So have decided to test new firmware update and DJI GO4 for CrystalSky. Took my Spark to  nice place here in Latvia, nice weather, maybe a bit stronger wind gusts, then i wanted, but UAV Forecast was not against my flight anyway.
So one battery was used with no problems at all, but during the second flight it happened! Heard this voice all of sudden " ATTI Mode" And my Spark started to drift on the wind extremely fast. So immediately i remembered all the things, i learned from my kind Guru on this forum - Hallmark:
1. try not to panic
2. stick movements must be much sharper and longer to take control over the AC
3. Try to bring it back if possible
4. also have tried to remember how to fly in  ATTI mode , by controlling cheap Eachine E58 ( was advised by Hallmark as well)
And somehow the miracle happened - i was able to regain control on Spark and safely land it down.
So my first words of gratitude to my best teacher and guru Hallmark! Mate thak You so much for every clever advise so generously shared here with us
But now i would very grateful as well to all clever guys here, who may have a look on my flight record ( screen record) and flight log and explain what really happened and what i have been done instictively trying not to loose my sparky
https://www.dropbox.com/s/b5r5ft ... 6_14_54_43.mp4?dl=0
and here
http://www.phantomhelp.com/LogViewer/5UKI2NS406D81DCVM21M/

I also use a Eachone E58 for practice and training in ATTI mode.

Here, again, such a GPS signal is a loser "Yaw error" error. And they are newer every day. And here we know only what publishers of the forum publish. There are so many more cases.

My friend, not only in your skill, but also in luck.
The log reveals that there were not as many mistakes as others who lost their Spark. There was no compass error and no interference error message.
Connection did not break and that was your luck. And then back to P-GPS mode.
Now you were very lucky ...
Tell us which firmware and app. are you using it?

Explain to someone how 16 GPS satellite breaks suddenly. My car navigation has never produced this. Exactly when I enter a tunnel.

Everyone talks about how to deal with, overcome, prevent, but no one talks about the worrying technical error here.

This issue is far too common. I’d be afraid to fly my replacement if I were to keep it.

So here's food for thought.  All you see on here is "I lost my drone".  If you read through all these threads and read the countless times people have lost their Sparks, Mavics, Phantoms, etc you'll drive yourself crazy and never take it back out of the box again.  What you don't see are the MILLIONS of people coming here to say "I didn't loose my drone today".  That's because they didn't loose anything and they are not upset and are still out flying.  I know when I first got mine and started flying and not having any issues I came to the forum just to learn more.  It scared the holy hell out of me and I was like what have I just done?  I literally had to walk away from the forum for awhile and get away from the negativity and go fly and have fun.  But what the forum did do for me however was teach me to be prepared, try not to panic, and educate myself.  So when issues or problems do occur I know how to handle it or where I can get help and bounce ideas off other people.  That's really what this is all here for is to help each other and share our experiences.  

JDavidTX Posted at 2018-5-26 21:41
So here's food for thought.  All you see on here is "I lost my drone".  If you read through all these threads and read the countless times people have lost their Sparks, Mavics, Phantoms, etc you'll drive yourself crazy and never take it back out of the box again.  What you don't see are the MILLIONS of people coming here to say "I didn't loose my drone today".  That's because they didn't loose anything and they are not upset and are still out flying.  I know when I first got mine and started flying and not having any issues I came to the forum just to learn more.  It scared the holy hell out of me and I was like what have I just done?  I literally had to walk away from the forum for awhile and get away from the negativity and go fly and have fun.  But what the forum did do for me however was teach me to be prepared, try not to panic, and educate myself.  So when issues or problems do occur I know how to handle it or where I can get help and bounce ideas off other people.  That's really what this is all here for is to help each other and share our experiences.

Couldn't agree more.

Hi nixuspix,

Great flying job to land your drone in this situation.

As you see in my chart your drone had some errors ; YAW error first, wich means that your drone don`t use compass data ; ATTI mode.
Interference just once and 5 time not enough power. Your flight log shows that the VPS vision is used wich means that OPTI mode was engaged.
Guess you did not see that on the display while watching and flying your drone.

DJI should tell you why the SPARK drones are suffering from YAW errors, i haven`t got a clue. Especially in your case as you did not fly in Sport mode with large heading excursions.
But the YAWerrorLage started after 100% left yaw for 0.2 seconds with 100% throttle up.

cheers
JJB

JJBspark Posted at 2018-5-27 00:25
Hi nixuspix,

Great flying job to land your drone in this situation.

Thank You so much for analysis. Really appreciate this a lot

Thanks a lot to All contributed in this thread. Anyway i am happy, that drone is alive so far, but am not sure at all about its future, due to the accidents like this

I still don't understand why Spark disconnects GPS through YAW error (compass error). Why Spark doesn't use GPS for hovering on a place and wait for the pilot intervene? Instead it's going to fly to hell.

JDavidTX Posted at 2018-5-26 21:41
So here's food for thought.  All you see on here is "I lost my drone".  If you read through all these threads and read the countless times people have lost their Sparks, Mavics, Phantoms, etc you'll drive yourself crazy and never take it back out of the box again.  What you don't see are the MILLIONS of people coming here to say "I didn't loose my drone today".  That's because they didn't loose anything and they are not upset and are still out flying.  I know when I first got mine and started flying and not having any issues I came to the forum just to learn more.  It scared the holy hell out of me and I was like what have I just done?  I literally had to walk away from the forum for awhile and get away from the negativity and go fly and have fun.  But what the forum did do for me however was teach me to be prepared, try not to panic, and educate myself.  So when issues or problems do occur I know how to handle it or where I can get help and bounce ideas off other people.  That's really what this is all here for is to help each other and share our experiences.

I couldn't agree more. I come here and enjoy the beautiful scenery in the various pics and vids taken with Spark. The negative stuff is something for me to try and avoid so I can continue to go out and just fly and enjoy my Spark. I've been flying GPS controlled UAS's for quite some time and have witnessed my fair share of glitches in these things. Sometimes you have to accept there are going to be glitches with devices that are essentially controlled by tiny computers. Small computers that are miraculous creations to say the least but like their larger desktop cousins, they are not immune to the occasional glitch. Happy flying.

JJB said: .. "But the YAWerrorLage started after 100% left yaw for 0.2 seconds with 100% throttle up."

Maybe here is the clue. One have to be careful with Yaw turns?
Anyway thanks God, that i was in VLOS with drone, otherwise it would be lost for sure.

Hi nixuspix, just had a look at your flight log and while it’s difficult to know exactly what happened, some things we do know, magnetic interference will cause a problem with compass and lead to yaw errors, aircraft will drop to ATTI Mode , and no mater where or when this happens it’s always difficult to control, so well done on a good job in bringing your drone to a safe landing.

From my experience most magnetic interference is picked up from the ground, and it starts a chain reaction that eventually leads to Atti/opti mode, if aircraft is low enough it will go to opti mode when gps is lost, it will go to ATTI Mode when Aircraft is above working parameters of opti mode.

Although this may not have happened in your case it’s something we all should be aware of.

I will try to explain.
First if you start up your Aircraft in a safe area, without taking off lift up your Aircraft by hand and rotate 90 degrees, both compass and IMU will follow to this new heading, so no problem this is how it should be.
Taking off from mag interference ground will cause your compass to move it’s heading this does not always show up in your app, so it will still allow you to take off.
Once you take off and get clear of mag interference your compass will then correct itself but the movement made by compass causes confusion in your IMU because it is designed to move with compass.
This you will see reported on your app as IMU exceptional heading compass error yaw error etc, switch to Atti mode, your aircraft cannot cope with conflicting data so it will drop gps and go to ATTI Mode .

It’s very unusual to get magnetic interference in the air unless flying around or over potential magnetic hazards.
Once again good job, I will leave a list below of potential hazards on the ground and some recommendations to keep clear from.

Compass distances.

Natural and Artificial Magnetic Anomalies Warning
Note
The following information has not been objectively tested to determine it’s impact on a Drones compass accuracy in flight.
        1        Many things can distort the earth’s magnetic field in the area you are flying:
        •        Steel framed or reinforced concrete buildings, bridges and roadways, iron pipes and culverts, high power electric lines, heavy equipment, trucks and automobiles, steel tanks, electric motors and even computers.
        •        Flying between steel framed or reinforced high rise buildings will distort the magnetic field in addition to causing GPS multi-pathing.
        2        Safe distances for compass calibration
        •        6” (15 cm) minimum: Metal rim glasses, pen/pencil, metal watch band, pocket knife, metal zipper/buttons, belt buckle, batteries, binoculars, cell phone, keys, camera, camcorder, survey nails, metal tape measure.
        •        18” (50 cm) minimum: Clipboard, data collector, computer, GPS antenna, 2-way radio, hand gun, hatchet, cell phone case with magnetic closure.
        •        6 ft (2 m) minimum: Bicycle, fire hydrant, road signs, sewer cap or drain, steel pole, ATV, guy wire, magnets, chain-link fence, bar-wire fence, data collectors
that use a magnet to hold the stylus.
        •        15 ft (5 m) minimum: Electrical box, small car/truck, powerline, building with concrete & steel.
        •        30 ft (10 m) minimum: Large truck, metal building, heavy machinery.

Thank You so much again Captain!

Sibstr Posted at 2018-5-27 03:51
I still don't understand why Spark disconnects GPS through YAW error (compass error). Why Spark doesn't use GPS for hovering on a place and wait for the pilot intervene? Instead it's going to fly to hell.

Hi!

How is Spark supposed to do that? It has no clue in which direction it is heading. Trial and error?

Greetz
Weesel

Weesel Posted at 2018-5-28 01:27
Hi!

How is Spark supposed to do that? It has no clue in which direction it is heading. Trial and error?

Pretty much the same way all other navigations do it.
Sample one set of coordinates (x1, y1), 0.1 sec later sample new coordinates (x2, y2).
Do some basic math to figure out drone direction. Compare to the stick input to figure out drone heading.
Yes, this will not account for the wind drift, but I guess should be still better than to shut down all the systems, occasionally video stream as well to kill any hope for those few ones who know proper FPV flying as well.

And yes, trial and error should be an option too... I mean, all PID control systems work exactly on trial and error principle.

JDavidTX Posted at 2018-5-26 21:41
So here's food for thought.  All you see on here is "I lost my drone".  If you read through all these threads and read the countless times people have lost their Sparks, Mavics, Phantoms, etc you'll drive yourself crazy and never take it back out of the box again.  What you don't see are the MILLIONS of people coming here to say "I didn't loose my drone today".  That's because they didn't loose anything and they are not upset and are still out flying.  I know when I first got mine and started flying and not having any issues I came to the forum just to learn more.  It scared the holy hell out of me and I was like what have I just done?  I literally had to walk away from the forum for awhile and get away from the negativity and go fly and have fun.  But what the forum did do for me however was teach me to be prepared, try not to panic, and educate myself.  So when issues or problems do occur I know how to handle it or where I can get help and bounce ideas off other people.  That's really what this is all here for is to help each other and share our experiences.

well said mate .. well said

eYeSkYeYe Posted at 2018-5-28 06:49
Pretty much the same way all other navigations do it.
Sample one set of coordinates (x1, y1), 0.1 sec later sample new coordinates (x2, y2).
Do some basic math to figure out drone direction. Compare to the stick input to figure out drone heading.

I think judging by how the OP managed to fly and land his craft safely shows that they’re is a system already in place, and it works.

eYeSkYeYe Posted at 2018-5-28 06:49
Pretty much the same way all other navigations do it.
Sample one set of coordinates (x1, y1), 0.1 sec later sample new coordinates (x2, y2).
Do some basic math to figure out drone direction. Compare to the stick input to figure out drone heading.

You can't fly in a fluid with just GPS coordinates.  You can fly with just a compass.  The compass keeps the nose stable when you don't have a rudder.  

You have two sets of coordinates but no way of knowing if correction is to the front, rear, left, or right.  Further, you have no way of knowing if the correction was in the right direction because winds keep changing the coordinates.  "blind person, you just moved south with the winds.  Now you have walked forward but are now further south.  Did winds move you that way or did your walk move you that way?"

hallmark007 Posted at 2018-5-28 00:45
Compass distances.

Natural and Artificial Magnetic Anomalies Warning

Can iron ore deposits be the cause of problems in open areas?

Tervist Posted at 2018-5-28 15:36
Can iron ore deposits be the cause of problems in open areas?

Yes I believe so, but anything that will cause magnetic interference is a potential hazard, all we can do is make preflight checks never be in to much of a hurry to send Aircraft away to soon I believe waiting with Aircraft hovering at low altitude for 60 seconds before flying off will hugely cut down the chance of flyaway, it also means any problems can be dealt with very quickly at close range.

Gunship9 Posted at 2018-5-28 14:54
You can't fly in a fluid with just GPS coordinates.  You can fly with just a compass.  The compass keeps the nose stable when you don't have a rudder.  

You have two sets of coordinates but no way of knowing if correction is to the front, rear, left, or right.  Further, you have no way of knowing if the correction was in the right direction because winds keep changing the coordinates.  "blind person, you just moved south with the winds.  Now you have walked forward but are now further south.  Did winds move you that way or did your walk move you that way?"

There is no just GPS, there are very useful set of sensors.... accelerometers and gyros. I am fairly sure there is mathematical model that can estimate drone heading even without the compass. Compass is there to save processing power as it gives absolute heading instantly, without the need for dynamic processing of the inputs. And now I suspect Hallmark might be right... this algorithm might be in place. It draws a lot of processing power causing "not enough power" errors as processor is drawing a lot of current from the battery to be able to calculate things and eventually even drops the video signal as it also requires serious processing so bird is desperately trying to save processor cycles for most critical operation.

Tervist Posted at 2018-5-28 15:36
Can iron ore deposits be the cause of problems in open areas?

Based on testing I have done with ferrous metals, for iron ore deposits to cause magnetic interference it would take massive iron ore deposit, extremely concentrated deposit of, and deposit would need to be very close to surface.

If you read up on Compass deviations, iron ore is a cause, but deviation is limited, and there are other causes for compass deviations - Geomagnetic storm, and Magnetosphere of earth's iron core.

There is prospecting for Iron ore done by looking for changes in earth's magnetic field, but it takes specialized equipment, computer analysis, and modeling to indicate potential for iron ore deposit.

eYeSkYeYe Posted at 2018-5-28 06:49
Pretty much the same way all other navigations do it.
Sample one set of coordinates (x1, y1), 0.1 sec later sample new coordinates (x2, y2).
Do some basic math to figure out drone direction. Compare to the stick input to figure out drone heading.

But Siubstr wondered why Sparky does not hover in position when the compass signal is dropped - there is no Stick Input. Wind pushes Spark into one direction - so it now has to move in every possible direction to determine its heading for a very short period until wind turns it into another one and all begins again? I guess seeing this makes you believe Sparky went havoc
Gunship9 also pointed this out.

In case of failures the Operator should take care and bring the drone home like OP did. IMHO there is no failsafe backup option you can/should rely on... But as drones nowadays are sold as smart selfie drones the majority of buyers is not ready for this.

Greetz
Weesel

Weesel Posted at 2018-5-28 23:16
But Siubstr wondered why Sparky does not hover in position when the compass signal is dropped - there is no Stick Input. Wind pushes Spark into one direction - so it now has to move in every possible direction to determine its heading for a very short period until wind turns it into another one and all begins again? I guess seeing this makes you believe Sparky went havoc  
Gunship9 also pointed this out.

Another brainstorming question is:
How drone knows when to throw yaw error?
It must have some mechanism that tells it there is an error.
Probably heading indicated by compass is not the same as heading gotten indirectly by calculating some data. Another brainstorming question: How drone knows that it needs to attribute error to EM interference? Being MEMS device, there are mechanical moving parts in compass that might stuck. If there are two of them and if readings are different from both, drone can know one mechanically stuck or if both are affected then it's most probably EM interference.  But with only one, I guess drone cannot reliably tell if issue is mechanical jam, EM interference, inertia artifact or maybe defect in coding. Since M200/M210 is suffering compass issues as well and it has 2 of them, I somehow suspect, it might be coding error somewhere when device cannot handle rapid heading changes correctly.

JJBspark Posted at 2018-5-27 00:25
Hi nixuspix,

Great flying job to land your drone in this situation.

And this is the first case I've ever seen of yaw error not in Sports mode. 100% yaw prior to issue might suggests it's inertia and not EM induced.

eYeSkYeYe Posted at 2018-5-29 00:18
Another brainstorming question is:
How drone knows when to throw yaw error?
It must have some mechanism that tells it there is an error.

Yeah, also came to the same conclusion. Compass data has to deviate from expected data which is calulated somehow. Probably via GPS the way you already mentioned?

Dont know anything about M200/210 - but EM interferences would affect both compasses?

I always do some preflight checks and try to avoid metal structures and other stuff like powerlines but TBH i hope to never come in a Situation like OP... ;)

Greetz
Weesel