A calibration warning appearing on the controller screen during pre-flight preparation throws most pilots off. At the other extreme, some people run a calibration as a ritual before every single flight. Neither habit is good. Once you understand what these procedures actually align, it becomes obvious when they are needed.
The two sensors do different jobs
The compass, or geomagnetic sensor (지자기 센서), reads the Earth\'s magnetic field to determine which way the aircraft is facing. When it is wrong, the drone misjudges its own heading, so it may rotate unexpectedly or fly slow circles even while commanded to hold position.
The IMU - inertial measurement unit, combining accelerometers and gyroscopes - measures tilt and rotation rate. It is the part that remembers where level is. When the IMU is off, the aircraft believes it is tilted while sitting on flat ground, and after takeoff it drifts persistently to one side.
- Compass fault: heading errors and rotation-related problems.
- IMU fault: level is wrong and the aircraft slides one way.
Because the symptoms differ, you can work out which one to address. If the aircraft keeps sliding in one direction, first decide whether that is wind or an IMU issue.
When to calibrate
Calibration is something you do when it is needed. Repeating it without reason risks performing it in a poor environment and making the stored values worse.
- After travelling a long distance: a substantially different region means a different magnetic environment, so a compass calibration is advisable.
- When the aircraft asks: follow the prompt if the app or controller requests one.
- After configuration changes: a new gimbal, added accessories, or frame repairs.
- After impact or a crash: sensor values are likely to have shifted.
- After a large temperature change: the IMU is temperature-sensitive. Let an aircraft brought from a warm room into winter air settle before checking.
Location determines the result
Most failed calibrations come down to where they were performed. The compass in particular is heavily affected by nearby metal and electrical current.
- Avoid: reinforced concrete surfaces, car parks, the side of steel structures, beneath power lines, above buried pipework, and anywhere near vehicles.
- Prefer: open ground on soil or grass.
- Check your pockets: phones, keys and magnetic accessories also interfere. Put them down.
IMU calibration needs the opposite: a completely flat and stable surface. Performed on sloping ground, a wobbly table or the roof of a car, the aircraft memorises a tilted attitude as level, and it will drift the moment it lifts off.
Procedure and signs of failure
The exact steps differ by manufacturer and model, so always follow the manual for your aircraft. The common principles hold, though: move slowly and at a constant rate during the procedure, and do not set the aircraft down or shake it until completion is confirmed. Stopping partway and restarting repeatedly produces unstable values.
Do not go straight into your main flight afterwards. Hover briefly at low altitude and check that position holds and heading changes behave normally. If the aircraft slowly circles, or slides continuously to one side with the sticks centred, the calibration did not take. Move to a different spot and do it again.
If you have a practical exam coming, avoid ending up calibrating in a rush on site. The exam ground may not be suitable, and time pressure in the waiting queue makes people hurry the procedure. Verify the aircraft at your practice field the day before, and keep exam-day work to inspection.
Light Beyond Drones covers sensor checks and calibration judgement inside the practical courses at our Daejeon centre. Knowing what to check when a warning appears makes you far calmer in the field. Tell us which aircraft you own and we will tailor the guidance.
