Can flying near radio towers interfere with Mavic Pro?

[Meta4]

Please do us the common courtesy to not call us "mostly from people who have no idea"

Well you two aren't most of the people that were making guesses, but neither of you has analysed the flight data and pointed out how any of what happened could be attributed to flying 200 metres from the tower.
So far all you've come up with is .. it might have.
And without analysis of the data and something to support your guesses, you may as well be blaming it on Medieval ghosts in the Reigate Hill Fort.

tell us what qualifications you are basing your 'theories' on ... If you have some professional experience and qualifications to put some weight behind what you say, then please do

I have a science degree (in an unrelated field) and 25 years working as a professional scientist.
On top of that, have been flying professionally for more than 4 years and a moderator on a sister forum where I have analysed data from hundreds of flight incidents to find the cause of the incident and/or find lost drones all over the world.

 

[ac0j]

I am pretty good with a YoYo.

 

[FoxhallGH]

Thanks for presenting your credentials Meta4. As a scientist you'll agree that it would be stupid to make a statement without using 'may' or 'maybe' if we aren't in a position to run an experiment. As a scientist, I'd expect you to haul me over the coals if I did talk in absolutes without experimental confirmation. I respect your experience and knowledge - but can't understand why you disregard not only my (and Congoblue's) experience - but the manufacturer's representative who tells us that DJI recognise that radio towers can be a source of trouble for their product, and the warning message of the drone itself that told the owner it was in an area of high RF interference. Even the compass error can be attributed to RF Interference. I've worked with a lot of systems that have a set of error codes that don't cover every eventuality. Due to the nature of RF interference it's very possible that the Mavic is using a limited vocabulary to try to tell us what's wrong, as the interference can literally drown out all its systems.
Perhaps we just have to agree to disagree on this one - and tho' you may want to fly your drone around towers bristling with microwave dishes, I certainly won't be joining you. Fly safe Meta4 ...

 

[Breugnir]

Out of topic - on this video in 10:44 - 13:00 you can see a guy flying Phantom nearby "Duga Radar" (Eye of Moscow) - the huge radar system located in Ukraine (a part of a former Soviet Union) close to Chernobyl. Some say that the "Russian Woodpecker" still transmits ;-)

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[Meta4]

but can't understand why you disregard not only my (and Congoblue's) experience - but the manufacturer's representative who tells us that DJI recognise that radio towers can be a source of trouble for their product, and the warning message of the drone itself that told the owner it was in an area of high RF interference. Even the compass error can be attributed to RF Interference.

I disagreed because:

• No-one has related their "hypothesis" that the tower was involved to the incident to show how the tower caused what was observed. So far your hypothesis is up to the perhaps stage.
• The observed behaviour is exactly what happens when launching from close proximity to steel items (I've seen hundreds of incidents like this).
• The flight problem disappeared and did not return later in the first flight or at all in the second flight. If it was as suggested, you would expect it to be a continuing problem around that area.
• DJI's comment was too vague and generalised to have any relevance to the incident. It was their standard copy/paste response given by someone that probably doesn't even fly.

Perhaps a competent flying physicist, known for his analysis of DJI flight logs could comment @sar104 ?

 

[sar104]

I disagreed because:

• No-one has related their "hypothesis" that the tower was involved to the incident to show how the tower caused what was observed. So far your hypothesis is up to the perhaps stage.
• The observed behaviour is exactly what happens when launching from close proximity to steel items (I've seen hundreds of incidents like this).
• The flight problem disappeared and did not return later in the first flight or at all in the second flight. If it was as suggested, you would expect it to be a continuing problem around that area.
• DJI's comment was too vague and generalised to have any relevance to the incident. It was their standard copy/paste response given by someone that probably doesn't even fly.

Perhaps a competent flying physicist, known for his analysis of DJI flight logs could comment @sar104 ?

I'd be happy to take a look. For those kind of errors we really need to see the mobile device DAT file as well as the txt log posted earlier:

How to retrieve a V3.DAT from the tablet

 

[FoxhallGH]

OK - here's my questions with my Engineers hat on ... The flight logs are telling us 'when' things occurred during the flight - but not 'why' (unless I'm not looking at the correct info). So ...
- The flight log is telling us that the 'Yaw errors', Compass errors and heading exceptions occurred after takeoff, at about 33 seconds into the flight, and at an altitude between 70 and 86 feet. So how can that be something interfering from the ground?
- The take-off point gave the drone 13 GPS satellites, and that improved to 15 after take-off. The Mavic then updated the home point OK and appears to have had a happy take-off and departure. Again - if there was something in the ground, why didn't it show up when the Mavic was near the ground, rather than 80 ft up and out over the middle of the grass field?
- DJI have used the same electronics as used in mobile phones for the key components in their Drones. DJI use 'Hall-Effect' magnetometer integrated circuit devices as a compass, capable of sensing the earth's magnetic field in 3 axis. These devices are sensitive to magnetic lines of force. Radio Frequency radiation is Electro-Magnetic in it's nature. I've had a quick look round but can't find an answer to the question "does RF radiation effect a magnetometer integrated circuit?"
- Wikipedia has a good entry regarding the Reigate Transmitting station [Reigate transmitting station - Wikipedia]. It lists a total of 15 transmitters covering Digital TV 474 to 576 MHz (6 transmitters each 2KW), Analogue Radio (2 transmitters 102.7 & 104 MHz @ 3.6 KW & 4 KW), and digital radio (7 transmitters 213.36 to 227.36 MHz @ 1 to 1.5 KW).
In total, the listed transmitters produce 26.71 KW of RF radiation. However, looking at the Google Earth and Google Map [ground] views of the mast at that site, there appears to be a lot more point-to-point link Microwave dishes (attached to the mast) that will be operating in the GHz bands - which are simply not mentioned in the Wikipedia article. In addition, there are large ground standing dishes which are pointing across the field that the Mavic was flying on, at a low azimuth i.e. they appear in google earth as ellipses rather than circles which indicate they are not pointing upward. These are also not mentioned in the Wiki article.
- So with all that in mind: What effect will 26KW of continuous wide frequency VHF radiation, plus unknown UHF microwave radiation, have on the un-screened (the body is plastic), electronics in the Mavic Pro? How resilient are magnetometers to high-power RF?? What effect does high power RF have on the Mavic Pro in general?? Is the Mavic capable of producing log entries showing the 'degree' of stress it is under from sources of interference (i.e. does it squawk just as loud for a little interference as it does for a whole heap!)??
And - why would it act differently to other sensitive electronic devices sitting in high-power RF radiation??

 

[sar104]

OK - here's my questions with my Engineers hat on ... The flight logs are telling us 'when' things occurred during the flight - but not 'why' (unless I'm not looking at the correct info). So ...
- The flight log is telling us that the 'Yaw errors', Compass errors and heading exceptions occurred after takeoff, at about 33 seconds into the flight, and at an altitude between 70 and 86 feet. So how can that be something interfering from the ground?
- The take-off point gave the drone 13 GPS satellites, and that improved to 15 after take-off. The Mavic then updated the home point OK and appears to have had a happy take-off and departure. Again - if there was something in the ground, why didn't it show up when the Mavic was near the ground, rather than 80 ft up and out over the middle of the grass field?
- DJI have used the same electronics as used in mobile phones for the key components in their Drones. DJI use 'Hall-Effect' magnetometer integrated circuit devices as a compass, capable of sensing the earth's magnetic field in 3 axis. These devices are sensitive to magnetic lines of force. Radio Frequency radiation is Electro-Magnetic in it's nature. I've had a quick look round but can't find an answer to the question "does RF radiation effect a magnetometer integrated circuit?"
- Wikipedia has a good entry regarding the Reigate Transmitting station [Reigate transmitting station - Wikipedia]. It lists a total of 15 transmitters covering Digital TV 474 to 576 MHz (6 transmitters each 2KW), Analogue Radio (2 transmitters 102.7 & 104 MHz @ 3.6 KW & 4 KW), and digital radio (7 transmitters 213.36 to 227.36 MHz @ 1 to 1.5 KW).
In total, the listed transmitters produce 26.71 KW of RF radiation. However, looking at the Google Earth and Google Map [ground] views of the mast at that site, there appears to be a lot more point-to-point link Microwave dishes (attached to the mast) that will be operating in the GHz bands - which are simply not mentioned in the Wikipedia article. In addition, there are large ground standing dishes which are pointing across the field that the Mavic was flying on, at a low azimuth i.e. they appear in google earth as ellipses rather than circles which indicate they are not pointing upward. These are also not mentioned in the Wiki article.
- So with all that in mind: What effect will 26KW of continuous wide frequency VHF radiation, plus unknown UHF microwave radiation, have on the un-screened (the body is plastic), electronics in the Mavic Pro? How resilient are magnetometers to high-power RF?? What effect does high power RF have on the Mavic Pro in general?? Is the Mavic capable of producing log entries showing the 'degree' of stress it is under from sources of interference (i.e. does it squawk just as loud for a little interference as it does for a whole heap!)??

The yaw errors appear after the aircraft has left the location of magnetic interference because that is when the compass data and the IMU data begin to disagree. On the ground, before takeoff, the IMU yaw is initialized to the compass heading so at that point, even if the compass heading is wrong due to interference, there is no disagreement. Once the aircraft takes off, if the compass heading changes as the interference goes away but the rate gyros detect no rotation (or different rotation), then the compass and IMU disagree and you now have a yaw error.

 

[ac0j]

OMG.....
I am putting my hobby drone flyer hat on and saying enough already. It happened on ONE flight, other flights in the same place were without problems. Kind of rules out the tower, YES? Since most of the frequency data you bothered to look up is mostly constant on type transmissions.
I have seen people flying near 100,000 watt radio and tv towers doing tower inspections without a problem. I have climbed one of these towers to make some repairs, had to have the output turned down to 1/2 or less to keep me from getting cooked near the top, but my 2-way radio to the ground crew worked fine.

 

[FoxhallGH]

The yaw errors appear after the aircraft has left the location of magnetic interference because that is when the compass data and the IMU data begin to disagree. On the ground, before takeoff, the IMU yaw is initialized to the compass heading so at that point, even if the compass heading is wrong due to interference, there is no disagreement. Once the aircraft takes off, if the compass heading changes as the interference goes away but the rate gyros detect no rotation (or different rotation), then the compass and IMU disagree and you now have a yaw error.

Interesting ... Are we seeing a magnetic Interference error before takeoff? Or are you saying that it's possible that the Mavic can have this condition and not show us anything until after it takes off?? Wow - if that's the case - its a little disturbing!

 

[ac0j]

Interesting ... Are we seeing a magnetic Interference error before takeoff? Or are you saying that it's possible that the Mavic can have this condition and not show us anything until after it takes off?? Wow - if that's the case - its a little disturbing!

I am beginning to wonder if you are as smart as your resume suggests. (joking!)
Read @sar104 's post ONE MORE TIME, this time dont look for errors, and look at what he said. The compass was effected ON THE GROUND where metal must have been present. When he lifted off the compass corrected, but it is too late for the IMU.

 

[FoxhallGH]

I am beginning to wonder if you are as smart as your resume suggests. (joking!)
Read @sar104 's post ONE MORE TIME, this time dont look for errors, and look at what he said. The compass was effected ON THE GROUND where metal must have been present. When he lifted off the compass corrected, but it is too late for the IMU.

I may be getting a bit jaded my friend ... it's 1:40 am in my time zone! ... What I mean is that it looks like everything was reporting OK by the Mavic when it took off. Now - if it took off inside an area of screwed up interference [e.g. metal in the ground] - that's telling me that the Mavic can appear to be a happy bunny before take-off, when it's actually far from it - That's not very nice that the drone can start up and take off in a mode where it's compromised, but not let you know until it tries to correct itself ... Is that what you are saying sar104?? - or should I just go and get some sleep!!

 

[ac0j]

I may be getting a bit jaded my friend ... it's 1:40 am in my time zone! ... What I mean is that it looks like everything was reporting OK by the Mavic when it took off. Now - if it took off inside an area of screwed up interference [e.g. metal in the ground] - that's telling me that the Mavic can appear to be a happy bunny before take-off, when it's actually far from it - That's not very nice that the drone can start up and take off in a mode where it's compromised, but not let you know until it tries to correct itself ... Is that what you are saying sar104?? - or should I just go and get some sleep!!

YOU GOT IT!
When taking off from a questionable site, one should always look the the heading shown in the app and make sure it is the same as the direction the Mavic is pointing before take off, if not, move and try again!

 

[FoxhallGH]

YOU GOT IT!
When taking off from a questionable site, one should always look the the heading shown in the app and make sure it is the same as the direction the Mavic is pointing before take off, if not, move and try again!

Brilliant! - That's the piece of advice that is the diamond at the end of this trail!!! Thanks sar104 and ac0j ... I've not realised that condition can exist in the Mavic without it doing something like flashing its tail lights and/or messaging the Go 4 app' before it lets you take off ... I thought you'd get the same sort of messages and LED signals as if you put the drone onto steel reinforced concrete. I'll add that gem to the pre-flight check.
[Unfortunately ac0j - 9 times out of 10, we won't know a site is 'questionable' until something like this happens ...]

 

[ac0j]

[Unfortunately ac0j - 9 times out of 10, we won't know a site is 'questionable' until something like this happens ...]

If on concrete, this is true. Always see if the map display is showing the same direction that the actual aircraft is pointing, EVERY TIME!

 

[Meta4]

I've not realised that condition can exist in the Mavic without it doing something like flashing its tail lights and/or messaging the Go 4 app' before it lets you take off ... I thought you'd get the same sort of messages and LED signals as if you put the drone onto steel reinforced concrete. ]

This is one of the most common causes of serious flight incidents.
If you put your drone on your car roof, there's so much steel so close that the compass screams its warning at you.
If you put it on reinforced concrete, you've bought a lottery ticket.
Perhaps the steel is too deep and/or the compass is above a big hole in the mesh, meaning your ticket was lucky and you fly unaffected.
Perhaps the compass is just an inch above a point where the mesh rods cross and the compass screams at you and you can't start the motors. Another lucky ticket.
Or .. perhaps you bought the losing ticket and the steel was too deep/small to set off alarm bells with the compass, but the magnetic field was still strong enough to cause compass initialisation problems.
Or maybe the additional field's alignment is too different from the earth's normal field (?)
When you fly with that unlucky ticket, the effect can vary but it often involves the drone taking off at speed and being uncontrollable.

The yaw errors appear after the aircraft has left the location of magnetic interference because that is when the compass data and the IMU data begin to disagree. On the ground, before takeoff, the IMU yaw is initialized to the compass heading so at that point, even if the compass heading is wrong due to interference, there is no disagreement. Once the aircraft takes off, if the compass heading changes as the interference goes away but the rate gyros detect no rotation (or different rotation), then the compass and IMU disagree and you now have a yaw error.

Thanks for the eloquent description of the compass initialisation/yaw error problem.
It's a difficult concept to understand at first and not easy to explain.

 

[Slim.slamma]

When you fly with that unlucky ticket, the effect can vary but it often involves the drone taking off at speed and being uncontrollable

First time I ever flew with my i1 it took me 10 minutes probably to get control again after take off. Luckily I had some phantom standard experience.
The only thing I could do was climb to counter the forward thrust. Eventually it settles down like riding a bulll

 

[FoxhallGH]

With the advice from above in mind, I've just reviewed the video from the flight and done some comparisons to the logs. It's now apparent that in the video, the Mavic's yaw axis is aligned with the tree-line on the edge of the field, and the camera is showing the main antenna site a few degrees off to the right, with the second tower a bit less than than that. The video also shows the Mavic as looking almost directly along a trodden footpath on the edge of the field, and that too shows up on the flight log display. It remains pointing in that direction through the vertical climb after the lift-off ... Would we expect to see the arrow representing the drone on our controller map display, pointing along the tree-line/footpath too? However, the first Log entries [up until 27.6 seconds], show the arrow representing the Mavic pointing about 20 degrees to the left of the camera view shown in the video. ac0j ... Is this showing us the proof of the misalignment you describe?? - and would this same alignment be showing in the controller's map view on the Go 4 app'??

 

[adam3112]

I must admit I'm pretty neutral in terms of who I feel is right or wrong in this debate and be honest in saying I don't have a clue about radio towers, and what effect they may potentially or not have on electronics, other than I suspected it may of had some effect, hence the post.

So far there isn't a clear answer on whether it was the tower or something in the ground from where i took off from which caused my issue but one thing I'll take away from this is I won't be flying in that field or anywhere near that site again lol. I strongly advise others to do the same, unless you want to practice flying in Atti.

I feel extremely lucky and delighted to have my Mavic back with me as I could have lost it in my first week of ownership and would have been one of the worst days of my life.

I'm grateful to everyone on this forum offering their informative and intelligent feedback in to the possible causes of what happened and interested in reading further posts about this. I think it is important for us drone enthusiasts to take extra precaution when choosing the areas to fly in.

When I get home from work this-evening I'll look to post the .DAT file if it might reveal further clues as to what had happened?

 

[Meta4]

So far there isn't a clear answer on whether it was the tower or something in the ground from where i took off from which caused my issue

It's pretty clear that it had nothing at all to do with the tower.