This is the very first time I have had a problem with my Mavic 2 Pro. It was at the start to take off.

  
  

You can see the following from a screen recording which I always do.

  

IMU and Compass was OK, Home point was on the map on the screen, but I never heard it being recorded. But display shows 16 satellites.

  
  

Started the motors OK and the went to take of. The drone took off about 5.10 cm up and motors closed down and the drone went on the deck.

  
  

Shut everything down, drone and GO 4 app and restarted all again and took of without any problems.

  
  

I have attached a link below for the flight data as well as a short screen recording of the accident.

  
  Appreciate any help. Thanks.


https://www.phantomhelp.com/LogViewer/9WBDWGILUY4PV53CGVR4

Your flight record only contains data for 2.8 seconds after you pushed the left stick to launch.
You were far too gentle with the throttle and in 2.8 seconds you had only pushed it to 15%.
The drone didn't lift far enough for the sensors to record any increase in height.

There is a potential problem showing in your data, but the flight didn't last long enough for it to cause a crash.
You launched from a reinforced concrete surface (always a bad idea) and the compass was deflected by the steel inside the concrete just below the drone.
The IMU takes its initial directional values from the compass, but because of the magnetic interference, this was bad data.

The flight record shows the drone at rest pointing just a little east of north at 18°.
But as the drone rises just a few centimetres from the concrete and away from the steel that deflected the compass, the compass heading changes to 3.5° without any rudder input to cause this.
If you had climbed higher, the heading angle would have changed more and you would have had a runaway yaw error incident.

Avoid launching from reinforced concrete surfaces in future and if you want to launch, push the throttle much harder to get the drone a couple of metres of the ground quickly.

For cases where you need to fly, can't relocate takeoff point, and it is from metal reinforced concrete; you can drastically reduced effects of steel in concrete by launching drone by hand or from a foot (or higher) non-ferrous (non-magnetic) platform.  Examples:  All wood picnic table, upside down plastic trash can, large tree stump, kids plastic play pool flipped over.  
Before launching, thinking about landing.  Hand capturing or landing on one of previous mentioned platforms.  A large tree stump is pretty small target with ground wind.

Agreed. The M2p is smarter than we are in shutting down. I think that is a good thing, especially now.

Labroides Posted at 4-30 16:00
Your flight record only contains data for 2.8 seconds after you pushed the left stick to launch.
You were far too gentle with the throttle and in 2.8 seconds you had only pushed it to 15%.
The drone didn't lift far enough for the sensors to record any increase in height.

Many thanks for your reply.

I understand what you are saying

However the deck on the pier was made of timber and the compass showed a low green value, as can be hard to see on the video clip.

Also how come that after restarting the drone again it flew fine? I also flew about 8 times from the same place during my stay there.

However, I must say that I can not remember that I actually test that the drone was pointing the same direction as on the map. I normally always do this. This time I also used a Suunto compass for checking that the drone faced north the correct way.

Any way, it all went well this time and many thank for your help.

HedgeTrimmer Posted at 4-30 19:04
For cases where you need to fly, can't relocate takeoff point, and it is from metal reinforced concrete; you can drastically reduced effects of steel in concrete by launching drone by hand or from a foot (or higher) non-ferrous (non-magnetic) platform.  Examples:  All wood picnic table, upside down plastic trash can, large tree stump, kids plastic play pool flipped over.  
Before launching, thinking about landing.  Hand capturing or landing on one of previous mentioned platforms.  A large tree stump is pretty small target with ground wind.

Yes, you are right, but the deck of that pier was made of thick timber, so I do not understand why this was happening.

GaryDoug Posted at 4-30 20:09
Agreed. The M2p is smarter than we are in shutting down. I think that is a good thing, especially now.

Yes. Absolutely much smarter and in this case quicker to shut down.

Labroides Posted at 4-30 16:00
Your flight record only contains data for 2.8 seconds after you pushed the left stick to launch.
You were far too gentle with the throttle and in 2.8 seconds you had only pushed it to 15%.
The drone didn't lift far enough for the sensors to record any increase in height.

Found a picture of what the pier look like. It is also mounted on concrete pillars. I also took off between the concrete pillars.

kyalami Posted at 4-30 21:39
Many thanks for your reply.

I understand what you are saying

However the deck on the pier was made of timber
OK .. It looked like concrete in the video.

and the compass showed a low green value, as can be hard to see on the video clip.
That makes no difference.
It shows green because the strenght of the problem magnetic field was not much stronger than the earth's normal magnetic field .... but the direction was quite different.
That made the drone's compass read incorrectly and I can see that because the compass heading started to swing as soon as the drone lifted an inch or so off the deck.
Normally the drone's heading won't change until you apply some rudder input.
Your heading data was changing as the drone rose as if you were rotating the drone clockwise (but you weren't).

There will have been a steel bolt or something near to where the drone was placed.

Also how come that after restarting the drone again it flew fine?
Because there was nothing at all wrong with the drone or its compass.
The problem was where you placed it to power up.

I also flew about 8 times from the same place during my stay there.
Not exactly the same place (to within a few centimetres).

Labroides Posted at 4-30 22:26
However the deck on the pier was made of timber
OK .. It looked like concrete in the video.

OK many thanks again for your further explanation Labroides and now I understand what happened. Yes there was some heavy bolts or screws down to the big timber beams underneath the top beams. I have learned a lot from you about this now.

kyalami Posted at 4-30 21:42
Yes, you are right, but the deck of that pier was made of thick timber, so I do not understand why this was happening.

Labroides likely nailed it.   Wood deck is most likely secured with steel bolts.  Perhaps steel rails and steel brackets are used too.  

There are free Smartphone Apps available which can detect and log electromagnet fields or disturbances to Earth's magnetic field.   

HedgeTrimmer Posted at 5-1 13:59
Labroides likely nailed it.   Wood deck is most likely secured with steel bolts.  Perhaps steel rails and steel brackets are used too.  

There are free Smartphone Apps available which can detect and log electromagnet fields or disturbances to Earth's magnetic field.

Yes, I saw the large row of bolts or screws and placed the drone between them about 30 cm from each side of the row of them to minimize the effect.

That is interesting to know about the Apps that can detect disturbances in earth magnetic field. I will certainly look for this. Many thanks for advising this HedgeTrimmer.

kyalami Posted at 5-1 22:44
Yes, I saw the large row of bolts or screws and placed the drone between them about 30 cm from each side of the row of them to minimize the effect.

That is interesting to know about the Apps that can detect disturbances in earth magnetic field. I will certainly look for this. Many thanks for advising this HedgeTrimmer.

Two Apps I like, GaussTeslaMeter and Tesla Recorder.  Both Apps use your SmartPhone's built-in electronic compass system.  Apps look at data from magnetic field sensors for each of three axis, X,Y,&Z.   

If you do get one of Apps, and have time, it would be interesting to see what App says when your SmartPhone is placed on wooden pier in position you described.  Then moved left to right and forwards and backwards.  Lastly slowly raised up.

You might want to test / practice with App before hand.  You can put a steel object on ground or even a small magnet to see how App shows data as you move your SmartPhone further/closer away in all three axis.

Cheers!    

HedgeTrimmer Posted at 5-2 05:35
Two Apps I like, GaussTeslaMeter and Tesla Recorder.  Both Apps use your SmartPhone's built-in electronic compass system.  Apps look at data from magnetic field sensors for each of three axis, X,Y,&Z.   

If you do get one of Apps, and have time, it would be interesting to see what App says when your SmartPhone is placed on wooden pier in position you described.  Then moved left to right and forwards and backwards.  Lastly slowly raised up.

Hi HedgeTrimmer,
Many thanks for advising the 2 apps for a smartphone. I will certainly try them. Unfortunately I am unable to try them on the wooden pier where I had the problems, as that was when I was down in Maldives on my holiday. Now I am back to my home country Sweden again. I probably test this by going closer to my car. So, I will from now on always carry this app in my phone and do a test everything I take off from a now place that I do not know anything about, just to be sure. Thank you very much again for your kind assistance HedgeTrimmer.
Cheers

kyalami Posted at 5-2 05:45
Hi HedgeTrimmer,
Many thanks for advising the 2 apps for a smartphone. I will certainly try them. Unfortunately I am unable to try them on the wooden pier where I had the problems, as that was when I was down in Maldives on my holiday. Now I am back to my home country Sweden again. I probably test this by going closer to my car. So, I will from now on always carry this app in my phone and do a test everything I take off from a now place that I do not know anything about, just to be sure. Thank you very much again for your kind assistance HedgeTrimmer.
Cheers

Your drone has a perfectly good magnetomer that can be used to show you magnetic interference problems with your launch point.
After power-on, check that the drone icon(arrowhead) on your map window is pointing in the same compass direction as the real drone is.
If not, the drone's compass has been deflected by magnetic interference.

The kind of problems you are wanting to avoid are usually small and close to the compass and an app on your phone isn't going to be any help.
Things like a nail just an inch from the compass etc.

Labroides Posted at 5-2 06:41
Your drone has a perfectly good magnetomer that can be used to show you magnetic interference problems with your launch point.
After power-on, check that the drone icon(arrowhead) on your map window is pointing in the same compass direction as the real drone is.
If not, the drone's compass has been deflected by magnetic interference.

Yes, you are absolutely right Labroides. I just did not think of this first. It makes fully sense what you are saying. Many thanks again for your kind assistance.
Edit: I actually do this everytime before I fly.

Labroides Posted at 5-2 06:41
Your drone has a perfectly good magnetomer that can be used to show you magnetic interference problems with your launch point.
After power-on, check that the drone icon(arrowhead) on your map window is pointing in the same compass direction as the real drone is.
If not, the drone's compass has been deflected by magnetic interference.

Your experience is different from mine.  The App on my SmartPhone (iPhone) does a better job of detecting and showing variations to earths magnetic field, aka warning of magnetic interference.

In my testing and experience with the Apps, amounts of magnetic interference which are to subtle because of drone's orientation and position on ground to deviate compass sufficiently to be noticed between drove's compass and another compass device, are better shown by apps.  When drone is launched, its position changes, and sometimes it's orientation, which effects magnetic XYZ axis field detector(s**).   **Mavic Pro has a pair of detectors.

Either way, (your preference) drone internal compass or SmartPhone app, the important thing to remember is to move drone to a nearby location where there is no interference; which takes litte effort and little time. With most intererence it only takes moving drone 1-foot.  With large metal buildings interference might push 2-feet.

HedgeTrimmer Posted at 5-2 08:43
Your experience is different from mine.  The App on my SmartPhone (iPhone) does a better job of detecting and showing variations to earths magnetic field, aka warning of magnetic interference.

In my testing and experience with the Apps, amounts of magnetic interference which are to subtle because of drone's orientation and position on ground to deviate compass sufficiently to be noticed between drove's compass and another compass device, are better shown by apps.  When drone is launched, its position changes, and sometimes it's orientation, which effects magnetic XYZ axis field detector(s**).   **Mavic Pro has a pair of detectors.

"drone's orientation and position on ground to deviate compass sufficiently to be noticed between drove's compass and another compass device"

Leading back to an option, I wish DJI would implement for GO - CrystalSky etc. software and SmartDevices.   

Instead showing only a needle; the graphic compass, in middle of it, would show Degrees 0-359.  

Eliminating the eyeball guessing of whether drone's internal compass is being effected by magnetic interference and by how much.

HedgeTrimmer Posted at 5-2 08:43
Your experience is different from mine.  The App on my SmartPhone (iPhone) does a better job of detecting and showing variations to earths magnetic field, aka warning of magnetic interference.

In my testing and experience with the Apps, amounts of magnetic interference which are to subtle because of drone's orientation and position on ground to deviate compass sufficiently to be noticed between drove's compass and another compass device, are better shown by apps.  When drone is launched, its position changes, and sometimes it's orientation, which effects magnetic XYZ axis field detector(s**).   **Mavic Pro has a pair of detectors.

The App on my SmartPhone (iPhone) does a better job of detecting and showing variations to earths magnetic field, aka warning of magnetic interference.
The kind of fields that are likely to cause trouble are often very small and wouldn't be detected unless your sensor is within just a couple of inches.

In my testing and experience with the Apps, amounts of magnetic interference which are to subtle because of drone's orientation and position on ground to deviate compass sufficiently to be noticed between drove's compass and another compass device, are better shown by apps.
If the magnetic field is too subtle to show any appreciable difference between the drone's heading and the representation of the drone's heading displayed on the map window, there isn't a problem.
A yaw error problem happens when the compass in the drone is deflected significantly from what it reads when away from the magnetic interference.
No deflection = no problem.

Labroides Posted at 5-2 17:34
The App on my SmartPhone (iPhone) does a better job of detecting and showing variations to earths magnetic field, aka warning of magnetic interference.
The kind of fields that are likely to cause trouble are often very small and wouldn't be detected unless your sensor is within just a couple of inches.

From my own testing, it depends upon what source of magnetic field interference is.  Large source like a metal building, chain link fence, 20-foot of 2-foot steel pipe, the distance is about 1-meter.  Most of effects of those sources fall off once past 1/2-meter.  Generalized the Field Strength falls off as reciprocal of distance squared (1/dxd).

The OPs case may be such a case of small amount of magnetic interference.  Where drone's compass system won't detect magnetic field interference, and App running on smartphone design for said purpose will.  Only in person testing would tell for OPs case.  I do know from testing, two Apps did show interference at further distances for even small amounts of steel.


The problem with comparing compass of drone to compass of SmartDevice is a compounded by needing to eyeball direction the drone is pointing and eyeball direction of SmartDevice running GO/4.   Along with estimating direction drone's analog compass is pointing and SmartDevice compass is pointing.  Issue being what is appreciable difference?  5-degrees, 10-degrees, 15-degrees.  And how well you can eyeball drone and read drone's analog compass.

If one is going to check drone's compass for incorrect reading, due to magnetic field interference, best to point drone in a verified N/E/S/W direction.  Eliminating eyeballing direction of SmartDevice.

HedgeTrimmer Posted at 5-2 19:14
From my own testing, it depends upon what source of magnetic field interference is.  Large source like a metal building, chain link fence, 20-foot of 2-foot steel pipe, the distance is about 1-meter.  Most of effects of those sources fall off once past 1/2-meter.  Generalized the Field Strength falls off as reciprocal of distance squared (1/dxd).

The OPs case may be such a case of small amount of magnetic interference.  Where drone's compass system won't detect magnetic field interference, and App running on smartphone design for said purpose will.  Only in person testing would tell for OPs case.  I do know from testing, two Apps did show interference at further distances for even small amounts of steel.

From my own testing, it depends upon what source of magnetic field interference is.  Large source like a metal building, chain link fence, 20-foot of 2-foot steel pipe, the distance is about 1-meter.  Most of effects of those sources fall off once past 1/2-meter.  Generalized the Field Strength falls off as reciprocal of distance squared (1/dxd).
Large steel items are obvious without using an app.
They have strong fields that trigger a magnetic interference warning in the DJI app.
They are not the issue.
The issue is magnetic fields of low strength .. not strong enough to trigger a warning.
Because they are close to the same field strength as the earth's normal field, but can still cause a compass sensor to give an incorrect directional indication.

Only in person testing would tell for OPs case.  I do know from testing, two Apps did show interference at further distances for even small amounts of steel.
If your app is that sensitive, it would be useless in an area like the OP launched from.
Your description makes it sound like it can pick up nails or bolts all around, when only those very close (a couple of inches) would matter.

Labroides Posted at 5-2 21:24
From my own testing, it depends upon what source of magnetic field interference is.  Large source like a metal building, chain link fence, 20-foot of 2-foot steel pipe, the distance is about 1-meter.  Most of effects of those sources fall off once past 1/2-meter.  Generalized the Field Strength falls off as reciprocal of distance squared (1/dxd).
Large steel items are obvious without using an app.
They have strong fields that trigger a magnetic interference warning in the DJI app.

The large items may not be so obvious.  Such as buried items like metal piping or in case of one member here a buried steel flatbed trailer.  Coupled to Distance from large items.   Like steel I-beams under a wood dock?

Clearly you have not used such Apps.  Or you would have seen how Apps adjust their sensitivity.  One of apps will back adjust it's graphing when it comes upon a strong source of magnetic field interference.

One thing about our discussion we are in agreement on.   The distance from and size of source magnetic field interference matters as to whether drone will be effected.  A drone has to be within a few feet of large ferrous metal object or within inches of small ferrous metal object for internal compass(es) to be effected.   The idea a drone is effected tens of feet away from steel, resulting in Toilet Bowl Effect crash has been hyped.