Mirek6
First Officer
Flight distance : 609724 ft
Canada
Offline
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Hey Jetto Black,
You said - "I never calibrated compass or IMU because I was never prompted (following advice on this forum).
Yes - frequent and unnecessary calibration may do more damage than help, especially if there is no reason for calibration. However, I would always advise new drone owners to calibrate compass and IMU before they fly it for the first time. Compass and IMU is calibrated in factory back in China, but if you fly on the other side of the world, magnetic declination in your place versus place of origin may be significant. This is why the forum also advises to calibrate compass when you move large distances between flights (several hundred kilometres).
Also, calibration of IMU may have gotten skewed in transport.
Having said that, and seeing what you went through, I believe that DJI software did not respond correctly to uncalibrated Compass and/or IMU and should have given you a warning. So no error on your part but just missed precautions.
Behaviour of your Spark is consistent with compass and/or IMU errors and/or, perhaps, losing satellite connection. Spark relies on ideal sync between what compass says and what IMU says. It also relies on GPS co-ordinates and compares all three together. If something is inconsistent, Spark switches to ATTI mode to avoid trouble since it cannot reconcile conflicting data. If it drops to ATTI and stays there, situation is not bad - you can fly manually. If it starts rapidly switching between GPS and ATTI for whatever reason, you are in trouble. As soon as it gets to GPS mode, it may recalculate its position and figure that it should be adjusted - so it moves. While moving it figures that compass is wrong so it drops to ATTI again. Than, for whatever reason figures all is OK and switches to GPS and the dance begins. Google "toilet bowl effect" so you will understand what I am talking about. Spark avoids toilet bowl effect by switching to ATTI and staying there unless it is absolutely sure that it can reliably switch to GPS again.
In my view - and to be confirmed by DJI Support - cause of your problem was lack of compass and IMU calibration. This still leaves question to DJI why Spark did not give you warning about that.
If Spark did not warn you about calibration because compass and IMU was calibrated fine, I see a hardware of firmware issue which should be fixed by DJI. Spark should never switch back and forth between GPS and ATTI willi-nilly because it makes it very hard to control.
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