Fly w/o compass calibration?

[natgild]

This morning my Mavic Mini called for a compass calibration. I had to do it 3 times to complete, possibly because of rebar in the cement bridge I was standing on?? By the time I completed it, my intended subject had moved on and I missed my shot. Can I fly without doing the compass calibration? What is the risk/downside? What functionality will be missing?

Nat

 

[PhantomFandom]

This morning my Mavic Mini called for a compass calibration. I had to do it 3 times to complete, possibly because of rebar in the cement bridge I was standing on?? By the time I completed it, my intended subject had moved on and I missed my shot. Can I fly without doing the compass calibration? What is the risk/downside? What functionality will be missing?

Nat

I believe you were very fortunate that the subject moved on and you missed the shot. The rebar in the road surface can definitely affect the compass. In such cases no number of compass calibrations will help you have a safe flight. In fact calibrating it can actually make it worse.

Taking off from a surface that causes compass interference will most likely lead to a mid-air issue which many refer to as a "fly-away". Always calibrate your drone away from any metallic objects and always launch from a surface that is non-metallic and not close to any other metallic objects.

 

[Meta4]

This morning my Mavic Mini called for a compass calibration. I had to do it 3 times to complete, possibly because of rebar in the cement bridge I was standing on??

The wording of DJI's warning is very poor.
Your drone was not asking for the compass to be calibrated at all.
Your compass was working properly but warning you of a magnetic problem with the spot where you had put it.
That you had problems calibrating there, was a further warning.

The proper action would have been to power off and move away from the problem the compass was warning you about.
Launching from steel and reinforced concrete surfaces is asking for trouble.

 

[Dakarenduro]

Hand launch

 

[AMRE2ME2]

Hand launch

Hand launching will not fix the magnetic interference and is just asking for problems.

 

[Meta4]

Hand launching will not fix the magnetic interference and is just asking for problems.

How?
Actually hand launching would probably provide enough distance between the compass and the source of the magnetic interference.

 

[AMRE2ME2]

Simple, If your Compass is warning you that it needs calibration, there’s a problem. The only way to fix the interference is to move farther away.

 

[Meta4]

Simple, If your Compass is warning you that it needs calibration, there’s a problem. The only way to fix the interference is to move farther away.

And hand launching would easily be moving far enough away from reinforcing steel in a concrete structure.
Read post #3 .. It's all in there.

 

[AMRE2ME2]

My point is that just saying “hand launch” will fix the interference is not always accurate. If your app is telling you to calibrate the compass, you still have interference. It’s certainly possible to still have interference when hand launching. There’s been plenty of folks that have had interference because they had a watch on.

 

[Dakarenduro]

OK, I didn't mean to cause any debate. And was getting ready to ask if the 5-6ft distance would be enough to eliminate the interface when I saw Meta4 reply, so great. Now I know (I haven't had this problem myself).

So would this be an accurate way to try if faced with the OP situation (and since the messages in the app are not very clear):

1. Attempt to launch from ground with rebar, receive the compass calibrate error/msg. (If you know you havent moved more than 50 miles from last flight and it hasn't been over 30 days idle, assume the message is interference and not a calibration request)
2. Power down AC, hold it at hand launch height and power back on.
3. If no warning msgs, hand launch and fly.

If there is a continued warning message then it might be an actual calibration required scenario?

 

[AMRE2ME2]

Yes, you are correct.

 

[Dave Maine]

Compass problems are likely to end up fatally for your drone, as multiplecposts here have established. Using raw distance estimates are not valid for assuming what is safe. Magnetic field strength is unknown, and may have effect for many feet. Change takeoff location is the only safe alternative. It is not a drone problem. It is the nature of the physics involved.

 

[DougMcC]

Interesting. For well over a year I have launched from the street in front of my house 3 feet from a manhole cover and 5 feet from my Jeep. Rarely have I been asked to recalibrate my compass nor have there been any flight mishaps. Flying a MP 2. I do regular surveillance of illegal “urban campers” (Californnia PC term) on a 20 acre open space behind our property. My own little census to pass to city council.

 

[Dakarenduro]

certainly keep using that spot and don't try it from on top of the manhole!!

 

[boblui]

1. Attempt to launch from ground with rebar, receive the compass calibrate error/msg. (If you know you havent moved more than 50 miles from last flight and it hasn't been over 30 days idle, assume the message is interference and not a calibration request)
2. Power down AC, hold it at hand launch height and power back on.
3. If no warning msgs, hand launch and fly.

Correct but in (3), you can actually put it back onto the ground. yes, back into the magnetic interference and launch within 3 minutes. After that, the drone will ask you to re-calibrate.

 

[NLOL]

OP wants to know what problems he might encounter gluing with a compass problem. I'd like to know too - flying with visual sight on ac, and good (or not) GPS lock, I dont see why the compass is important. What is the risk?

 

[PhantomFandom]

I dont see why the compass is important. What is the risk?

It's not just important. It is VITAL.

If I put you in the woods and told you that you can find your way out by heading 100 yards at a heading of 38 degrees, you could likely find your way out correct? What if I asked you to do the same with a blindfold on?

The drone is able to adjust its heading by having an accurate compass reading. If the compass is incorrect (i.e. the compass does not agree with the IMU) then the drone gets completely confused and cannot fly properly. You will most likely lose the drone.

 

[sdold]

I used to do a lot of surveying, and was surprised at how much buildings and steel structures could swing the compass on the transit. Once it was off by about 45 degrees when I was about eight feet from a small concrete block building, so I can imagine problems form nearby rebar and other structures even when hand launching.

 

[Flycaster]

When the compass (es) do not agree with the GPS, once aquired, there is usually a flight incident....

 

[boblui]

OP wants to know what problems he might encounter gluing with a compass problem. I'd like to know too - flying with visual sight on ac, and good (or not) GPS lock, I dont see why the compass is important. What is the risk?

This is the result when the compass ( more accurately, the yaw sensor ) of my Mini was off by about 180 degree. With no stick inputs, the craft accelerated by itself and hit my balcony at full speed :

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