If you want to check your chosen takeoff spot or area you plan to calibrate your drone's compass at, there is an easy way to detect Magnetic Intereference, even if cause is hidden.

All you need is a Smartdevice (iPhone, iPad, Android phone or tablet) that you can download and install one of several Tesla or Gauss magnetic field strength Applications on.

What makes this method easy is all you do is walk around area, observing magnetic field strength.  No need to walk straight line with digital compass or align your smartdevice running GO-4 with direction your drone is facing, then check GO-4 compasses.

If you observe any major field strength changes upwards or downwards, usally reported in Gauss or µT (micro Tesla), you avoid that spot as possible takeoff point or area for compass calibration.  If you are going to takeoff from within that area, last step is to check your chosen takeoff spot.  Done by lowering Smartdevice down to ground, then moving smartdevice around spot looking for any changes from what you previously observed over the area.  This last steps checks for buried ferrous metals (aka rebar, steel pipe, scrape metal) and underground power lines.  Best to check spot in sweeping motion covering few feet from center.

I do not have an Android phone / tablet to test with, but basics of built-in compasses should achieve results similar to two iPhone 5s, and iPhone X I used.  Surprisingly the three Apple devices gave nearly same µT readings, and almost same readings when tested with the different Apps  Plastic or rubber smartdevice protectors did not appear to make a difference.  But again you are looking for change, not a specific value.

An app that allows you to look at overall field strength (combination of X, Y, Z axis sensors built-in to Smartdevice) is most desirable feature.  Followed by an app that gives you a running graph or radar like chart are  easiest to use.  Still even an App that provides a gauge style reading  works too, as shown below.  

Few examples in next two posts (forum won't allow entire post in a single post):

First basic gauge style app

First shows gauge of normal Magnetic Field Strength for the area:

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Second shows deviation as Smartdevice approaches metal building in the area

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Third shows deviation as Smartdevice got within inches of rebar in cement near the area.

Next examples are from running graph style chart app

First shows chart of normal Magnetic Field Strength for the same area:



With above chart you can see minor changes up and down in magnetic field strength.

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Second shows a dip (change downward) on chart as Smartdevice was moved close to metal building,
then rise (change upward) on chart as Smartdevice was moved away.



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Third shows a rise (change upwards), dip (change downward), and rise (change upwards) on chart as Smartdevice
was moved first over steel guard rail near side of metal building, then away from metal building back over steel guard rail.



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Hope this helps make picking drone takeoff spots and checking drone calibrations areas for magnetic interference easier for droners.

Very interesting information, thanks for sharing.

DJI Diana Posted at 2018-5-15 02:21
Very interesting information, thanks for sharing.

Thanks.  I hope it helps others.

HedgeTrimmer Posted at 2018-5-14 22:35
Next examples are from running graph style chart app

First shows chart of normal Magnetic Field Strength for the same area:

So from your tests we can conclude it's not wise to calibrate or take off near steel building, steel guard rails or steel reinforced concrete ?

What would be the benefit of this over the DJI Go App' when it reports 'magnetic interference' ?

Aardvark Posted at 2018-5-16 14:37
So from your tests we can conclude it's not wise to calibrate or take off near steel building, steel guard rails or steel reinforced concrete ?

What would be the benefit of this over the DJI Go App' when it reports 'magnetic interference' ?

In regards to taking off:
There has been a long discussion about possible Magnetic Intereference causing a Toilet Bow Effect, which can result in a crash.  In particular case there was no warning in Flight Log about possible Magnetic Intereference.  There was error messages after take off about Compass Error.  From what pilot said, there was no warning by GO-4 app about Magnetic Interference.  Thus possibility of something hidden causing Magnetic Interefence, not detected / reported by drone prior to take off.

The supposed scenario is - a drone may be placed near Magnetic Intereference prior to takeoff and drone flight system does not detect it's compass is being influcenced.  Shortly after taking off, the drone gets clear of Magnetic Interference, which confuses drone's flight systems (IMU, flight processor) because drone's compass shows a sudden deviation from its recorded take off heading.  
There has been two similar suggestions (one by me, other by another forum member) to use GO-4 App's compasses (drone's vs. smartdevice's) to check for deviation prior to flying.  

In regards to compass calibration:
During calibration, the drone's compass and flight systems are being setup to accurate indicate Magnetic North.  Part of that process is correcting for any Magnetic Interference by drone itself.  At same time, any outside magnetic influce is going to become part of compass vector corrections (X,Y,Z).  Ideally you want to minimize any external Magnetic Interference that causes deviations from Magnetic North.  At time of calibration, the drone's magnetic field sensors (aka Compass) is most suseptible to Mangetic Interefence.

In regards to steel reinforced concrete:
The steel reinforcing or rebar is hidden because of concrete.  Not all conrete pads or sidewalks have steel reinforcing.  My concrete pad does because of heavy equipment.
As with steel reinforcing being hidden from view, so can be things like underground powerlines (metal conduit), metal pipes (water, gas, oil).  There can also be hidden steel in form of covered over access hatches for sewers, water main valve risers, and steel in covered over cement septic tanks.

In regards to steel building / guard rails:
Used for three purposes.  
One, to show the Smartdevice Apps for detecting Magnetic Fields do indeed work.  Known steel was causing Magnetic Interference that was detected by App.
Two, to show that we need to watch for Deviations from Earth's Magnetic Field.  Restated, we need to watch out for both an Increase in Magnetic field strength, and a Decreases in Magnetic field strength.
Third, to show that Magnetic Interference rapidly declines as distance is increased from source of Magnetic Interference.  The formulas for calculating magnetic field strength varies based on type of Magnetic Intereference (simple static field of ferrious metal to active field of motor windings), along with amount of ferrious metal and its general shape (panel, bar, sphere).  General formula for Field Strength is Reciprocal of Distance x Distance.  Strictly for example: At 2-feet distance you would have 1/(2x2) or 1/4th field strength you would have a 1-foot, 1/(1x1) or 1.

In sumarry:
The built-in magnetic field detctors (X,Y,Z) of smartdevices like iPhone which are used for Compass function, can also be used with Application that shows deviations from what would be Earth's normal magnetic field in a given location.
With smartdevice running one of Magentic Field Strength Tesla or Gauss detectors Apps, a drone pilot can check an area for unknown / hidden sources of Magnetic Interference that could cause a problem as to chosen takeoff spot or as to chosen area for calibrating a drone's Compass.
Being using GO-4 compasses (drone's vs. smartdevice's) is not easiest (grainy & jumpy) and can't be done prior to calibration, I went looking for another method to alert drone pilots of unknown or hidden sources Magnetic Interences.

Hope all this answers your questions.
  

HedgeTrimmer Posted at 2018-5-16 15:44
In regards to taking off:
There has been a long discussion about possible Magnetic Intereference causing a Toilet Bow Effect, which can result in a crash.  In particular case there was no warning in Flight Log about possible Magnetic Intereference.  There was error messages after take off about Compass Error.  From what pilot said, there was no warning by GO-4 app about Magnetic Interference.  Thus possibility of something hidden causing Magnetic Interefence, not detected / reported by drone prior to take off.

What benefit does this have over the compass and DJI Go 4 App' ?

If the compass and App' cannot detect interference that might cause problems then there is none.

Thanks Hedge.  This is an add-on to the conversation we just finished.  Very good information.

Aardvark Posted at 2018-5-16 16:16
What benefit does this have over the compass and DJI Go 4 App' ?

If the compass and App' cannot detect interference that might cause problems then there is none.

If the compass and App' cannot detect interference that might cause problems then there is none.

Not according to another forum member.

And from what I have seen with testing, there can be Magnetic Intereference that is below detection threshold where a drone is placed for takeoff, but right after takeoff before drone gets more than few inches above ground, drone can cross that threshold.
From futher testing, I have found that even rotating drone can change from no detection of Magnetic Interference to detecting.  The location of compass appears to be near front of Mavic Pro.
From checks for Magnetic Intereference, what I have seen is most of interference falls off when distance from source goes past 1/2-meter.  At 1-meter most sources of Magnetic Intereference are negligible.  A few 1-meter examples, CTL weighing 6-tons, (5-tons of steel), 60'x40' metal building, 8-foot chain link fencing, 2'x20' steel pipe, and 12-inch diamter gas pipeline.


What benefit does this have over the compass and DJI Go 4 App' ?

In regards to calibration, using those prior to compass calibration to detect Magnetic Interference in area chosen for calibration, would be misleading and confusing.  
You would be trying to use drone's compass that is out of calibration to compare against smartdevice's compass.

Benefit is you can make sure the chosen takeoff spot's or calibration area's does not deviate from Earth's Magnetic Field from general area.

If you are wondering why a specific Tesla or Gauss value can not be assigned, and droners watch for deviation from that value: The Earth's Magnetic Field varies over large distances.  
For example: (following from World Magnetic Model)
New York -- 51.7 microTesla
San Fransico -- 48.0 microTesla
Hawaii -- 34.5 microTesla
London -- 48.8
Port Elizabeth -- 26.6 microTesla
Further, the above numbers vary over time. A surprise to me.

Overall, using Smartdevice with one of Apps that detect Magnetic Interference is Easy and serves as pre-check to drone's compass system.

HedgeTrimmer Posted at 2018-5-16 17:15
If the compass and App' cannot detect interference that might cause problems then there is none.

Not according to another forum member.

I think it’s fair to say that case your talking about user was 6 feet from his car and had never checked his compass in his app.
If he had he most likely would have seen compass issues, he also has the option to check his correct heading on his telemetry.
If you are in an area of magnetic interference you can see this small red triangle moving and if you check your app you will see a change in your compass values this should be done by all users and if this is checked before flight along with other preflight checks then the risk of magnetic interference is low, so this is what your app is for.

While your app may not always give you warnings on your telemetry this doesn’t mean that your app won’t see a change in compass values.

HedgeTrimmer Posted at 2018-5-16 17:15
If the compass and App' cannot detect interference that might cause problems then there is none.

Not according to another forum member.

1) If the compass and App' cannot detect interference that might cause problems then there is none.

You said:- "Not according to another forum member.
And from what I have seen with testing, there can be Magnetic Intereference that is below detection threshold where a drone is placed for takeoff, but right after takeoff before drone gets more than few inches above ground, drone can cross that threshold."

By your example here the compass must be able to detect a difference between being on ground or up in air. So as primary detector of the aircraft it would make sense that if it did not detect any difference then the aircraft would not react in any way.
Many times I have seen compass error warnings when indoors or very close to large metal objects. These disappear when I move the aircraft, usually just a few inches. So there is nothing to suggest to me that the compass or software is not working correctly or capable of measuring what is required.

2) What benefit does this have over the compass and DJI Go 4 App' ?

You said:- "In regards to calibration, using those prior to compass calibration to detect Magnetic Interference in area chosen for calibration, would be misleading and confusing.  You would be trying to use drone's compass that is out of calibration to compare against smartdevice's compass."

I last calibrated my compass 6 months ago, and it will not need calibrating again until advised by system. You say that any interference detected by the compass would be misleading and confusing. Why would that be, the compass is used by the aircraft as it's primary detector ?

3) You also said:-  "And from what I have seen with testing, there can be Magnetic Interference that is below detection threshold where a drone is placed for take off"

If it's below detection threshold then how can your smart device detect it ? And if the aircraft cannot detect it then it is of no consequence.
I believe that what can happen is that if a compass is badly calibrated on the ground because of some strong magnetic field disturbance very close to it, these bad offsets measured, which are supposed to represent any affect the aircraft itself might have on the compass are then invalid after it takes off. As the aircraft starts to move the other instruments can get some measurement about which general direction it is traveling. The badly calibrated compass is sending conflicting data (far enough out to cause concern). The system has no idea which is correct as it initially tries to automatically adjust, being unable to adjust automatically it then choses the safest option which is to default to ATTI mode and let the pilot decide.

4) You said:- "Benefit is you can make sure the chosen takeoff spot's or calibration area's does not deviate from Earth's Magnetic Field from general area."

And my point is, if the chosen area is not suitable then the aircrafts compass and DJI Go 4 App' will inform you. That is the data that the system is measuring and using. And that is the system recommended by DJI themselves.
If what you say is true, then the system and compass themselves are not to be trusted, the evidence against this is that the vast majority of flights that are planned, and with pre-flight checks done, are completely successful.

So I do not believe there is any benefit in using data not measured (and therefore not used) by the aircraft and DJI Go 4.
Once the aircraft leaves the take off point then there is no way to measure what it may or may not encounter on its journey. That's where the pilot comes in to react and control the device as needed.

Aardvark Posted at 2018-5-17 01:45
1) If the compass and App' cannot detect interference that might cause problems then there is none.

You said:- "Not according to another forum member.

When I have time later today, likely late tonight, I will go over your comments.

In mean time, since the forum member (hallmark007 - see his post above) has decided to come forward - you can discuss the scenario, and his statements on magnetic inteference from one known source, drone pilot's car.

A car that was 5 to 6 feet away from drone takeoff point, and the assertion that drone crossed threshold point (going from magnetic interference to no magnetic interference) after it took off and was couple feet in air.  

Keeping in mind there was no Magnetic Interference reported in Flight Log, only Compass Error after takeoff, and operator never reported seeing any display warnings or errors.  
Along with my testing showing Magnetic Inteference from cars or suv (Jeep) starts at 18-inchess (1-1/2 feet).   About 1/3rd to 1/4th hallmark007's position on Magnetic Interference caused by car.

Till later.   Have a good day!

HedgeTrimmer Posted at 2018-5-17 07:42
When I have time later today, likely late tonight, I will go over your comments.

In mean time, since the forum member (hallmark007 - see his post above) has decided to come forward - you can discuss the scenario, and his statements on magnetic inteference from one known source, drone pilot's car.

I will give the background on this thread, the OP said he took off from 6 feet from his car, he showed his log and explained what occurred. From these explanations and from seeing his phantomhelp log which was very short, I deducted he had got magnetic interference from taking off so close to his car causing aircraft to fly off and crash, all the symptoms and from what the OP had said pointed to magnetic interference on the Ground.
Dji also came to the same conclusion but had the benefit of the .dat file finding that his aircraft picked up magnetic interference before take off, so both came to exact same conclusion.

Now as regarding app I have said on several occasions that the app will not always give you on screen warning of magnetic interference, but that does not mean that checking the app that compass values will have changed along with movement of heading triangle. If the OP had checked any or both of these he would have picked up a problem.

You can measure with as many gadgets as you like and it’s likely that you will come up with different answers every time , but the point here that Ardvark is making is simply you are dealing with this aircraft which will always show if there is magnetic interference but you always in preflight have to check this.
You don’t know what Interference his car may have had or for that matter what my car has so giving measurements of magnetic interference from a third party app for your car is for you it’s not for anyone else, so your measurements or levels of interference for your car have no relevance to anyone else.

But the main point here is that your app has the information and that’s why you should check it before you fly and there is no need for other gadgets.

Aardvark Posted at 2018-5-17 01:45
1) If the compass and App' cannot detect interference that might cause problems then there is none.

You said:- "Not according to another forum member.

Me: And from what I have seen with testing, there can be Magnetic  Intereference that is below detection threshold where a drone is placed  for takeoff, but right after takeoff before drone gets more than few  inches above ground, drone can cross that threshold."

Aardvark: By your example here the compass must be able to detect a difference between being on ground or up in air.

No.  I was not trying to imply compass detects whether its on ground or up in air.  It was a matter of unclear wording by me.   
What I was trying to say, drone has taken off, yet drone is still few inches above ground, thus able to move horizontally (X-Y plane), and drone crosses magnetic interference threshold by moving forward/backward, left/right, or possibly by rotating 180-degrees.  From my testing amount of horizontal movement it takes to cross threshold can be as little as an inch, between Good to Go (Green) and Magnetic Interference (Red).


Me: "In regards to calibration, using those  prior to compass calibration to detect Magnetic Interference in area  chosen for calibration, would be misleading and confusing.  You would be  trying to use drone's compass that is out of calibration to compare  against smartdevice's compass."

Aardvark: I last calibrated my compass 6 months ago, and it will not need  calibrating again until advised by system. You say that any interference  detected by the compass would be misleading and confusing. Why would  that be, the compass is used by the aircraft as it's primary detector ?

Because drone compass needing calibration would likely be pointing different direction than smartdevice's compass.  Otherwise, why would system be calling for calibration?  As such, you can't compare drone compass against smartdevice compass as means of detecting possible Magnetic Interference as has been suggested.


Me: You also said:-  "And from what I have seen with  testing, there can be Magnetic Interference that is below detection  threshold where a drone is placed for take off"

Aardvark: If it's below detection threshold then how can your smart device detect  it ? And if the aircraft cannot detect it then it is of no consequence.

Smartdevice running App detecting Tesla or Gauss magnetic field strength levels is reporting what three magnetic field sensors (X,Y,Z) of smartdevice are seeing individual, and as combined amount.  The drone may be detecting those fields, but it appears DJI has set some level of magnetic field different from earth's magnetic field that is torerable.   The smartdevice running magnetic field strength detector allows drone pilot to beaware of possible interference problems prior to calibration or prior to chosing a takeoff point.  

With regrads to aircraft not detecting magnetic field, thus not being of consequence - all it takes is for drone to move from just outside threshold to inside threshold of magnetic interference to cause problems.  From what we have both seen that distance can be a matter of inches.  



Me:  "Benefit is you can make sure the  chosen takeoff spot's or calibration area's does not deviate from  Earth's Magnetic Field from general area."

Aardvark: And my point is, if the chosen area is not suitable then the aircrafts  compass and DJI Go 4 App' will inform you. That is the data that the  system is measuring and using. And that is the system recommended by DJI  themselves.

I believe reasoning has already been covered.  But, once again.  The drone may show you Good 2 Go (Green), prior to take off.  But as drone takes off, it only has to move a very short distance for magnetic field strength to increase enough to cause problems.  There is also the flip, drone does not detect or fails to warn drone pilot of magnetic intereference prior to take off then moves out of area of interfence, causing drone to experience and unexpected change to Earth's true magnetic North.

hallmark007 Posted at 2018-5-17 09:31
I will give the background on this thread, the OP said he took off from 6 feet from his car, he showed his log and explained what occurred. From these explanations and from seeing his phantomhelp log which was very short, I deducted he had got magnetic interference from taking off so close to his car causing aircraft to fly off and crash, all the symptoms and from what the OP had said pointed to magnetic interference on the Ground.
Dji also came to the same conclusion but had the benefit of the .dat file finding that his aircraft picked up magnetic interference before take off, so both came to exact same conclusion.

You gave the background, along with adding your usual SPIN.

hallmark007: Dji also came to the same conclusion but had the benefit of the .dat  file finding that his aircraft picked up magnetic interference before  take off, so both came to exact same conclusion.
  
Neither DJI admins here, let alone DJI Technical support, responded in thread as to cause.  
You try to inject that DJI looked at .dat file, but there is no evidence DJI did.  Total assumption on your part.
You also state DJI found aircraft picked up magnetic intereference before take off, again no evidence DJI made such a determination.

What was said, is as follows:
2wenty: Okay heres the results and even more rants.
2wenty: DJI wont cover the flyaway.  The are saying magnetic interference and its out of warranty anways.  
(more but its about costs)

Nothing in 2wenty's comment says anything about .dat file or ''before take off''.


hallmark007: Ardvark is making is simply you are dealing with this aircraft which  will always show if there is magnetic interference but you always in  preflight have to check this.
hallmark007: Now as regarding app I have said on several occasions that the app will  not always give you on screen warning of magnetic interference, but that  does not mean that checking the app that compass values will have  changed along with movement of heading triangle.

What you are saying then is - DJI's drone some how shows there is magnetic intereference to drone pilot (How?), while DJI's app (GO-4?) will not always warn drone pilot of magnetic interefernce?
How is that not a DJI problem?

As for checking drone compass values against compass values of GO-4 screen that has already been pointed out to have problems.  But one more time.
The compass for smartdevice on GO-4 app is jump and grainy.  There is no digital compass output as in (18-degrees for drone and 20-degrees for smartdevice).  The drone pilot must very accurate point smartdevice (which has no Pointer marking) in same direction as drone to look for difference, indicating possible magnetic interference.  And as I pointed out, the smartdevice can not be in same proximity as drone; otherwise smartdevice compass will be effected by magnetic field that is effecting drone.
  
If we go by your warnings on avoiding sources of Magnetic Intereference - at a minimum the drone pilot would need to move 10-meters (32.8 feet) away from drone to compare GO-4 app compasses for drone and smartdevice.  At that distance, it is nearly impossible to be in alignment with center axis of drone, and point smartdevice in same direction the drone is aimed at with need accuracy.

To Aardvark and hallmark007:

It appears both of you are essentially saying - The way I have suggested of detecting Magnetic Interference, using a free app on smartdevice, that is both easy and simple to use is of no need or no value, (aka pointless)?

Which leads to question - Have either of you tried using one of free Apps to detect Magnetic Interference as I outlined at opening of this thread, before dismissing suggested way?

Being there is no cost involved, no risk, and only small amount of time involved - Why not try using a smartdevice App that shows Magnetic Field strengths in the area / proximity of smartdevice?  

HedgeTrimmer Posted at 2018-5-16 15:44
In regards to taking off:
There has been a long discussion about possible Magnetic Intereference causing a Toilet Bow Effect, which can result in a crash.  In particular case there was no warning in Flight Log about possible Magnetic Intereference.  There was error messages after take off about Compass Error.  From what pilot said, there was no warning by GO-4 app about Magnetic Interference.  Thus possibility of something hidden causing Magnetic Interefence, not detected / reported by drone prior to take off.

Actually there is warning in the RC if you fly with Mavic Pro or Platinum about the Mag interfere, as the same just happen to me yesterday.  Usually it has symptom of multiple compass error before take off.  Once this Mag interfere show land immediately is the only choice.

HedgeTrimmer Posted at 2018-5-16 17:15
If the compass and App' cannot detect interference that might cause problems then there is none.

Not according to another forum member.

Very well explained thank you

HedgeTrimmer Posted at 2018-5-17 19:03
You gave the background, along with adding your usual SPIN.

hallmark007: Dji also came to the same conclusion but had the benefit of the .dat  file finding that his aircraft picked up magnetic interference before  take off, so both came to exact same conclusion.

So again you are saying dji asked twenty to send in his drone to find out what happened and they just made up magnetic interference.
Do you realize how silly that sounds. His case was without a doubt magnetic interference and this was the decision of dji, you are now saying that dji are lying and being untruthful and maybe it’s not a good idea to send your drone into dji for analysis. Think about that for a minute.

I will make this as simple as I can for you.
You take your drone to a safe open area to fly, free from metal structures concrete structures, you put your drone on the ground start it up and do your preflight check one of these should be to check your compass , just open your app and check it, if the values of your compass are good then you don’t have any problem with your compass.

Your way. Place your drone 20 inches from your car , Start it up get a seperate device (because no point checking with device being used to fly the drone)  check all surroundings don’t need to check your compass on the ground just use seperate device to check if your drone is to close to your car, check with device that there is no magnetic declination in the air the ground. (Which we already know will be picked up by your drone) and you call this simple compared to checking compass values in your app.

Everything is there in both your drone and app to check for interference along with all other checks needed to fly your drone, it’s pretty simple to do and it’s best advice, and you don’t need a second device or app to check as it won’t change anything.
But of course if you want to use it that’s your choice.

HedgeTrimmer Posted at 2018-5-17 19:16
To Aardvark and hallmark007:

It appears both of you are essentially saying - The way I have suggested of detecting Magnetic Interference, using a free app on smartdevice, that is both easy and simple to use is of no need or no value, (aka pointless)?

I don’t need another app to check my drone is ok to fly, and not everyone has an extra device to check for something they can clearly check with equipment they already have.

HedgeTrimmer Posted at 2018-5-17 19:03
You gave the background, along with adding your usual SPIN.

hallmark007: Dji also came to the same conclusion but had the benefit of the .dat  file finding that his aircraft picked up magnetic interference before  take off, so both came to exact same conclusion.

And BTW this is dji’s analysis , you seem to spend your time trying to twist what really happened and although you believe dji are lying this is their results.
It’s amazing that they could get so much information from not checking the log.


NON-WARRANTY PER DATA ANALYSIS. Compass interference FLY037 1. User took off from a metallic object causing immediate compass error. 2. At t=86s, unit started to drift. 3. At t=100s, user attempted to correct the course but unit drifted to obstacle. Force impact date: 4/22/18 Force impact GPS location: 34.3622815 -117.8660737 Activation date: 2017-01-23 SN: 08RDDBH00102Y9 Conclusion: Magnetic interference caused compass error. Unit drifted to obstacle and crashed. [Non warranty] Dear Customer, Unfortunately, damage that is not caused by a product malfunction or is out of the warranty period is not covered by DJI aftersales policy. We will either repair it or replace it with a product that's new or equivalent to new in both performance and reliability after payment has been received. For more information, please visit

hallmark007 Posted at 2018-5-18 00:36
So again you are saying dji asked twenty to send in his drone to find out what happened and they just made up magnetic interference.
Do you realize how silly that sounds. His case was without a doubt magnetic interference and this was the decision of dji, you are now saying that dji are lying and being untruthful and maybe it’s not a good idea to send your drone into dji for analysis. Think about that for a minute.

Hallmark007: His case was without a doubt  magnetic interference and this was the decision of dji, you are now  saying that dji are lying and being untruthful and maybe it’s not a good  idea to send your drone into dji for analysis.

Never said DJI lied.  But I have said in past you are a Twister, Spinner, Derailer, and Troll.

HedgeTrimmer Posted at 2018-5-18 08:25
Hallmark007: His case was without a doubt  magnetic interference and this was the decision of dji, you are now  saying that dji are lying and being untruthful and maybe it’s not a good  idea to send your drone into dji for analysis.

Never said DJI lied.  But I have said in past you are a Twister, Spinner, Derailer, and Troll.

You said no proof dji looked at log, think about it if they didn’t look at log how could they do the analysis.

hallmark007 Posted at 2018-5-18 00:36
So again you are saying dji asked twenty to send in his drone to find out what happened and they just made up magnetic interference.
Do you realize how silly that sounds. His case was without a doubt magnetic interference and this was the decision of dji, you are now saying that dji are lying and being untruthful and maybe it’s not a good idea to send your drone into dji for analysis. Think about that for a minute.

hallmark007: Your way. Place your drone 20 inches from your car , Start it up get a  seperate device (because no point checking with device being used to fly  the drone)  check all surroundings don’t need to check your compass on  the ground just use seperate device to

Not my way.  Nor have I advocated people doing such.  

What I did was demonstrate effects of Magnetic Intereference are rapidly reduced as distance from source of interfernce is increased.  

But let us cut to what really has your panties in a bunch.  I showed that your warnings of magnetic interefrence to a drone takeoff, out to distances of 10-meters was baseless.  Along with showing your smoke blowing claim that magnetic interference from a car could effect a drone takeoff placed 5-6 feet away.

hallmark007 Posted at 2018-5-18 00:38
I don’t need another app to check my drone is ok to fly, and not everyone has an extra device to check for something they can clearly check with equipment they already have.

hallmark007: I don’t need another app to check my drone is ok to fly, and not  everyone has an extra device to check for something they can clearly  check with equipment they already have.

If you fly with a Smartdevice, then that is all equipment you need.  Plus some effort to load one of Apps that show magnetic field strengths.

One thing is clear from you response.  You have not tried it.  
Thus you have no experience to comment upon as to ease of use, and ability to detect magnetic fields of vary kind you have claimed caused TBE / crashes.

hallmark007 Posted at 2018-5-18 00:56
And BTW this is dji’s analysis , you seem to spend your time trying to twist what really happened and although you believe dji are lying this is their results.
It’s amazing that they could get so much information from not checking the log.

NON-WARRANTY PER DATA ANALYSIS. Compass interference FLY037 1. User took off from a metallic object causing immediate compass error.  

The Flight Log did not indicate Magnetic Compass Intereference until after takeoff.
DJI has never said how they came to conclusion the pilot (drone) took off from a metallic object.  

What drone operator said was he placed his drone 5-6 feet away from car, not on the car.  You yourself acknowledge that with your claims that drone was very near magnetic intereference, not enough to trigger warnings (nothing in log and pilot said nothing about errors or warnings), and as drone cleared area of magnetic interference from car, the drone became confused and went into TBE.

Now we are back to Catch-22.
DJI looks at log(s) and can see drone pilot took off from metallic object.  Yet, the drone did not signal Magnetic Interferenc Errors to RC / Smartdevice, and an after the fact note, no Magnetic Interference Errors entered in Flightlog.

If DJI can see drone is taking off from a metallic object, then there is a software problem for DJI's system failing to warn DJI pilot.

hallmark007 Posted at 2018-5-18 00:36
So again you are saying dji asked twenty to send in his drone to find out what happened and they just made up magnetic interference.
Do you realize how silly that sounds. His case was without a doubt magnetic interference and this was the decision of dji, you are now saying that dji are lying and being untruthful and maybe it’s not a good idea to send your drone into dji for analysis. Think about that for a minute.

hallmark007: Everything is there in both your drone and app to check for interference along with all other checks needed to fly your drone,  

Except according to your own analysis involving magnetic intereference that results in TBEs, the drone fails to detect and there is no Red flag on Field.

If you are going to use the GO-4 app compasses to check for magnetic inteference, then drone pilot must ensure he/she is far enough away from drone (according to your position over 10-meters) to ensure smartdevices compass is also not being effected by same magnetic interence source.   

hallmark007 Posted at 2018-5-18 00:36
So again you are saying dji asked twenty to send in his drone to find out what happened and they just made up magnetic interference.
Do you realize how silly that sounds. His case was without a doubt magnetic interference and this was the decision of dji, you are now saying that dji are lying and being untruthful and maybe it’s not a good idea to send your drone into dji for analysis. Think about that for a minute.

hallmark007:  You take your drone to a safe open area to fly, free from metal  structures concrete structures, you put your drone on the ground start  it up and do your preflight check one of these should be to check your  compass , just open your app and check it, if the values of your compass  are good then you don’t have any problem with your compass.

Is method you describe of comparing drone compass against smartdevice's compass using GO-4 app - pointed to or outlined in manuals for DJI's Mavics?

If yes, please post page number and paragraph numbers.  Thanks in advance.

If no, then two things:
1) Something similar needs to be in manuals.
2) Why is method you describe - THE only way?

HedgeTrimmer Posted at 2018-5-17 19:16
To Aardvark and hallmark007:

It appears both of you are essentially saying - The way I have suggested of detecting Magnetic Interference, using a free app on smartdevice, that is both easy and simple to use is of no need or no value, (aka pointless)?

"It appears both of you are essentially saying - The way I have suggested of detecting Magnetic Interference, using a free app on smartdevice, that is both easy and simple to use is of no need or no value, (aka pointless)?"

That is correct, and the logic is simple, the aircraft relies solely on data from its compass to fly, not the compass on the device. So in my mind the information from the display device compass and the App', has absolutely no bearing on how the aircraft detects or sees things. Whether or not it is accurate.

The technology that DJI provide is more than capable of detecting unwanted magnetic interference when working correctly. If you wish to use some other device to back up its findings then that's entirely your choice. But I see it as unnecessary.

Aardvark Posted at 2018-5-18 09:21
"It appears both of you are essentially saying - The way I have suggested of detecting Magnetic Interference, using a free app on smartdevice, that is both easy and simple to use is of no need or no value, (aka pointless)?"

That is correct, and the logic is simple, the aircraft relies solely on data from its compass to fly, not the compass on the device. So in my mind the information from the display device compass and the App', has absolutely no bearing on how the aircraft detects or sees things. Whether or not it is accurate.

Me: "It appears both of you are essentially saying - The  way I have suggested of detecting Magnetic Interference, using a free  app on smartdevice, that is both easy and simple to use is of no need or  no value, (aka pointless)?"

Aardvark: That is correct, and the logic is simple, the aircraft relies solely on  data from its compass to fly, not the compass on the device. So in my  mind the information from the display device compass and the App', has  absolutely no bearing on how the aircraft detects or sees things.  Whether or not it is accurate.

Issue is you are assuming drone's compass is not being effected by magnetic field prior to takeoff and drone will always Flag an Error to drone pilot.  Best example is one being talked about in this thread.  

There was no indication (according to pilot) prior to drone takeoff that drone's compass was being effected by magnetic interference (whatever source), which resulted in a crash.  It wasn't till after crash that Compass Errors were found in flightlog, and even then it was after takeoff.  DJI did come back with magnetic intereference prior to takeoff.  However no explanation as to how DJI came to that conclusion, nor did DJI explain why there was no entry in Flightlog prior to takeoff or why Drone Pilot was not alerted prior to takeoff.

I belive idea of comparing drone's compass against smartdevice's compass on GO-4 app screen prior to takeoff - bares out need.
Whether that is best and easiet method is questionable.

HedgeTrimmer Posted at 2018-5-18 09:19
hallmark007:  You take your drone to a safe open area to fly, free from metal  structures concrete structures, you put your drone on the ground start  it up and do your preflight check one of these should be to check your  compass , just open your app and check it, if the values of your compass  are good then you don’t have any problem with your compass.

Is method you describe of comparing drone compass against smartdevice's compass using GO-4 app - pointed to or outlined in manuals for DJI's Mavics?

No it’s not and I never said it was.

HedgeTrimmer Posted at 2018-5-18 08:59
NON-WARRANTY PER DATA ANALYSIS. Compass interference FLY037 1. User took off from a metallic object causing immediate compass error.  

The Flight Log did not indicate Magnetic Compass Intereference until after takeoff.

I think the use of the word metallic just simply means some kind of metal that caused magnetic interference, that is very easy to work out.
How did dji know magnetic interference simply because .dat file is furnished with much more information.

I think the mere fact that you would recommend anyone taking off within 18 inches of a car is the worst information I have seen given around here by a long way and helps no one.
It also rubbishes your whole idea , I don’t need another app your welcome to it.

hallmark007 Posted at 2018-5-18 10:08
No it’s not and I never said it was.

I did not say you did.  I only asked if it was.  As such compass comparing method is not DJI's, nor officially ''blessed'' by DJI.  Only one-way with possible problems.

I find petty god-like of you to push your method of comparing drone compass and smartdevice compass via GO-4 App; while poo-pooing another method.  

Along with poo-pooing another method - without having ever tried it.

hallmark007 Posted at 2018-5-18 10:20
I think the use of the word metallic just simply means some kind of metal that caused magnetic interference, that is very easy to work out.
How did dji know magnetic interference simply because .dat file is furnished with much more information.

hallmark007: I think the mere fact that you would recommend anyone taking off within 18 inches of a car is the worst information I have seen given around here by a long way and helps no one

Post a Screen Snap shot where I specifically "recommend anyone taking off within 18 inches of a car ".

hallmark007 Posted at 2018-5-18 10:20
I think the use of the word metallic just simply means some kind of metal that caused magnetic interference, that is very easy to work out.
How did dji know magnetic interference simply because .dat file is furnished with much more information.

hallmark007:  How did dji know magnetic interference simply because .dat file is furnished with much more information.

Is that not pointing to a failure of drone and/or firmware running on it?  

Drone detected magnetic interference, recorded it internally, but failed to send a very critical error message to RC / GO-4 App, which would have Alerted Pilot before takeoff.

Should not the drone have at least refused takeoff command (or to spin up props); until it was moved away from ''detected magnetic interference''?

HedgeTrimmer Posted at 2018-5-18 14:27
hallmark007:  How did dji know magnetic interference simply because .dat file is furnished with much more information.

Is that not pointing to a failure of drone and/or firmware running on it?  

Look Hedgetrimmer I’m here to try get help from others learn from their experiences , and try to help others with what I know, but at every hands turn you have been there trying to knock everything I say.

And while you try to knock my opinions that’s fine, but I will continue to try to help other users with what I have learned and what is best practice for flying dji drones, I have many years experience flying both commercially and as a hobbyist and I try to relay this experience to other users. You differ with almost everything I say, so it’s probably best we-end this bickering and move on because I believe most members have the savvy to choose what is best for them flying dji drones.

hallmark007 Posted at 2018-5-18 17:25
Look Hedgetrimmer I’m here to try get help from others learn from their experiences , and try to help others with what I know, but at every hands turn you have been there trying to knock everything I say.

And while you try to knock my opinions that’s fine, but I will continue to try to help other users with what I have learned and what is best practice for flying dji drones, I have many years experience flying both commercially and as a hobbyist and I try to relay this experience to other users. You differ with almost everything I say, so it’s probably best we-end this bickering and move on because I believe most members have the savvy to choose what is best for them flying dji drones.

hallmark007: I think the mere fact that you would recommend anyone taking off within 18 inches of a car is the worst information I have seen given around here by a long way and helps no one

Post a Screen Snap shot where I specifically "recommend anyone taking off within 18 inches of a car ".

Still waiting hallmark007.  

OK here's my story.  I just had my drone replaced by DJI due to Compass error and IMU defect.  I tested it in the back yard first with great results.  Next I placed it on my concrete front step and lifted off to about 40 meters.  It was just hovering there and suddenly took off over my roof and out of sight. I grabbed the sticks and regained control and was amazed just how far it had flown; approx. 300 Meters!  I was very concerned and thought that this drone would also have to be returned defective.  Then I happen to come across this posting, I downloaded the app and immediately went to my step to check for EMF.  I was there folks and the meter went RED!  It varied in strength as I moved it across my step and I realized I had found my problem.  So lets not "knock" this information or analyze it to pieces.  My Mini 2 did not pick up this magnetic interference before lifting off however the EMF Detector App did.  I will continue using this since it's a great tool to have and could save your drone from a flyaway.  Thanks for the post.