Z) with those he has stored in the magnetic plane. This allows you eliminate erroneous positions restore compass reliability. The mobile not only uses the magnetometer readings, it also compares them with the accelerometers and gyroscope. This increases the orientation reliability.
By making a figure eight with the mobile, the system adjusts the position of the phone in space, eliminating the erroneous data which had caused the magnetic interference
The figure eight trick is much more useful than it looks and it really works: with this calibration the system can determine the orientation of the phone. And, given that for said calibration position readings should be taken in all three axes of spaceto “zero the compass”, there is no choice but to move the mobile in the air.
You usually only need to do the figure eight trick when apps like Google Maps ask you to. Even though you can also perform this gesture just before opening the Maps application, for example. This ensures that your location arrow points correctly to where you are looking.
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