When DJI says to calibrate the compass
Older DJI advice pulled in two directions. The Inspire 1 FAQ, written for the DJI GO app, told pilots to calibrate the compass at every new flight location. The Mavic Pro safety guidelines from 2016 said the opposite: only calibrate when the app or the status indicator asks you to.
The DJI Fly manuals for the Mini SE and Mini 2 SE give a concrete list. When you fly outdoors, DJI recommends calibrating the compass if:
- the location is more than 50 km from where the drone last flew;
- the drone has not flown for more than 30 days;
- DJI Fly shows a compass interference warning, or the status indicator blinks red and yellow alternately.
The same manuals say there is no need to calibrate for indoor flying. Newer manuals such as the Mini 4 Pro and Mini 5 Pro mostly leave it to the app: DJI Fly warns you when the compass or IMU has interference and needs calibrating, and you follow the on-screen instructions. In the Mini 4 Pro, Mini 5 Pro and Avata 2 manuals, a status indicator blinking red and yellow alternately still means "compass calibration required".
Where not to calibrate
Where you calibrate matters as much as how. The Mini 2 SE manual lists places to avoid: magnetite deposits and large metal structures such as parking structures, steel reinforced basements, bridges, cars and scaffolding. The Avata 2 manual adds magnets and construction sites with reinforced concrete underground.
Your own pockets count too. DJI says not to carry anything with ferromagnetic material near the drone during calibration, and gives the mobile phone as the example. The Inspire 1 FAQ adds keys. Put them down away from the drone before you start.
How to calibrate the compass
Menu names have moved between DJI Fly versions. The Mini 4 Pro manual puts the compass and IMU status under Safety, Sensors, where you can also start a calibration. Uplink Imaging, a DJI retailer summarising DJI's help center, gives the path from the camera view as ··· > Safety > Sensors > Compass > Calibration. The Mini SE and Mini 2 SE manuals describe the motions:
- Go to an open area and start the calibration in DJI Fly. The status indicator turns solid yellow.
- Hold the drone horizontally and rotate it 360 degrees. The indicator turns solid green.
- Hold the drone vertically and rotate it 360 degrees around a vertical axis.
- If the indicator blinks red, the calibration has failed. Move somewhere else and try again.
Two details from the manual are easy to miss. If the indicator blinks red and yellow alternately after a successful calibration, the spot is not suitable for flying because of magnetic interference, and DJI tells you to choose a new location. Also, the drone can take off straight away, but if you wait more than three minutes, you may need to calibrate again.
On the Avata 2 everything runs from the goggles: under Settings, Safety you can view the IMU and compass status of the aircraft and calibrate them. The motion controller has its own compass, IMU and accelerator calibration under Settings, Control, Motion Controller, RC Calibration, and DJI says to calibrate any of them immediately when prompted. The DJI RC 2 remote has a compass as well. The Mini 4 Pro manual says it may need calibrating after use near electromagnetic interference. Tap the warning prompt when it appears, or start it yourself from Quick Settings, System Settings, Compass.
The IMU
The IMU contains an accelerometer and a gyroscope, which measure linear acceleration and rotation. DJI's developer documentation calls it a sensitive system that depends on temperature and sometimes needs recalibration. Unlike the compass, it is calibrated with the drone sitting still. The Mini 2 SE and Avata 2 manuals list a red blink of the status indicator as an IMU error.
Uplink Imaging's summary of DJI's help center steps:
- Charge the battery to at least 50%.
- Put the drone on a level, dry surface. For Mavic series drones, DJI says to fold the arms.
- In DJI Fly go to ··· > Safety > Sensors > IMU > Calibration.
- Set the drone down in each orientation the app shows, one after another, and do not touch it while each step runs. A placement that does not match the picture can make the calibration fail.
If it fails, restart the drone and try again. If it keeps failing, the drone needs testing by DJI.
There is one symptom where the IMU and compass go together. For gimbal drift in flight, the troubleshooting sections of the Mini 4 Pro, Mini 5 Pro and Avata 2 manuals give the same answer: calibrate the IMU and compass in DJI Fly, and contact DJI Support if the problem persists.
Take off where the compass can work
DJI's manuals put a lot of weight on where you take off. The Mini 4 Pro manual says tall buildings and large metal structures may affect the accuracy of the onboard compass and GNSS. It tells you not to take off from a balcony or within 10 m of buildings, and to keep at least 10 m from them in flight. The Avata 2 manual sets the same rule at 15 m.
After takeoff, wait for the prompt that the Home Point has been updated before you fly off. If you did take off near buildings, DJI warns that the Home Point may not be accurate. Watch the drone's position closely during an automatic RTH, and when it gets close, cancel RTH and land it yourself in a suitable place.
If the warning appears in the air
When the vision systems are unavailable and the GNSS signal is weak or the compass has interference, the Mini 4 Pro and Mini 5 Pro switch to ATTI mode. The drone cannot hover or brake on its own any more, and wind pushes it sideways. DJI's instruction is to land as soon as possible. The Avata 2 manual describes the same case in Normal and Sport mode, and adds that RTH is unavailable. The article on flying a drone in wind on this site covers how to handle ATTI mode when the wind is strong.
The Mini 4 Pro manual also asks you to avoid areas with strong electromagnetic fields, such as power lines, base stations, electrical substations and broadcasting towers. If DJI Fly keeps reporting interference at one spot even after a successful calibration, take the hint from the manual and fly somewhere else.