To those who are saying they calibrate the compass every time, please read this:
http://www.phantompilots.com/threads/compass-calibration-a-complete-primer.32829/
A faulty calibration can be a source of a flyaway or unexplained behaviour, and calibration is not necessary unless you have travelled at least a hundred miles from the site of your last calibration.
Interesting and very important topic.
I read that thread and it seems to make sense but a few things leave me confused.
The DJI manual for MY Phantom says this....
7. GPS & Compass Calibration
If the Compass Module is not used, you can skip this step.
The GPS module has a built-in magnetic field sensor for measuring the geomagnetic field, which is not the same indifferent areas. The GPS module will not work unless the Compass Module has been connected. Make sure theCompass Module connections are correct.
Please always keep the compass module away from the magnet. If this situation occurs please change the compass module before flying. Otherwise it may damage the compass module and lead the aircraft to work abnormally or evenbe out of control.
Calibrate the compass before the first flight or when flying in a different area.
Maybe it's in the Chenglish translation?
I took that to mean "First Flight of the Day"....because surely they don't mean ONLY before the first flight ever, then no more except if you move 100 miles or more away? Or do they?
Maybe I interpreted it wrong.
In the Phantom 2 manual it says....
Please carry out the calibrating procedures in the flight field before flight.
Again, they don't specifically say if they mean only the first flight after purchase or the first flight of the day at the field.
I really can't see how the 100 mile thing could be accurate given the DJI manual says the calibration can require changing due to things as simple as metal in the ground.
I am going to contact a well known compass manufacturer and pose some of these questions.
On the other hand, I can see how you could potentially botch a compass calibration in the field and without connecting to the assistant and checking the mod values, you won't know if it's within specs.
I guess if you were to go through enough threads where flyaways occurred and determine how many occurred without calibration and how many after calibration you might get a more accurate picture?
Let's note that in this thread....
The OP of THIS thread DID NOT do a calibration before the flight in question...and had a flyaway. Perhaps it would not have if he had done one? Hard to say.
Hopefully going to get some answers and maybe a better end to this.
