I FINALLY resolved my non-level horizon issue with my P3 Professional - and the fix has lasted, so far, through three flights at two different locations which intentionally included multiple 360-degree turns in both directions, many camera tilts up and down, and flying with 15-17 mph gusty winds at the second location. The tilted horizon issue was solved - for me - with an extended chilling of the P3 and battery for one hour in my refrigerator followed by an immediate IMU calibration and gimbal auto calibration.  The lens was completely fogged over with condensation during most of the IMU calibration.  But it worked. This was after performing an earlier P3 IMU calibration where I only kept the P3 in the refrigerator for 30 minutes followed by multiple auto gimbal calibrations that did NOT fix the tilted camera horizon.  It is important, I think, to have everything set up - Remote Controller on, linked to mobile device, DJI Pilot app open to camera page, with IMU calibration menu displayed PRIOR TO taking the P3 out of the refrigerator.  Place the P3 on your perfectly level platform (see below for setup I used), turn on the P3 battery, and as soon as the DJI Pilot app shows a live camera view from the P3 (which will be very foggy due to condensation on the cold camera lens), START the IMU calibration.  Ignore any IMU warming up, IMU problem or compass error warning messages during the IMU calibration.  As long as the IMU progress bar percentage is increasing, just be patient.

Please note that during my second IMU calibration attempt, the P3 beeped throughout most of the IMU calibration progress, the camera pointed nearly straight down until the IMU calibration got to 90%, and there were IMU and compass warning messages until the final minute or so of the IMU calibration when the camera suddenly snapped up to a perfectly-level, straight-forward position, the beeping stopped, and the IMU calibration completed (93-100%).  And my camera appeared perfectly level for the first time!  I went ahead and did an auto gimbal calibration and the camera remained level at the end of the gimbal calibration.  YES!  Now that I finally have a level camera horizon (and contrary to my previous practice), I will not be performing any more IMU calibrations after future firmware updates unless I notice IMU sensor value issues or flight instability issues.

I did install firmware upgrade 1.2.6 prior to performing these two IMU calibrations.  But I don't know if the firmware update really had anything to do with the second IMU calibration actually working. I don't know if the strange camera behavior (pointing nearly straight down) and the repeated beeping throughout the IMU calibration are just coincidental or related to finally getting a good level camera at the end of the IMU calibration.  Multiple forum posters have recommeded chilling the P3 - either in your car in front of an A/C vent or in a refrigerator - prior to starting IMU calibration.  I have tried this before, but it didn't resolve my tilted horizon issue throughout multiple flights.  Others have also recommended doing at least two IMU calibrations.  So, I went hard core and chilled my P3 for an hour before the second IMU calibration.  YES - this will result in your camera lens completely fogging over throughout most of the IMU calibration and it will be hard to see anything until nearly the end of the IMU calibration, and possibly for 10 minutes after it is finished.  I was concerned about the fogging, but I was desperate.  I also know it probably wasn't necessary (or even advisable) to chill the battery as well as the P3 because cold temperatures aren't good for lipo batteries.  Well, I forgot to remove the battery before putting the P3 in the refrigerator the second time for an hour, and my second IMU calibration successfully corrected my tilted horizon issue.  Just reporting what FINALLY worked for me.

Finally, to eliminate any possibility of the metal rebar in my home foundation messing up the IMU calibration, I used the following setup as a leveling platform.  I found a perfectly level spot on the wood floor in my foyer. I then inverted a cylindrical all-plastic kitchen trashcan and placed it on the level floor.  Finally, I placed a 2' by 2' wood board on top of the inverted plastic trashcan and checked that the wood was level front-to-back and side-to-side with both a carpenter level and an iPhone level app.  If needed, you could always use sheets of paper under any low side of the trash can to get it perfectly level.  This configuration insures the P3 is at least 30" above any rebar in the concrete foundation.

If this procedure helps anyone else resolve their non-level camera horizon, let me know.  Maybe I just got lucky.  But at least this indicates that for folks that have been having tilted horizon issues for an extended period after multiple IMU calibrations and firmware updates, there may be hope of resolving this problem.  Only time will tell if this FIX is permanent.

Hey, is it still working alright? I have been struggling with the same issue.

Hi, I've same issue. Please can you tell me if the fix is still valid?
What is the temp of your refrigerator..? I mean.. -6 degree Celsius, or -18?
Thank you. I'm struggling over this problem..

"Finally, to eliminate any possibility of the metal rebar in my home foundation messing up the IMU calibration"

You were outrageously thorough in both your actions and your description. Glad you made excellent progress in your quest.

I copied part of your quote about the rebar in your home. I don't think the IMU calibration is affected by metal. The compass - yes - big time! But the function of the IMU is to identify the orientation (whether or not you're level front-to-back and side-to-side) of your Phantom.

To my knowledge, metal has no effect on the action/function of the IMU.

I welcome being corrected if I'm mistaken.

I saw the size of the post and the subject and mentally rolled my eyes. Then I saw who made the post and I read it carefully - your reputation is pretty solid with me. If you told me the sun came up in the west this morning, instead of saying "B,S!" I would go outside and look!! LOL

Happy flying.

Art - N4PJ
Leesburg, FL

aburkefl@gmail. Posted at 2015-12-27 09:11
"Finally, to eliminate any possibility of the metal rebar in my home foundation messing up the IMU c ...

If he drugged you and flew you to Australia, he could appear to be absolutely right!

Same issue here

The main issue that I want to address is that i do not have a gimbal calibration option in my app at all (that I can find) it appears that you are referring to a "DGI Pilot" application that does not exist. I am using "DGI Go" and I assume this has replaced the older version called "DGI Pilot" not sure. This is very confusing for new users and very sad that I am having this problem day one!

I am looking for some guidance as I have tried the above steps except the mentioned that I am unable to find. I don't know what is going on with this thing but I am losing faith in it.

Any advice or clarification will be greatly appreciated. Thanks!