Hi,

I hear a lot about the IMU of the P4
But what i like to know what does the IMU calibration does exactly and how often do i need to calibrate it.

Thanks for helping me understand

As far as I see it, IMU calibration on a level surface updates a table of values the flight controller software uses as a reference for a level stationary hover. From there the craft responds predictably to flight commands.  It also likely measures any sensor noise and thermal drift so that these technical imperfections are accounted for when using IMU sensor data in flight. - this is likely why there must be no vibrations during the calibration process.


Bad IMU calibration could cause drift and attitude issues as the flight controller fights to hold the craft in what it thinks is the correct attitude as opposed to the correct physical attitude.


The IMU usually has 2 types of sensors – angle and acceleration and in turn 3 sensors of each type measuring in the X,Y and Z axis. These sensors can, through vibration, aging, impact etc, drift in their response over time and thus an IMU calibration will establish a new reference for the IMU’s level/stationary state that the flight controller can work with to restore stable flight.


Think of calibration as the bringing back into line the measured craft attitude with the true physical craft attitude.


As to how often an IMU calibration is needed, I wouldn’t like to say; certainly after any impact or if there are suspicions the craft can’t hover in a level attitude in a windless environment. Also after a firmware update is a good opportunity just in case the stored values get corrupted or are incompatible with the later firmware.


Hope that helps!

Right, so it's like zeroing all the sensors on your smartphone, so level is actually level, at at rest is actually at rest.... That is why they make such a big deal out of having it level, stationary on solid surface, and left alone, so free of vibrations ad such... If IMU think's that level is actually .5deg tilt, you rally gonna have a lot of issues!
One additional catch is also ambient temperature.. Say you recalibrate it in 80F temperature, it will need to bring itself up to 80F on every flight before IMU will be ready to fly..that is one reason so many people chose to "chill" the drone before calibrating IMU....
I did not understand the warmup, but just so happened that I was flying a few days ago in sub 40F temp, and I was surprised to see the message that the IMU needed to warm up.. it lasted about 20 sec, and I was set. So if majority of your flying is at 40, you probably want to make sure the whole unit is cooled down, preferably even a bit lower than the ambient air temp around you.

IMU stands for "Inertial Measurement Unit". Along with the very good points brought up by davidson_g and Phantomski, it's also good to mention that the IMU is the reason why you are able to shut off the motors using just the throttle down command when on the ground. The IMU reads that the aircraft is unable to move any further, and after three seconds it determines that is has officially landed and can shut off the motors safely.

Most commonly the Go app will prompt you if an IMU calibration is absolutely needed, however, being proactive does not hurt should you notice either some performance issues or if you know that the aircraft has been shaken around during travel etc.

I think this video could help you: