Aluminum

[Dome]

@taroh is right.
Take it easy: IMU doesn't have nothing to do with aluminium in any way. Accelerometers and gyroscopes AREN'T sensible to metals, they are MEMS (mechanical). Just keep away from magnets (aluminium is not magnetic). IMU need flat and leveled plane surface and temperature must be the one of you bird just switched on, not after a flight or when p3 is hot for any reason.
BUT I don't really know what kind of IMU is using DJI, because many IMU has magnetic field sensors of 3 DOF (X,Y,Z) inside!
Anyway, compass dance is relative to a separate DJI sensor in any case, and DON'T calibrate it on a aluminium table (or tinny place), because it is conductive and can deflect earth field!
Just to explain, the problem is not the magnetic effect, but tinny surfaces deflect and modify the earth magnetic field, that's why compass can get poor calibrated.

COMPASS sensor:

GOOD:

BAD:

NOISE:

 

[Gary E]

...Don't take off on your car hood, car roof, or pickup beds, or side walks-- they have rebar and/or wire mesh...

Sidewalks. Depends on the state your in. In Oregon, the rule is NO rebar or screen/mesh in sidewalks or driveway approaches. Only concrete is allowed. As a result, I have launched from sidewalks a lot with no issues.

 

[BlackHawk388]

For those asking about the compass being incorporated into the IMU.

Does the bird not rely on every system to allow itself to remain stable in flight hover with hands off the sticks?

 

[bobmyers]

Sidewalks. Depends on the state your in. In Oregon, the rule is NO rebar or screen/mesh in sidewalks or driveway approaches. Only concrete is allowed. As a result, I have launched from sidewalks a lot with no issues.

Well, yes, but you wont know, because you cant see the rebar or wire-- in San Antonio, it is guaranteed.

 

[acherman]

Sidewalks. Depends on the state your in. In Oregon, the rule is NO rebar or screen/mesh in sidewalks or driveway approaches. Only concrete is allowed. As a result, I have launched from sidewalks a lot with no issues.

Any idea why that's the rule? Just curious. I feel like there would be a lot of crumbling sidewalks. Haha I take off from the sidewalk around my house all time, and others. I wouldn't do a compass calibration on them though. [emoji6]

 

[bobmyers]

Any idea why that's the rule? Just curious. I feel like there would be a lot of crumbling sidewalks. Haha I take off from the sidewalk around my house all time, and others. I wouldn't do a compass calibration on them though. [emoji6]

unfortunately, none of these causes are set in stone-- May not happen but there is always a chance if that compass is near or directly over the metal. Wire mess in sidewalks may be on the bottom of the concrete, because the workmen failed to pull it up when they poured the concrete.. In that case, probably would not be an issue-- but if they did pulled it up closer to the surface of the concrete, it then could become an issue... you just have no way of knowing, except that it is a common concrete construction practice to place wire mesh in concrete sidewalks and drive ways for reinforcement. "If the water is clear and looks good to drink, it may be contaminated."

 

[acherman]

I have taken off from plenty of metal or metal containing surfaces. I get a compass error while on the surface, but once you take off and are 5' above it there is no issue. The magnetic field disturbances drop significantly as you move away from these objects, even just a foot or two.

 

[bobmyers]

I have taken off from plenty of metal or metal containing surfaces. I get a compass error while on the surface, but once you take off and are 5' above it there is no issue. The magnetic field disturbances drop significantly as you move away from these objects, even just a foot or two.

If it's working for you -- just keep doing it-- if it stops working and it does cause a compass issue and you crash, then I guess you can still make up your own mine if you want to continue. I had some issues with mine after I ignored the compass error, so I just don't take off or land anywhere near ferrous metal or surfaces that could contain ferrous metal.


Cheers

 

[acherman]

unfortunately, none of these causes are set in stone-- May not happen but there is always a chance if that compass is near or directly over the metal. Wire mess in sidewalks may be on the bottom of the concrete, because the workmen failed to pull it up when they poured the concrete.. In that case, probably would not be an issue-- but if they did pulled it up closer to the surface of the concrete, it then could become an issue... you just have no way of knowing, except that it is a common concrete construction practice to place wire mesh in concrete sidewalks and drive ways for reinforcement. "If the water is clear and looks good to drink, it may be contaminated."

I was confused by this. I know sidewalks and most concrete have some sort of steel reinforcement in it - (I have done plenty of concrete and construction work in my time) and its effects on a compass. I was curious as to why @Gary E said the rule in Oregon was to NOT use any reinforcing. Seems like a strange rule/code.

I suppose better safe than sorry in some cases. I believe that as long as you have a good compass calibration from somewhere, then the compass activity doesn't matter while the P3 is on the ground, in the air is different. Some people also choose to calibrate the compass before every flight.

 

[Dome]

I have taken off from plenty of metal or metal containing surfaces. I get a compass error while on the surface, but once you take off and are 5' above it there is no issue. The magnetic field disturbances drop significantly as you move away from these objects, even just a foot or two.

Yes, this is the way it works. Often is enough 1mt distance to avoid disturbance. But the worst problem can arise flying in the mountains, where you can face ferrous stones or veins inside and compass can act weird also at distance. I got scared more than once...

 

[scottoftheforest]

I didn't know about this last summer with an invite to go out on a 70' boat for a couple of days with a huge open upper deck- perfect place to take off and land and get shots of the gorgeous scenery.

When I tried to take off the P2 just tipped over. Yes the boat was a welded aluminum craft. Flight deck closed... ...hate hard lessons.

 

[n4uxy]

I purchased a roll up aluminum table to use out in the field. Since it is not a ferrous metal can i calibrate my IMU on it?

jv

Simple set a compass on the table if it changes heading then you know it's affecting the IMU. the legs on the table might not be aluminum. My boat has a compass and guess what it is made of , yep

 

[ianwood]

I don't believe the compass has anything to do with the IMU calibration but without input from DJI, there's no way to be sure. I don't think there would be an issue calibrating the IMU on a sheet of aluminum.

But, depending on the type and mix, it can have a weak impact on the compass due to passive interference (magnetic permeability) so I would think twice about calibrating the compass near it. Unless you know the exact metal type, your best bet is to use wood, plastic or just plain old dirt/grass for the compass calibration.

P.S. The only reason the compass is physically separated from the other IMU sensors is the multitude of systems that can interfere with it. It is tightly coupled with those sensors to do all the AHRS (attitude and heading reference system) functions.

 

[mfr1340]

I use a piece of 1 1/2" X 4' block styrofoam insulation (from Home Depot) for $5.00. It has a aluminum on one side and is white on the other side. I made one piece that is 2' x 2' and I set it on my foldable trailer that I use to bring all my stuff out to the middle of the field. It makes a great table. Then I made a round one to use as a take off and landing pad. But it was too light and would start to lift up a little bit when I was above it hovering to line up for setting it down. So I added some long nails (8"X1/8") and stuck them into the styrofoam. Then I put a ring of Duck Tape Around the outside, and its just right now. It is so easy to land, just take your time. It just hovers and you can make 1" moves.
With 13 flights and 25 landings I have no stress cracks and no close calls. I still have 17 more short (30% batt usage each flight) Flights to do to do the proper break in process that they say you should do. (10 for 10) and I have 3 batteries.
As far as filming I just start the recorder before I lift off and stop when I land. That way I'm not thinking about the filming. My last one was pretty good. It was 8.2 minutes long and you learn a lot each time you fly.
And I treat it like a &1,300.00 toy, with respect. I watched hundreds of videos on u tube while waiting for it to arrive.
I also got the special signal booster for the antenna and I don't worry about the signal cutting out, the signal is supper strong.

 

[Daniel Voyer]

I'm driving in a long grassy field with my car and decide to use my car's trunk carpet. Compass Error message (with a help message). After investigating a few minutes, noticed the platform had aluminium or metal structure in it. Minimal it is, it still had too much in it for the bird to take off.

 

[Gary E]

Any idea why that's the rule? Just curious. I feel like there would be a lot of crumbling sidewalks. Haha I take off from the sidewalk around my house all time, and others. I wouldn't do a compass calibration on them though. [emoji6]

...it is a common concrete construction practice to place wire mesh in concrete sidewalks and drive ways for reinforcement....

I was confused by this. I know sidewalks and most concrete have some sort of steel reinforcement in it - (I have done plenty of concrete and construction work in my time) and its effects on a compass. I was curious as to why @Gary E said the rule in Oregon was to NOT use any reinforcing. Seems like a strange rule/code...

Not stange at all. Here the property line ends at the owners side of the sidewalk. Even the though the property owner is required to maintain there portion of the sidewalk, as well as the driveway approach from the street and the landscape strip (if there is one) between the the sidewalk and the curb, those portions of land are part of the city rightway. There are usually underground utilities in those areas. For ease of access to their property, as well as to private and public utility company lines, no rebar, mesh, or screen for concrete reinforcement is allowed. Curbs and driveways, side walks and retaining walls, etc. on your property, knock yourself out with reinforcement.

 

[acherman]

Not strange at all. Here the property line ends at the owners side of the sidewalk. Even the though the property owner is required to maintain there portion of the sidewalk, as well as the driveway approach from the street and the landscape strip (if there is one) between the the sidewalk and the curb, those portions of land are part of the city rightway. There are usually underground utilities in those areas. For ease of access to their property, as well as to private and public utility company lines, no rebar, mesh, or screen for concrete reinforcement is allowed. Curbs and driveways, side walks and retaining walls, etc. on your property, knock yourself out with reinforcement.

We have such harsh winters and temp swings that without reinforcement the concrete would be cracking and crumbling after 1-2 years. Typically they have utility right of ways a couple of meters in from sidewalks - for example, the gas company is digging up my front yard this week to tie into a gas main for a new development across the street. A few months ago they were horizontal drilling along the side of my house (corner lot) for fiber to the house, all without touching the sidewalks.

 

[Gary E]

We have such harsh winters and temp swings that without reinforcement the concrete would be cracking and crumbling after 1-2 years. Typically they have utility right of ways a couple of meters in from sidewalks - for example, the gas company is digging up my front yard this week to tie into a gas main for a new development across the street. A few months ago they were horizontal drilling along the side of my house (corner lot) for fiber to the house, all without touching the sidewalks.

They have that here too. Some utilities are in from the sidewalks. They like diging up yards; easy work.

No doubt it's not near as cold here as your location, latitude 42 20' here, but we do get winter temperatures in the teens (F) and summers over 100 (F). It was 108 (F) here a couple of days ago. Concrete sidewalks here do fine in those temperatures. Concrete will crack and crumble with or without reinformencement. All of the concrete cracks I have here are all in areas with reinforcement. No sidewalk or driveway approach cracks at all (non-reinforcement areas). I use those areas to launch, but land anywhere.