I feel the need to share the following:

I almost had a fly away yesterday due to my own stupidly.... but was very, very lucky.

Piloted the Spark in the front garden in the procimity of a cell tower, about 200m away.
Everything was normal for the 1st 5 minutes of the flight at an altitude of 30m.
I then increased the altitude to 38m and then all went wrong . Got electromagnetic interference and the Spark just took off. I could also not see it as from my view point trees were in my way and was also not sure in which direction it went.  No cell feedback and not unsure if it was in front or at the back of me and panic set in.

To cut a long story short it travelled about 300m+(the max distance was set at 100m) away from me (connection with the cell and GPS recovered) and it wanted to land behind a house.
It lost signal with the RC and it activated RTH up to 100m away from home point and then paused. I then reactivated the RTH and it come all the way home. Safe and sound and I was shaking like a leave. All of this I only learned afterwards on reviewing the flight log, cell video and HD video.

Lessons learned.

Always make sure that you pilot LOS. If you cannot see it you cannot control it.

Stay away from cell phone towers (The Spark at 38m was directly inline with the cell tower antennas).

Look less at the cell phone screen and more at the drone, 10% at the cell and 90% at the drone if you pilot via RC.

Thank you very much for sharing your experience and the tips. This is a great help to our co-pilot. Always have safe flight and enjoy!

Congrats on not losing it!
When you finally found it what was it doing? Hovering? Moving?
It would be interesting to finally find out why magnetic interference makes it go berserk instead of just hovering or even RTH.  

Thank you DJI Natalia
Could you please remove the 2 photos as it is not relevant to my story.

Hi Antipaxi
What I can figure out is that the drone was in a direct path between 2 cell phone towers Tx/Rx antennas (high power transmitters) that are about 1km apart. So the drone also lost GPS P capability. According to the flight record it was just 4m away from the home point at the time of the interference and then within a second 208m away. Complete straight line. According to the HD video footage it was trying to land.
So glad that no damage were done and got it back with out damage or loss.

I always feel saddened when someone reports a flyaway but in this case relieved you didn't lose your robotic minion.

All these reported incidents, all with a common theme, do give me cause for concern. The route of this concern is the reliability of the internal digital compass and the bad science that gets banded around with respect to electromagnetic interference. In a previous life I worked in the space industry with emphasis on radio communications (DC to light) and remote sensors, so I have a reasonable knowledge of the inner workings of flight controllers and associated ancillary components. So the notion that a Spark, or any consumer “drone”, can be downed by a distant powerline or radio mast interfering with the onboard electronics to a degree defies logic. The Spark uses similar, if not identical, magnetometers as those found in the compass circuits of cellphones. When you take into account the inverse square law  governing near field RF and magnetic field strengths over distance the strength of the field created by even a powerful cell tower a few meters away is less than that experienced by the compass in a phone from the internal WiFi and cellular associated RF circuitry. Also these sources are AC in nature so significantly less problematic than a DC source.

The ambient, or natural, magnetic field strength is around 40uT to 50uT, depending on ones position on the globe. The measurements I’ve done with my Spark show that the level at which the onboard compass becomes compromised at is around 400uT and that’s with the source, a small permanent magnet (a DC source) placed right on the front of the Spark. Another measurement I took was from a 400Watt UHF transmitter, at twenty feet from the antenna, produced a level of negligible difference from that of the Earths natural magnetic field.  I’ll emphasise that these are not detailed scientific measurements rather done with common Arduino components.

So why does the apparent failure of the onboard compass  result in a sudden flyaway? And why does it fail in the first place. Theoretically the Spark should still be able to operate in GPS mode without a compass as it knows it’s attitude from the IMU and it’s location and bearing while in motion from the GPS circuitry. At the moment only DJI can answer this as they have seen fit to reimburse many users whom have experienced such failures based on the post analysis of the flight data. I’ll admit that I place some credence on the popular hypothesis that the last FW update may have a hand to play in it but I don’t have any hard evidence to back this up, only the opinions of others.

62+,

Would you be so kind and download your flight log to http://www.phantomhelp.com/LogViewer/Upload/ and share it with us?
While your description and explanation is plausible it would be good to confirm what really happened. The 4 metres from home point one second and 208 metres the next - as you say - is almost certain proof that AC lost its GPS bearings and could not calculate distances properly. The question is - why? Distant cell towers? Hmm..

There are many threads in this forum recently where people try to really understand what is going on. It is too easy to jump to conclusions - I side with Nidge here. Your flight log may help.

Nidge Posted at 2018-6-14 14:26
I always feel saddened when someone reports a flyaway but in this case relieved you didn't lose your robotic minion.

All these reported incidents, all with a common theme, do give me cause for concern. The route of this concern is the reliability of the internal digital compass and the bad science that gets banded around with respect to electromagnetic interference. In a previous life I worked in the space industry with emphasis on radio communications (DC to light) and remote sensors, so I have a reasonable knowledge of the inner workings of flight controllers and associated ancillary components. So the notion that a Spark, or any consumer “drone”, can be downed by a distant powerline or radio mast interfering with the onboard electronics to a degree defies logic. The Spark uses similar, if not identical, magnetometers as those found in the compass circuits of cellphones. When you take into account the inverse square law  governing near field RF and magnetic field strengths over distance the strength of the field created by even a powerful cell tower a few meters away is less than that experienced by the compass in a phone from the internal WiFi and cellular associated RF circuitry. Also these sources are AC in nature so significantly less problematic than a DC source.

Nidge,

Good analysis.
You say: "Theoretically the Spark should still be able to operate in GPS mode without a compass as it knows it’s attitude from the IMU and it’s location and bearing while in motion from the GPS circuitry."

DJI drones (and not only DJI) are designed to fly by co-operation between compass, IMU and GPS co-ordinates. While, as you pointed out, it is theoretically possible to return home with GPS and IMU only (AC would need to do a bit of random "hunt" at first before setting on a right course), it is not possible to manually control flight without compass. This is basically due to the method drone designers use by comparing COMMANDED to PHYSICAL co-ordinates of the drone and adjusting flight path accordingly. It's a bit complicated and too long to explain here but Google it.

Because of this DJI did a simple and effective design shortcut. When compass and IMU do not agree, Spark is dropped to ATTI mode. It is basically saying - I have no idea what is wrong: compass or IMU (or to what extent it is wrong) so I better give up and let the pilot control me manually. So even with a strong and good GPS signal it exits P-GPS mode.

Whether we like it or not, it is by design. Of course, one can argue that instead of dropping to ATTI, Spark could simply return to home without compass. Sure - but think about ramifications. Designers would need to block the pilot from any manual intervention since allowing for manual control with GPS on and compass and IMU misaligned could very well result in the "toilet bowl effect" where controlling Spark would be, saying the least, very difficult.

So, either Spark returns home and lands without giving pilot any opportunity to control it on its way back, or it goes ATTI and allows full manual control with all its benefits and dangers. DJI chose the latter.

I do not side with DJI here. As a matter of fact, I am very interested to really understand what is going on and why, it seems, Spark is so vulnerable while, with today's technology, it should not be. Good example is wifi connection between mobile and RC which is giving us such a headache that pilots are switching to OTG in droves. Wifi technology is so mature these days that there is simply no excuse for DJI to have video jitter and lag on 10cm Wifi connection between RC and mobile. So if they can't quite figure out Wifi over 10 cm distance, think about Wifi used to control the drone and what a distant cell tower can do to it... Food for thought :-)

Thanks for sharing this event I felt the rush you did while reading.lol

Mirek6:" Wifi technology is so mature these days that there is simply no excuse for DJI to have video jitter and lag on 10cm Wifi connection between RC and mobile."

I get video lag and jitter while using OTG. So either the RC-AC connection has a problem or there is another cause.

marlowe Posted at 2018-6-14 17:47
Mirek6:" Wifi technology is so mature these days that there is simply no excuse for DJI to have video jitter and lag on 10cm Wifi connection between RC and mobile."

I get video lag and jitter while using OTG. So either the RC-AC connection has a problem or there is another cause.

Yes - you may get a video jitter and lag with OTG as well. I use OTG. And yes - this is most likely caused by RC to AC Wifi connection. However, with Wifi connection between RC and mobile it is much worse.
This is why so many Spark pilots switched to OTG (including me).
This also puts in question Wifi technology DJI is using for mobile to RC connection.
Frankly speaking I am impressed with RC to AC Wifi range DJI was able to get. And I do not mind a bit of video lag which happens occasionally if Spark is far away.  However, I cannot understand why, when Wifi connection between mobile and RC is used, it gets so much worse. There was a video posted on this forum few months ago when somebody did experiment with Spark, RC and mobile sitting on his desk. Video lag when he was moving Spark was terrible. It ebbs and flows with different versions of DJI GO. But it is invariably sub-par.

Nidge Posted at 2018-6-14 14:26
I always feel saddened when someone reports a flyaway but in this case relieved you didn't lose your robotic minion.

All these reported incidents, all with a common theme, do give me cause for concern. The route of this concern is the reliability of the internal digital compass and the bad science that gets banded around with respect to electromagnetic interference. In a previous life I worked in the space industry with emphasis on radio communications (DC to light) and remote sensors, so I have a reasonable knowledge of the inner workings of flight controllers and associated ancillary components. So the notion that a Spark, or any consumer “drone”, can be downed by a distant powerline or radio mast interfering with the onboard electronics to a degree defies logic. The Spark uses similar, if not identical, magnetometers as those found in the compass circuits of cellphones. When you take into account the inverse square law  governing near field RF and magnetic field strengths over distance the strength of the field created by even a powerful cell tower a few meters away is less than that experienced by the compass in a phone from the internal WiFi and cellular associated RF circuitry. Also these sources are AC in nature so significantly less problematic than a DC source.

Nice Icon, Laser with a 22 cc motor ?

Do not forget the 4 electrical motors on the Spark itself. Maybe these are the problem for the compass errors. On the other hand the CS of DJI has also a compass built in and until now there are quite a lot of issues with it. The quality of the compass device could give also some unpredicted behavior (temperature, vibration, electric noise). With the flight log you will never know, because they use the info of the device itself , there is no second compass to check with.

I believe on the Phantom and Mavic Pro there are two sensors.

To my opinion an aircraft should have always redundant sensors. I do not not say it will have no issues, but at least you can find out what was going wrong and improve things.

I see in this forum a lot of compass errors with back to ATTI, the Spark is sold as a very easy to fly drone for anyone, so DJI should do some work on this.

Regards

Mirek6

I have down loaded the flight log as requested
Your comments would be highly appreciated.

http://www.phantomhelp.com/logviewer/1QH4XJPQW1AUW89HHYY9/

62+ Posted at 2018-6-15 01:50
Mirek6

I have down loaded the flight log as requested

62+,

You provided flight record which is very different than the flight you described in your original message. You said that you flew out of your front garden, with proximity to cell towers and experienced electromagnetic interference.

The flight log you provided shows you flying in the mountains with very strong N-W winds and with no electromagnetic interference, no compass or yaw errors and with excellent GPS lock.

It shows Spark being pushed away from you after RTH sequence was initiated. The winds are too strong for Spark to come back. It is trying its best but can't (I can see it by the way it is tilting trying to come back). You do try to get it back but to no avail, your input and thrust forward does not work because Spark is already in full speed ahead towards you while flying back pushed by the wind. Gusts of wind - according to my quick napkin calculations - go as high as 80 km/hour from North West.

You are flying into valley - valleys act as wind corridors in the mountains especially if their positioning is the same as prevailing wind directions.

After over 7 minutes of flight fighting with wind,batteries get depleted and Spark autolands almost 900 metres from you to the South-East, 221 metres lower than its starting point.

Did you recover it? It's geo position when landing was 39.66349289N 105.56520043W.

Hey 62+,

I just discovered that you provided somebody else's log. See this therad: https://forum.dji.com/forum.php?mod=viewthread&tid=152651&page=1&extra=#pid1407839.

Or, perhaps you use two aliases on this forum?

If you provided this log by mistake, upload the correct one and let us know.

SORRY my mistake

http://www.phantomhelp.com/LogViewer/P32AMWAWLEW0LMUN6BJE/

Nidge Posted at 2018-6-14 14:26
I always feel saddened when someone reports a flyaway but in this case relieved you didn't lose your robotic minion.

All these reported incidents, all with a common theme, do give me cause for concern. The route of this concern is the reliability of the internal digital compass and the bad science that gets banded around with respect to electromagnetic interference. In a previous life I worked in the space industry with emphasis on radio communications (DC to light) and remote sensors, so I have a reasonable knowledge of the inner workings of flight controllers and associated ancillary components. So the notion that a Spark, or any consumer “drone”, can be downed by a distant powerline or radio mast interfering with the onboard electronics to a degree defies logic. The Spark uses similar, if not identical, magnetometers as those found in the compass circuits of cellphones. When you take into account the inverse square law  governing near field RF and magnetic field strengths over distance the strength of the field created by even a powerful cell tower a few meters away is less than that experienced by the compass in a phone from the internal WiFi and cellular associated RF circuitry. Also these sources are AC in nature so significantly less problematic than a DC source.

Why would you transmit a UHF signal at the spark to see if you can jam a GPS signal with a cell tower?  I doubt GPS or cell towers are around the UHF band.  Overloaded its selectivity circuit by signals around the 2.4g range?  How well made are the GPS radio circuits so they work in harsh radio environments (between communicating microwave antennas).  Jamming resistant?   

I doubt the Spark  has shielded circuitry and plenty of noise and spurious signals can be induced if I line it up in a microwave dish.  Consumer products designed to accept interference and not give off interference by FCC regs.

As far as if a compass is needed when you have GPS and an INU/IMU,...try being blindfolded in a canoe (no heading info or turn info), me spinning your around a few times, on a river (moving fluid) and having me help you stay in one spot by yelling out how your position has moved south, then north, then south.  Hard to tell which way to row or if your row made it worse (wrong direction) or if the fluid moving made it worse.  

You need a compass with your IMU more than you need a GPS with your IMU so the Spark defaults to following the compass when it's data disagrees with GPS data.  RC pilots being fine flying in ATTI mode without GPS stabilization.  Photographers promptly lose the drone when in ATTI mode because they need the autopilot (GPS stabilized) to do the work for them.  Photographers are seldom pilots.

This guy would be fine if the Spark had a compass error and went into ATTI mode.  Sliding a flying drone down a railroad rail.

Where is the cell tower in relation to your flight path, I looked at the sat view but failed to see it.

Northwood

The cell phone tower is new and will not appear on Google maps. It was activated about a week ago.
The new tower is about 200m to the west of  the drone position before it crossed its path and them the "fun" started.
You will notice no lights are on on top of the tower - refer to attached immage.

Here is what I see:

You are flying happily over your front yard and, as you said, nothing happens until 5m 12 seconds when you raised your drone up to 38 metres while just 5 metres away from home point over your garden.
Out of blue yaw error which indicates misalignment of compass and IMU. Your drone drops to ATTI (as per design).
There is short (1 sec) input on your gyro stick but drone does not budge. Otherwise you do nothing for 5 seconds.
During this time it starts to drift North East with the speed of 8km/hour – perhaps a little bit of wind at 38 metres altitude.

And then log just cuts off – no communication for 1 minute 23 seconds.
After that the sequence is as you described.
Communication is lost until drone is 207 metres away (consistent with drifting in 8-10 km/hour wind) and 5 metres above the ground. Going down is consistent with Spark’s design. When signal is lost and in ATTI mode, it will attempt to land.
After communication is restored you initiate RTH and drone responds as it should – raises up to 30 metres, faces your direction and flies back.

At 7m 33 sec it start losing altitude with speed of about 1 meter per second – it simply responds to your commands.

When it gets to the 100 metres maximum distance boundary which you set, it starts slowing down. It is consistent with Spark design – it will start slowing down before the max distance boundary is reached. However, in your situation, what DJI designers likely did not foresee is that the Spark is coming from wrong direction! So it drops to P-GPS and waits for your instructions.

You hit RTH again and it raises up from 23 metres to 30 metres and starts flying towards you.

When it autolands it switches to P-GPS (perhaps you cancelled autoland) and you direct it using your throttle down. At 9 m 11 sec it loses connection from you for 18 seconds. This is while it is 2 metres up and 1 meter away from home point. When connection is restored, it is hovering 1 meter above the ground and 3 meters from its home point.

In summary – let DJI analyze this log. The behaviour of Spark is consistent with strong interference which affects not only compass but WiFi link between RC and AC as well. Cell towers as you said? It is weird though if you are 200m away. In addition it retained signal and came back with no issues (outside of stopping to rest at 100 metres boundary). Why blasted one way and happy returning?
Also – why did it lose signal while landing so close to you? Landing behind the house so Wifi interrupted? And then restored?

One definite design flaw, which is feedback to DJI is Sparks behaviour at 100 metres boundary. It should have known that it is decreasing its distance and it should have known not to stop.

Mirek6
Thank you very much for your feedback and detailed analysis.
I am very impressed with the link that provide such a detail analysis of the flight log and will use it often if some glitch happens during a flight.

I'm still a rookie and the mishap got to me and the fact that I could not see it  confused me and I looked in all directions thus also holding the RC in the wrong direction.

I got the detailed design plan of the new tower as all land owners could object to the construction of the tower in terms of a environmental investigation. Must just find all the paper work.  This was done about 2 years ago.  30m is properly below the antennas polar transmission pattern.  At 38m it would seem that the drone was in the polar transmission pattern.

I flew in my back garden up to 50m with no problems and none of the antennas of the cell tower is pointing in that direction.



To give more perspective on the incident I attached a map showing the cell phone towers in question.

62+ Posted at 2018-6-15 10:27
Mirek6
Thank you very much for your feedback and detailed analysis.
I am very impressed with the link that provide such a detail analysis of the flight log and will use it often if some glitch happens during a flight.

62+,

To get access to all the data, you need to download .CSV (Excel) file from the link. You will see almost everything there, including attitude of Spark, your stick movements etc. With a bit of experience you can even guess how strong is the wind and from which direction it is blowing. It shows through pitch and roll telemetry of Spark when it holds GPS position.

When your Spark got into ATTI it was not directly between the two towers (not that it would matter though). I would be surprised if the culprit was the old tower - too far away (in my opinion - I may be wrong). However, the new cell, while still not too close - who knows? It is 200 metres away which is much closer than Spark's Wifi range. The important thing is that interference was strong enough to first unbalance you compass and than interrupt WiFi communication between RC and Spark. I believe that Spark operates on 2.4GHz frequency. LTE communication bands are crowded around it.  Only band between 2,400 MHz and 2,496 MHz is unregulated for drone use. Perhaps too close for comfort? If your new cell tower blast LTE signal in band 40 (2,300 MHz-2,400 MHz) who knows? This would need to be consulted with a telecom engineer to know for sure.

Having seen all that, my bet is on strong interference on the border of 2.4GHz band from the new tower.

Of course, it could also be a Spark malfunction. But if your Spark behaves just fine everywhere else, than you know the answer - don't fly in your backyard or, one day, your are going to lose your Spark :-).

Good luck and many happy flights!

Thank you Mirek6 and to all the other co-pilots for the interesting discussions and  valuable comments.

Enjoy the hobby and although it would be a big loss to anyone loosing his Spark drone for sure ,but,  it can be replaced.
It is only money and not a life.

Nidge Posted at 2018-6-14 14:26
I always feel saddened when someone reports a flyaway but in this case relieved you didn't lose your robotic minion.

All these reported incidents, all with a common theme, do give me cause for concern. The route of this concern is the reliability of the internal digital compass and the bad science that gets banded around with respect to electromagnetic interference. In a previous life I worked in the space industry with emphasis on radio communications (DC to light) and remote sensors, so I have a reasonable knowledge of the inner workings of flight controllers and associated ancillary components. So the notion that a Spark, or any consumer “drone”, can be downed by a distant powerline or radio mast interfering with the onboard electronics to a degree defies logic. The Spark uses similar, if not identical, magnetometers as those found in the compass circuits of cellphones. When you take into account the inverse square law  governing near field RF and magnetic field strengths over distance the strength of the field created by even a powerful cell tower a few meters away is less than that experienced by the compass in a phone from the internal WiFi and cellular associated RF circuitry. Also these sources are AC in nature so significantly less problematic than a DC source.

Hello!

I'm glad you like the same thing as me. I learned as an electric machine mechanic. I have an intermediate level software school too. My logic is working.
On this forum I tried to explain this, but it was an attack (mostly from a DMX creature).

"I hold the Spark in an aluminum-covered case and take off from the cover. He has not caused any problems yet.
"I saw video footage where they flew vertically next to a national radio tower, just like its height, without any problem.

If it were true that they would interfere with the compass, there would be virtually no space to fly anywhere, as there were widespread wires, radio transmitters, GSM cell broadcasters, Wifi routers, communications satellites, reinforced concrete buildings, etc.

If that were the case, hundreds or thousands of drone would fall out every day.

So, with only precautionary measures, you can not avoid the random error.

Who can solve this: the DJI. But beyond this board they have a strong influence.
There is no real solution, there is a unique indemnity (not for everyone).

Mirek6 Posted at 2018-6-14 16:24
Nidge,

Good analysis.

Yes Yes!
You just said it was designed. So this is a design flaw.
It is a mistake because the fault of a unit of direction (due to the perceived or the real one) is abandoning advanced 3D navigation.

Can you resign from the GPS to give the lead to a novice pilot who may not even see the drone?

So is a product advertised with a woman and a child (which is not that cheap ...) ignoring advanced management, handing it over to a man?

I would say that the drone could never have been widely sold, if there is no GPS (can only be trained by the pros and close) and will it disable this mode? Do you consider this to be reasonable? I do not!

If this can be improved in software, the engineers need to think about it ...

Mirek6 Posted at 2018-6-14 17:59
Yes - you may get a video jitter and lag with OTG as well. I use OTG. And yes - this is most likely caused by RC to AC Wifi connection. However, with Wifi connection between RC and mobile it is much worse.
This is why so many Spark pilots switched to OTG (including me).
This also puts in question Wifi technology DJI is using for mobile to RC connection.

Without OTG cable:
(AC) --- WiFi--- (RC) --- WiFI--- (PHONE)

OTG cable:
(AC) --- WiFi --- (RC) --- OTG cable --- (PHONE)

Therefore, using OTG cable does not have to handle 2 WiFi streams
Logically, there is less to do, less lag.

Image Transmission AC --- RC may be a bug this is not a problem.
The problem is the wrong compass. Do not mix these two things.

Hello 62+ last time you remember you had a Picture and I told you stay away from that Antenna about a week ago ?

You told me you have a Radio License. I am glad you recovered the drone, RTH most probably worked as the Drone entered P-GPS again ! Very happy for your recovery brother.

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

Here it is -

https://forum.dji.com/thread-151339-1-1.html

See comment #11

''62+ just something I am noticing now. I was focusing too much on the Sunset.

When flying try to avoid the areas where there are -  PowerStations, SubStations, Antennas, Radars, and Powerlines as these  all create Interference with your Drone.

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

I have made a Post on a Summary / Collection of -

Errors / Preflight Checklist / Compass Checking (Before Flight)

Which is worth Watching during your Free Time as for sure you will Learn something new''

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

A friend of mine crashed his Mavic Pro near a Electrical Substation, the Mavic Pro went nuts with Interference. He smashed into the Iron Fence and it fell inside the substation where there are the Large Transformers, he had to contact Enemalta (Electrical Company) to recover it, Thank God he didn't get a Big Fine for flying there, as its Out of Bounds.

Mirek6 Posted at 2018-6-15 12:14
62+,

To get access to all the data, you need to download .CSV (Excel) file from the link. You will see almost everything there, including attitude of Spark, your stick movements etc. With a bit of experience you can even guess how strong is the wind and from which direction it is blowing. It shows through pitch and roll telemetry of Spark when it holds GPS position.

There are also 5.8Ghz channels, if you just did not switch to 2.4Ghz manually, it switches automatically.

Jakab Gipsz Posted at 2018-6-15 15:46
There are also 5.8Ghz channels, if you just did not switch to 2.4Ghz manually, it switches automatically.

Yes, but if you are very near to a high power antenna.
It will overload the high-frequency amp, blocking all the signals.
No reception of any channel.

So keep away from this antenna's.
These kind of antenna's have a cylinder like field, so some distance will help a lot.

Do not fly into a RX/TX beam between a two dish setup, distance will not help you...
So do not "facing" the dish on a tower.

SubUser Posted at 2018-6-15 16:57
Yes, but if you are very near to a high power antenna.
It will overload the high-frequency amp, blocking all the signals.
No reception of any channel.

Yes, the connection (and live broadcasting) can be disrupted by the transmitter tower, but it is also described in the 6 # comment: the compass is not sensitive to the high frequency signal (mostly from this distance)
And it's unclear why I do not use GPS signals at this time (usually 15-17 satellites)

Quote from wikipedia if you do not believe that GPS can work as a compass:
GPS receivers used as compasses [edit]
GPS receivers using two or more antennas mounted separately and blending the data with an inertial motion unit (IMU) can now reach 0.02 ° in heading accuracy and have startup times in seconds rather than hours for gyrocompass systems. The devices accurately determine the latitudes, longitudes and altitudes of the antennae on the Earth, from which the cardinal directions can be calculated. Manufactured primarily for marine and aviation applications, they can also detect pitch and roll of ships. Small, portable GPS receivers with only one antenna can also determine directions if they are being moved, even if only at walking pace. By accurately determining its position on Earth at a few seconds apart, the device can calculate its speed and the true bearing of its direction of motion. Frequently, it is preferable to measure the direction in which a vehicle is actually moving, rather than its heading, i.e., the direction in which its nose is pointing. These directions may be different if there is a crosswind or tidal current.

GPS compasses share the main advantages of gyrocompasses. They determine true North [26], as opposed to magnetic North, and they are unaffected by perturbations of the Earth's magnetic field. Additionally, compared to gyrocompasses, they are much cheaper, they work better in polar regions, they are less prone to being affected by mechanical vibrations, and they can be initialized far more quickly. However, they depend on the functioning of, and communication with, the GPS satellites, which may be disrupted by an electronic attack or by the effects of a severe solar storm. Gyrocompasses remain in use for military purposes (especially in submarines, where magnetic and GPS compasses are useless), but have been largely superseded by GPS compasses, with magnetic backups, in civil contexts.

Jakab Gipsz Posted at 2018-6-15 17:07
Yes, the connection (and live broadcasting) can be disrupted by the transmitter tower, but it is also described in the 6 # comment: the compass is not sensitive to the high frequency signal (mostly from this distance)
And it's unclear why I do not use GPS signals at this time (usually 15-17 satellites)

Your right, a GPS compass would work better.

But they have both disadvantages :

GPS compass needs a good reception from the satellites on both antennas , bad : buildings, inside buildings, under big trees, mountains, high power transmitter .

Compass needs a magnectic free zone, bad : electric wires, iron construction, running electric motors, mountains with high iron content.

So you need both, maybe redundant.

I am afraid you cannot put it all into a small Spark.

I think they will not change anything on the good old Spark soon.
They are too busy with the Mavic Pro II now Parrot lanches their model this summer.
Maybe a new model at end of this month ?

SubUser Posted at 2018-6-15 17:35
Your right, a GPS compass would work better.

But they have both disadvantages :

There are both of them ...
Just if the magnet shows a different value then it will turn off the GPS !!! ??

He's why he passes the controll, despite receiving 15-17 satellites?

Jakab,

DJI design to exit P-GPS when compass errors start is a correct one. Compass and IMU must be in sync. If they are not you may experience toilet bowl effect when flying which is almost impossible to control. ATTI is much safer choice.

In other words, if Spark was left in GPS with compass/IMU misaligned than it would keep its position until you touched the sticks to fly it. The moment you tried to fly it it could go crazy with TBE.

Please note that if Spark is closer to the ground and in misaligned state DJI will not put it on ATTI but in OPTI mode. It will behave almost as in GPS but without danger of TBE.

These are correct decisions in drone design.

Mirek6 Posted at 2018-6-16 04:11
Jakab,

DJI design to exit P-GPS when compass errors start is a correct one. Compass and IMU must be in sync. If they are not you may experience toilet bowl effect when flying which is almost impossible to control. ATTI is much safer choice.

Mirek you are making me very angry lately. I cannot find a Single Comment which I disagree with You !!

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

I am amazed with Mirek's Comments.

When I read them, I have nothing to add. He is always Spot On !

Admire You Mirek ! You are one of the Best Technical Guys here for me.

Almost cut my hair.

Avoid interference sources, and have fun flying. Spark is an amazing machine for its price.

Hello DMX_MT,  my friend,  reply #27

I do remember your advice.
As a HAM we like always to  push the envelope (with in the law) and see what we can achieve. Example.. using as low power as possible and see if one can make contact  with an other Ham halfway around the world.

I do have some racing drone experience however find it difficult to master the art fully due to the reversing of the right stick when changing you flight direction. (VLOS not FPV)
Back to the interference issue,

Flying at home is done for practice and the poor drone got a lot of potential hazards.

What I have learned at my own home environment to date:

1. Cellphone tower - If I stay at a max altitude of 30 meters it should be fine.
2, 8 Wifi security cameras  plus PC s and cell phones  connected to home router (2,4Mhz)  can not fly with cell phone only as very little bandwidth left for reliable connection. I use cell phone and RC (no OTG cable) working fine.
3.  Electric fence on perimeter walls, 9 kV - no problems
4. Wireless alarm system 430 Mhz system with frequency hopping - no problems
5. Overhead power lines  in front of my property  220V - no problems.

In closing: As a rooky DJI product owner , regarding DJI products, service and forum. Highly impressed all around. Also learned many new things to date. .
As an additional hobby, it is really giving me very good exercise for my grey matter as retired person.

Mirek6 Posted at 2018-6-15 12:14
62+,

To get access to all the data, you need to download .CSV (Excel) file from the link. You will see almost everything there, including attitude of Spark, your stick movements etc. With a bit of experience you can even guess how strong is the wind and from which direction it is blowing. It shows through pitch and roll telemetry of Spark when it holds GPS position.

The  .CSV  file info is great!!  Now I can use some my almost forgotten skills on Execl  again which I haven't used for the last 5 years. The  .CSV file could be very interesting to analyse should I encounter a hick-up with a drone flight or has a concern.
Thank you.

62+ Posted at 2018-6-17 10:06
The  .CSV  file info is great!!  Now I can use some my almost forgotten skills on Execl  again which I haven't used for the last 5 years. The  .CSV file could be very interesting to analyse should I encounter a hick-up with a drone flight or has a concern.
Thank you.

Hey 62+,

Yes - I learned a lot on my own logs because I could correlate info in Excel file with what I knew about conditions when I was was flying. Later I learned even more by analyzing other people's interesting cases (yours is a good example). It is fascinating - continuous learning while having fun with a marvel of technology.

you are very lucky