Got this GPS message today

[Dabrain]

Okay, I have read all the posts in this tread, here goes even though I posted the above new recommendations from DJI, I have only re-calibrated my compass a few times. The first time, then a couple of times after just to make sure I remember how to. I take off from my driveway all the time and I have two carports all metal a shop with a metal roof and the house with a metal roof all within twenty feet. Never had a problem with the compass, don't dare walk under the roof of the house though I loose RC contact almost immediately walk back out and regain contact. I have taken off out of the back of the truck no problem, tried to land in the back of the truck just once didn't go so well, MP went left then right then left, not sure if interference of the compass or just the air foil under the MP was disrupted. If there is a need to re-calibrate at least I know how because I practiced it a couple of times. LOL Msinger, Budwalker, Sar104 thank you for all the information you provide to all of us.

 

[Dextra]

Can you provide an AirMap data report?

 

[HighlandsVideo]

My Mavic, asks me to calibrate the compass at startup about 90% of the time. No big deal, to me it is just part of the preflight process.

I've had my MP for one year and one week and have made 164 flights, (admittedly all within 100K of my home) without ever needing to calibrate the compass. If you are being asked to re-calibrate often, it probably indicates there is some serious magnetic interference present.

 

[Mac]

I calibrate my Compass and IMU every time I have a firmware change

 

[ac0j]

If it Needs calibration, the mavic will tell you. If you are in a bad spot to calibrate, the mavic will tell you.
If it doesnt ask for it, probably better to not do it.

 

[J1mbo40]

Mine asks to be calibrated too every time I change places. Or start up after a few days of no use

 

[silverdragon]

I guess it's out of the question if I should start a new topic on 'Should I compass calibrate before each flight'

 

[Howcroft22]

I guess it's out of the question if I should start a new topic on 'Should I compass calibrate before each flight'

I think that one has been done a few times.

Recalibrate before each flight?

 

[mstrmavic]

Just my 2 cents. I've owned my Yuneeck H pro for a year, my Mavic just short of a year, fly all the time. I have NEVER calibrated eighter bird, & they both fly fine, I fly all over the city. Just make sure you have satellites & wait to confirm HOME. Don't be in a rush to get into the air, a rush could be your last flight.

 

[HWCM]

Mine asks to be calibrated too every time I change places. Or start up after a few days of no use

I doubt it does. you are probably just seeing the settings menu.

 

[dwallersv]

I would not recommend calibrating every flight or simply because you have changed location (despite what the recent DJI article said) because that has nothing to do with what calibration is trying to achieve. It's a waste of time, it represents messing unnecessarily with a critical part of the FC, and "why try to fix something that isn't broken" applies here.

Sure, but what's the problem calibrating every time if there's no risk at all in doing so?

Shouldn't the stock advice be, "sure, calibrate away! It's harmless!"

--------------------------------------------------

Of course, I strongly disagree with this opinion, and do not think it is absent increased risk, and therefore "harmless". As such, I believe it prudent to tell people to only calibrate when required, and inform them as to the reason why I am advising caution.

If the risk is very small, fine. However, unnecessary risk should never be taken.

 

[dwallersv]

A compass looks for one thing. Magnetic north.
If you get a compass error, how does this tell you that you must be in a magnetic field? The compass points to the magnetism, so the craft has nothing to believe but the compass. It tells me the compass isnt communicating with the mavic. Or there are two conflicting compass's on board the Mavic.

Nope. Let's discuss how a flux-gate compass works.

It can sense the magnetic field vector it is sitting in, and its orientation via the gravity vector via the IMU. When it has a GPS lock, it knows its location on the earth.

With location and orientation, it can calculate the direction the magnetic field vector should be pointing. Only at the equator (roughly) does the vector point horizontal relative to the earth. In the northern hemisphere the vector has an increasing upward tilt until you're over the magnetic north pole, where the vector points straight up. All of this is reversed in the southern hemisphere.

The point of all this is the mag vector has a defined orientation in space at a given location on the surface, and a magnetic flux compass can sense this orientation. So, if what it senses doesn't match what it calculates it should be, it knows there is some magnetic distortion that's affecting the field.

The vast majority of the time this is a very reliable system. However, it is not fail-safe. This is why it is a bad idea to calibrate when it's not required.

Two NASA sites that have a ton of information on this stuff for those that want more:

Historical Magnetic Declination
and
Compute Earth's Magnetic Field Values

 

[dwallersv]

I find it amazing. I cant believe that 4 high current motors running at constantly varying frequencies, the wires connecting those to the battery, and all the currents flowing INSIDE of the the mavic (along with the compass) dont disrupt the compass, but the static rebar in my driveway could?

Yeah, it IS pretty amazing, isn't it?

It's called "engineering". It's why we guys get paid A LOT.

To an EE, it's not amazing. It's a EM and shielding problem.

 

[dwallersv]

[reasonable lay speculation elided]

But then again, I am a dumb guy, and must yield to input from the lofty crows nests of the educated.

I wouldn't say that. You're not dumb, I just don't think your an engineer or scientist (physical sciences), so you lack the knowledge to discuss this at this level of detail.

You've taken grade-school science (DC currents in wires make magnetic fields), "common-sense" knowledge of construction techniques, and tried to analyze a sensitive, complicated electronic component.

You might as well dispense medical advice too, in lieu of consulting a physician.

I'm an EE (among other higher education). I minored in physics. Not trying to brag or anything, just obvious that you lack certain knowledge. Nothing bad. You just don't understand the underlying technology, and the physics, to have a prayer of speaking authoritatively about this. Your comments being addressed here are screaming that.

 

[ac0j]

Welcome to the whipping post.....

Glad you chimed in, (however late, just like an engineer) I was feeling a shortage of being ridiculed by another nerd.
Hes a joke for you to lighten the mood:

Three guys go down to Vegas one night, get drunk and wake up in jail. They find out that they're to be executed for their crimes but none of them can remember what they have done.

The first one is strapped in the electric chair and is asked if he has any last words. He says, "I am a priest and I believe in the almighty power of God to intervene on behalf of the innocent." They throw the switch and nothing happens; so they figure God must not want this guy to die, and let him go.

The second one is strapped in and gives his last words. "I am an attorney and I believe in the eternal power of Justice to intervene on the part of the innocent." The switch is thrown and again nothing happens.Figuring the law is on this guy's side, they let him go.

The last one is strapped in and say's "I'm an electrical engineer, and I'll tell you right now, you'll never electrocute anybody if you don't connect those two wires."

 

[HWCM]

Welcome to the whipping post.....

Glad you chimed in, (however late, just like an engineer) I was feeling a shortage of being ridiculed by another nerd.
Hes a joke for you to lighten the mood:

Three guys go down to Vegas one night, get drunk and wake up in jail. They find out that they're to be executed for their crimes but none of them can remember what they have done.

The first one is strapped in the electric chair and is asked if he has any last words. He says, "I am a priest and I believe in the almighty power of God to intervene on behalf of the innocent." They throw the switch and nothing happens; so they figure God must not want this guy to die, and let him go.

The second one is strapped in and gives his last words. "I am an attorney and I believe in the eternal power of Justice to intervene on the part of the innocent." The switch is thrown and again nothing happens.Figuring the law is on this guy's side, they let him go.

The last one is strapped in and say's "I'm an electrical engineer, and I'll tell you right now, you'll never electrocute anybody if you don't connect those two wires."

Thank you for contributing nothing.