Compass calibration issue in port

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My company owns a Phantom 4 Pro V2 for surveying its inventory, recently I was surveying our pile in Port Newark and ran into an issue where I could not keep the compass calibrated. When I first booted the drone up, I had to calibrate the compass as I normally do, I would then do a quick test hover using the DJI app. Typically after that, I would land, launch map pilot pro and it will survey the site. However when I landed the compass would be out of calibration. It went on like this multiple times. Eventually, I got it to hold a calibration, launched the drone on the map pilot route but multiple times it lost compass calibration and I needed to manually override and land it. I couldn't get it to keep a calibration prior to the expiration of my LAANC with Newark ATC and couldn't complete my survey of the site.

I am assuming the issue is the fact Port Newark is a huge container port, would that cause all the interference? We operate in other ports with metal structures, cranes etc but this was by far and away the most containers I operated around.

Screenshot 2024-02-02 112150.png


See attached for the site I as trying to survey. As you can see there are a lot of containers, cranes and other metal objects in the area. I requested the LAANC up to 250ft (76.2 meters), should I try to fly higher so there is less interference or is this site just a no go with that much material around? TIA.
 
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When I first booted the drone up, I had to calibrate the compass as I normally do
There are two reasons that this is ringing alarm bells for me.
There is no need to recalibrate the compass before a flight.
That you are, indicates a poor understanding of what compass calibration actually does (and doesn't do), and when it might be needed (almost never).

There was nothing wrong with your compass and recalibrating it wasn't going to solve the problem.
Your compass was warning you that you had placed the drone close to a source of magnetic interference and to start up there could cause problems.

If you startup and see a message suggesting you should recalibrate the compass, you probably shouldn't.
DJI's warning message is poorly worded and confuses everyone.
It also moves across the screen so you can't see it all at once.
Here's what looks like:
i-5CPNRw6-M.png


It says Move aircraft or calibrate compass.
But most people only notice the calibrate compass part.
That's unfortunate because the problem that's caused it has nothing to do with the compass (which is perfect) and recalibrating won't do anything to fix the problem.
In that screenshot, I placed the drone on my car roof, which puts the compass sensors in the legs, very close to the steel of the car.
The compass senses a magnetic field significantly stronger than the normal field of the earth and so gives the warning.
The fix is to turn the drone off, move away from the magnetic interference and start again.


I am assuming the issue is the fact Port Newark is a huge container port, would that cause all the interference?
Probably not.
The problem was probably much smaller and closer to the drone.
Where were you trying to launch from?
What steel objects were close by (including hidden steel underground or in reinforced concrete?)

As you can see there are a lot of containers, cranes and other metal objects in the area. I requested the LAANC up to 250ft (76.2 meters), should I try to fly higher so there is less interference or is this site just a no go with that much material around? TIA.
At 200 ft, no amount of steel on the ground is going to cause a problem, so there's no need to fly higher.

What's needed is a better understanding of compass calibration.
There has been confusion and misunderstanding around the drone's compass for years.
DJI has contributed to this with misleading information in their manuals and error messages.

The drone comes from the factory already calibrates and there is no need to recalibrate.
I've flown for 8 years without recalibrating.
Compass calibration has nothing to do with the environment you fly in and magnetic influences outside the drone.
It's all about the drone itself and the magnetic influences that are part of the drone.
You calibrate the compass so the flight controller knows what magnetic fields belong to the drone, so it can ignore them and focus on the earth's magnetic field.

The topic is complicated and I've only touched on it.
The excellent first post in this thread, explains what you need to know about the compass and calibration.
Come back and ask if you need more information after reading that.
 
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This is exactly what I was looking for, very informative thank you so much. So it appears the fact I turn the drone on nearly every time on a concrete pad is the potential issue. All the terminals are located 50 to a few hundred miles apart and in industrial marine locations. Grass is exceedingly rare, what can I do? Turn it on holding it or put it on a wooden stand or something? 9/10 I turn it on on the ground or on the aluminum tailgate of my truck, both are probably less than ideal. Thank you again. Much appreciate.
 
What Is the white material that’s in two piles in your picture?
Could you use the pile with some sort of landing pad as you launch point?
 
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What Is the white material that’s in two piles in your picture?
Could you use the pile with some sort of landing pad as you launch point?
Correct, half a million short tons of salt. They are angled for drainage and covered when not in use but I can probably carve out a spot. Thanks.
 
So it appears the fact I turn the drone on nearly every time on a concrete pad is the potential issue.

Many drones have been lost because they were powered up on a reinforced concrete surface where hidden steelwork was close enough to the compass sensors to deflect the compass giving it a false reading.
If the magnetic field is stronger than what the drone is expecting, it will bring up a compass warning.
But if the field strength isn't stronger, it can still cause an incorrect compass reading without giving a warning.
The gyro sensor takes its initial heading information from the compass.
When the drone climbs away from the magnetic interference, the compass goes back to reading properly.
But the gyro doesn't and there's now a serious difference between the heading information given by the gyro and compass.
This is the start of a yaw error and it almost always ends badly, with the drone suddenly zooming off sideways at very high speed.

All the terminals are located 50 to a few hundred miles apart and in industrial marine locations. Grass is exceedingly rare, what can I do? Turn it on holding it or put it on a wooden stand or something?
If you have to launch from concrete surfaces, powering up on a plastic box or crate might be a good way to get the compass sensors far enough from any potential magnetic interference.
You can confirm that the compass is reading properly by checking that the drone icon in the map window of the app, is pointing in the same direction as the real drone is.
 
Plastic table? Two feet off the ground usually works for me. Every chunk of concrete i've tried has same effect. Interfered I mean. Asphalt is usually not.

I have a rolling plastic tool box that might be perfect for the job. Throw a section of 3/4 ply on top to give me a bit more space to work and we might be in business.


Many drones have been lost because they were powered up on a reinforced concrete surface where hidden steelwork was close enough to the compass sensors to deflect the compass giving it a false reading.
If the magnetic field is stronger than what the drone is expecting, it will bring up a compass warning.
But if the field strength isn't stronger, it can still cause an incorrect compass reading without giving a warning.
The gyro sensor takes its initial heading information from the compass.
When the drone climbs away from the magnetic interference, the compass goes back to reading properly.
But the gyro doesn't and there's now a serious difference between the heading information given by the gyro and compass.
This is the start of a yaw error and it almost always ends badly, with the drone suddenly zooming off sideways at very high speed.


If you have to launch from concrete surfaces, powering up on a plastic box or crate might be a good way to get the compass sensors far enough from any potential magnetic interference.
You can confirm that the compass is reading properly by checking that the drone icon in the map window of the app, is pointing in the same direction as the real drone is.

Fortunately no gyro issues thus far with this drone, I will give the plastic buffer a try.

Thanks to all.
 
It's a little scary, at first, but have you considered a " hand-launch ".
I have seen photos of scientists gathering shark data off Cape Cod.
They launch from the bow ( from ) of the boat.

On land, when you hold the aircraft by the landing gear, there will be
plenty of distance from potential interference in the ground.
 
@Meta4 stated!
"You can confirm that the compass is reading properly by checking that the drone icon in the map window of the app, is pointing in the same direction as the real drone is."

That is it!
Before you start the motors!

Rod ..
 
@Air Mass,

103?

I tell people you can drive your age, my dad is mine +26, and he has to corvettes, one is a Vader, I have no intention to ever drive it..

Rod ..
 
It's a little scary, at first, but have you considered a " hand-launch ".

On land, when you hold the aircraft by the landing gear, there will be
plenty of distance from potential interference in the ground.
The launch isn't the real problem.
It's where you power up the drone.
That's when the gyro sensor gets its initial values from the compass.
 
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