EMI canceling / shielded landing pad?

[Bad Santa]

Your response back in post #5 indicates that you have a very poor understanding of compass calibration does.
The video you just posted has more misinformation.

I'll suggest again that you need to read the first post in the thread I linked to get a proper understanding of what compass calibration actually does and when it might be required (almost never).

The video says that if you move more than 50 miles from the last flight (which I've done 6 times) or more than 1000 feet of elevation (which I've done 4 times) then calibration is recommended.
It's recommended to do it before you get the warning.
I have received the warning.

Both of those seem to counter what you are saying but I understand that you can't change your mind.

 

[Meta4]

The video says that if you move more than 50 miles from the last flight (which I've done 6 times) or more than 1000 feet of elevation (which I've done 4 times) then calibration is recommended.

Your video says those things and they are completely wrong.
Whoever that video guy is, he's not someone you want to pay attention to.

It's recommended to do it before you get the warning.

Recommended by some misinformed video guy who has no idea what he's talking about.

I have received the warning.

And you misinterpreted it.
I explained what your compass was warning you about.

Both of those seem to counter what you are saying but I understand that you can't change your mind.

I can't tell what you are trying to say here.
But I can tell you that you have some screwy ideas about compass calibration and have been fed a load of misinformation.
Now get some factual information and read the first post in the thread I linked.

 

[Starz]

Mine has asked

There are several notices that DJI inserts in their apps that the ignore button is the better remedy. I’ve always thought they were there as a CYA(cover your _ss)item that many manufacturers utilize merely for their benefit. Some of these warnings are somewhat annoying like the one that warns the drone is exceeding the 400 foot limit as I fly up the side of a 6000’ mountain ridge.

 

[waynorth]

I have several Mavic 2 drones. Most of them never asks for compass calibration unless I power up the drone close to iron, and even then the message is wrong. As Meta4 explains, it does not need calibration. You need to shut down the drone and move it to a place further away from iron/metal that can affect the compass.
A better way to check if you are too close to metal is to go into the Go4 menu and find "sensor state". Here you can see if the compass is affected by metal close by. A green bar means the compass is fine, no matter what the on screen message says.
On every startup you should always check that the red arrow (your drone) in the map or radar display always points in the same direction as the nose of your drone. This indicates that the compass is good.

Now, some (not many) Mavic 2 drones has a software glitch that gives the "calibrate compass" message almost every time you turn it on. I have one of them, and it is a false message. I check the sensor state and it is OK. I take off, and it flies perfectly fine.

 

[msinger]

The video says that if you move more than 50 miles from the last flight (which I've done 6 times) or more than 1000 feet of elevation (which I've done 4 times) then calibration is recommended.
It's recommended to do it before you get the warning.
I have received the warning.

These tips will keep you safe:

DJI Mavic Compass Calibration Guide | Mavic Help

Mavic Help is a site for help with DJI Mavic drones. Find the latest fixes, how-tos, guides, accessories, modifications, and more.

www.mavichelp.com

 

[MS Coast]

If the compass is biased by a ma

Thanks all! Great discussion.

I do like the idea of powering up the drone outside the truck and waiting for gps lock, then placing it on the roof / hood / bed. As @KB9Radio mentioned, I've had interference issues from both concrete pads and gravel parking lots, so holding it while powering up should totally work in this situations as well.

For that matter, at that point I suppose I *could* just hand-launch it...as I've been reading thru this thread it occurs to me that I'm more "ok" with hand launching it than I am with hand-catching it. And as was also mentioned, I've not had any interference issues when landing it, and I have actually landed it both on the roof and in the bed with no issues.

So looks like I'm going to try hand launching it and then landing it on / in the truck and see how that goes. I'm still going to get a heavy mat to land on so I don't scratch up my truck, but it won't have to be a "shielded" mat.

If the compass is biased, hand launching won't help.

I don't see any concern about a drone scratching anything when it lands. Never had an issue with my car. Stick a cut down felt furniture pad on each leg if it's a big concern for you.

 

[msinger]

If the compass is biased, hand launching won't help.

The purpose of hand launching is to ensure the compass remains unbiased. When held at should height or above, that's normally high enough to keep it away from all nearby magnetic metal sources.

 

[MS Coast]

The purpose of hand launching is to ensure the compass remains unbiased. When held at should height or above, that's normally high enough to keep it away from all nearby magnetic metal sources.

After the drone has been started without compass bias (by holding it waist high), is it not possible to then place it near ferrous material without an issue? That seems to have been my experience

 

[msinger]

After the drone has been started without compass bias (by holding it waist high), is it not possible to then place it near ferrous material without an issue?

I haven't tested that myself, but I wouldn't chance it when in a location where there's known interference since it's easy to hand launch.

 

[waynorth]

After the drone has been started without compass bias (by holding it waist high), is it not possible to then place it near ferrous material without an issue? That seems to have been my experience

Yes, that is also my experience. Only during startup it needs to be away from metal.

 

[MS Coast]

I haven't tested that myself, but I wouldn't chance it when in a location where there's known interference since it's easy to hand launch.

I tinkered quite a bit with starting a Mini 4 on the hood and roof a car, and near and on top of a large iron spike. Startup seemed to be the critical period with respect to compass bias.

Regardless of the launch location or method, I always confirm that the compass agrees with reality immediately prior to takeoff.

 

[msinger]

Startup seemed to be the critical period with respect to compass bias.

What happens when you place the drone near an area of interference after starting up? Does the compass agree with reality?

 

[MS Coast]

What happens when you place the drone near an area of interference after starting up? Does the compass agree with reality?

Yes. There's a spot on my patio where compass bias occurs if I start the drone sitting on the concrete. If I start it while holding it at waist height and then place it in the same place, there's no issue. I found the same result launching from one location on the car roof.

 

[msinger]

If I start it while holding it at waist height and then place it in the same place, there's no issue.

Good to know! I was thinking the direction might remain skewed until the drone is several feet away from the interference.