Sometimes it is needed to calibrate your IMU.
First, let me explain what an IMU is:
An IMU is a unit which collects angular velocity and linear acceleration data and contains two separate sensors.
The first sensor is the accelerometer.
This generates three signals describing the accelerations along each of its axes produced by the drone or external factors like wind
The second sensor is the angular rate sensor.
It also outputs three analog signals that describe the drone’s angular rate.
The data from these sensors is collected by the IMU and returned to a main processor.
In some DJI drones you have 1 IMU, and in some (like the Mavic) you have 2 IMU’s and calibrating these makes sure that the drone knows what 100% level is.
If your IMU has wrong data the drone can (over) react to wind and stick input and may even cause the drone to over correct and crash!
Normally the DJI app gives you a notice when calibrating is required, but calibrating the IMU is also a good idea when you have updated your firmware.
How to calibrate your IMU
To start you need a 100% level underground.
I normally use a vinyl record and make that level.
It is also highly recommended to do this cold! so best to do it before you head out to fly.
Start up your drone like to normally would.
First the controller, then the drone, and make sure the tablet or phone is connected to the drone either by WiFi or cable depending on your type of drone.
Also, make sure the props are not installed, just in case!
Next start the DJI app.
Once the app is started follow these steps to start the calibration of the IMU.
And when you have tapped OK the calibration starts.
This can take up to 5 minutes to complete.
And when it is finished the app shows the following.
That is it, your IMU(s) is calibrated, and you are ready to head out and fly.
But, before you go.. you might want to check and calibrate your gimbal as well!
You can read all about that process here