Got this GPS message today

[HWCM]

That makes no sense whatsoever (at least to me) . It is akin to saying I am depending on my car's intelligence to tell me when to go perform oil changes and preventive maintenance. Much like, if my car does not tell me it is time for an oil change, I am going to go against common sense and not do it, even if I have been driving for ever and am past the normal mile range for maintenance.

Experts, can you please elaborate on this? True/false, good practices/BS? I personally feel I would do those things even if not required just to make sure I do everything in my control not to crash my drone.

@sar104 @msinger

He is exactly right. DO NOT calibrate your compass before every flight. Do it once and leave it alone.

 

[HWCM]

I appreciate the link to the prompt, but most of the answers there are speculative/experiential (had already seen that discussion). I am wondering about this from two angles:

1. Why would the manufacturer recommend it?
2. Even so, how (and by how, I mean a scientific explanation) would it hurt to align your device's compass, or let me say, re-align it every time you fly? As long as you make sure that you are not calibrating it around metal or any of the caveats as we know, how is it detrimental? It is only being cautious, in my opinion.

I am just curious about this from an electronics/systems point of view, more like gathering in-depth knowledge.

DJI does NOT recommend calibrating the compass before every flight, only if the APP tells you too.
Your magnetic deviation does not change enough from location to location to require a calibration.Unless you are flying maybe thousands of miles away from your last calibration point.

 

[HWCM]

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.

It does not ask you too. It is only showing the place in the app to tap when it needs calibrating. If it needs calibrating, you will see red lettering that says CALIBRATE COMPASS REQUIRED.

 

[HWCM]

I appreciate the link to the prompt, but most of the answers there are speculative/experiential (had already seen that discussion). I am wondering about this from two angles:

1. Why would the manufacturer recommend it?
2. Even so, how (and by how, I mean a scientific explanation) would it hurt to align your device's compass, or let me say, re-align it every time you fly? As long as you make sure that you are not calibrating it around metal or any of the caveats as we know, how is it detrimental? It is only being cautious, in my opinion.

I am just curious about this from an electronics/systems point of view, more like gathering in-depth knowledge.

The more you calibrate, the more chances you have of inserting errors. If you have a good calibration, leave it alone. If you get a compass error, move to a different spot a few feet away and try to launch again. You were probably close to something metal. This does not mean you need to calibrate. If you stay at the same spot where you are getting the compass error and calibrate, you have just inserted a bad calibration.

 

[msinger]

Experts, can you please elaborate on this? True/false, good practices/BS? I personally feel I would do those things even if not required just to make sure I do everything in my control not to crash my drone.

From my experience:

• DJI GO will never ask you to calibrate the compass when it needs to be calibrated
• In most cases, a compass-related message displayed before takeoff is a prompt to move your Mavic away from a nearby magnetic metal object
• Calibrating the compass often doesn't hurt anything (it's usually not needed though)
  
• It's impossible to store a bad compass calibration by doing the compass calibration incorrectly

For more details, check out the Compass Calibration Guide.

 

[dwallersv]

I think when I did calibrate it. The vehicle was like 30 feet away. Maybe it was not an open enough area?

30' is plenty.

 

[dwallersv]

From my experience:

• DJI GO will never ask you to calibrate the compass when it needs to be calibrated
• In most cases, a compass-related message displayed before takeoff is a prompt to move your Mavic away from a nearby magnetic metal object
• Calibrating the compass often doesn't hurt anything (it's usually not needed though)
  
• It's impossible to store a bad compass calibration by doing the compass calibration incorrectly

For more details, check out the Compass Calibration Guide.

From my experience:

• I've been told by GO4 to calibrate the compass on my Spark, and it needed to be calibrated.
• Calibrating often increases the chance you will save a bad calibration over a perfectly good one, go out and fly, and lose your aircraft.
• The possibility of storing a "bad compass calibration" depends entirely on what one means by, "doing the compass calibration incorrectly". Many of us include calibrating in a distorted geomagnetic field to be doing it incorrectly, however the aircraft is completely unable to detect this (if it could, you wouldn't need a reference calibration, which requires a detailed technical explanation to understand) and will successfully calibrate.
  
  As such, many of us do not consider frequent calibration to be harmless. It increases the chance of introducing errors.

Only calibrate when you are getting compass errors while up in the air, at least a good 50 feet away from anything. That't the conditions under which compass calibration needs to be working properly, and that's where you need to be paying attention to warnings.

Of course you're getting errors on the ground, move to a different take-off locale. Don't launch with errors. However, don't calibrate unless it is very clear, in flight, the compass is not functioning properly.

 

[msinger]

Calibrating often increases the chance you will save a bad calibration over a perfectly good one

I've never heard of such a thing. Got a link to even one case where this happened?

 

[Howcroft22]

That can't be right. My mavic and phantom 4 never ask to re-calibrate the compass.

Mine will usually say “recalibrate compass or move to a different area”. Usually that’s because I’m too close to my vehicle or inside my house. There is apparently a lot of rebar or some type of metal in my house. My drone does not like to start inside. Which is fine because I bought it to fly outside.

 

[dwallersv]

I've never heard of such a thing. Got a link to even one case where this happened?

It's not a matter of proof, it's a matter of logic. If you're calibrating often, the probability that you will perform a less optimal calibration than the existing offsets, and replace it, is obviously higher.

There's another more colloquial term for this statistical fact: "If it ain't broke, don't fix it".

There's a very real-world reason for that colloquialism.

As for a link citing an example of this happening I'm not going to bother. You and I both have read plenty of threads with people screwing up compass calibrations, and having their aircraft fly strange.

 

[msinger]

As for a link citing an example of this happening I'm not going to bother. You and I both have read plenty of threads with people screwing up compass calibrations, and having their aircraft fly strange.

I guess we'll have to agree to disagree then. I've never seen such a thread before. That's why I asked you to share a link (I'm always up for learning new things).

 

[dwallersv]

Mine will usually say “recalibrate compass or move to a different area”. Usually that’s because I’m too close to my vehicle or inside my house. There is apparently a lot of rebar or some type of metal in my house. My drone does not like to start inside. Which is fine because I bought it to fly outside.

Yes, and give this a try, but don't fly: Calibrate your compass there where it's telling you to "recalibrate or move to a different area". You will likely successfully calibrate. Then, when you take it outside to fly, it will tell you again to "recalibrate compass or..." hopefully (very likely, since it was unhappy in the first location).

However, I've gotten the recalibrate message inconsistently in the same place, which obviously means the whole situation is not deterministic. This is why, when you have a good calibration following all the best practices, stay with it unless there is some reason while flying that makes the compass suspect.

 

[dwallersv]

I guess we'll have to agree to disagree then. I've never seen such a thread before. That's why I asked you to share a link (I'm always up for learning new things).

I'm surprised. I've read many posts here complaining about erratic flight behavior after a compass calibration (could be I'm merging phantom and mavic boards in my memory). Happens to green people all the time.

Not worth proving... if you want to advise people that calibrating their compass as often as they feel like carries little to no risk, I'll simply disagree.

 

[msinger]

I'm surprised. I've read many posts here complaining about erratic flight behavior after a compass calibration (could be I'm merging phantom and mavic boards in my memory). Happens to green people all the time.

~6+ months ago many people (even myself) believed it was possible to store a bad compass calibration because the cases being discussed did not provide the data to prove the compass-related issues were caused by something else (like taking off near a magnetic metal source). Since looking at actual data from many flyaway cases since then (and thanks to the tools created by people like @BudWalker), it was in fact proved that bad compass calibrations weren't really to blame. If you have time to bother to learn more about this, check out this thread.

As for a link citing an example of this happening I'm not going to bother.

So, we should all just take your word for it?

 

[Flycaster]

Since I have owned my Mavic, (running .400 on the bird, and 4.0.4 on the app, (what it was when I open the box for the first time), I have never calibrated my compass. I always check my sensor readings (IMU and Compass), All solid and green, AND I make sure my location has been updated on the map (the little voice tells me so) and I verify it on my downloaded maps......

 

[BudWalker]

I'm surprised. I've read many posts here complaining about erratic flight behavior after a compass calibration (could be I'm merging phantom and mavic boards in my memory). Happens to green people all the time.

Not worth proving... if you want to advise people that calibrating their compass as often as they feel like carries little to no risk, I'll simply disagree.

I've seen a lot of posts making the same claim. I.e. that there exists other posts claiming that a flawed calibration caused erratic flight. At the moment I only know of a couple of direct claims that a flawed calibration caused erratic flight. And these have no compelling evidence to support the claim.

I've also seen several "Not worth proving" posts usually relying on the idea that it has happened so many times it doesn't need proving. But, then no one has provided even one example where there is at least some evidence to support the claim that a flawed calibration caused erratic flight.

 

[dwallersv]

Fair enough. We have different experiences, and opinions.

As far as digging up links and proving things, it simply isn't worth it to me for something as relatively minor as this. If someone wants to calibrate every time they change a battery, I've no problem with that. I simply say they are increasing the risk they will screw up their compass, and have a bad result.

You and msinger seem to disagree, believing there is no increased risk. Based on analysis of a handful of crash incidents that turned out NOT to be the result of a compass malfunction. In Risk Analysis, this hardly proves the compass can not be the source of a crash due to a bad calibration.

I'm very comfortable with agreeing to disagree. Some here know me, and will accept or reject my opinion based on that. I'm very comfortable with people "simply taking my word for it" -- or not.

I don't have to be "right". Knowing and sharing "right" is more than enough, in this context.

 

[geigy]

I often fly from the same location in a nearby park, and fairly often I power the Mavic up sitting on a picnic table with a steel frame. Each time it warns me, and asks me to re-calibrate the compass. I know the drill, and put it on the ground well away from the table. The message goes away, and I fly with no problems. If I did re-calibrate, sitting on the table, I'm sure the calibration would be incorrect since it is in the presence of an external magnetic field, and I would be in for some unpleasant surprises if I flew at that point.

 

[SwatKat]

I often fly from the same location in a nearby park, and fairly often I power the Mavic up sitting on a picnic table with a steel frame. Each time it warns me, and asks me to re-calibrate the compass. I know the drill, and put it on the ground well away from the table. The message goes away, and I fly with no problems. If I did re-calibrate, sitting on the table, I'm sure the calibration would be incorrect since it is in the presence of an external magnetic field, and I would be in for some unpleasant surprises if I flew at that point.

Yes, but then calibrating it in the presence of external effects that could screw up your compass falls within the caveats of calibrate correctly, no? Which means look for a position with low magnetic interference. If you still go ahead and calibrate it at the table, then you, as an operator are not demonstrating due diligence, no?

 

[geigy]

Yes, but then calibrating it in the presence of external effects that could screw up your compass falls within the caveats of calibrate correctly, no? Which means look for a position with low magnetic interference. If you still go ahead and calibrate it at the table, then you, as an operator are not demonstrating due diligence, no?

I guess my point is if you are a beginner, don't calibrate unless you determine that you have to. People will suggest that you calibrate for every little problem, and if you want to practice due diligence, I suggest that you be cautious and skeptical before calibrating.

And don't be afraid to fly because of all the problems you see here. This group is a magnet for people who want to discuss problems. That does not mean you should leave your Mavic in the box and not fly until you've read every article and know how to solve every problem. Only a small percentage of owners actually have problems of any kind.

Go out and fly.