What is IMU Calibration and Do I Need to do it on My Drone?

IMU calibration is a super important part of owning a drone. If you don’t calibrate it, you may not be able to fly your drone or you could end up crashing it.

In today’s post, we’ll be going through everything you need to know about IMU calibration. From what it is and why you should do it, to the steps on how to do it as well as how often.

Contents:

What is IMU Calibration?

How to Calibrate the IMU

Why Do You Need to Calibrate the IMU?

How Long Does IMU Calibration Take?

Do I Have to Re-Calibrate My Drone Every Time I Use It?

So, When Should I Calibrate My Drone’s IMU?

How to check the IMU status on your drone

 

What is IMU Calibration?

IMU stands for Inertial Measurement Unit and is essential for keeping your drone stable and level in the sky. It’s a built-in device that measures force, angular velocity, and attitude (yes, attitude, not altitude). It does this through the drone’s accelerometer, barometer, gyroscope, and thermometer. Let’s dig a little deeper into these components.

Accelerometer – Accelerometers measure a drone’s proper acceleration (acceleration relative to its freefall). If you find that your drone is tilting when hovering, this could be an accelerometer issue meaning you need to recalibrate your IMU. It could also be a gyroscope issue. If you don’t calibrate your drone on a level surface, this issue is usually quite common.

Barometer – Barometers measure atmospheric pressure, but on DJI drones, they use this to help measure your drone’s altitude. If your drone ever switches into ATTI mode in a low GPS area, the barometer will help keep it from falling out of the sky.

Gyroscope – Gyroscopes are simple MEMS (Micro Electronic Mechanical Systems). They help to measure the drone’s attitude (read more about attitude and ATTI mode here) so that the drone remains steady and stable in the sky.

Thermometer – Therometers keep the temperature of the drone in check. When you switch on your drone, its IMU warms up based on what the temperature was the last time you calibrated it. So, if you calibrated it at room temperature it’ll aim for that. Sometimes, if you’ve calibrated the drone when it was particularly hot, you’ll find that it takes too long for the drone to warm up. If this is the case, do a recalibration and allow the drone to cool before calibration. You can even place it next to a fan or air conditioning if you have it.

Put simply, The IMU detects any discrepancies in attitude and movement on the horizon to help your drone straight and prevent drift.

Some drones, including DJI models, have multiple IMUs, all of which you’ll need to calibrate if you’re experiencing issues or are prompted to do so. Others, like some First Person View (FPV) drones, don’t have an IMU at all.

 

How to Calibrate the IMU

Thankfully, calibrating the IMU on your drone is simple and easy if you just follow these steps (other drones will have a similar process, too):

Before IMU Calibration, please make sure:

• The aircraft is on a level surface and tries to avoid concrete, metal, and electronics where possible. The steel bars in concrete and metal could cause interference.
• If you’ve recently flown your drone, wait a few minutes for it to cool before you start the calibration.
• Check that you have at least 50% battery.

Let’s take DJI Mavic Air 2 for example to show you how to do the IMU Calibration.

Step 1 Remove the gimbal cover and power on your drone. The drone will restart during the calibration process, make sure you remove the gimbal cover so it won’t cause damage to your camera.

Note: We recommend that you remove the propellers. The reason you should remove your props is to ensure that if the drone starts up, it won’t fly off, and also prevents any inaccurate calibration. Some pilots leave the propellers on, but it genuinely only takes a few extra minutes to remove them so we think it’s best to do that. If it’s a Mavic Mini or DJI Mini 2, then it’s not necessary to do that because it takes too much time and trouble to remove the propellers.

Step 2 Power on your controller and launch the DJI Fly App, then connect your drone.

Step 3 Tap on Go Fly, then tap on the 3 dots in the upper-right corner, find IMU normal under Safety.

Step 4 Tap on ‘Calibrate’ to start the process.

Step 5 Press Start on the screen and follow the on-screen steps and move your drone into the positions it prompts you to finish the IMU calibration.

Once you’re finished. Take your drone to an area with high interference and see how it flies. If all is well then your IMU calibration has been a success!

 

Why Do You Need to Calibrate the IMU?

Drones can be a huge investment of your time and money, so you want to ensure that you’re looking after it correctly and giving it the appropriate care.

Calibrating the IMU allows you to set standards for the drone and fly it safely with minimal accidents. By correctly calibrating the IMU, you can reduce errors caused by inaccurate sensor measurements and therefore prevent drone crashes.

It’ll also make a big difference in terms of the performance of the drone. You’ll likely notice that it will fly better and behave better in sub-optimal conditions, like when it’s windy for example.

 

How Long Does IMU Calibration Take?

IMU calibration is a fairly quick process. It takes around 5 to 10 minutes to complete depending on the brand of the drone. However, if you’re eager to fly your drone once you’re out and about we recommend re-calibrating before you set off on your trip so you’re not sat, waiting around, wasting precious battery life.

 

Do I Have to Re-Calibrate My Drone Every Time I Use It?

In short, no. it’s not necessary to recalibrate the IMU on your drone before each flight. Having said that, if you do want to do this, it shouldn’t damage the drone in any way.

 

So, When Should I Calibrate My Drone’s IMU?

DJI isn’t too clear about how often you should calibrate the IMU in their manuals. However, it’s always a good idea to pay attention to signs that it may need calibration whilst you’re flying it.

If the drone is leaning to one side when hovering, this is a sign that things could be out of whack. Other times, the app will just give you a notification. Nevertheless, we recommend recalibrating your IMU in the following situations:

We recommend calibrating your IMU the first time you open/use the drone. DJI doesn’t say that this is necessary, but it will ensure that you get off to a good start flying your drone.

Anytime that you are flying your drone in a new location or environment. This means that if you travel to another part of the country, or even overseas, you should consider recalibration.

Anytime when you’re flying the drone outside a 50km radius from the last place you flew it is good practice. Flights can majorly interfere with a drone’s components so I always check my IMU’s status and recalibrate after flying.

Just like you should re-calibrate if you change locations, you should also calibrate your IMU every time you change elevation. 1000ft increments work best.

If you get a compass interference warning in the app.

If you have a Mavic drone and notice the drone starts blinking yellow and red lights when you’re trying to start it up, it likely needs a recalibration.

If you’ve had a crash. Anytime you have an accident with your drone, a full recalibration will ensure that everything flies as it should; as long as there’s no physical damage to the drone that is. In these situations, we recommend exercising caution on your first flight after take off. Just to make sure everything is OK.

 

How to check the IMU status on your drone

Normally, if your drone has an IMU problem, you will be prompted a message when you try to fly your drone.

If you’re wondering what the status of your IMU is, you can check this on the DJI Fly, DJI Go 4, or DJI GO App.

Go to the main controller settings, then advanced settings, then sensors. You’ll see with both the gyroscope bias and the accelerometer bias, alongside a reading in bar format. Excellent will show as green 3 bars, goodwill be 2 yellow bars, and bad will show 1 red bar.

Usually, if there are red/yellow ratings, the drone will prompt you to do an IMU calibration, even if you’re not in the settings at the time.

 

Conclusion: Is IMU Calibration Essential?

So, as we’ve established, the IMU is an integral part of your drone’s functionality and calibration is an essential process. Sadly, many drone pilots don’t do it, or worse, don’t know what it is.

We hope this article has helped to educate you on the importance of IMU calibration and how easy it actually is. If you have any other tips for calibrating your IMU, we’d love to know. Have you ever had any issues mid-flight? Do you bother to remove the props?

Let us know in the comments below and remember, calibrate often, in open spaces, with zero interference.

 

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How to Calibrate a DJI Drone’ IMU, Compass and Gimbal?