Hello everyone!
This question might sound stupid, but please indulge me with any clarification needed.
What are the constraints and recommendations for doing a good quality IMU Calibration?
What are your thoughts on the following?:
- Aircraft and battery inserted to be cool (room tempeture) and not powered in the last 5 minutes
- Surface on which the I1 is placed to be at perfectly leveled horizontaly (can we assume floors and planary streets at a good horizontal level?)
- Safe distance from potential interference (what is to be considered an interference? WiFi networks, power lines, big metal fences / structures, running engines,...)
- Aircraft should not be in Travel Mode (should we bring it in Landing Mode before starting the IMU Calibration?)
Please comment on the above points and please add any related concerns as well.
It might be useful to have a similar list for Compass Calibration also, because the more we understand how to best prepare for a flight the less unexpected situations we will have during flight.
Best regards,
Bogdan

Hi Bogdan, sounds good to me so far.

The distance from potential interference is in my understanding important for the compass calibration and not necessarily for the IMU calibration.

So for IMU:
+ check if calibration is necessary
+ Aircraft Shutdown for at least 5 minutes or do IMU cal. when you startup the aircraft (which is the normal way).
+ Leveled (as far as possible in the field)
+ Aircraft in Flight Mode
+ don´t touch or move the aircraft during calibration (important)
+ check values in the app (should be 0.99 to 1.01)

For compass calibration:
+ Best if there are no potential interference like: power lines, concrete with metal, big metal structures, wifi/cellular networks (iphone in your pocket) and keep the remote away while you calibrate
+ take the copter in both hands, straighten your arms (nose front) and turn it around your body axle (leveled) counterclockwise, then bring nose down and turn ccw until lights show successful calibration.
+ check values in the app (should be 1400 - 1500)

Thats it. Never had any issues about that and since the app has the check IMU Button i don´t do the calibration before every flight. Compass is easy and takes 30 secs, so should be done before each flight just for safety reasons - but if the values are in it´s range, there is no need to calibrate (DJI recommends compass cal. after bigger change in position after your last flight position).

Cheers, Christian

In addition seems to be important to not move the remote during IMU calibration.  Doesn't make sense to most of us but apparently the manual says it so better safe than sorry.

Don't have the proof in front of me but someone posted a screenshot on another thread.

Hi Jim, this was an incorrect information and it´s absolutely not necessary to do this - so don´t care about it.
Cheers, Christian

Thank you Christian for your input.
I have been flying a P2V+ for almost 1 year and always had a feeling that the compass calibration is extremely sensitive, even that I did not have to degauss it even once. I have traveled with the P2V+ a few times and besides the known issue with the WiFi module in the P2V+ loosing or stopping to transmit video signal, I had no in-flight issues with the P2V+. I can understand that living in urban areas with a lot of interference (speakers, various electronics and WiFi networks everywhere) may easily de-calibrate a compass. Thus, I have always checked and redo any needed calibration. I had many reasons to upgrade to the Inspire 1 and to tell the truth, everything I wanted in my P2V+ has been offered by I1 when announced (Nov 2014), plus a few features extra. I have replaced the WiFi module in my P2V+ and sold it with all accessories (including a custom made slim travelling case) to a lucky buyer. Since I1 is much more expensive and still difficult to repair due to unavailability of parts (local dealers don't even have spare props), my concerns when flying it are much greater. I am trying to understand and learn everything there is to know about it. I will not be afraid to even ask stupid questions or obvious things, as long as I still have doubts on a subject. All replies are greatly appreciated!

I was under the impress when doing the compass calibration that the craft should not move around you, but you should move around craft? Il it that's not how Christian describes it. His way is easier.

Amazing info you guys!
Jims right on!!  first rule of thumb set craft and remote(TX) down don't touch them during start up is great advice! Especially imu calibration.
Let the craft conduct all it needs to do and only after GPS lock engage the air craft. This was how we all did thnigs with the phantom back in the day ,Old habits

Don't be in a rush to fly . Funny a few times via weather I had to let my phantom sit for several mins before a full sat lock .. Good habit to follow with the inspire.

When calibrating the compass I personally use the counter clock wise move and have never  had any issue to date fingers crossed

Hi Jake, it is much more easier to turn the copter around your body axle instead of turning your body around the copters axle. Technically, there is no difference, cause the magnetic deviation is not measureable within this distance (copter around body, body around copter).

And, you´re right colonel: I always power up my aircraft, than check all my settings, start the engines and wait a little bit to takeoff. After takeoff to about 5 feet i check left/right, front/back and how stable the copter holds it´s position. If everything look fine, let it go... Never had a single problem for more than 30 flights yet.

Makes one proud to know many here have insight and discipline with this beastie.
The crew here is beyond SMART! Lots of great tips and reading here on this forum.
Hats off to all responsible flyers!

Keep on keepin on!

Mike

On the IMU calibration I have actually had to make a platform that I sit on a level surface in order to get my Inspire off of the ground because the concrete drive way and surroundings all have re-bar in them. So I make sure that when at home I am on this 40" high platform to prevent any issues.(No I dont carry this around with me, this is just for use at home) When I am out and about I look for anything not made with sheets of concrete.

However I have a question regarding the compass calibration. There is times I have to re-calibrate the compass up to 3-4 times before a flight (as I do this before EVERY flight) as a extra precaution and I had a couple people ask me which direction I start my rotations for the calibration, specifically they asked if "I'm remembering to start the calibration facing north".   Does this really matter? Just curious as there is no clear answer anywhere that I have been able to find.

PureSQNut Posted at 2015-2-27 04:52
On the IMU calibration I have actually had to make a platform that I sit on a level surface in order ...

Would not have expected re-bar in concrete to have any effect as it should be covered with at least 50mm of concrete cover.

You know I was thinking I was going crazy but then I remember one of the guys at CES that was flying the Inspire in their demo's in their CES booth talking about the challenges they had setting it up in the convention center and there was only one spot in their booth they could calibrate it due to that this one spot had a gap in the rebar.

As soon as I started putting mine ABOVE the ground and not on the concrete it fixed "some", not all of the bugs i was experiencing.

GB44 Posted at 2015-2-27 04:55
Would not have expected re-bar in concrete to have any effect as it should be covered with at leas ...

On another side note I have found deviations in my calibrations if it is done even within a few feet of a fence, car, building, metal, tool box etc. Im sure some people are going to think I am crazy but since I started following these little rules for calibration Ive had FAR less issues and basically non existent issue related to IMU and IMU calibration causes.

Hi PureSQNut, regarding your questions on calibration:
I think, if you have to do the compass calibration sometimes 3-4 times, there must be an huge interference in the proximity of the copter. So choose your position to do the calibration carefully - i always calibrate once and it´s good to go. If you are not sure, check your values in the app, there should be most of the time between 1400-1500.

There is also no rule that you start your calibration facing the copter north - also you can find nothing about that in the manual. Never considered about the direction.

Christian Posted at 2015-2-27 07:04
Hi PureSQNut, regarding your questions on calibration:
I think, if you have to do the compass calibr ...

Thanks,

just curious on that as I've heard it mentioned a couple times. I personally don't see how it would have effect on it.