Question on taking off from Building Roof and Magnetic Interference

[gregw]

I just did a flight today, taking off from the roof of a high rise building... I placed the Mavic on the floor of the building and turned it on, I get magnetic interference and the GPS will not lock, and the controller asks me to check the app. Looking at the app, it asks me to calibrate the compass... Luckily, since I know that this is not the proper environment to calibrate, I DID NOT do a compass calibration. During my last flight from a beach, I checked my compass and IMU calibration, it was all green, so I knew my Mavic didn't have any calibration issues.. I assume the magnetic interference is due to all the metal on the roof of the building.

I then turned off the Mavic, put it on the ledge of the wall running around the building, about 4 feet from the floor, carefully holding on the Mavic, turned it on... After IMU initialised, it gave me a green GPS lock with ready to take off... I then put the Mavic back on the floor of the building and immediately get a magnetic interference signal again, but this time, I still had GPS lock, and still ready to take off.

I did take off, and the Mavic had a perfect flight... No issues at all... However, once landed, the magnetic interference message happens again.

My questions regarding such a flight are these:
1. How safe is it to do what I did? e.g. Initialise the IMU away from metal, but take off with magnetic interference? Should I have launched by hand instead?
2. Will the metal in such an environment screw around with the compass calibration even if you DO NOT calibrate it?
3. What is the proper procedure to startup a DJI aircraft in such an environment?

 

[Random155]

I don't have answers to your questions but in your situation I would have hand and launched and hand catch. Maybe you were right above the elevator area? Next time try a different area of the roof to see what happens. On a side note, I put my Mavic on the hood of my truck (truck off) for a minute to tune my settings and I got the strong magnetic field message. This things hates to be near metal, which is a little concerning to me.

 

[gregw]

I don't have answers to your questions but in your situation I would have hand and launched and hand catch. Maybe you were right above the elevator area? Next time try a different area of the roof to see what happens. On a side note, I put my Mavic on the hood of my truck (truck off) for a minute to tune my settings and I got the strong magnetic field message. This things hates to be near metal, which is a little concerning to me.

This is a 30 storey high rise, and I was on the roof of the penthouse apartment... So, the building has lots of metal since it has to hold up the entire building... The Mavic is my first DJI aircraft, so I'm not sure what is the correct procedure to startup in such an environment, but I'm pretty sure I'm not the first one to try flying from such a location..

 

[Kilrah]

Same, I'd had hand launched/caught so that the warning is not present. BUT without being sure of what's best, since depending on how the logic works under the hood it could actually be better to have the warning and be sure it doesn't use that data as it knows it's invalid...

Since we don't know how it works we can't evaluate the risk, so the only "proper" procedure is probably simply not to fly from such a place. Up to everyone to gamble beyond that.

 

[msinger]

Will the metal in such an environment screw around with the compass calibration even if you DO NOT calibrate it?

It's not guaranteed to screw around with it, but it could. Play it safe and keep your Mavic away from all magnetic metal objects.

What is the proper procedure to startup a DJI aircraft in such an environment?

If you must fly in this environment, then it would be best to either hand launch or launch from some type of platform that is not made of magnetic metal.

 

[seanmclean]

Proper procedure if you have a good calibration is just to put it down and launch it. You'll have wonky readings on the ground, as soon as it's airborne it will be fine. Nothing to worry about.

 

[CAPTAINDRONE]

I just did a flight today, taking off from the roof of a high rise building... I placed the Mavic on the floor of the building and turned it on, I get magnetic interference and the GPS will not lock, and the controller asks me to check the app. Looking at the app, it asks me to calibrate the compass... Luckily, since I know that this is not the proper environment to calibrate, I DID NOT do a compass calibration. During my last flight from a beach, I checked my compass and IMU calibration, it was all green, so I knew my Mavic didn't have any calibration issues.. I assume the magnetic interference is due to all the metal on the roof of the building.

I then turned off the Mavic, put it on the ledge of the wall running around the building, about 4 feet from the floor, carefully holding on the Mavic, turned it on... After IMU initialised, it gave me a green GPS lock with ready to take off... I then put the Mavic back on the floor of the building and immediately get a magnetic interference signal again, but this time, I still had GPS lock, and still ready to take off.

I did take off, and the Mavic had a perfect flight... No issues at all... However, once landed, the magnetic interference message happens again.

My questions regarding such a flight are these:
1. How safe is it to do what I did? e.g. Initialise the IMU away from metal, but take off with magnetic interference? Should I have launched by hand instead?
2. Will the metal in such an environment screw around with the compass calibration even if you DO NOT calibrate it?
3. What is the proper procedure to startup a DJI aircraft in such an environment?

No issue. Some new pilots to DJI Phantoms/Mavics/Inspires will place their drones on their car and receive the message you received. Moving it a few feet away from the car removes the warning. No harm done to the drone.

 

[fakbik]

So the interference warning thing is something I get in certain environments. If I take off despite the errors and maneuver it manually to an area with less interference I tend to not have the issue at all.

However there are two possible resulting issues I've found.

1)If you're in an urban or industrial area, there tends to be more than one pocket of interference, LOS is really important to avoid harming your drone or someone else.

2) once in a while, the interference zone is larger than you bargained for and when the unexpected comes along, it makes it all the harder to fly safely.


Sent from my iPhone using MavicPilots

 

[gregw]

So the interference warning thing is something I get in certain environments. If I take off despite the errors and maneuver it manually to an area with less interference I tend to not have the issue at all.

However there are two possible resulting issues I've found.

1)If you're in an urban or industrial area, there tends to be more than one pocket of interference, LOS is really important to avoid harming your drone or someone else.

2) once in a while, the interference zone is larger than you bargained for and when the unexpected comes along, it makes it all the harder to fly safely.


Sent from my iPhone using MavicPilots

Line of sight is vitally important in an urban environment. However, I was actually flying on the edge of the urban area, and aside from 9 tall blocks of 30 storey apartment buildings, there were only low rise village buildings (3 storey high), a mountain range in one direction, and the sea in the other direction. So, aside from the metal on the roof, and whatever wifi was in the apartments, there wasn't much noise in the environment... Once away from the roof, the Mavic performed perfectly.

I just turned on my Mavic at home to check the sensor calibrations to see if there was any impact from my last flight, and everything is green. So, taking off and landing from magnetic interference doesn't seem to affect the compass calibration.

I think next time, I will simply hand launch and catch in such situations. It doesn't take much distance to get away from interference from metal in the floor..

 

[mightydiesel]

Gregw- About a month ago I almost lost my Mavic2 by ignoring those messages "magnetic interference and the GPS will not lock, calibrate compass" I was on the 22nd floor of a hotel and I just wanted a flyaway shot from the balcony. The done flew back and then it took off( "fly away" and the drone was unresponsive to the controllers commands) around the building avoiding the building and then set it's home point a block away. I ran to the elevator and thank God it was a fast elevator and tried to reconnect the drone and the controller. For the longest 13 minutes of my life fearing the drone would crash into a building or fall and hurt someone or property. I was unable to get a correct location on my iPhone. With a stroke of luck and the grace of God I found the drone and the battery in some bushes.
I have taken off with that message in Panama on a rooftop because I knew it was a false message and the drone flew flawlessly. I do recommend never to fly until your drone has initiated a home point and without a compass error message.

 

[Meta4]

There's plenty of very bad advice in this thread.
If your compass is warning you of a magnetic influence (like a steel roof), no amount of calibrating the compass will "fix" the problem.
If you understood what compass calibration actually does, you'd also understand that it doesn't fix problems.
The only solution is to move your drone away from that problem.
Launching from a steel or reinforced concrete surface has been responsible for the loss of many drones.

 

[mightydiesel]

Basically this is what happens when your compass is not calibrated. Copy the youtube link.