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The problem is that magnetic north is not true north and the error varies at different places on the earth. If you want to fly accurately from one point to another, you need to know your position and orientation. GPS will give you an accurate location but not your heading (until you move.) Also the compass is actually a 3d compass. It is measuring the magnetic field in more than one plane. That's why you must rotate the drone about multiple axes. In addition to magnetic north, it is establishing a gravity vector (which way is down.) There are many magnetic sources on the H which are also mapped during calibration. There are magnets in the motors and gimbal as well as fields generated by high currents in the wiring.Ok. I'm not trying to be sarcastic here. I am just trying to understand and learn the need or reason to constantly calibrate the H compass all the time. I was curious so I called Yuneec support a while back to find out what type of compass system the H has. Is it magnetic, electronic or does it use GPS to find it's heading? The tech told me that the H uses a magnetic compass. So my question is if you correctly and successfully calibrate your H compass and you do not add anything to your H that will effect it why would you need to recalibrate it every time you fly or if your location changes by more that 100 miles from your original location? Again, I'm not being sarcastic but do you recalibrate (swing) the magnetic compass on your boat if you go more than 100 miles from your home to marina? If you are a private pilot do you recalibrate (swing) the magnetic or standby compass on the aircraft every time you land at a different airport or state more than 100 miles away? No you don't so why would you have to do it to the magnetic compass in the H? Just trying to understand or learn why?
My first drone was the Q500 that I bought over 2 years ago. I knew nothing about drones and I flew it right out of the box and still to this day I have never done a compass calibration. Even after firmware updates. I have never had any flight issues with it or compass problems at all and it is still flying rock solid till this day.
It seems to be the new firmware causing all these compass problems because that seems to be when they start after the update to the latest firmware. With all the new features and capabilities they designed into the H maybe there is a design issue (EMI) that is causing interferance with the compass system that no amount of calibration will fix or maybe the compass manufacturer has a bad product?
The flight controller merges data from the compass and GPS. As the aircraft moves, a heading can be calculated from the old position to the current one. This heading is compared to the compass data. If they disagree by a large amount, then the aircraft may fly erratically trying to sort it out.
If you have ever flown a quad with an external GPS/compass module, you can easily see the effect of having the compass pointed slightly off.
The other issue with a drone is wind. The flight controller must constantly correct for wind as it moves, so the heading calculated from positional data alone would not match the actual heading of the aircraft.
I am certainly not an expert on the matter, but I do understand that it is more complicated than just a simple compass. I do recalibrate if I travel more than 100 miles. It's easy and just takes a minute. I expect that it is not really necessary in most cases. Perhaps the worst that will happen is that you will have some toilet bowling if there is a difference in magnetic declination.