I have read on this forum about guys who take off their watch when calibrating the compass and avoid all other metal objects.  One guy said he had problems when he used the (steel) tailgate of his pickup truck as a take-off and landing pad.  My question is . . . What if you have an aluminum carrying case?  Can you use it as a take-off and landing pad without interference, because aluminum is not magnetic?

Provided the entire case is aluminum with no ferrous materials like hinges, locks, or lid supports, you should be good to go.

Are you using a case like a Zero Halliburton? If so, the lid supports are steel not aluminum.

gregg1r Posted at 2015-6-6 09:19
Provided the entire case is aluminum with no ferrous materials like hinges, locks, or lid supports,  ...

I want to know how you know sooo much?

Yes... Most aluminum cases have steel or chrome plated magnesium hardware.  

In general... An aluminum case should be OK if the hinge & latch hardware is made from non-ferrous materials.

Also keep in mind that concrete slabs often have steel reinforcing rods that can affect your compass as well.  Asphault typically does not contain steel reinforcing rods.

gregg1r Posted at 2015-6-6 09:19
Provided the entire case is aluminum with no ferrous materials like hinges, locks, or lid supports,  ...

The plan was to CNC a custom foam insert for a Rimowa Topas, which is made of a magnesium-aluminum alloy.  I'm not sure what the hinges and locks are made of . . . probably stainless steel.  But how much difference would that make?

Is there a distinction between compass calibration and setting the home point on take-off?  Assume I step away from the case for calibration, but use it for take-off and landing.  Does that make a difference?

Calibrated and launched from the aluminum roof of a pontoon boat with no issues..for what it's worth..

Rob88 Posted at 2015-6-6 09:52
The plan was to CNC a custom foam insert for a Rimowa Topas, which is made of a magnesium-aluminum ...

Once you run the compass calibration you shouldn't have an issue with the case interfering with the compass.

There used to be a place where you could check on magnetic fields that were out of the ordinary. I seem to remember it was part of NOAA or the Coast Guard.

Some locations have a very strong field, ie areas rich in iron ore.

FlyGirl Posted at 2015-6-6 09:24
I want to know how you know sooo much?

Age my dear. That and having worked in an aerospace engineering lab as the technical guru.

If I had an interest in something I dug for information until I was satisfied that I had a grasp of the concept. Then I went out and did the experiments to prove to myself it could be done.

I worked with a lot of PhD type folks that were book smart, but no practical experience. One was 28 years old and had never held a paying job.

gregg1r Posted at 2015-6-6 10:45
Once you run the compass calibration you shouldn't have an issue with the case interfering with th ...

OK, so there are two issues.

One is the compass calibration, and i can step away for that.  The second issue is the return-to-home point.  If the compass is calibrated without interference, can you take off from a block of solid steel with no issue . . . in other words, are compass calibration and home point separate functions?

BTW, thanks again to all of you guys who actually understand this stuff.  Some of you on this forum are electrical engineers (God bless you for your help), while others sell shoes or work at MacDonald's . . . . but we all share the same hobby.

Rob88 Posted at 2015-6-6 10:56
OK, so there are two issues.

One is the compass calibration, and i can step away for that.  The s ...

The return flight provided you are using the P setting on the transmitter is going to use the GPS and compass for it's guidance system. The compass is more so for you being able to steer your craft while on the screen to a true or magnetic north. Or so it is my understanding.

Page 14 of the users manual appears to indicate that the compass is more so used for the RTH function than GPS. This would explain the Phantom not landing on the exact spot that you took of from.

I'm sure that there is an algorithm that weighs all of the data being collected and then decides what it thinks needs to occur.  Needless to say, DJI isn't going to give that info up.

You are going to run into some areas which are going to have a great effect on the compass due to a magnetic field generated. If the interference field is greater that the natural north magnetic field, the compass is going to use that field as north. Radio towers, high voltage power lines are the biggest offenders.